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View Full Version : BUILD LOG: 8x4 Build based on plans by Joescnc Hybrid R&P



GrahamWhite
19-03-2018, 10:58 AM
Hi all :)
My name is Graham and I'm new to all things cnc,got a 3d printer I built from a kit though so cnc on a very small scale then!
I'm starting a build based on plans I bought from Joescnc website- now I know not everyone will like or agree with the build materials and I definitely would like to spend a lot more on the build .... the wife says no!
So in the whole it will come from the plans but I'm hoping maybe there will be some input along the way as well.
As I said it's based on plans that once bought gives access to the builders forum and has approx. 250 machines built or being constructed all based off of the plans- giving dxf files/templates for cutting various parts etc.
The plans suggest a welded steel box frame base ,but as I don't weld I opted for a timber base.
Constructed out of structural 18mm ply ready to take the aluminium rails when they arrive.
so a few pictures of things so far then...
2392823929239302393123932
As you can see I doubled up on the ply thickness and the box section rails really improved the stability and strength.
23933
The rails fit together like mortice and tenon joints, the long sides are glued to the legs.
23934
The side rails are 10ft long so I extended them on opposite sides at the ends.
The width is 5ft.
23935
I again doubled the ply for the cross rails and screwed them in dry so take down is possible for relocation if needed.
so this is where I am at now-
239362393723938
The front rails are bolted with nylock nuts.
I also scooped the front rails to allow an 8x4 board to go between the legs for storage, still need to add some rails yet.
With a few sheets stored under there is should add some considerable weight.
The legs have screw adjusters on them for levelling.
So that's where I'm at now, I have some aluminium profile on order which I'm hoping will be with me soon.

JAZZCNC
19-03-2018, 02:13 PM
I posted on another thread but I'll comment here as well.

Somewhere else I see you mention 3k. With that much you can get long way to building proper machine made from steel.
Yes, it would be basic to start off with because of low budget but you would have a good foundation that truly can be upgraded as you go along without wasting money.
For a fully finished machine with decent quality components and few bells whistle you'll need about 4-5K but this will give you a machine that will last for years even in small production enviroment but more importantly be reliable and repeatable/accurate.

You will regret building this machine at some point that's for sure.

GrahamWhite
26-03-2018, 07:54 AM
So after much thought ,I have decided to go with the original plans- which are V bearings and Rack and pinion.
This is purely a cost thing for me - the entire build should come in at under 2k. I can understand peoples views on linear rails and ball screws but as pointed out by some ,it would take the build cost to nearer 4k which I am not prepared to spend.
Also the fact that this is an 8 x 4 machine for that price I can't see me having any 'Regrets' building it! like I have said before I would rather have a cheaper machine running than no machine at all.
If there is some upkeep to maintain performance then so be it.
Speaking to one of the guys who have built this he said he would build it again in a heartbeat.... but no need as its still running 7 years later ,now upgraded to aluminium carriages but still running V rails.
So bearings are ordered and aluminium profiles and angle iron are in this week :)

GrahamWhite
30-03-2018, 04:10 PM
So after my rails apparently having had a tour around England before reaching my supplier, I finally managed to pick them up Wednesday ... a 9 3/4hr round trip:(
So busy day today fitting them:)
24008
24009
Bearings for V rails are on their way from USA so hopefully things will start moving soon!

CNCKitMan
05-04-2018, 11:01 AM
Hello fellow adventurous newb,

I'm doing the same thing as you it seems (well it is a CNC forum).
I wish i had more input for you , to help you on your way.
I'm looking at purchasing Linear rails as i've used them before and the seem to give a better result (V Bearings on my Laser CNC work ok thou).

My input is i've searched and searched and think i've found a supplier of rails which don't cost the earth.
How much is the rack and pinion costing you??

GrahamWhite
05-04-2018, 10:40 PM
Hi,
I just couldn't justify the cost for linear rails I'm afraid :(
I have been looking at a UK supplier that is selling the rack MOD 1.0 at 74.99 for a 2m length pre drilled.
I'm hoping that's a fair price as when I google rack and pinion I get car steering racks a lot!
For the pinion drive i'm looking at a 3:1 drive plate module that I will probably order from cncrouter parts in the USA. No one over here seems to make them :( I think they are about 60 each+ postage and import tax.- I need 3

GrahamWhite
08-04-2018, 04:39 PM
So I'm looking at motor/driver choices and yes while i'm after advice can I ask that you switch off the 'best possible solution 'head and use the 'I expect that will be suitable' head!
This is a kit for nema 23 4Nm with 48 psu instead of the 36v they offer with other kits.
https://www.cnc4you.co.uk/CNC-Kits/Professional-Stepper-Kits/Stepper-Motor-PRO-Digital-Kit-4Nm-x-4-Axis-Nema-23
I know I will need screened cables as well but is there anything glaringly obvious missing?
Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)

driftspin
08-04-2018, 05:56 PM
So I'm looking at motor/driver choices and yes while i'm after advice can I ask that you switch off the 'best possible solution 'head and use the 'I expect that will be suitable' head!
This is a kit for nema 23 4Nm with 48 psu instead of the 36v they offer with other kits.
https://www.cnc4you.co.uk/CNC-Kits/Professional-Stepper-Kits/Stepper-Motor-PRO-Digital-Kit-4Nm-x-4-Axis-Nema-23
I know I will need screened cables as well but is there anything glaringly obvious missing?
Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)Hi

Graham White

People here like to go for 68v diy psu and 80volt digital drivers.

And you can too, for about the same price.


Grtz Bert.

Verstuurd vanaf mijn SM-A320FL met Tapatalk

JAZZCNC
08-04-2018, 08:13 PM
Sorry if it seems like i'm doing it all wrong but I'm loving my build so far as it's starting to take some shape :)

Your loving it now but you won't be if you keep ignoring advise cutting corners trying to save a few extra pounds. It's very easy to spoil a machine when just few 100 more would make a great machine and unfortunatly you only realise this after the money is spent.!

I won't give Bum advise so I'm not giving you a "just good enough" solution but will give you solution that is what's required for good machine.

Because your using R&P which is only 50-60% efficient compared to ball screws which are 90-95% couple this with linear rail system that's is even less efficient then you'll need extra power to deal with lower efficiency. Also because you'll be using ratio 3:1 then you'll want motors which spin little faster but still have torque higher up the RPM range and 50V drives with 48Vdc won't provide enough power. (Also 48V is too close to the Drives 50Vdc max so you risk blowing drives up)

Ideally, with R&P setup, esp one that isn't very efficient then you'd run Nema 34 motors with Mains voltage or higher Dc voltages around 100Vdc.
So if you must use Nema 23 motors then you want to be running them around 70Vdc with 80Vdc drives.
Also you want Unregulated PSU not Regulated Switch mode supply. Reason for this is that under de-acceleration the motors become dynamo's and dump the power back to the drives which then dump this back to the PSU (Back EMF) and if the PSU as protections built into it then will shut down which is bad news.
On Small slower machine with light gantrys then can sometimes get away with this but on large machines with heavy gantry traveling at higher feeds whcih routers tend to do then it will become a problem.
The PSU you want is Unregulated toroidal PSU which use capacitors that store energy and absorb any Back EMF. These are actually very easy to make and will work out cheaper than buying a large PSU, it also means you can tailor Voltage and Amps to your exact needs.

So the setup I suggest with nema 23 motors is this.
4Nm motors
80Vdc Digital drives running motors at 68-70Vdc.
Toroidal PSU transformer spec'd to output 68-70Vdc

With Nema 34 Motors:
4.5Nm Nema34
80Vac (100Vdc) Drives
Toroidal PSU transformer spec'd to output required.

Stay away from kits they are always compromised in some way.

GrahamWhite
09-04-2018, 07:59 AM
Appreciate the info:)
I can understand all you have said and will take it on board and not order the kit :)
so the steppers are fine ,will have to go with the 4Nm 23's as the mounting holes are already drilled.
An 80vdc board
https://www.cnc4you.co.uk/Microstepping-Driver/Digital-DSP-Stepper-Driver-7.2A,-80VDC-or-60VAC-CWD872
I have no clue on building a toroidal PSU!! lol so would need a touch of help there!

Clive S
09-04-2018, 08:31 AM
I have no clue on building a toroidal PSU!! lol so would need a touch of help there!

Look at these two vids.

https://www.youtube.com/watch?v=4OoQQg76ar4&list=PL1FIADAKba_tiLqXbUkzD30sZjtp_VyqY

Rapidonline https://www.rapidonline.com/ is a quick and simple place to buy the bits.

JAZZCNC
09-04-2018, 09:33 PM
Appreciate the info:)
I can understand all you have said and will take it on board and not order the kit :)
so the steppers are fine ,will have to go with the 4Nm 23's as the mounting holes are already drilled.
An 80vdc board
https://www.cnc4you.co.uk/Microstepping-Driver/Digital-DSP-Stepper-Driver-7.2A,-80VDC-or-60VAC-CWD872
I have no clue on building a toroidal PSU!! lol so would need a touch of help there!

Yes, I had a feeling you were stuck with 23's hence why didn't push 34's which would be the better option.

Regards the Drives and PSU then those you linked can use AC so all you would need is Transformer the drives will do the AC/DC conversion so don't need Caps and Bridge rectifier. However I prefer to use DC supply as I feel it takes some of the stress off the drives and can have little bit more smoothing.
This will work for you either way. Just add Caps and Bridge rectifier if want to go with DC.

https://www.rapidonline.com/vigortronix-vtx-146-625-125-625va-toroidal-transformer-230v-primary-2-x-25v-88-0012

GrahamWhite
18-04-2018, 08:07 AM
So this is the progress so far
24075
The Y axis to X are not finished yet, still have more support for the gantry to be fitted.
The plans called for ACME lead screw on the Z but after hunting for the elusive 1/2"-8 2 start bar across the planet, I gave up and bought a ball screw 16mm 05 lead off of ebay with the mounts and coupler.
I'm hoping they are similar - the acme was a 1/4" lead per turn where as the ball screw is 5mm - not sure how that will affect the Z performance at all?
I will be running the 4Nm 23 motors at 68-70vdc as Jazzcnc suggested so there should be enough extra oomph I hope to compensate for the Z?
Now onto a redesign of my Z to allow for the ball screw mounts

Clive S
18-04-2018, 10:08 AM
I'm hoping they are similar - the acme was a 1/4" lead per turn where as the ball screw is 5mm - not sure how that will affect the Z performance at all?
The ball screw is far superior than the acme. With the ball screw I would go with nema 23 3.1Nm

JAZZCNC
21-04-2018, 11:37 AM
The difference in screw pitch will mean very little performance difference. The difference in efficiency, however, will be a lot better.

Now your not going to like this next bit but it's in your interest it's said.!
The Z axis is THE most important part of the machine so whether Acme or Ballscrew won't make a jot of difference because of the weak nature of this Z-axis design. Those V bearings are simply not good enough for Z axis and this design will be massive weak link. It would be wise choice if you changed the design and invested in some profiled linear bearings.

GrahamWhite
21-04-2018, 02:04 PM
Yes I have to agree with you:( lol
although it's not so much of a problem now that I have to modify it for the ballscrew anyway.
I'll probably do a quick fix for the vee bearings to make sure on clearances and then the first decent mod. i'll redo the Z.
Would supported round rail be an option over the vee bearings?
-------------
I've gone for SBR16 rail- looking at a few z axis they seem to be built with the idea I have in mind
Also got the 84mm long bearings so plenty of stability I hope
All mounted on 19mmx 90mm 6062 ali plate with 6" piece crossways for the spindle mount
This option works with the X axis as I have bearings studs through the front face so hopefully I can make it work

JAZZCNC
23-04-2018, 03:42 PM
Would supported round rail be an option over the vee bearings?
-------------
I've gone for SBR16 rail- looking at a few z axis they seem to be built with the idea I have in mind
Also got the 84mm long bearings so plenty of stability I hope


Yep that will be lot better than V bearings. Just make it strong.

GrahamWhite
24-04-2018, 10:14 AM
So I've ordered my spindle -was going to go for air cooled as I didn't want the hassle of water pipes and pump but the breakout board I will be using has a dedicated pump relay built in so no real issues there!
Also they seem very quite and the price was right as well- seems to be a shop that just sells loads of items in bulk so undercuts everyone else selling the same stuff.
https://www.ebay.co.uk/itm/272749081454?ViewItem=&item=272749081454
That's the spindle,vfd,pump,water pipe,spindle mount and 1-13mm collet set! 238 delivered from Germany so no import fees unlike my pinion drive plates-just cost me 65 import fees this morning!

JAZZCNC
24-04-2018, 03:35 PM
Suggest you don't use the Relay on BOB and save for something else. Instead, use the Relay built into the VFD.
Reason to not use it is to keep potential Noise away from the BOB where it's more vulnerable to interference.

GrahamWhite
24-04-2018, 04:40 PM
I spoke to cnc4you today and they suggested for rack and pinion instead of running nema23's 4Nm with 3:1 reduction I could have just gone with 34's at 8.7Nm and run them direct or fit a larger pinion for slower speed??? would that be the same?

JAZZCNC
24-04-2018, 05:43 PM
I spoke to cnc4you today and they suggested for rack and pinion instead of running nema23's 4Nm with 3:1 reduction I could have just gone with 34's at 8.7Nm and run them direct or fit a larger pinion for slower speed??? would that be the same?

Bad advise for several reasons and just shows how little experience CNC4YOU have.!
#1 The resonance directly on the motors will play havoc with the drives causing rough running. It will also Kill the motor bearings quick time.
#2 Bigger pinion will make go faster not slower.
#3 Bigger pinion will reduce resolution.

The reason for the ratio is two-fold.
#1 To increase resolution. Even a small pinion of say 15T (Mod1) will have a pitch of 47mm which is too high and will give a low resolution. It will go like the clappers but resolution or in simpler terms Smoothness will be rubbish and this shows in the cut. You want to aim for pitch between 10mm-20mm Max.
The CnC-router parts pinion I believe is 1" or if Mod 1 will be 25T which will give pitch of roughly 78.5mm with 3:1 ratio this brings down to 26mm which is still little high for me if want to do very detailed work.

#2 It increases the motor torque which is required to overcome the inefficiency of R&P.

Also, the belts help lower Resonance which affects motor/drive performance. DONT under estimate Resonance because it will and DOES cripple machines performance. This is why you'll often see recommend Digital drives because they handle Res so much better, but still they have limits and Direct driving R&P off the motor would challenge them and your abilty to tune the resonance out.

Edit: Just to go little further on why direct drive is bad idea and pinion sizes etc.
When using a machine it's important that you spec your components so that you have best performance while cutting. One important consideration with stepper based machine is that you aim to be cutting in the motors RPM range which gives best performace while cutting.

So if you have direct drive with big pinion and say your feed is low becasue say doing 3D work, then your problems start to multiply because now your motors are hardly turning. This scenario puts the motors/drives in place which isn't always good.!
Yes torque will be higher but do really need it while going slow.? However motor smoothness will suffer and this will often show in the finished cut which very much matters on say 3D work. OR affect the drives thru resonance causing rough running and others problems.

Hope this helps.

GrahamWhite
25-04-2018, 07:03 AM
Ok Thanks ,so I have gone the sort of correct ish route!

GrahamWhite
25-04-2018, 12:32 PM
I'm finally looking at the motors and drivers and found this place -omc-stepperonline.com
in particular this driver
https://www.omc-stepperonline.com/stepper-motor-driver/digital-stepper-driver-24-72a-18-80vac-or-36-110vdc-for-nema-34-motor-dm860t.html
is that pretty much the same as the cnc4you one?
https://www.cnc4you.co.uk/Stepper-Motor-Plus/Microstepping-Driver/Digital-DSP-Stepper-Driver-7.2A,-80VDC-or-60VAC-CWD872
The stepperonline place don't do the 4Nm stepper though but they do have a 3Nm that pulls 4.2a as well as a 3Nm pulling 3.2a
They have nema 24 @4Nm would they fit my pinion plates ?
---
read more so the 24's will fit ,they have the same mount hole spacing within .1mm
Agghhh - I know I need a Bob as well-one full of connectors or just a basic one, I have ordered a UC300eth for connecting to my pc so need 5v to power that- it that then an extra psu I need or can I pickup 5v from somewhere!

JAZZCNC
25-04-2018, 06:03 PM
I'm finally looking at the motors and drivers and found this place -omc-stepperonline.com
in particular this driver
https://www.omc-stepperonline.com/stepper-motor-driver/digital-stepper-driver-24-72a-18-80vac-or-36-110vdc-for-nema-34-motor-dm860t.html
is that pretty much the same as the cnc4you one?

Yep pretty much and will work fine for your needs.



The stepperonline place don't do the 4Nm stepper though but they do have a 3Nm that pulls 4.2a as well as a 3Nm pulling 3.2a
They have nema 24 @4Nm would they fit my pinion plates ?

read more so the 24's will fit ,they have the same mount hole spacing within .1mm

When comes to motors whats more important is the inductance which is rated in mH. Lower the better and when wired Bi-polar parallel you want to be looking for around 2.5-3.5mH for best performance.

Be careful when comes to Nema sizes because some companys state Nema 23 which should = 56mm but the frame size is actually Nema 24 which =60mm. Prime example is that exact Cnc4you motor you linked to. The data sheet gives Dims of 60mm but they sell it as Nema 23.!!




Agghhh - I know I need a Bob as well-one full of connectors or just a basic one, I have ordered a UC300eth for connecting to my pc so need 5v to power that- it that then an extra psu I need or can I pickup 5v from somewhere!

Don't try to pick up 5V from else where like PC or USB. You need a stable 5V supply and ideally to lower risk of noise affecting controller you want it separate to any other devices.

Ideally you want to be getting away from 5V for things like E-stop, Limits etc because it's very susceptible to electrical noise which gives all sorts of weird and wonderful hair pulling mysterys.

Re- Bob's then you won't want to go the route I'd recommend because of price. Which would be UB1.
So in which case I'd say go with cheap Bob and just make sure it uses isolated Inputs. Most Simple Bob's don't have isolation so stay clear of those.

Highly recommend you draw up schematic and use 24Vdc safety circuit using relays. This will allow you to use 24Vdc to run thru E-stop and limit wires on the machine lowering any chance of false e-stops etc thru noise. The 5V signals you need for the Controller/BOB can then be kept to short wire runs and inside the control box which lowers chance of noise affecting machine.

Machine just relying on 5V for everything is very open to electrical Noise. Crazy things can occur.? ie: Mr's turns on hairdrier machine E-stops, Boiler fires up machine E-stops, Kettle on, Door bell etc etc.!!. . . think you get the picture. Anyone who's been affected by noise will tell you it's pain in the arse and only beat by resonance to which pulls the most hair.!

GrahamWhite
25-04-2018, 06:24 PM
Wow, thanks :)... Can I ask just one more question? The nema 24s should be fine, although 60mm size the hole mounting is the same but they have 8 wires! Is that 4 more than usual! Or is 8 OK (they only have 8 wired ones in UK warehouse)

JAZZCNC
25-04-2018, 07:06 PM
Wow, thanks :)... Can I ask just one more question? The nema 24s should be fine, although 60mm size the hole mounting is the same but they have 8 wires! Is that 4 more than usual! Or is 8 OK (they only have 8 wired ones in UK warehouse)

Ok let me explain the difference between 4, 6 & 8 wire motors. Steppers can be wired in several configurations with each making a difference to how they operate. There are 2 commonly used methods #1,#2 and one not so common #3.
#1 Bi-polar parallel (8 wire)
#2 Bi-polar Series (4 wire)
#3 Uni-polar (6 wire)

8 Wire motor is known as Hybrid Motor and can be wired in any of the 3 configurations. Each Config will affect the current used and how the motor performs. (8 & 6 give roughly same performance but unipolar require drives that allow it, hence why not often used on modern machines)

So if using 8 wire motor this would be wired Bi-polar parallel and requires roughly 2x the amps of Bi-polar series to give rated torque. However In performance terms it holds the Torque much higher up the RPM range than does a Series wired motor for the same given voltage.
But like all good things this comes at a cost. You have less torque lower down the RPM range.

What this means to YOU and US is that for Router where your cutting at higher feed rates and higher up the RPM range then Bi-polar parallel is best way to go.

If you was building say a Milling machine then you'd wire in Bi-polar Series because require more Torque lower down the RPM range. Still uses 8 wires just wired differently. Also requires less current than parallel so lower amp drives can be used. However for the same voltage the RPM will be lower because inductance is higher due to how it's wired.! . . . Again back to can't have something for nothing.

Now 4 Wire motors are Fixed by the manufacturer and you buy them either Bi-polar Series or Parallel wound. Often they are Series wound.
The difference being that Series wound will require roughly twice the voltage to reach the same RPM as Parallel wound motor.

Won't get into 6 wire unipolar because it's a throwback to old tech and drives so not really relevant here.

So for best performance with a router, you want 8 wire motors and wire them Bi-polar parallel.

If you look at the Datasheet on the Cnc4you it will show you how the wires are connected for each method. All 8 wires are used but joined in different ways.

GrahamWhite
25-04-2018, 10:27 PM
Many thanks again, most of the basics ordered now, steppers, drivers and 24v psu.
Will look a bit more into Bob's.... Yes ub1 does look the bees knees but will take more kidneys than I can afford to sell! Lol
I'll have a look at some others that have opto isolation:)