Messages

1

General Mach Discussion / Re: Very Accurate Homing (No, It's not like all other Homing posts)

« on: July 30, 2014, 04:05:15 AM »

I am currently designing a similar board and would be making it open source. Anyone keen on helping is most welcome to do so. If you could wait about a week maybe, i should have a design tested and proven.

2

General Mach Discussion / Re: Homing accuracy

« on: June 30, 2014, 01:01:29 PM »

Dear Hood,

Thank you very much for your reply, once again!

I feel like a bit of an idiot having struggled along all this while- i was unaware that the CSMIO/IP units are available and was under the impression that the product had been discontinued. (I have read about them earlier). I'm planning on picking this up now that you've mentioned this, and seems like a tailor made solution for my current needs.

You've answered quite a few of my questions- and what interests me the most is the closed loop aspects of the motion controller mentioned. As you're getting the encoder feedback from the servo drive, it would not be compensating for backlash through the closed loop system (from what i understand). Have you tried external encoders/linear scales for this? For one specific machine of interest in my case, i have analog servo drives with multipole resolver feedback to the servos (Fanuc M series drives), and digital encoder feedback does not appear available from the drives.

As for using the Z reference- i am planning on designing a circuit for that which i would most likely make open source once it works- for cost effective deployments. (this should help people keep their machines cost effective. From what i see, the motion controller is for 600 euros, which may be a constraint for some people)

Thanks and best regards

JSS

 

3

General Mach Discussion / Re: Homing accuracy

« on: June 30, 2014, 05:27:53 AM »

Dear Hood,

That's exactly the answer i was looking for! Thank you for your response!

I have been doing homework on the index pulse method which you are using, and as i am still not very experienced, this wasn't know to me till about a week ago.

I am using the parallel port method, along with IO extension using a Modbus based PLC. (I am using the PLC to the best extent possible with logic programmed into it, as i am not happy with the Mach3 brains. I guess i'm doing something wrong, but I've found the Mach3 brains unreliable in my build)

So the problem comes to this- my encoder is at 2500ppr physical, with multiplication of 4 in the servo drive. I do not know how to make the servo drives reference on their own (the Siemens v60, to the best of my knowledge, isnt that smart). The v60 drives do have the index pulse output.

My PLC response time is 8ms, hence it is unable to catch the pulse from the servo drive (pulse duration at 1rpm speed of the motor is 2.4 ms. We normally run at higher than 1 rpm at any given point of time).

If you don't mind me asking, which motion controller/which servo drives are you using which is able to manage this on its own? And are you running on a closed loop with these external motion controllers? And how is the implementation? did you need to make a separate brain for this? (The reason why i ask is because i do not know how to change the referencing logic of Mach3)

With best regards

JSS

4

General Mach Discussion / Re: Homing accuracy

« on: June 30, 2014, 04:37:59 AM »

In addition, has anyone developed any interesting logic to reference the machine accurately? assuming anyone else if facing the same problem.

I am currently designing a circuit to help me with this. Any suggestions in the field would be helpful- my circuit is currently only theoretical, and any inputs would be appreciated

5

General Mach Discussion / Homing accuracy

« on: June 30, 2014, 01:30:12 AM »

Hi!

I'm somewhat new on this forum, and may be posting this in the wrong section- Moderator, please put this into the correct section.

A little background information to my problem: I've done a retrofit for a 3 axis machine (A beaver NC5, originally on a Heidenhain TNC 355 when i purchased it) with a Mach3 system. The system i've built has the following configuration:

1. PC:

AMD Phenom 2x4, 920, quad core running at 3.2 Ghz (i think- don’t remember at this point), with 4gb ram, a graphics card, SSD and 1 lpt port (all well above the min requirements)
operating system: Windows 7 x86

2. Servo drives:

Sinamics V60 series, 6NM torque- 3 sets

3. Modbus device:

ABB AC500 series PLC, with approx 96 IOs (including 4 Analog out and 2 in). PLC program takes care of most of the machine functions and safeties, as i, with all due respect, do not trust the mach3 brains system from my experiences in building this machine.

This is for a 3 axis machine with ATC, and has a number of sensors and feedbacks, hence all the IOs.  The machine is in good condition mechanically; with guides being quite fresh (the machine wasn’t used much and was a demo machine at a college. This is the second retrofit the machine is going through- it was originally a NC machine)

Now the problem i'm facing is that the homing reference accuracy isn’t good. The Heidenhain system, with the same switches, had fantastic home reference accuracy (to 10 microns or less- we never had to pay attention as the surfaces generated were always matched). The machine would home in what appeared to be the same fashion as the Mach3 system.

However, the Mach3 implementation is a slight tragedy in comparison- the repeatability of position after reference is not worthy by machine tool standards. Now the limit switches are the same as earlier. The ball screws are the same as earlier. The components which have changed are the motors, servo drives, controller and electricals.

In order to solve my problem, I’ve done a little homework on how the other controls reference their axes, but will post that afterwards after receiving some ideas back on this forum.  Posting that now may turn the conversation in a direction which I would prefer to avoid at this moment.

Now, for my understanding, how accurate is the home reference for the others on this forum?


The homing accuracy is of very high importance to me as we have frequent power outages in the place where I am, and a system which loses position in the process becomes extremely tedious to run.

With best regards

JSS