Small PLC with 3 Axis Stepper Control

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Thread Starter

Curt Wuollet

Hi all

I'm looking for a small, reasonably inexpensive PLC that can do trapezoidal motion on 3 axes of step and direction outputs. Modbus RTU would be great. I know the more recent offerings have been emphasizing motion. Reasonable software cost would help.
I need to run two 3 axis stations, (simple motion, one axis at a time, don't need coordinated motion), and using 6 PLCs doesn't appeal to me.

AB has a micro that will do 3 but the software, CCW, was not ready for prime time last time I tried it.

Regards
Curt Wuollet
Maintenance Team

----------------------------------------------------------
BAYER BUILT WOODWORKS, INC.
Quality Millwork, Unbelievable Service
www.bayerbuilt.com
 
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Curt Wuollet

Hi All

As I said before, I want to control 3 axes of steppers from a PLC. There seems to be a piece missing. Stepper motors and drives are now truly commodity items. I can find all kinds of hardware for doing trapezoidal control directly to motors from a USB or parallel port due to the popularity of DIY CNC. But these are generally small motors. What I haven't been able to find is a module that will accept commands from RS485 and provide 3 direction lines and three step lines to feed the commodity stepper drives. I could design something, but I really don't want to reinvent the wheel. Has anyone seen this type of gadget? I know there are a lot of people doing motion out there.

Regards

Curt Wuollet
Maintenance Team

----------------------------------------------------------
BAYER BUILT WOODWORKS, INC.
Quality Millwork, Unbelievable Service
www.bayerbuilt.com
 
You might look at Automation Direct. There 4850 Stepper Drives can handle up to 5 amps and there 8100 can handle 10amps. They take serial inputs and use a SCL language. One of our engineers designed a multi axis system just using the serial commands and a simple VB app. I know the drive is not a PLC but it might get you pointed in a good direction.

Donny
 
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Bob Peterson

While I am a fan of most of the AB PLCs, the AB Micrologix 800 family and the CCW software does not impress me in the least.

I seem to recall that the Micrologix 1400 has 3 fast outputs.
 
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Curt Wuollet

Hi Donny

I've been there and considered just that solution. But, I would need either 6 PLCs or a rather expensive Do More system. First I considered 6 DL05s but they only output to 7 kHz. It wouldn't break the bank to put 6 Clicks in a cabinet and I could use the ones with Modbus built in and have a solution, but have no way to assess the reliability of the ascii SCL serial links.
 
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Curt Wuollet

Scary, yet another thing we agree on. Although I think the PLCs might be OK with usable software, I'll re-examine the MicroLogix line.

Regards
cww
 
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Curt Wuollet

After much research and beating my head against the wall, I think I've found a solution that fits. Someone wise once said: "If the problem is insoluble, change the problem". or something like that.
Instead of thinking of this as motion control of 6 steppers, I just changed the problem. All the _automation_ solutions I was finding had serious drawbacks, too expensive, too much hardware, too much........
So, I changed the problem. Really what I need to do isn't much different from a CNC router or even a 3D printer. They obviously don't use a whole cabinet full of PLCs and they cost a lot less these days than the _automation_ solutions I was seeing.

I just called it CNC and followed the maker crowd.

I have a proposed solution that will control 3 axis of stepper drives and motors and will set me back less than $100. Maybe much less. An Arduino UNO is about $16 and the software is free. We see the Arduino mentioned here occasionally. Some folks have written a G code interpreter and motion controller that runs on an Arduino.
It's called Grbl and looks to be a great fit. In fact it's pretty much overkill, but should work fine for what I have to do and it's all pretty much OTS and open source to boot. I'd much rather use two of these tiny SBC's and write in standard G code than spend hundreds and have to learn an(other) oddball proprietary language. So, I think the problem is solved or at least I have a good prospect.

Thanks for the replies

cww
 
The XYZ Da Vinci 3D printer uses the same microcontroller as the Arduino Duo and there is Arduino software available to replace the firmware in the printer - check out Repetier.
 
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The plan right now is simply to use Grbl on a DUO. The ballscrew slides will be coming with 2.8Nm steppers and drives to suit so all i need are the step and direction outputs for 3 axes. Grbl accepts Gcode directly, so I'll just set up a Click to send Gcode. Since the DUO wants USB, i'll either use a converter or, I've got a few arduino clone board blanks that have a serial port. I'd prefer a checksum protocol, but we'll see how it goes. It must be reasonably reliable, it takes a lot of Gcode to print something or even mill something. It's been a while since I've played with Gcode, but what I need to do is very simple. Grbl provides a lot of handy inputs that save PLC IO as well. It's a great fit.

Regards
cww
 
> I'd prefer a checksum protocol, but we'll see how it goes. It must be reasonably
> reliable, it takes a lot of Gcode to print something or even mill something.

How has this project turned out Curt? In the past six months I've done a little motion control hooking a PC (with 3 Ethernet sockets) up to a Kollmorgen drive.
 
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