Messages

401

General Mach Discussion / Re: New setup...and having a problem.

« on: June 01, 2011, 06:41:30 PM »

Found the problem.  The new G201X drives are capable of running with either a common ground or 5V, but the state of the step signal has to match.  I'm using a 5V common, so I changed the state of the step pulse to active low and it all works great.  When I checked "Sherline" mode and it worked, I knew it had to be a pulse issue, which a call to Gecko confirmed.


 

402

General Mach Discussion / New setup...and having a problem.

« on: May 30, 2011, 04:21:51 PM »

I decided to try something new.  I've been using the Gecko G540 drive with no problems, but decided to go to larger motors than what the G540 could handle.  Here is the new setup...

- 65V unregulated power supply
- PMDX-122 breakout board
- Gecko G201X drives

The problem is that the motors move in an erratic manner and make a horrible growling noise that resonates through the machine.  It should be running at 600IPM on the rapids but instead is running at about 150, give or take, and bucking and jerking to the point that this 2000 pound machine is moving.  It's a plasma with a 250 pound gantry.

Here's what I've checked...

- Power supply has a clean 63V while the axis is moving, so I know I have enough power.

- Driver test is clean.  Nice flat line.

- Adjusted the Gecko's with no difference.

- Adjusted acceleration up and down and still get growling erratic motion.

- With the electronics shut down, you can move all axes by hand and motion silky smooth.  No binding anywhere.

Any ideas on what could be causing this?  I've used the every component before except the PMDX-122 BB.  Could there be a setting in Mach that I'm missing?

Thanks

403

General Mach Discussion / Re: Help w/ cnc plasma issue

« on: May 03, 2011, 09:14:20 AM »

Sounds like lots of HF noise.  Which plasma are you running?  Does it have HF or contact arc start?

404

General Mach Discussion / Re: burned out stepper motor? Symptoms.

« on: April 24, 2011, 03:55:33 PM »

I have a 6 axis mill, all the axis are already taken up from the C23 board;)

Then you can build an amplifier circuit that would provide the same output current to both drives.

405

General Mach Discussion / Re: burned out stepper motor? Symptoms.

« on: April 24, 2011, 03:28:58 PM »

When you connect two drives to one output, you pull twice the current from that output.  If the current on one of the lines going to the drive drops below what the drive needs, the drive will act as if it is missing steps, or worse case, not work at all.  It's not reliable because sometimes it works and sometimes it doesn't.

You should be running a slaved axis.  Let Mach send step and dirextion signals to the A axis on the BOB and connect your A axis drive to the A axis on the BOB.  You already have the parts to do it.  You just need to rewire a little and set up the A axis in Mach.

406

General Mach Discussion / Re: Z axis control PROBLEMS under THC control

« on: April 21, 2011, 12:06:17 AM »

Maybe a bad motor?  That's happened before.  It drove me nuts because the motor showed no signs of being bad.  It was the last thing I changed and it fixed the problem.  It's definitely not normal.  I did a job today that ran for 22 minutes.  An intricate design in 1/4" plate.

407

General Mach Discussion / Re: Z axis control PROBLEMS under THC control

« on: April 18, 2011, 09:14:44 PM »

I've seen missed steps with the THC set at higher than 40%, but it does that because THC Up/Down commands are at full speed...or a percentage of full speed...with no acceleration added.  I typically run it at 10-20%.  I bump it to 20 if the surface is highly irregular.  Everything seems to work best at between 10 and 15.

408

General Mach Discussion / Re: Growling Y AXIS Motor

« on: April 17, 2011, 07:34:39 PM »

What's the current draw on the motors?  What do you have for a power supply?  Try turning your acceleration down to 30 or so.  With your steps per unit at around 1800 per, you should be able to go back to 30 or so and not see any corner rounding in CV mode.  An inadequate power supply will also cause stalling.

409

General Mach Discussion / Re: Pockets Made Easy

« on: April 17, 2011, 07:22:25 PM »

Rest machining is what you're trying to do.  Machine using a large bit to remove the bulk of material, then come back with a smaller bit to get what the large one couldn't get.  Imagine you have a simple pocket with 1/32" radius corners.  Using rest machining you can run a large bit, like 3/8" first to clear most of the material, then follow with a 1/32" bit to finish the corners.  The toolpath for the 1/32" bit would only be generated for the portions of the part that the large bit could not machine due to it's size....IE: The corners.

Gerry explained how to do it manually.  Most 3D CAM programs do this automatically.  SheetCAM is 2/2.5D which is pobably why it doesn't.  In ArtCAM, you just list the tools you want to use from larges to smallest and it figures the toolpath for each tool automatically.

410

General Mach Discussion / Re: pwm

« on: April 17, 2011, 04:25:30 PM »

Not directly, but there are spindle drive boards out there that connect either via the PP or modbus.  Peter Homann sells both varieties I think.  Some break out boards have that built in.