First Proper CNC Router

[Desertboy]

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]

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/st...it-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]

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]

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]

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]

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=4OoQ...zD30sZjtp_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

[Desertboy]

Listen to Clive I speak from experience lol
http://www.mycncuk.com/threads/10880...6816#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]

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.

[Boyan Silyavski]

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]

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.


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.


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.