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diycnc
21-01-2018, 02:16 PM
After building a couple of 3d printers, and building and struggling to do anything with an MPCNC, iv decided its time to make a proper cnc router.

Design criteria are,
Desktop machine with foot print no bigger than 1050 by 850 to fit on my existing bench.
Make use of the 4 750mm SBR16 rails, and 2 300mm SBR16 rails I have buried somewhere in the workshop.
Capable of cutting the end of sheet timber to make box joints.
Reduce costs where possible without affecting performance.

After alot of reading, and a few design iteration, this is what i have come up with.
23634

Z axis,

Both plates are 15mm thick aluminium ecocast. 140mm travel, 1605 ball screw. mass aprox 7kg.
3.1nm motor connected by belt drive. (The motor plate inst shown in the image)
Tramming will be done by a eccentric bush and shims between the X axis plate.
23635

X axis and Gantry

Gantry is made from welded steel box section. Bottom piece is 100x60x3, top 60x60x3, short connecting pieces are 60x40x3.
The two end end connecting pieces will be bolted in place so the ball screw mounts can be easily adjusted if needed. Also if at some point in the future i decide to swap the SBR16 rails for hiwin stile rails I will be able to easily move the ball screw back into the gantry to suit. Rail surface will be epoxy leveled.
23636

X axis plate is 10mm thick ecocast. I dont think there is any need for anything thicker here as it will be bolted to the 15mm thick Z axis plate.
Gantry ends are 10mm thick aluminium flat bar or plate. The Y axis bearing are fixed almost directly to the underside of the gantry, so the gantry ends will only carry load in the Y direction, so no need for anything too thick.The gantry ends will be fixed to both the top and bottom steel gantry tubes. Two small pieces of 20mm thick aluminium ecocast are bolted directly to the underside of the gantry, these will be bolted to the Y axis plates. Shims can be placed between these two plates to level the gantry if needed.
Connecting the bottom of the gantry ends will be a piece of 60x20 extrusion. The Y axis ballnuts will be attached to this.
X axis drive will be 1610 ball screws, with 3.1nm motor connected with belt drive.
I plan to connect the motor to the gantry end plate with some long spacers. This hasnt been included in the model yet.
23637
Total length 900mm, rail length 750, travel 600mm.
Mass approx 25-30Kg

Base frame and Y axis

Base frame is made from wedled 60x60x3 and 60x40x3 steel. Rail surface will be leveled with epoxy. 1610 ball screws are under the bed to reduce the machine foot print. Id like to drive this with just 1 nema 23 3.2nm motor. Is this possible with a gantry approaching 40kg?
The machine will sit on 4 adjustable feet which are not in CAD yet.
23638


To give you an idea of the space constrains, this is a plan view of the current design with the workbench parameter shown.
23639

Total machine weight is around 70kg.
Cutting area will be around 600x600.
Gantry clearance 140mm from the steel base frame. 120mm ish after adding a bed.

Id love to get some feed back on the design before I start ordering parts or cutting metal.
Also im struggling with where to buy the electronics and what to buy, any advice would be really helpful.
im also yet to choose a spindle. Id love a 2.2kw water coolded one, but they are bloody expensive and if possible id rather not have to bother with water cooling. Any suggestions?

Desertboy
22-01-2018, 06:35 PM
Design is crazy simple this is a good thing! I can understand why you want to use the SBR16 BUT sell them and get 15mm Hiwin's you're router design is too good for SBR and it will be the weakest link.

Except the truth this is going to cost more than you think it will, if that doesn't scare you off and it shouldn't mostly your costs go up because someone tells you not to buy this but to buy that instead and you do but in the end you end up with a router not a Xmas cracker toy like the MPCNC.

I speak from experience my plan was to build an xmas cracker but along the way it turned into a router and the budget went to Honolulu for a holiday ;)

diycnc
22-01-2018, 08:03 PM
Thanks for the feedback.
During the design I considered hiwin a number of times as I know they will be loads better, but to get things started at least I will stick with the SBR16 I already have.
If fully expect to upgrade to hiwin at some point, hence the x axis ball screw been fixed to a bolted in piece of tube, not welded, so it can be easily adjusted to suit the smaller rails. The y and z rails can be replaced buy just drilling some new holes in the aluminium plates and a few new spaces I can mill (probably slowly with the sbr16 rails) on the machine before I dismantle it.
This also helps cash flow a little! As you say I expect this to be a rather expensive project, and spreading out the cost a little will please the missus!

I noticed on your build log you mention you wanted to use arduino and raspberry for the controller. Did you do this in the end?

Desertboy
22-01-2018, 08:27 PM
Thanks for the feedback.
During the design I considered hiwin a number of times as I know they will be loads better, but to get things started at least I will stick with the SBR16 I already have.
If fully expect to upgrade to hiwin at some point, hence the x axis ball screw been fixed to a bolted in piece of tube, not welded, so it can be easily adjusted to suit the smaller rails. The y and z rails can be replaced buy just drilling some new holes in the aluminium plates and a few new spaces I can mill (probably slowly with the sbr16 rails) on the machine before I dismantle it.
This also helps cash flow a little! As you say I expect this to be a rather expensive project, and spreading out the cost a little will please the missus!

I noticed on your build log you mention you wanted to use arduino and raspberry for the controller. Did you do this in the end?

No in the end I spent £300 on a toroidal PSU build and AM882's lol. Now I have I consider this the bare MINIMIUM for any router I would build, the arduino setup (If you use cheapo Polou or equiv) is not going to drive the motors quick enough and with enough torque I tried with mine and it was gutless.

An arduino can drive pretty much any stepper drivers but the question is do you want it to? I'm using a parallel port breakout board <£5 on ebay to connect to the steppers and my PC running linuxcnc is doing the processing which with grbl the arduino would be doing.

The PC even a really old one is a lot faster than the arduino so can drive more pulse per second more pulses== more speed.

Arduino is a really wicked little device and works for an xcarve because it's so flimsy you could never run it fast enough to matter but that steel beast you want to build can cut faster than the arduino will keep up with it and you will want to cut at max speed.

Arduino though might be a good fit for a laser cutter or a plasma.

If I had one word of advice on electronics if budget is the issue don't buy a USB controller for £100 and spend £200 on Mach 3. Instead spend £200 on 4 AM882's and £100 on PSU, Breakout board and sundries and use linuxcnc. I see so many people buying shit drivers and then a £200 controller (On cnczone) and I tear my hair out thinking such bad bad advice from people that should know better.

I spent ~£2k building mine but I also got all the aluminium in my build and a lot of other things already so it would cost me £3k to do it again.

Routers aren't cheap and when they are well you saw yourself with MPCNC, even the upper end like xcarve and shapeoko (Common history intersting read) they all at best finicky and at worst unsable. The age old adage is even more true here you get what you pay for.

If you think about problems you had with 3d printing at the beginning and then times them by 10 and you get to cnc routing lol.

One thing though my microswitches are not moving anywhere and that's what you need.

Although I still like to pay less just check my signature and you'll know where I want you to buy you cnc stuff lol.

diycnc
22-01-2018, 09:37 PM
Whats so great about A882 drivers, Iv seen a number of people recommend them.
Do they offer any great benefits over something like this,
https://www.omc-stepperonline.com/stepper-motor-driver/digital-stepper-drive-24-72a-20-80vdc-for-nema-34-stepper-motor-cnc-kit-dm860i.html

Both are capable of handling 80V and more current than my motors can cope with.

The only difference I can see is stall detection. Is that really worth £20 per axis, £80 for all 4?
Any suggestions where to buy a toroidal PSU? Id rather not make on.

The only PC I have are laptops, so no serial ports unfortunately. Which means i either need to buy a PC or an expensive usb or ethernet controller. Hence why i was hoping an arduino might do the job.

Desertboy
22-01-2018, 09:39 PM
Yes it is worth £20 an axis, don't be scared of the PSU build I was then it turned out to be nothing but if you're near Leicester I'm happy to help build it with you to take the scary edge off with and you can check out my router so you don't make the same mistakes I did, you can make other ones lol.

I do love your design because it's just so raw but over engineered that raw becomes pure.

diycnc
22-01-2018, 10:21 PM
Is there much of a saving when building rather than buying?
I see zapp automation sell a 68v one for £115.

Im in north Manchester, so Leicester is a little far. I do travel with work from time to time, so i might take you up on that offer if im in the area soon.

I tried to keep with the KISS (Keep It Simple Stupid) methodology when designing this. I find is often the easiest, cheapest, and quickest way to design and make stuff.

JAZZCNC
22-01-2018, 10:53 PM
Is there much of a saving when building rather than buying?
I see zapp automation sell a 68v one for £115.

Depends on how many motors your running and motor size. Zapp 68V PSU only provides 6A which isn't really enough for 4 motors or leaves any room for upgrades with 3 motors.
Can make one for about £70-80 with exactly what you require and bit to spare for upgrades.

Regards the Drives then if your using slaved axis then go with AM882 for stall detection it's a Must Have feature really.
If not then save the money and put to motion control card it will be worth the investment.

Clive S
23-01-2018, 12:05 AM
Is there much of a saving when building rather than buying? I see zapp automation sell a 68v one for £115.


Check out Joe's excellent vid.
https://www.youtube.com/watch?v=4OoQQg76ar4&list=PL1FIADAKba_tiLqXbUkzD30sZjtp_VyqY

here is a shopping list from Rapidonline https://www.rapidonline.com/

I would go with a 45-0-45 V toroidal instead of the 50V

23658

Desertboy
23-01-2018, 08:30 AM
Listen to Clive I speak from experience lol
http://www.mycncuk.com/threads/10880-New-build-with-recycled-parts-on-a-ridiculous-budget-120cm%2A60cm-work-area?p=96816#post96816

get a 45v not a 50v, if you do insist on a 50v buy mine of me it's only had 10 minutes on time before I bought a 45v one lol. Luckily I got both 1/2 price so it evened out in the end and one day I shall find a use for it.

If you were in mainland europe 50v is fine as the mains is 10v-20v less.
Best thing about having screws under the bed is they're out the way so not crap can get into them, I also toyed with slinging the hiwin under the bed but too much hassle, for reference hiwin's are 95%+ efficient in sideways or upside down mounting vs horizontal it's for me their main selling point.

diycnc
24-01-2018, 06:23 PM
Thanks for the info guys.
The power supply build looks a lot less scary than I expected, and I will defiantly consider this when I get around to buying electronics.

Regarding drivers I plan on just using 1 motor to drive both Y axis screws, so will go with the cheaper drivers.
Does anyone have any thoughts on how well a single 3Nm motor will move a 40Kg gantry, assuming im using 1610 screws and ~70V PSU?

Other than noise, are there any other major benefits of digital drivers over analogue drivers?

At the moment I am finalising the mechanical side of the design, particularly the stepper motor brackets and connection to the ball screw.
The plan is to use 16mm HTD belts on all axis.
To connect the two Y axis ball screws I will go with the setup jazzcnc sugests here
http://www.mycncuk.com/threads/4513-3-Axis-CNC-router

I just need to get a custom end machining on the ball screws so I can fit 2 pulleys on the drive end. All 3 X and Y axis screws are the same length, so will just get the same extra long end machining on all for simplicity.

Desertboy
24-01-2018, 07:14 PM
My thought is ditch the 1610 for a 2010 with BK15/BF15 you can spin it 30% faster before it whips (Ballscrews become skipping ropes at a certain speed the thicker it is the quicker you can spin it)

Also if going the single motor, dual ballscrew route cnc4you do a 4nm nema 23 not sure how good it is but worth investigating.

Also the prices of Hiwin's from cnc4you is very good, the rail is clone but the carriages originals I intend to buy mine from there for my upgrade.

Clive S
24-01-2018, 07:56 PM
1610 screws are a good choice for X & Y with 1605 on Z. With a cutting area of 600x600 you could use just one screw for the Y put up the centre. Get the end machining to suit the machine it makes no difference to the supplier.

I would not buy any electronics until you have the frame built. Re the Spindle in post #1 The water cooled ones are very quiet and generally cost about £210 inc. the VFD that drives it.

Good luck with the build.

JAZZCNC
24-01-2018, 11:07 PM
My thought is ditch the 1610 for a 2010 with BK15/BF15 you can spin it 30% faster before it whips (Ballscrews become skipping ropes at a certain speed the thicker it is the quicker you can spin it)

Nope bad idea with nema 23 motor.!! The inertia of the larger diameter screw and ballnut means more load on motors and less speed before torque falls away.
However there is one way to use 20mm screws while keeping same speed and lower whip. Use 2020 and gear 2:1 this increases torque and halfs the screw speed while keeping same speed as 10mm pitch.

DIYCNC:

There's massive difference between Analog and digital drives. Night & Day difference don't buy Analog drives you will regret it.

Watch or should say listen to these to see difference. Same machine same Motors only change was drives.

Analog https://www.youtube.com/watch?v=WnuLnKtqDX0
Digital. https://www.youtube.com/watch?v=K2-Aub2fetw&t=4s

diycnc
25-01-2018, 10:28 PM
The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.

Thanks for the stepper driver advice JAZZCNC.

How do you guys attach linear rails to a steel frame. Do you just drill and tap straight into the 3mm wall?
An M5 screw has 0.8mm pitch, so will be over 3 full threads in the steel, which is the rule of thumb iv come across a few times.

JAZZCNC
25-01-2018, 10:50 PM
The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.

Don't get caught with the Critical speed trap doesn't often work out that way. So many variables come into play to screw the job up.

Let me put it this way you wouldn't find me using 16mm screws much over 1600mm on any machine I build and even then they would have fixed end BK bearings on both ends to help support.

Yep M5 screws are ok in 3mm box provided you don't swing on them with breaker bar. Make sure you loctite them.

A_Camera
26-01-2018, 10:07 AM
The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.


I am using 1605 screws driven directly with NEMA23 motors and get more than enough speed with that solution. My X and Y has 9m/min and Z has 7m/min. Stalling speed is about 11m/m on all three. My machine is though a moving table type (https://adapting-camera.blogspot.se/2017/02/cnc-upgrade-progress-current-status.html), which I think is better for DIY because it is easier to make and more rigid than a similar one with moving gantry would be.

Here is a short video, running all axes at 10m/min.


https://youtu.be/m1zxi-BjIhc

I am using analogue drivers, DQ542MA and it may be better with digital drivers, but the biggest difference in speed is made by the PSU which is based on toroidal transformer. The second difference is the external motion controller I am using (UC300ETH).

Speed wise I don't think Arduino would be an issue actually. I am running a 3D printer with Arduino and that 3D printer has even more speed than my CNC, currently has 15m/min on X and Y and 5m/min on Z but the Z is driven with simple dual 8mm threaded rods with 1.25mm pitch. Though I am using A4988 drivers, I am pretty sure that I could drive my CNC with the same Arduino but with the drivers from my CNC if I wanted to. Pulsing is generally not the problem, the problem is the drivers and the power supply. To get the speed I have in my printer I changed the delivered 12V PSU to a 24V PSU and that made a HUGE difference. Of course, if I'd run the CNC with the Arduino board (GT2560) I would not be able to use UCCNC or Mach3, but in theory it should not be an issue.

Davek0974
26-01-2018, 11:12 AM
Also if going the single motor, dual ballscrew route cnc4you do a 4nm nema 23 not sure how good it is but worth investigating.


I have only ever used these motors along with their "digital" DSP drives - the pair make a great combination.

Boyan Silyavski
28-01-2018, 08:20 AM
Whats so great about A882 drivers, Iv seen a number of people recommend them.

Leadshine are a brand name already that is proven these last years for top quality and reliability. Or you could buy a copy of a copy and cross your fingers it will work properly.

diycnc
31-01-2018, 09:22 PM
Thanks for the advice. I will defiantly use fixed supports on both ends of the ball screw. it will add no extra cost, and as JAZZCNC suggests will improve rigidity.

I have been working through some of the final details of the design. major changes since last time are i have added the motors belts and pulleys.

Y axis motor is attached to the gantry end plate (which is now 15mm thick, 10mm just look to flimsy!) with 4 50mm long spacers. 1:1 drive to the screw is achieved with two 15 tooth htd 5 pulleys and 15mm wide belt. Can anyone suggest if this is enough teeth on the pulley, or point me towards the datasheets and formulas to work it out. i assume there is a max load per tooth to keep below.
23695

X axis motors is attached the base frame with a long 5mm thick steel plate (I think i need to added a stiffener to this, looks very long and floppy at the moment!). The motor hangs down quite far to avoid the piece of extrusion connecting the bottom of the gantry end plates. I tried removing this extrusion, and replaced it with two small plates to connect the ball nut to the end plates, but a little FEA showed this was a very bad idea! The long end plates twist allot!!
1:1 drive to screw again with 15 tooth pulleys. I can increase to bigger pulleys here if needed.
Larger taper lock pulleys and 15mm wide belt are used to connect the two screws. I will size the pulleys later to suit the available belt length and tensioner adjustment. Belt tensioner will just be couple of bearing on bolt in a slot, no need for anything complicated here.
23696

Next thing to do is add all nuts and bolts to the model to make sure nothing clashes!

I also managed to pick up a used kress 1050 for little over £100. Would rather have one of the Chinese water cooled ones that everyone else uses, but at 300+ they are pricey. If i dont like the Kress i can always sell it on and probably get back all my money anyways.

Davek0974
31-01-2018, 09:43 PM
Looks good but i have a general dislike of motors mounted on long tubes - not too stable and prone to loosening.

Clive S
31-01-2018, 09:57 PM
Y axis motor is attached to the gantry end plate (which is now 15mm thick, 10mm just look to flimsy!) with 4 50mm long spacers.Have you thought about how you are going to tension the belt?

diycnc
31-01-2018, 10:21 PM
Have you thought about how you are going to tension the belt?

I was planning on slotting the holes in the gantry end plates so I could just slide the whole motor up and down.

routercnc
31-01-2018, 10:34 PM
My first ever machine had 4 posts like that and it took a while to get them all the same length. I didn't have a lathe back then. If they are out a bit the motor will be skewed and the belt won't run straight on the pulleys.

The other more popular option is to put the motor behind what is in your drawing the small orange box section, and run the belt horizontally out the back of the gantry, between the upper and lower beams. You just need a big L bracket to mount to and it is a bit more tucked out of the way.

For your other question - there are lots of pulley engagement formulae around but you can tell by looking that you are OK there with ~180 degree contact.

Make sure you have pulley / belt clearance should you ever want to do 1:2 instead of 1:1 to get more speed, and have adjustment in the motor plate to accommodate.


On the overall design it will work fine, but do think through if the underslung ballscrews will be easy to set up and align. Imagine that the base frame cross members (which the ballscrew blocks mount to) is not perfect, and end up on a different plane to the rails. It will tend to bind the ballscrew at some point and you will have to shim something in the system.
If you go the more traditional route with the ballscrews mounted down the side, driving the side members of the gantry directly (no underslung part), I think all the connections can be made with the appropriate 'slip plane' to get it aligned. This will quicker, cheaper and simpler to build and would be my preference.

Up to you but just make sure you can visualise the adjustment process for any scenario if it is not perfectly built.

If you are going underslung just to stiffen the gantry I'd put the efforts in on the gantry itself, e.g. plating across the back etc. (Not saying it needs further stiffening mind).

diycnc
31-01-2018, 10:49 PM
I have a Clark mini lathe so getting them the same length should be easy.
I did consider putting the motor behind the gantry... can't remember why I chose not to. I'm sure there was a reason. I'm gona look at this again cos it would be a nicer design.
Thanks for the pulley info, I will take a look at the design formulas for reference anyway. They might come in useful one day.

JAZZCNC
01-02-2018, 12:24 AM
The motor location is a no-brainer to me. Machine the gantry side to accept motor with a slot for adjustment and lengthen ball screw so goes thru side then put the belt on outside of gantry out the way from chips etc and put a cover over. Simple and neat.

Pulley size is little small but nothing to do with teeth but because you won't have enough Boss left after machining for grub screws. This will then mean putting grub screws thru the teeth which isn't ideal.
I find 20 teeth gives good balance leaving enough boss for M5 grub screws. Certainly no less than 18T.

diycnc
01-02-2018, 02:18 PM
That's a brilliant idea! Can't believe I missed that.
Any suggestions how I could cut a pocket in the aluminium end plate? I currently only have hand tools, a pillar drill, small lathe, trim router, circular and jig saw, no cnc or mill.
I guess I could just cut out a big slot in the aluminium end plate, big enough to fit the motor through. Bolt the motor to a thinner aluminium or steel plate, which is then bolted onto the end plate. No need to cut any pockets.

Or I could just pay someone to cut them to me, but where's the fun it that!

I didn't know the boss dimensions changed when pulley size changed. Will take a closer look at this later today.
I would prefer to use taper lock pulleys on the motors but I can't find any that will fit my 8mm motor shafts.

Clive S
01-02-2018, 03:02 PM
Any suggestions how I could cut a pocket in the aluminium end plate? I currently only have hand tools, a pillar drill, small lathe, trim router, circular and jig saw, no cnc or mill.
Have a look through Joes vids his machine is completely build with a few tools and a hand held router

https://www.youtube.com/watch?v=22cCYY5pVMI&list=PL1FIADAKba_vww3ZjQf-dWEjqhAPJw0Bz

JAZZCNC
01-02-2018, 04:45 PM
I would prefer to use taper lock pulleys on the motors but I can't find any that will fit my 8mm motor shafts.

You won't find taper lock that go that small on teeth size. 32-34 is about smallest you'll find. Plus they are heavy so have lots of inertia which can live without on small motor.

Like Clive says get the router out if want some pockets. It's easy done just go at it steady.

diycnc
14-02-2018, 08:59 PM
On the overall design it will work fine, but do think through if the underslung ballscrews will be easy to set up and align. Imagine that the base frame cross members (which the ballscrew blocks mount to) is not perfect, and end up on a different plane to the rails. It will tend to bind the ballscrew at some point and you will have to shim something in the system.
If you go the more traditional route with the ballscrews mounted down the side, driving the side members of the gantry directly (no underslung part), I think all the connections can be made with the appropriate 'slip plane' to get it aligned. This will quicker, cheaper and simpler to build and would be my preference.

Up to you but just make sure you can visualise the adjustment process for any scenario if it is not perfectly built.

If you are going underslung just to stiffen the gantry I'd put the efforts in on the gantry itself, e.g. plating across the back etc. (Not saying it needs further stiffening mind).

Thanks for the advice. The way i imagine it is the screws first need to be on the same plane as the gantry travel. With the current design this can be achieved just with shims. Then the screws need aligning to the axis. Hopefully there will be enough play in the holes in the BK supports to allow enough adjustment. If not i can simply drill over sized holes in the underside of the frame, and use either nuts inside the tube, or if i cant get a spanner in there make a small plate with 4 threaded hole. This will give me plenty of adjustment to compensate for the inevitable poorly assembled frame!

diycnc
14-02-2018, 09:35 PM
So iv moved the motor as JAZZCNC suggested. Im pretty happy with the whole gantry design now so iv started figuring out where im gona put all the nuts and bolt. The whole thing is held together with about a million M5 screw! Takes bloody ages to figure out where they need to go. But id rather do it now in CAD where its easy to move things around, rather than during the build where mistakes could be costly.

Iv also been thinking about Z axis alignment, both spindle to the axis, and the axis to the machine bed. For spindle to axis measurement I plan to use the same method I used to align my lathe head stock. Its called rollies dads method (http://manuals.chudov.com/Rollies-Dads-Method-of-Lathe-Alignment.pdf). Probably massive overkill for this aplication, but its easy to do so why not. Rotation adjustments about the X axis will be made using shims, and Y axis by just roating the spindle by hand and some oversizes holes in the spindle mount.

For measurement of alignment of the Z axis to the bed i will use a this (http://homews.co.uk/page249.html) DTI method.

Adjustment will be achieved with shims between the stationary Z axis plate and the X axis plate, plus two M3 leveling screws though small blocks shown in the attached image. The two screws are just over 100mm apart, and m3 screws are 0.5mm pitch. This gives me 0.3 degree adjustment per turn. I can lock the leveling screw when the axis is allied, and hopefully I will be able to remove and replace the Z axis if needed without the need to realign anything.

diycnc
07-03-2018, 07:49 PM
So i'm finally ready to order steel and aluminium for the frame.
Can anyone recommend suppliers in the Manchester area.
Im currently looking at ordering only from Aluminium Warehouse and Austen Knapman.

Davek0974
07-03-2018, 07:58 PM
I use Aluminium warehouse, i have heard various stories about them but i still cant find anyone better/cheaper

JAZZCNC
07-03-2018, 10:51 PM
I use Aluminium warehouse, i have heard various stories about them but i still cant find anyone better/cheaper

ASC metals in lincoln usually knock spots off AW
http://www.ascmetals.com/

cropwell
07-03-2018, 11:48 PM
ASC metals in lincoln usually knock spots off AW
http://www.ascmetals.com/

I have used Forward Metals for small purchases of Ali, and they seem good. https://www.forwardmetals.co.uk

diycnc
05-12-2018, 09:04 PM
So after 6 months my CAD models are starting to turn into a CNC!... Slowly....

The design has changed a bit, but the concept is mostly the same.
25221
25222

I went with aluminium flat bar rather then cast plate in the end. Very quickly learned that was a bad idea! Flat bar is very far from flat!
Managed to get everything moving freely so far despite the not flat bar using plenty of shims to level things up. First project when this thing is up an running will be new cast aluminium plates.

So far I have the gantry carriage and ball screw all made and assembled. Made my own ball screw end supports from 50x50 aluminium bar with angular contact bearings, and bored out and threaded the HTD pulley to replace the lock screw. Everything moves freely and feels rock solid, so very happy with the result.

Sick of drilling and tapping holes now.

diycnc
19-12-2018, 08:47 AM
As I slowly edge closer to the electronics step, I was wondering why we have to over spec a switch mode power supply.

The stepper drivers we use limit the current to the motors, so why do we need to make sure we choose a power supply that can supply say +20% more current? Surely a driver set to say 2A will only draw 2A from the PSU?

I'm sure there is a very logic explanation.

driftspin
19-12-2018, 04:22 PM
As I slowly edge closer to the electronics step, I was wondering why we have to over spec a switch mode power supply.

The stepper drivers we use limit the current to the motors, so why do we need to make sure we choose a power supply that can supply say +20% more current? Surely a driver set to say 2A will only draw 2A from the PSU?

I'm sure there is a very logic explanation.Hi diycnc,

Why not build one yourself.

It is only 5 orso electrical parts.

Grtz Bert.

Verstuurd vanaf mijn SM-A320FL met Tapatalk

Neale
19-12-2018, 11:12 PM
As I slowly edge closer to the electronics step, I was wondering why we have to over spec a switch mode power supply.

The stepper drivers we use limit the current to the motors, so why do we need to make sure we choose a power supply that can supply say +20% more current? Surely a driver set to say 2A will only draw 2A from the PSU?

I'm sure there is a very logic explanation.

Well, there's a very technical explanation! Actually, the stepper driver does not quite limit current to the nominal value. In fact, it's often unclear what that nominal value means anyway - peak current? Average current? So the value that you set the stepper driver to will be somewhere near the maximum current drawn from the PSU but not necessarily exactly the value you expect. The other problem is that the stepper driver doesn't actually supply a steady current over the whole pulse, but chops it alternately on/off so that the average is around the desired value. So peak current draw might be higher than expected during the pulses, even if the average is around what you would expect. The SMPS must be able to cope with these short-duration pulses without going into "overload" when it might shut down altogether for a brief period, until the "overload" has gone away. This can be pretty catastrophic for the machine overall and losing steps might be the least of your problems. Hence the need to over-spec a SMPS just to make sure that it never goes into current-limiting or overload mode. I would be worrying if the SMPS is only capable of supplying 20% over nominal current - doesn't seem like much headroom to me. That's why the usual advice (even from people like Leadshine who should understand these things) is to use a "linear" power supply which is very tolerant of pulse current overloads.

This is a bit of an over-simplification, but the fact is that the current draw is very "peaky" and not steady, you are adding together the loads of multiple drivers without any idea of whether their pulse loads will occur simultaneously or not, and you have a power supply that is not capable of handling overloads gracefully. A linear PSU will be heavier, probably larger, more expensive - but more reliable. And they're easy to build - there are several "how-to" threads on the forum. If you go SMPS, over-spec the rating to make sure!

Voicecoil
20-12-2018, 01:36 AM
The other option might be to add a decent size capacitor (maybe 4700...15,000uF) on the output of the SMPS to deliver short term current pulses without tripping the protection. I say "might" because some wimpy SMPS's are just so wimpy that they find it difficult to start up into a large capacitive load, so you'd be b******d from the start. However some do have a "soft start" provision that avoids this and such an approach has got me out of a hole once or twice before.

diycnc
27-12-2018, 12:32 PM
Thanks for the explanation.

If you were going to use a SMPS, how much extra over the nominal current would be recommended?

m_c
27-12-2018, 08:05 PM
In terms of current draw, there is no real reason to overspec a SMPS. Once it's overcome the initial start-up surge and charged up it's various internal capacitors, and the stepper driver capacitors, the average current draw is minimal at idle/slow speeds. At idle, with say a 5V 2A stepper motor, it should be seeing a combined total of 2A at 5V through either or both of it's windings, so 10W. Now say you've got a 2A 50V SMPS, that's a 100W source. The stepper driver (which is essentially a fancy SMPS), although switching currents might peak at 2A, the various capacitors will smooth that somewhat before it reaches the SMPS circuitry.
Even at higher speed/load where you happen to be in the optimum point to be applying 50V to get the full 2A through the motors, due to the switching nature of the stepper drivers you're not likely to draw the full 100W capacity. Plus once you get beyond the optimum voltage/current point, back emf will limit the amount of current the available voltage can push through the stepper motor windings, and power consumption will actually reduce. This is why it's recommend for a typical 3 axis machine, you only need a supply capable of delivering 2/3 the maximum combined current.

The real big problem with SMPS's is there inability to handle the regenerated energy from stepper motors/drivers as axes are decelerated. During deceleration all that kinetic energy gets dumped back into the power supply, which can cause it to go overvoltage. SMPS rarely have the ability to handle that, with the better ones simply shutting down (often until they get power cycled), and the cheaper ones releasing their magic smoke. Bigger SMPS will normally have bigger capacitors so they'll absorb a bit more energy before going over voltage.
You can get around this by installing a reverse energy dump circuit which will dump any regenerated energy to a big resistor rather than into the supply, but for the cost, you should be able to build a suitable linear supply that will avoid all these problems, be far simpler, and have less bits to potentially go wrong.

diycnc
31-10-2019, 01:54 PM
So after almost a year, the mechanical part of this build is still progressing .... very slowly!

For the electronics, I have just got 3 DM860T drivers from stepper online to power my 3.1Nm Nema 23's.
I would quite like to wire up the motors just to check everything is working correctly, so starting to think more about BOB and PSU.
The drivers can take either AC of DC input.
I like the idea of AC as it make the power supply build a little simpler, but is there any downside to using an AC input?
Any advice for BOB? I plan on using linuxCNC.

Thanks,

AndyUK
31-10-2019, 03:59 PM
I would quite like to wire up the motors just to check everything is working correctly, so starting to think more about BOB and PSU.

If you have a spare arduino lying around and a PSU that can run 1 motor temporarily, you can test them reasonably easily just to check everything is okay.

andy1989
31-10-2019, 05:40 PM
-

diycnc
31-10-2019, 10:23 PM
Dont have a PSU to hand, so looking to put together a simple 70vac transformer, but im struggling to find a suitable toroidal transformer.
Only 230v to 70v transformers I have found so far are max 500va, which im not sure is sufficient for 3-4 motors. The current design is 3, but want to leave room for a 4th if i choose to upgrade later
https://www.rapidonline.com/vigortronix-vtx-146-500-135-500va-toroidal-transformer-230v-primary-2-x-35v-88-0007

Clive S
31-10-2019, 11:43 PM
Dont have a PSU to hand, so looking to put together a simple 70vac transformer, but im struggling to find a suitable toroidal transformer.
Only 230v to 70v transformers I have found so far are max 500va, which im not sure is sufficient for 3-4 motors. The current design is 3, but want to leave room for a 4th if i choose to upgrade later
https://www.rapidonline.com/vigortronix-vtx-146-500-135-500va-toroidal-transformer-230v-primary-2-x-35v-88-0007

This company will make any voltage you want for you. https://airlinktransformers.com/category/chassis-mounting-toroidal-transformers-standard-range

I use a 500V a toroidal with 4 nema 23 on 2 different machines with out problems. The next size up generally is 625Va

aprex
01-11-2019, 09:13 AM
Mine went from TME. Quick sending and good prices.

https://www.tme.eu/fr/katalog/transformateurs-toroidaux_100028/?page=1

Best regards

diycnc
01-11-2019, 06:24 PM
I think i need to check my PSU calcs. Can someone point me towards some example PSU design calcs?
Also, any idea if there is any benefit of AC vs DC?

Kitwn
02-11-2019, 02:20 AM
This is quite a good introduction...
http://www.skillbank.co.uk/psu/

The stepper driver must be rectifying the AC into DC anyway, though with little or no smoothing. My guess is that making drivers that can be fed with AC is done merely to reduce the cost of the power supply. Whether a smoothed DC supply noticeably reduces motor vibration compared to AC will need some research.

kit

JAZZCNC
02-11-2019, 02:30 PM
I think i need to check my PSU calcs. Can someone point me towards some example PSU design calcs?
Also, any idea if there is any benefit of AC vs DC?

There is absolutely no difference. I've built loads machines using both and see no performance or reliability differences between AC or DC.
The AC is simpler for obvious reasons so my suggestion is go with AC.

Also, 525Va transformer will do what you need. 625Va will give you a bit more overhead, which you won't need, but does increase inrush and that could give you issues with MCB trips. However easily solved with D rated MCB.

cropwell
02-11-2019, 03:23 PM
dump any regenerated energy to a big resistor

Resistor ?

diycnc
02-11-2019, 05:59 PM
Thanks JAZZCNC. Will go with AC.

Only 70v toroidal transformer I can find is 500va, which I think should be plenty.
https://www.rapidonline.com/vigortronix-vtx-146-500-135-500va-toroidal-transformer-230v-primary-2-x-35v-88-0007

What size MCB would you recommend?

Clive S
02-11-2019, 07:25 PM
Thanks JAZZCNC. Will go with AC.

Only 70v toroidal transformer I can find is 500va, which I think should be plenty.
https://www.rapidonline.com/vigortronix-vtx-146-500-135-500va-toroidal-transformer-230v-primary-2-x-35v-88-0007

What size MCB would you recommend?

I pointed you to one in post #47

routercnc
02-11-2019, 08:26 PM
I went with a 10A Type D MCB in the end after trying a 6A Type D MCB that kept tripping on start up.

Note that my transformer was 750VA, 2x24v in series, (I'm running 5 steppers, with 2 steppers on X and Z) so you could try the 6A one first as they are not too expensive.

diycnc
05-11-2019, 08:30 PM
Thanks for the MCB advice. Will try 6A type D to start with.
After a little more reading, going to go for a 500va 230v primary, 2x 30v secondary. This should give me nominal 60vac when wired in series, and max voltage of 69vac when considering the mains can vary +10%, and transformer output by +6%.
A 2 x35 would give max of 81vac which is above the driver max of 80vac.

What's the recommended connectors for the high voltage wires from the PSU to the drivers?

diycnc
05-11-2019, 09:52 PM
Just been watching some of Joe Harris videos, and have had discovered the world of DIN rail connectors!
I finally understand what the rows and rows of plastic blocks are in everyone's control boxes now.

JAZZCNC
05-11-2019, 10:35 PM
Thanks for the MCB advice. Will try 6A type D to start with.

Nearly always needs a 10A



What's the recommended connectors for the high voltage wires from the PSU to the drivers?

Directly wire from the transformer output to Fuses then to drives. Fewer connections the better. Every connection or connector is a potential problem area so fewer the better.

routercnc
05-11-2019, 11:47 PM
I guess you are referring to the fact that the psu will have a single positive cable and single negative cable output, and you need to connect these to 3 or more drivers.

Daisy chaining the drivers power input is not advised, so separate runs should be used.

Maybe Jazz has a neater solution but most people use a distribution block to connect each power output to multiple outputs, often mounted on the psu board.

JAZZCNC
06-11-2019, 05:54 PM
Maybe Jazz has a neater solution but most people use a distribution block to connect each power output to multiple outputs, often mounted on the psu board.

Every connection is a potential problem down the road so if you can limit connections you eliminate potential problems. So why have connection blocks on the PSU when you can remove those connections by wiring directly to fuses.? Put the fuses on or close to PSU.

Also, note that when using AC drives your only using a Transformer so often there's no PSU board involved because you don't need Caps or Bridge.

diycnc
06-11-2019, 09:20 PM
Just wondering is there a reason why we use a MCB before the PSU, but then a fuse before each driver?
Do they not both perform the same job? Why not use the same everywhere?

AndyUK
06-11-2019, 09:24 PM
One drive should only ever pull x amps. Multiple drives connected to the same PSU can draw more than x amps quite normally. That's the theory at least - although at this point I think we're trying to stop things going up in smoke rather than protecting the drives themselves.

diycnc
06-11-2019, 09:40 PM
Totally understand the need for protection before and after the PSU, just wondering why we don't use MCB on both sides, or fuses on both sides.
I still have a lot to learn about the electrical side of things, so this might be a silly question.

AndyUK
06-11-2019, 09:55 PM
Ah yes now your question makes more sense. I'm no expert so I'm sure someone will put us right, but the way I see it is the MCB is placed before the PSU because it's 3-4x (however many drivers you have) more likely to trip, so easy and inexpensive resetting is helpful. It's also very obvious when it's tripped rather than digging out fuses. There's also the chance of inrush to the torroidal tripping it, so again more likely. It's also a convenient way to isolate the PSU. As for the fuses on the drivers, they're cheaper than adding an MCB.

JAZZCNC
06-11-2019, 11:06 PM
The main reason is protection.
The MCB protects the transformer in case of a short circuit. You don't actually need an MCB type fuse, any fuse type of correct size will work but due to the nature of Transformer and inrush, etc MCB is just easier to reset when trips.

The fuses for the drives protect each drive in case of short circuit or excess current draw. The transformer can supply many more amps than each drive can handle so if, for instance, motor shorts out the drive will keep dumping current up to it's rated output or until it destroys its self. some drives have built-in current protection but it's not advised to rely just on this, hence why a fuse.
Fitting a fuse same size or just slightly higher than the drives rated load will offer it some protection. In fact, I often fit fuses at a lower rating than the drives max rated current if the motors are not rated at or close to drives Max current.

diycnc
08-11-2019, 06:05 PM
Drivers are rated to 7A, and motors just to 4.2A. Probably will be running them at over 3.14A ref I think.
Would a 4A fust be okay?

Currently looking at the industrial DIN rail fuses holders like this one, unless anyone can suggest anything better/cheaper.
https://www.rapidonline.com/mersen-cms-81-single-pole-din-rail-8x31-fuseholder-26-5786

Also looks like most people are using double pole MCB's on the live and neutral before the PSU. Is this essential? I thought only the live would need one?

JAZZCNC
09-11-2019, 09:15 PM
Drivers are rated to 7A, and motors just to 4.2A. Probably will be running them at over 3.14A ref I think.
Would a 4A fust be okay?

5A would work better. Gives some safety to drives but won't trip when motrs are being worked hard.


Currently looking at the industrial DIN rail fuses holders like this one, unless anyone can suggest anything better/cheaper.

These are what I use, cheap and easy to wire and change.

https://www.ebay.co.uk/itm/5X-FS101-10A-6-30mm-Fuse-Socket-With-Indicator-Light-DIN-RAIL-Mounted-Fuse/253512397370?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649



Also looks like most people are using double pole MCB's on the live and neutral before the PSU. Is this essential? I thought only the live would need one?

No don't need double pole.

I prefer these to Din rail connectors when creating Busbars. Lot cheaper as well.

https://www.ebay.co.uk/itm/Set-6Position-600V-15A-Dual-Row-Wire-Barrier-Block-Screw-Terminal-Strip-Panel-UK/183989489621?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

diycnc
10-11-2019, 12:13 PM
Thank for your help JAZZCNC.

When it comes to settings the driver current, the drivers have peak and REF values labeled on them. Which one should I be concerned with?
I found the same question in routercnc MK3 build thread, but couldn't find an answer.

JAZZCNC
10-11-2019, 06:01 PM
Thank for your help JAZZCNC.

When it comes to settings the driver current, the drivers have peak and REF values labeled on them. Which one should I be concerned with?
I found the same question in routercnc MK3 build thread, but couldn't find an answer.

Use Peak values.

diycnc
10-11-2019, 09:02 PM
Transformer, fuses, mcb, and terminal block on order. Wish me luck!

diycnc
12-11-2019, 07:09 PM
Whilst I wait for the psu parts to arrive, I was thinking about the driver fuses. With the current setup, if one fuse blows on say the z axis, the other axis will just continue regardless, potentially damaging the part or even the machine. Is there a software or hardware tool to stop this happening?
Would a 3 pole fuse holder work? Or is each fuse still independent of the others?

JAZZCNC
12-11-2019, 09:22 PM
What drives you using.?

AndyUK
12-11-2019, 09:23 PM
Each fuse is still independent.

You might be able to detect an unpowered driver with a properly configured fault output and a controller that is checking for this signal?

diycnc
12-11-2019, 10:09 PM
DM860T drivers from stepper online.
https://www.omc-stepperonline.com/download/DM860T.pdf

ericks
13-11-2019, 09:13 AM
Nice, looks like you making good progress:)

diycnc
13-11-2019, 08:02 PM
Just stumbled across this on YouTube and thought it was worth sharing. This guy cuts aluminium on a 3D printed MPCNC better than most videos iv seen from people with a "propper" diy cnc router! Mighty impressive!
Hope my machine can perform even half as well as this.
https://youtu.be/zefnrPRvc9Q

Kitwn
14-11-2019, 02:35 AM
Very impressive! That just goes to show how important it is to spend time learning how to use the tools you have to their maximum capability.

I'm certainly tempted to try out my router on aluminium. I hadn't really though it was up to any serious work it until I saw that.

JAZZCNC
14-11-2019, 07:58 PM
I'm certainly tempted to try out my router on aluminium. I hadn't really though it was up to any serious work it until I saw that.

It's the adaptive tool paths that allow him to get away with it as they take very lite cuts but at full depth. If you notice when profiling using typical profile toolpath he was using a very small depth of cut(DOC) and feed rate because the machine wouldn't be able to handle taking correct DOC to suit the tool diameter. However Still impressive to say 3D printed.!

diycnc
14-11-2019, 10:23 PM
Transformer arived today. Very please to see it came with a mount bracket too. Couldn't wait to test it so wired it up, only to spend half hour trying to figure out why there was no output voltage... turns out my multimeter had died! Try again tomorrow with a new one.

Thinking of building a small wooded cabinet for all the electronics, maybe with a plexiglass window if I can keep my wiring looking nice and tidy. Are wooded cabinets considered safe?

AndyUK
14-11-2019, 11:52 PM
Thinking of building a small wooded cabinet for all the electronics, maybe with a plexiglass window if I can keep my wiring looking nice and tidy. Are wooded cabinets considered safe?

I don't think theres anything wrong with a wooden cabinet - plenty of people do it. I think metal is probably better at keeping moisture out, (electrical) noise in, and means anything that manages to go bang is contained by a strong earth-connected box, but its probably overkill for many of these machines. From a financial perspective, my metal cab certainly wasn't cheap, and I'm pretty sure its not going to add any functionality to my build. I have a sneaking suspicion mine is mainly for aesthetics....

Another option is to grab yourself a server rack with a glass front (reasonably inexpensive on ebay - especially the kits or 2nd hand), or use a large PC case.

cropwell
15-11-2019, 01:39 AM
Another option is to grab yourself a server rack with a glass front (reasonably inexpensive on ebay - especially the kits or 2nd hand), or use a large PC case.

Server cabinets are cheap enough, the larger ones can't be given away sometimes. I have one dismantled in storage, deep enough to put a tool cabinet in the front and the control electronics in the back.

I built my control box in an old computer case, with the computer in another :-
26740

It got a bit messy recently when I splashed it with a solution of black ABS, nothing like the mess when a spray can exploded on my garage:upset:

Cheers,

Rob-T

Kitwn
15-11-2019, 02:04 AM
With the current setup, if one fuse blows on say the z axis, the other axis will just continue regardless, potentially damaging the part or even the machine. Is there a software or hardware tool to stop this happening?

I've been wondering about how to retro-fit stall detection to deal with every 2-motors-on-one-axis-machine owners worst nightmare using DIY rotary encoders. So far I have a bag of 15 optical detectors (under $10AUD including delivery from RS), a nice Postcript file that Google found for me that will draw the encoder pattern and a piece of 0.25mm stainless shim. The plan is to use the 'toner transfer' method beloved of DIY circuit board builders to acid etch my own discs to fit onto my ballscrews and use an Arduino to detect when one axis moves and the other doesn't. You could always use this to detect lack of movement on any axis by comparing the encoder output with the step pulse input.

This is going to be one of those 'something to do while the varnish dries on my main activity' projects so don't hold your breath, but I will be reporting my success (if any) on the forum.

Kit

Kitwn
15-11-2019, 02:10 AM
It's the adaptive tool paths that allow him to get away with it as they take very lite cuts but at full depth.
I noticed that. I think it's something my beloved CamBam software cannot do and might just be the last straw that kicks my a**e into gear and makes me put the effort into learning to use Fusion 360. I'm sure my machine is rigid enough, or it will be when I finally find a suppllier for the right sized Ally plates to convert my Z-axis from it's current plywood prototype assembly.

diycnc
15-11-2019, 08:55 PM
Got a new multimeter and I'm getting 33v from each secondary. Glad I didn't get a 35v transformer or I would be very close to the 80v max.
26744
To wire this thing in series, am I correct in thinking I connect the yellow and black?
26743

Also the drivers dont have positive and negative marked on the input, both are just labelled AC. I'm guessing that because it AC it doesn't matter which way around it connected?

AndyUK
15-11-2019, 09:06 PM
To wire this thing in series, am I correct in thinking I connect the yellow and black?
26743

Yep.

diycnc
16-11-2019, 02:36 PM
The drivers dont have positive and negative marked on the input, both are just labelled AC. I'm guessing thats because its AC it doesn't matter which way around its connected?
Does this also apply to the location of the fuse?

JAZZCNC
17-11-2019, 01:21 PM
The drivers dont have positive and negative marked on the input, both are just labelled AC. I'm guessing thats because its AC it doesn't matter which way around its connected?
Does this also apply to the location of the fuse?

Yep often they are labeled R S but can put anyway around. I always connect live to R and Nuetral to S

diycnc
24-11-2019, 08:25 PM
Finally got around to putting some test electronics together, just need to connect the motor and flash grbl onto the arduino. Would be awesome if someone could take a look at my wiring befor I do anything too stupid. I'm a bit unsure about the earth at the moment. The negative enable, step, and pulse are all connected together and the ground pin on the arduino. And mains earth isn't connected to anything at the moment.
Once I have one tested and working, will test all three together.
26770

diycnc
24-11-2019, 09:11 PM
Just spotting I have the fuse on the zero volt side of the psu!

Voicecoil
24-11-2019, 09:25 PM
If it were me I'd run the enable, pulse and dir. signals as twisted pairs - common the -ve ends up at the Arduino. This approach gives much cleaner waveforms and better resistance to interference.

Voicecoil
24-11-2019, 09:27 PM
Just spotting I have the fuse on the zero volt side of the psu!

Maybe because you've used brown for 0V and blue for +68V & hence thought the fuse was in the "live" side?? I tend to try to keep blue and brown for mains N and L and use other pairs of colours e.g. red/black or orange/violet for other power rails, helps to know what's what if the wiring gets "busy". As it's AC and floating it really doesn't matter anyway!

Doddy
24-11-2019, 09:51 PM
<deleted - thought I was replying to a recent post about wooden enclosures... >

diycnc
24-11-2019, 10:46 PM
That's exactly what I was planning on doing, but at some point I managed to wire brown to + and blue to 0! Not really sure how.
When it comes to the finally wiring I'm definaltly planning on using other colours to differentiate. Is there a standard when it comes to control panel wiring?

diycnc
02-12-2019, 09:50 PM
All three drivers tested and working perfectly. Thanks for everyone's help with this!

Iv got a feeling it might be a while before I make any more progress on this. Some genius (me :culpability:) decided to start decorating three rooms at the same time, so that has to take priority now or the missis won't be too happy if it ain't finished before Christmas

Kitwn
03-12-2019, 01:11 AM
Think on the bright side: You may be able to lose the cost of a tin of Hammerite in the housekeeping paint budget:glee:

diycnc
04-12-2019, 10:29 PM
Found a little bit of time to wire up the motor on X axis (side to side one on the gantry) to see something moving.
I very quickly seamed to find the limit of these motors+drivers+screws at between 4000 and 5000mm/min (800-1000RPM at the motor). I was hoping for a little more than this. Acceleration is down at 20mm/sec2.
Do these sound like reasonable numbers when compared to other similar machines? Im a little more used to deal with lightweight 3D printers which are happy fly around at 150mm/sec+ all day. Guess a heavy CNC is a totally different animal though.

Spec is; 3.1Nm Nema 23 wired in parallel, 3.08A peak driver current, 68Vac, 1600 steps per rev (1/8th micro stepping), 1:1 belt drive, 1605 screw.

I know 1610 would be much more appropriate, but 1605 was sooooo much cheaper!
Motors are rated to 4.2A, so I could push the peak current upto 3.77A. Would heat dissipation become an issue running at 90% the rated current?
A quick google seams to suggest around 1000RPM is the limit before torque starts to drop of significantly, so im starting to think this is the genuine limit of the motors.

Its bloody loud too! Was expecting digital divers to be nice and quiet! I know increasing microstepping would help. What microstep settings do other people use?

Neale
04-12-2019, 11:58 PM
My machine is a very similar size, and also with 1605 driven 1-1 from a NEMA23/3Nm. I get around 5000mm/min as well, although I haven't really tried winding it up much more as that is about as much as the long axis will take anyway. That was my design goal in any case as, as you say, that is about the corner speed of those motors when they start to lose torque. Can't remember the acceleration I'm using - I'll try to check next time I fire it up.

Brian's law of motor current tuning is - "keep winding it up until it starts to get about as hot as you can comfortably hold when it's been running for a while." I'm not sure how accurately those driver current limit numbers are given that they are averaging a pulse output, and the motor current ratings are RMS? Peak? Who knows - the only issue is whether or not they get too hot in practice! Stepper motors are designed to run hot and mine have run using that adjustment technique for a few years now with no apparent ill effect. As for noise - that one's very difficult to judge!

Kitwn
05-12-2019, 01:04 AM
I know 1610 would be much more appropriate, but 1605 was sooooo much cheaper!

I'd be interested to know where you found cheaper 1605 ballscrews. A quick scan of Fred's BST Automation's site has 1000mm long ballscrew sets of 5 and 10mm pitch at $148 AUD and $135 respectively, including delivery to Australia. Interestingly he also has 1616 screws for those wanting an ultra-fast machine.

diycnc
05-12-2019, 07:22 AM
Ebay.
850mm 1605 screws are just £30, and are delivered from the UK so no need to worry about getting stung with import tax.
To my in experienced eye they seem ok. Were packaged well, and dont appear to be to bent.

AndyUK
05-12-2019, 09:05 AM
That might be why things are sounding loud. Are they lubricated well?

diycnc
05-12-2019, 09:28 AM
That might be why things are sounding loud. Are they lubricated well?
Not at all! Just the sticky grease they come with at he moment. Pretty sure the noise is just the motor vibration on the metal frame, not the screw. Might try taking the belt off tonight to test without any load.

JAZZCNC
05-12-2019, 10:25 PM
Not at all! Just the sticky grease they come with at he moment. Pretty sure the noise is just the motor vibration on the metal frame, not the screw. Might try taking the belt off tonight to test without any load.

This vibration could be causing resonance which will affect the performance.

However, at 5Mtr/min your close to reaching the limit and other factors will come into play so resonance could be clipping your wings a little.
Also depending on the controller then you might be better off dropping the micro-stepping. When reaching limits the controller and quality of pulses starts to play its part.

With 68V and digital drives on a machine with decent rails, aligned and set up correctly with average gantry weight of 30-50kg then I'd expect to top out around 7mtr/min with 5mm pitch. I would tune to run at 5mtr/min.

diycnc
06-12-2019, 01:02 PM
If it were me I'd run the enable, pulse and dir. signals as twisted pairs - common the -ve ends up at the Arduino. This approach gives much cleaner waveforms and better resistance to interference.

Would something like a CAT 6 cable be a good idea?

Kitwn
07-12-2019, 06:45 AM
Would something like a CAT 6 cable be a good idea?

CAT6, CAT5 whatever you have lying about. Try one length of cable per driver with all the screens grounded at the Arduino end as well. If you can keep the cable runs for driver input signals and high current motor outputs separate that helps too.

diycnc
09-12-2019, 10:02 PM
Had an experiment with micro-stepping today. Increasing micro-stepping reduced noise, and increased the speed before it started skipping steps.
Im using GRBL for testing, which has a limit of 30kHz, so 1/8 is about as high as I can go and still achieve a sensible speed. Any higher and the Arduino crashes.

What micro-stepping settings do others tend to use when running Mach 3 or similar from a parallel port?
The drivers go up to a whopping 1/256!

Doddy
09-12-2019, 10:13 PM
A lot depends on the stepper drivers - many max out around 100kHz-200kHz.

My recent tinkering are with a lathe conversion and I'm settled at 8x, though I'm re-using modified drivers that will take 250kHz

diycnc
09-12-2019, 10:38 PM
A lot depends on the stepper drivers - many max out around 100kHz-200kHz.

These drives are rated to 200khz. Assuming I'm running at max for 5m/min, I could get to 32x with a very healthy margin of safety.

Neale
11-12-2019, 09:46 AM
I'm running Nema 23 / 3Nm steppers driving 2005 ballscrews up to 1000 RPM via 1-1 belt drive giving 5m/min rapids. I use x8 microsteps and it all works fine. General opinion is that somewhere around x8 is the sweet spot between smoother, quieter, motion and losing torque (which happens as you wind up the microsteps). I wouldn't exactly say that my machine purrs but it isn't a bag of nails either!

JAZZCNC
11-12-2019, 07:11 PM
These drives are rated to 200khz. Assuming I'm running at max for 5m/min, I could get to 32x with a very healthy margin of safety.

Pointless because your motors cannot resolve that low and it just stresses the pulse engine, Also if I'm reading correctly and you are using an Arduino then I'm not sure it can output pulses at this rating.? . . . But i don't know much about them so could be wrong.

The main reason to up the MS is to give smoother running motor but there is, as always a cost, much past 16x is waste and just stresses out the controller and wastes torque.

diycnc
17-12-2019, 08:41 PM
The max frequency for a GRBL on an arduino is 30kHz, which effectively limits me to 1/8 anyway.

I just tried running a motor off the machine, with zero load, and it's 50:50 if it will run at 900rpm, which is only equivalent to 4.5m/min. I can feel the motor start to vibrate as it accelerates up to speed.

Going to try tidying up the wiring to see if that helps. Got twisted pair for the control side. For the motor side, this might be a silly question, should I run all 8 wires all the way to the driver and connect the pairs there, or join the pairs close to the motor and just run 4 wires from there. For the purpose of testing I'm not using shielded cables at the moment, would that impact motor performance at all?

Doddy
18-12-2019, 01:00 AM
Going to try tidying up the wiring to see if that helps. Got twisted pair for the control side. For the motor side, this might be a silly question, should I run all 8 wires all the way to the driver and connect the pairs there, or join the pairs close to the motor and just run 4 wires from there. For the purpose of testing I'm not using shielded cables at the moment, would that impact motor performance at all?

I'm assuming you mean you have 8-wire steppers? In which case it depends on how you're wiring them. If in series then definitely wire the phases together at the motor - you'll reduce your losses due to the resistance of the wiring that way. If in parallel then its less obvious to me (5:30am in the morning for me) - paralleling at the motor and only taking half of the cables back to the driver suggests greater losses in the motor leads. Ideally short the motor pairs at the motor without cutting the cables and take the pairs back to the driver and terminate there as well (i.e. run the cables in parallel back to the driver). Or just wire in parallel at the motor and use wire with a large CSA to export the motor drive back to the driver. It will make some marginal difference.

Shielding will not affect motor performance, thought it might help to avoid any induced noise into signal cables.

diycnc
23-01-2020, 09:26 PM
Could someone help shed some light on the correct orientation of AC bearings?
I thought I had a handle on it, but iv just come to install some pulleys and iv spotted iv got some face to face, and some back to back, so now I think i must have misunderstood something.

My current understanding it face to face is the preferred orientation and to preload them to remove any backlash I shim the outer race.
Face to face is with the larger inner race face pointing towards each other?

A second opinion on this would be great!

diycnc
23-01-2020, 09:36 PM
Scratch that.

If I'm shimming the outer race, I need them back to back.... with the larger inner race face pointing away from each other...?

27145

Lee Roberts
24-01-2020, 11:53 PM
Yea, for this application back to back is what you want.

diycnc
04-04-2020, 09:37 AM
I'm struggling to decide between to different belt arrangements for my y axis (the one that moves the gantry). I will have to ball screws driven by one motor, with either one belt connecting all three pulleys. Or two separate belts, one connecting the screws, and one connecting the motor to a single screw.
I have space for either setup, and enough shaft on the end of the ball screws for the two pulleys needed for the dual belt arrangement.
I can see pros and cons for each, but struggling to make a decision.
Any suggestion?

JAZZCNC
04-04-2020, 03:47 PM
Use the one that allows the shortest belt arrangement. They will all work equally well as each other but shorter belts are easier to find and implement.

This is my preferred setup.

27732

diycnc
08-04-2020, 09:12 PM
Thanks Jazzcnc.

Can anyone recommend a method of reinforcing my bolted connections on my steel frame. Currently have 4 m5 bolts at each connection between the steel box section, and after moving the machine around a few times during construction I'm certain the joints have moved.
I'd rather avoid buying a welder, so that leaves either more bolts, or glue.
There isn't much room for more bolts, so I think glue would be better, but I'm not sure what type would be best. Would a slow setting epoxy be a good idea?

Voicecoil
08-04-2020, 10:00 PM
What's the orientation of the sections you're joining? Do you have plates/brackets? (a pic or drawing might help) Either way, 4 x M5's sounds a bit light duty to me, do you have room to go up in diameter? Properly done with the correct surface preparation and curing, epoxy can give a very strong bond - seems to work OK in aeroplanes :-)

diycnc
08-04-2020, 10:11 PM
I'm not in the workshop at the moment, but take a look at the pic in post 36.
Agree 4 x m5 isn't enough, and I dont think there is room to go up in diameter. The existing bolt holes are a little too close to the side walls to go up in size.
Will try some thin slow setting epoxy on a test piece befor I apply to the frame

Voicecoil
08-04-2020, 10:41 PM
I'm not in the workshop at the moment, but take a look at the pic in post 36.
Agree 4 x m5 isn't enough, and I dont think there is room to go up in diameter. The existing bolt holes are a little too close to the side walls to go up in size.
Will try some thin slow setting epoxy on a test piece before I apply to the frame

From the pic. and the few screws that are visible it looks like there might be a bit of room to go larger - but then again it's not a close-up, so do check it. If you're using slow setting epoxy do check the manufacturers curing instructions. Araldite Precision for instance cures with better strength at a slightly elevated temperature - as well a a lot quicker. And remember that once it sets you can't adjust stuff any more - so make sure everything gets properly lined up!

JAZZCNC
09-04-2020, 12:08 AM
You are always going to have this problem even with larger bolts unless the holes are reamed and a very close fit to the bolts. ie Sholder bolts. It will be to a lesser degree because you'll have more torque with larger bolts but still it could move. Epoxy will help but only upto a point, it certainly won't hurt until you come to take it apart again or decide to weld it up, then it will be a bitch to get off.!!

Don't you know anyone with a welder.? it will take 20Mins max to weld those few pieces together and it will be so much stronger. Forever.!!

diycnc
14-04-2020, 09:10 PM
Unfortunately not, atleast not near me. Going to test the epoxy method on some scrap before trying on the frame.

On a separate note, my ballscrew arive from china today. How would you prepare the screws before assembly? Is it worth pulling them apart, cleaning, and re greasing?

diycnc
11-05-2020, 09:17 AM
Turns out there was a mig welder sitting no less than 5m away from my machine in my neighbours shed!
Just waiting on a new mask and gloves before I can start welding.

Whilst I wait, im thinking about my limt/home switch setup. I currently have 3 NPN proximity sensors.
For the X and Y I will use 1 sensor mounted on the moving parts as both the limit and home switch.

For Z do i need both limit and home?

Also thinking about cable chain sizes. Will the 37x18mm stuff be big enough?

Clive S
11-05-2020, 09:26 AM
For Z do i need both limit and home?

Generally you don't use a bottom limit switch but you can use soft limits. on all axis.

Kitwn
11-05-2020, 10:37 AM
Generally you don't use a bottom limit switch but you can use soft limits. on all axis.

I've gone with common sensors for limits and homing plus soft limits. Sooooo easy in LinuxCNC. I have a low limit switch on my Z axis, but that's because on my design there's a crash risk with the gantry ends if it gets too low. There is a soft limit as well so it's really belt and braces.

In practice you should never need limit switches to prevent a crash as long as you have the soft limits set correctly and always home the machine before you do anything else after switching it on.

BUT. There may be a risk if you have a pendant for manual control of the machine which does not operate through the controlling software and therefore moves the machine without the software knowing. I think this is possible with some of the cheap Chinese break-out boards and is a train-wreck waiting to happen for the blissfully ignorant.

Boyan Silyavski
11-05-2020, 07:26 PM
Use the one that allows the shortest belt arrangement. They will all work equally well as each other but shorter belts are easier to find and implement.

This is my preferred setup.

27732

Dean what size is that profile that allows for easy mounting the 16xx ball screw?

JAZZCNC
11-05-2020, 08:41 PM
Dean what size is that profile that allows for easy mounting the 16xx ball screw?

This one.

https://www.motedis.co.uk/shop/Slot-profiles/Profile-45-B-Type-slot-10/Profile-45x90S-B-Type-slot-10::99999415.html

diycnc
26-05-2020, 09:03 PM
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diycnc
26-05-2020, 09:06 PM
After welding the frame, i did a quick check to see how straight and planer the two Y axis tubes are using a small surface plate with a DTI on a long arm. The surface plate was placed on a piece of plywood with three jack screws used to level the plate to three reference points on the tubes at the front left, rear left, and rear right.

Both tubes are now convex, and not planer. Measurements are below. Max deviation is 3mm!
I cant tell you how much is from the welding, and much was there before, but given that both are now convex my bet is its dominated by the welding.
28210

My original plan was to use shims under rails to bring them into alignment, but given the level of error I'm having second thoughts about that.
Is my only option epoxy?

JAZZCNC
26-05-2020, 10:08 PM
I'm not sure I'd trust your method of measuring as it won't be very accurate, just the length of the arm its self will deflect a fair bit. Unless you have a flat reference surface to measure from then you'll never truly know for sure how far your measurements are off.

To me you have 2 choices, Fit the rails as it is and see how it cuts and then shim out any issues. Or just bite the bullet and go with epoxy.

What size machine and what's the main usage.?

Neale
27-05-2020, 12:04 PM
The long rails on my machine are 1.8m, 100x50x3 box steel. One dipped in the middle by about 1.5mm, the other side a little bit more. Like you, don't know if that was welding or how it came, but in my case epoxy filled the hole:smile:

diycnc
27-05-2020, 09:15 PM
I appreciate the concerns about the measurement method.
Did some more measurements today to check the repeatability and accuracy of the method.
I deliberately rotated by plywood platform 180 degrees, and positioned the surface plate differently to really test the approach, and pretty surprised to the 1st and 2nd measurements vary by only a max of 0.1mm, that more than good enough for me.
I also used the same method to measure the polished edge of a piece of granite upstand, its the straightest thing I have to hand. I got less than 0.1mm deviation along its 500mm length. Again I'm happy with this.

All in all im very happy with the measurements, and im confident they are accurate enough for me.

28217

X and Y axis are 750mm.
Intended for wood and plastic, and hopefully aluminium. I know ill have to take it easy with aluminium, and I'm not expecting it hog out anything more than the smallest of cuts, or the highest of surface finish quality.

Going back to shims, my concern is will there be a noticeable lack of stiffness with the rails supported on just a handful of points?

driftspin
27-05-2020, 09:28 PM
HI diycnc

I can say epoxy is a bit of a mess, result is excelent.



But i do feel when you do 2 pours like 1 to get in to plane where thinnest film is 3mm thick or so and then do a final pour of another 3 or 4 will give you excellent results.

Please read up on best practices on this forum.

I had about 3 mm of warp over 1850mm
i did a single pour 4 to 7 mm

I did ignore the reports about epoxy shrink differences where layer thickness is different, which is solved by a second pour.
Maybe I will do a second pour some day...

I have no jobs that need such accuracy yet.

Grtz Bert




Verstuurd vanaf mijn SM-A505FN met Tapatalk

Boyan Silyavski
30-05-2020, 08:36 AM
Going back to shims, my concern is will there be a noticeable lack of stiffness with the rails supported on just a handful of points?

No problem if you use epoxy putty. I have never tried it but if you think of mounting the rails and then pouring epoxy, i believe it will be difficult to take the air out, though probably will work if you use West System epoxy as its quite thin.

To be 100% sure, best method is pouring the epoxy 5mm deep and 40mm wide, you could use only one channel to connect but make sure channels extend additional 20cm from the frame, there is a lot of info on forum. In my second build from signature i have explained in great detail how to do it properly and most economically for that matter. It cost me a couple of hundred $$ to understand the process in detail.


Another cheap option is use calibrated steel bar like 40x5mm or something, put epoxy putty on it and straighten it on place with straight edge. When dry, dill and mount. Its precise and cheap flat surface

At the end all depends on what shape you rails are in, in most of the cases they are perfect and easy to mount and shim, plus its a small machine, so easier




But epoxy makes that even easier, if you do the epoxy right . Most of the people i am 100% sure do the epoxy in the wrong way or have no way of measuring the result. As funny as it seems i went to that conclusion, measuring my results on a 3m rails and reading the build logs at that time





Similar machine like yours done with 100x100x3mm box , 40x100cm x/y , was well under 0.05mm frame bend when finished.

diycnc
02-07-2020, 09:14 PM
I have persevered with the shimming approach, and after a couple of evening measuring then shimming, both my Y and Z axis are planer to within 0.05mm.
Measurements are 100% repeatable too, and I have no reason to believe the method has any error at all. For example, after adding a 0.1mm shim to under a bolt, the measurement increases by pretty much exactly 0.1mm at that location.

Only slight tweak to the method is I now do the leveling of the measurements in excel, rather then physically moving the surface plate.

Iv tried to solve the amount of support under the rails issue by adding more bolt, lots more bolt! I have 50mm spacing between bolts now, rather than 150mm as they arrived.

I initially started aiming for a 0.25mm deviation over the Y-axis but blew past that on the first attempt, so just did 1 more iteration to see how good I could get it, and ended up at 0.05mm deviation from a flat plane. It was almost 3mm when I started.
At the moment I reckon the play in the cheep bearings, and maybe even the deflection of the frame under the gantry weight will be more than this, so its total overkill!

Shims are just small pieces of aluminum sheet, cans, and foil. Nothing special.

Im pretty chuffed with the results, it's one of the few things that's gone better than expected.
I painted the frame too, blue Hammerite spray paint, and the paint is so soft I can scratch it off with my fingernail! I clearly didn't do a very good job of cleaning it before painting.
2850328504

Any suggestions for how to measure straightness of these round rails?

Voicecoil
02-07-2020, 09:53 PM
[QUOTE=diycnc;118473]
I painted the frame too, blue Hammerite spray paint, and the paint is so soft I can scratch it off with my fingernail! I clearly didn't do a very good job of cleaning it before painting.
/QUOTE]

It may not necessarily be your fault - over the years I've had very mixed results with Hammerite - it's never dried particularly quickly, but some coats/colours have hardened OK after a week or so, other were still soft months later even with lots of care with surface prep. I don't know whether temperature is an issue in your case, but I've heard other people say it's best to keep it warm to accelerate the drying.

Well done on the shimming BTW :thumsup:

diycnc
16-07-2020, 07:52 PM
Paint does really seam to have got any better, and can still be scaped off with a finger nail. What a waste of 2 tins of hammerite!

Think im going to take the opertunity to repaint it now before I fully assembly the rest of the machine.
Any recomendations for paint?

Also just finishing off the design of some covers. Would some thin 0.7mm galvenised sheet steel be okay?
Little concerned about it rattling.
Plan is to print out some paper templates, cut with a jig saw or scroll saw when sandwhiched between some scrap MDF to stop it bending to much, then fold and pop rivit into shape.

Doddy
16-07-2020, 07:54 PM
Paint?, I'd use some of the hard enamel paints used on the machines of old - check out Paragon paints for something as reassuringly expensive as hammerite, though altogether better!

Doddy
16-07-2020, 07:58 PM
...and covers?, for what?, belts?, etc? 3D-printer can be a friend here for complex shapes.

0.7mm a bit thin - they'll quickly attract, erm, character :) Stainless might be prettier (though altogether harder to work well). Why not standard MS and paint in sympathy with the machine?

Clive S
16-07-2020, 07:58 PM
Think im going to take the opertunity to repaint it now before I fully assembly the rest of the machine.
Any recomendations for paint?


I find Hammerite paint very good even without a primer but you have to clean any oil off with a solvent first.

I have never used the spray tin version

m.i.k.e
16-07-2020, 10:56 PM
Paint?, I'd use some of the hard enamel paints used on the machines of old - check out Paragon paints for something as reassuringly expensive as hammerite, though altogether better!

Did you give it a good stir? I've never had any trouble with Hammerite.

diycnc
17-07-2020, 07:57 PM
Machinery enamle sounds like the right paint! Going with a tin and brush this time. Never have much luck with spray paints.

Cover on the Z axis will go over the whole thing, like this one on one of JazzCnc machines.
http://www.mycncuk.com/threads/8701-Jazzcnc-the-right-choice-in-a-custom-made-machine

Looks like aluminium from the picture.

diycnc
18-10-2020, 04:29 PM
Moving onto final assembly at last. Total gave up with paint in the end. After 4 tests with the second tin of enamel paint that all went soft even after drying for over a month, im going for the bear metal look! Its bone dry in the garage so dont see it been a problem.

Y (forward - backwards) axis rails have been leveled and are parallel, and both ball screws are have been aligned with the axis.

Struggling with aligning the pulleys that connect both ball screws to my single stepper. Any tips for getting them aligned would be appreciated.

Thanks28995