Messages

41

General Mach Discussion / Re: Steppers out of sync and skipped steps?

« on: February 18, 2011, 07:36:16 AM »

Nah I know it's not going to be the best machine ever, however I've come this far, not going to let some off centre pulleys stop me

42

General Mach Discussion / Re: Steppers out of sync and skipped steps?

« on: February 18, 2011, 07:13:28 AM »

No, I made sure that all the stepper driver chip ratings were not exceeded. These are only small steppers, they dont have to move anything close to the 100 pounds you mention.

One thing that crossed my mind was, the holes in the pulleys are a few mm too big for my stepper shafts. Could off centre pulleys tightening and loosening the belt cause the steppers to miss steps? My thoughts say yes, although I'm not sure what the correct method for properly fitting them on the shafts are.

Somehting else just came to mind. At the moment, between the stepper shaft and the pulley, there is a bit of silicone tubing that helps keep the pulleys centred. it could even be a case of the pulleys slipping on the shaft.

How are you supposed to deal with shafts being too small for the pulley?

Cheers,
Dan

43

General Mach Discussion / Re: Steppers out of sync and skipped steps?

« on: February 17, 2011, 09:49:18 AM »

The 2 steppers on each belt are wired together, with 1 wired in reverse obviously so it spins the other way. They are in parallel, not series, so I think they should be fine running like that.

What would the belt do to drop steps? Too tight/too lose? I didn't do the belts up extremely tight, but they aren't loose either.

I think all of the axes actually loose steps, which would point to more of a software problem (Maybe the parallel port priority idea?), although the 2 sides not running together is a bit odd. The way the steppers are wires, each of them should do the exact opposite of each other.

I didn't consider interference on the controller board, might try covering it in some foil and grounding it.

Cheers,
Dan

44

General Mach Discussion / Steppers out of sync and skipped steps?

« on: February 17, 2011, 06:18:55 AM »

Hi, I've finished the X axis on my DIY laser cutter (I keep calling it Y in the video!)

http://www.youtube.com/watch?v=lepq-4LaV4g

I explain it in the video, sorry about the video being so dark, didn't realize until after I had filmed it.

Basically, I have 2 belts to move the X axis, with 2 steppers on each belt (4 steppers in total)

2 of these steppers are wired onto channel A on my controller board, and slaved.

Now for some reason, my steppers occasionally seem to loose steps, and the right side of the X axis seems to loose significantly more, and eventually they get so out of sync the carriage comes off the track!

The steppers have plenty of torque, and don't make any kind of noises to suggest they are skipping steps, they are set to 1/8 microstepping and 200 steps per in Mach3.

I have tried increasing the dir and step pulse durations with no success. One theory I have is that the computer is occasionally provided with a background task, which causes the parallel port to loose priority and miss steps, while Mach3 is still counting.

Anyone else have this problem?

Cheers,
Dan

45

General Mach Discussion / Re: Doubling up output?

« on: January 15, 2011, 05:27:57 AM »

Ah, perfect! Cheers Hood

46

General Mach Discussion / Doubling up output?

« on: January 15, 2011, 02:43:22 AM »

Hi, for my DIY laser cutter, I am going to use 4 stepper motors for the Y axis, and 2 for the X. The 2 for the X I have already tried with my CNC controller and Mach 3, and they work beautifully. However, reading the specification sheet on the stepper driver chips, they are only rated for around 1.5A continous each, 2 steppers just falls under this limit, however 4 seems like a bit too much for 1 driver.

My CNC controller is just a generic 4 axis Chinese board, however I was wondering, is there a way to have mach3 output Y axis pulses to 2 sets of pins? I don't htink there is, and if not, I can simply connect the step and dir pins from 1 chip to the other, but if I could do it in software, no point wasting solder

Cheers,
Dan

47

General Mach Discussion / Mach3 and laser?

« on: January 10, 2011, 11:21:55 PM »

Hi, I'm currently building a laser cutter, and making great progress! Instead of copying a whole thread, if you'd like to know more about it, I've got a thread going here: http://laserpointerforums.com/f57/my-holiday-project-d-58283.html

Anyway, I have a question about using mach3 to control a laser. I have a 4 axis CNC controller board (Generic Chinese one), and it has a spindle relay. It works, however it only turns on when you start a program, and off when the program stops. I can see that the Z axis is what I actually need to control the laser, but I'm not sure how. Also having mach3 able to control the power thru PWM would be nice, however just simple on/off is fine as well.

I'm lost here, and very new to this, so any help would be appreciated

Cheers,
Dan