Help to choose motors and drivers

Auarhau
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Help to choose motors and drivers

Post by Auarhau » Tue Feb 25, 2014 9:44 pm

Hi.
I just ordered the shapeoko 2 mechanical kit (and what I could find in stock of what I need to make a complete machine). I have a dremel, and a 24v 12,5A powersupply. So what I need are some motors and a way of controlling them. I have no previous cnc experience by the way, but I have read about it for some time now.

From what I gathered about controllers this is what I'm thinking at the moment (please correct me if I am wrong):

The Ardruino / Gshield option looked nice, but it's not in stock anywhere..
Pros: Can be controlled from a laptop via usb. The shapeoko documentation is written for it, and many users use it.
Cons: If understand correctly it can't be used with mac3 or linux cnc? I would like to keep things simple to begin with, but I'm pretty sure I would like the option to try out all the nice software options out there.

Gecko G450:
This is supposedly the best drivers (at least many prefer these). But they seem overkill for a small bench-top machine with nema 17 motors? Thy are also very expensive. Good documentation and support.

Hobbycnc:
These looked good, except that they wont accept every type of stepper motor. The deal breaker here is that shipping to Norway cost like $70 iirc, which is more then the board itself. I liked the idea of soldering the kit myself, since the instructions looked good.

Various ebay chinaboards:
I'm afraid these will cause me trouble due to low quality control and lack of documentation. Mostly though I dont want to end up with a setup very few, or only me, have. Since this is my first go at CNC I want something that is commonly used (so I can get help) and works easily with popular software like linuxcnc etc. Price is nice though!

Motors:
I need 4 nema 17 obviously but these are not in stock at inventables. Any tips on what to get? When I go look for motors elsewhere, what specs are important to look for? Are there any advantages or disadvantages with using 400 step/rev motors vs 200/step rev?

Hope I can get some help clearing this up, as I have read until my head spins. And I can't make sense of it all :)
I need ideas of well tried, well supported cnc controller board and matching motors.
Thanks.
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

cvoinescu
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Re: Help to choose motors and drivers

Post by cvoinescu » Wed Feb 26, 2014 12:47 am

Other options are the buildlog.net stepper shield by Bart Dring (available from Reactive Substance) or the very similar GAUPS (which I designed, and is available in my store, shipped from the UK). Both work with GRBL on an Arduino Uno, or TinyG2 on an Arduino Due -- same as the gShield. Unlike the gShield that has three built-in drivers, they take up to four drivers (ideal for dual Y drive), and the drivers are replaceable Pololu modules (which is nice in case you manage to destroy a driver).

It is possible to connect the gShield or the GAUPS to LinuxCNC or Mach3, either directly to the parallel port, or using a breakout board. This is easier if you don't solder the Arduino headers, but it can be connected even if you did solder them. I am waiting for my cheap parallel port breakout board to arrive from China to test and document the connections for LinuxCNC (they should also work with Mach3). Once done, they'll show up here.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Auarhau
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Re: Help to choose motors and drivers

Post by Auarhau » Wed Feb 26, 2014 11:21 am

Hi.
You'r board looks nice, and the instructions too. I'm sure I can assemble this (which I think is a cool little project in it's own, since I haven't built a pcb before).

If I understand correctly the GAUPS board will work like any other controller via parallel port. But to use grbl it need to be mounted on an arduino? If this is the case, I can experiment with both which would be great! Is it possible to add limit switches and auto tool zero functions with this setup?

I am a little unsure on what driver to choose. You'r page lists three. Any recommendations?
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

cvoinescu
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Re: Help to choose motors and drivers

Post by cvoinescu » Wed Feb 26, 2014 11:42 am

Thank you.

The GAUPS is designed primarily to plug into an Arduino, but any such board also works with a parallel port, if you know how to wire it.

GRBL supports limit switches. There is no specific circuitry on the GAUPS for that, but the Arduino pins are exposed, so you can simply plug them into the correct inputs (between GND and D9, D10 and D11). The current version of GRBL does not support tool auto-zero (touchplate or similar), but I think it's on their to-do list.

About the drivers: the green and the black drivers use the same chip capable of 2 A, but the black one has a PCB with thicker copper traces for better heat dissipation. The purple driver has a different chip with slightly more current capability (2.2 A), finer microstepping (up to 32x -- not really that useful in practice), and even better thermal dissipation. The chip on the purple driver is reportedly more robust, too. The green driver is fine for 3-D printers and for smaller motors, but for CNC machines I'd choose the black or the purple.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Auarhau
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Re: Help to choose motors and drivers

Post by Auarhau » Wed Feb 26, 2014 10:10 pm

Are there any difference in performance between the gshield and the GAUPS?

What motors do you recomend for the shapeoko 2? I notices you sell three different kinds of nema17,and they all cost about the same, which one would you pick for this machine? I also noticed that the purple driver is rated at 2,2amp and your 67oz motor is 2,5 where the other alternatives are 1,7 (oh and one is 400 steps/rev vs 200 which I see more often). Does this matter, or what are the practical differences? If it matters: I'm planing to upgrade the dremel to a trim router at some point, and I want to be able to mill everything the shapeoko2 say's it can, including trying aluminium.
(I apologize for my ignorance in electronics, but It's a bit much to digest all in one go :) )

And just so I don't fry something before I get started, is my Mean Well S-320-24 24v 12,5A power supply ok for these electronics? If not I have some (3 or 4) very nice Omron S8VS -12024BP 24V 5A I could use (by nice I mean they are neat looking and have a cool display! :mrgreen: )
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

cvoinescu
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Re: Help to choose motors and drivers

Post by cvoinescu » Wed Feb 26, 2014 11:32 pm

Your Mean Well power supply is more than you need (but doesn't hurt); even the 200 W model would be plenty. A 24 V 5 A (that is, 120 W) power supply is okay for NEMA17 motors, but may not be enough for NEMA23 at maximum current.

The 400 step-per-rev motors are inherently slower, and have a little less torque than 200 step-per-rev motors, but their positioning is twice as precise. Also, all things being equal, motors with a lower impedance (higher current rating) are faster. The 2.5 A motor is fast, but you are right, the Pololu drivers can not make the most of it; it's a good match for slightly larger drivers. I have a batch of even more powerful 200 step-per-rev motors that are rated at 1.7 A, which are a perfect match for Pololu drivers (they're not in the shop yet).

The performance of the GAUPS depends on the drivers you use with it: the purple Pololu drivers (DRV8825) are slightly better than the built-in drivers on the gShield (DRV8818); the black Pololu drivers (A4988) are better in some ways and not as good in other ways -- no difference in practice; and the green Pololu drivers (also A4988) are slightly worse. For most practical purposes, they're the same.

However, the main advantages of the GAUPS are the fourth driver (which increases the performance of your Y axis significantly), the replaceable drivers, and, at the moment, the fact that it's in stock; and its main disadvantages are that it comes only as a kit that requires soldering to assemble (easy as pie, though), and that it ends up a bit more expensive than the gShield once you've factored in the Pololu drivers.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Brian
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Re: Help to choose motors and drivers

Post by Brian » Wed Feb 26, 2014 11:54 pm

I have a xylotex 4 axis control board laying around if you want something cheaper thatll run on 24v. I upgraded to some more potent drivers on my machine.
Brian
Shapeoko 2 #I have no idea
HF cutout tool, 72oz nema 17 steppers, TB6600 stepper drivers, Mach3 control

Auarhau
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Re: Help to choose motors and drivers

Post by Auarhau » Thu Feb 27, 2014 5:24 pm

Thanks for the offer Brian. I decided to go with the grbl/GAUPS option. I think it will be nice to try the open source alternative all the way both hardware and software:)

@cvoinescu: Thanks again for your assistance. I am also looking forward to your tutorial on how to use the shield separately via paralell port to linuxcnc/mach3.

Just missing the gt2 belts and pulleys now, and I should be set:)
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

Auarhau
Posts: 243
Joined: Tue Feb 25, 2014 8:46 pm

Re: Help to choose motors and drivers

Post by Auarhau » Tue Mar 11, 2014 9:01 pm

cvoinescu wrote:It is possible to connect the gShield or the GAUPS to LinuxCNC or Mach3, either directly to the parallel port, or using a breakout board. This is easier if you don't solder the Arduino headers, but it can be connected even if you did solder them.
I got a nice package from the UK in the mail today :D Looking forward to starting assembling the shield. However, before I start I want to make sure I understood you about the Arduino headers. Are the headers im not supposed to solder (for making it easier to connect to a breakout board) the ones on step 8 of the assembly guide?

Also, the long headers for the drivers: Do I solder those on, or just stick them on and let friction keep them in place?
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

cvoinescu
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Re: Help to choose motors and drivers

Post by cvoinescu » Tue Mar 11, 2014 9:17 pm

The tall headers replace the ones that come with the Pololu driver modules. Please solder them to the driver modules.

Yes, step 8: don't solder those. You could solder regular headers instead (the ones that came with the Pololu drivers, which you're not using because you replaced them with the tall headers), or you can solder wires directly to the board.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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