Messages

1

General Mach Discussion / Re: ok enough stepping, how do I add encoders?

« on: March 12, 2013, 03:20:27 AM »

That is a good point, maybe the motors are not at full torque.  (More power )

The motors are 6.4 mH/phase and are rated at 3.5 Amp/phase powered by a 36 Volt 10 A supply.
My drivers are rated up to 50 VDC. 4.2 Amp peak.

I am also running at 1000 Pulse/rev (down from 1600) in an attempt to trade accuracy for power.
Unless I miss understand the concept,  less steps equals more power but less accuracy.
That said 1000 Pulse/rev still should still hold .00025 on my setup.

Maybe a 48 volt supply would help out, just don't want to bake the drivers. 

Randal

2

General Mach Discussion / Re: ok enough stepping, how do I add encoders?

« on: March 11, 2013, 07:30:45 PM »

Thanks Hood.

I did not realize Mach was only open loop, I was thinking it could do closed loop also...
Based on Mach being open loop, it seems like a chasing my tail to track it.

Maybe I just need to go overkill on the motors and put ball screws in...
OK, who has a step-by-step how to select the correct ball screw setup for a RF 30...


Randal

3

General Mach Discussion / Re: ok enough stepping, how do I add encoders?

« on: March 11, 2013, 02:11:50 PM »

Thanks for the reply.
I agree with what you are saying about stepper useage, and I know it won't prevent lost steps.
Most people I have talked with run 425 oz/in motors on this mill with little or no issue at faster feed rates.

I "assumed" the motors were just to weak, So I went bigger.
I have moved up to  570 oz/in, and raised the current to the maximum these drivers will allow. (Slightly more than the motor lists)
I also have torn the system down, cleaned,lubed and adjusted until it is very easy to move, with no binding. (I even reduce some of the backlash.

But...
The unpredictability of the skipping combined with with the backlash of this mill adds to the mess. (I have not switched to ball screws yet still researching)
So even when it does not skip, the backlash is an issues even if I adjust the setting till I'm blue in the face.
My backlash compensation is great for some jobs like drilling etc. but radius pockets etc, no way.
Actually I get much more consistant milling results with backlash compensation off...


Summary:
I have motors I think are big enough.
And the only way to know where the matrial is really located, is to drive to a position measured off of the table and not count steps.

Did I make any sense?
And will mach3 drive a stepper to a position based on an encoder value?

Cheers

4

General Mach Discussion / ok enough stepping, how do I add encoders?

« on: March 11, 2013, 10:37:39 AM »

OK, my RF30 mill moves great with no load but, I am tired of getting %70 through a 25min real job then having the motors skip steps killing $50 worth of stock...
When I use backlash correction it confuses the issue more...

Like I said above, air cutting runs the job fine and going back to 0,0,0 is almost dead on, but add any load and its crap shoot...


Can I add encoders directly to the table?
I would like to:
- Track the X,Y, & Z actual positions via encoders.
- Keep the motors, drivers, and ESS if possible.


I am sort of new to this stuff but not afraid
I have, RF30, Mach3, ESS, wanati drivers, wanati steppers. (425 in/labs)
So I assume someone has done this?
Would be great to see video or step-by-step tutorial of this being done...

Thanks for you help.

5

General Mach Discussion / Re: Lost at low speeds

« on: March 03, 2013, 05:50:15 PM »

OK short update.
I changed the X and Y to 400 from 1000 and adjusted steps per in motor tuning.
Still had the issue but much less.

So I decided to crank the acceleration way up I went for 1.5 to 55.
Wow night and day, still is off a bit but much better.

note: with it set up this may the motors do make much more noise, and if I get below 10 IPM It creates a vibration in the stock.

So any feed back on acceleration would be helpfull, such as is 55 to high?
Like you said Chaoticone  I think 10000 will be smother, maybe with acceleration  cranked up it might work...

Thanks again.
Now to start asking how to deal with backlash 0.o

6

General Mach Discussion / Re: Lost at low speeds

« on: March 03, 2013, 01:58:51 PM »

 
When you say round to the next step, I assume Micro Step?

Base on the video you linked more micro steps just adds resolution, not real accuracy, or torque.
--This explains why the motors skipped at 1600 and not 1000...

So what I gather so far is:
- I want fewer micro steps for torque and more micro steps for resolution.
- But to few steps and I get ringing etc. and to many steps low torque.

So the answer to my earlier question about best Pulse/rev is to set it where I get enough torque, and still maintain accuracy needed.
Since .0001 is beyond my machines ability to repeat any way, I should drop to 400 pulses/rev and get more force and still have about .00025"   (.1/400)

Am I making any sense here or wanting off down the wrong road?

BTW. Thanks for the help I might actually learn something




 

7

General Mach Discussion / Re: Lost at low speeds

« on: March 03, 2013, 01:03:02 PM »

OK silly question...
If the stepper motor is 200 steps per rev (1.8 Degrees), what is the proper setting for the driver?

Not sure I see the relationship between them.
My little brain doing no real math etc, says 200 steps = 200 pulses, or a multiple such as 10 x 200 = 2000.

Basically what drives the setting on the Driver?
I pulled the 1000 setting from the air, just because I was having skipping issues at 1600...

Cheers

8

General Mach Discussion / Re: Lost at low speeds

« on: March 03, 2013, 12:36:14 PM »

Oops I misspoke!
looking at Mach3 tuning again, actually I have the Axis "steps per" set at 16018 . not 20065...

9

General Mach Discussion / Re: Lost at low speeds

« on: March 03, 2013, 12:25:26 PM »

OK I'm new to this but here it goes.

- My steppers are also 1.8 degrees. so (200 pulses per revolution)
- Micro stepping = 10. So 200 X 10=2,000 (Not sure about this but seems true)
- Motors X & Y are direct 1:1 via solid coupler.
- My table is 10 turns per inch so .1" per turn of the shaft.


so:
1.0 divided by 0.100=10. So 2,000 X 10=20,000.

So 20K..
Looking at my tuning setup I am real close. 20063.
I added the 63 to make it move the full distance based on 1.0" move with a dial indicator.


---
Also on the side of the Driver(s) it has a list of dipswitch settings for Pulse./rev I picked 1000.
Originally (out of the box) it was 1600, but the motors would skip every time I reversed the table, moving to 1000 seemed to help.

10

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: March 03, 2013, 02:16:17 AM »

Greetings all,
I have just started learning CNC. (NOOB!)

I bought a used RF30 and added a Wantai conversion kit, Smooth Stepper, Mach3.
I am using Alibre Design Pro for CAD and CamBam for CAM...
Still working out the kinks but it moves

I own a very small Industrial Software/Automation Consulting company and want to start producing products instead...
My back ground is VB.net, C++, AB PLCs and industrial vision.

Hobbies: uumm to many to list.
Guns/Cars/Computers/Bagpipes... and so on.

Cheers