[corrie]

not sure if this is the place to ask this question but here it goes. What would cause all three axes to move when jogging only one axes , directly after startup. Problem goes away after jogging a different axes.And all seems fine after. Thanks.

[trubleshtr]

Are they trying to find home position or locate the marker pulse on the encoder of the axis?
what type of machine/controls?

[corrie]

Hello Shooter, no encoders,running Mach3.The axes, all three are usually left in the center of the table.What happens is this, i,ll start the computer, launch Mach, turn on the power supply, jog the Z with shift button pressed while pageing up or down,depends if anything may be in the way.At this point all three axes move simultaneously. While holding the shift, I,ll move the Y and all seems normal. Keyboard is not USB,nor the mouse.I also noticed that while in a holding pattern I can hear the X-axes creeping/stepping slowly and spuraticaly but the DRO shows no X movement in numbers. I may have to put a seperate P.Port...The P.C is a IBM net vista ,no virus protection and all background saving features are turned off ,including updates.I had someone put a scope on the power supply and some slight noise is visible.By all means I,m not any type of electronics Guru,far from it,..... I,m stumped. Thanks in advance and hope my info can help you think of something,cheers,Corrie.

[trubleshtr]

Hmm and thisis only at start up you say...I thought maybe you need to tune the drives/adjust any gains going to the axis...but if it is only at start up????
Is it possible you are picking up some "noise" on the feedback and the drive starts trying to compensate?
I am sure there are other guys here at the zone that have seen this before.

[corrie]

I,m going to look into the breakout board it might be the culprit. It,s almost like cross talk between the axes.If not the B.O.B then it must be the P.Port.This may explain some of the lost steps when doing a 3d carve,not sure though.Where in canada are you?Cheers and thanks.

[corrie]

Well as stated before I could hear my X axes creeping but giving no DRO movement, and now all three axes are creeping simultaneously. Now scratching my head with both hands instead of one any ideas, anyone.

[trubleshtr]

Well, something in the way of power has to be coming down the line to the motors to make them move.
If you know how...?With a volt meter on the motor connector, measure what you are getting when it is drifting. Work your way back to the drive and then power supply to trace it.

[corrie]

Hey Shooter, is this probing to be done with only the controller powered up while the axes are moving or should the computer be connected as well.

[trubleshtr]

Hi Corrie,
I would unplug the break out board from the pc so you know that no step and direction signal is being sent to the drives. Turn your power supply on. If the axes start creeping, measure the votage at the drive output.
The drive should not be allowing anything to go out to the motors until the step and direction signals are sent to the drive in a normal situation.
Check also the voltage coming out of the power supply. If the output from the power supply is within the range that you built it to, and does not exceed the rated voltage for the drive, then you should be ok.
If you are seeing voltage coming out the drive to the motors then your drives are not "holding back" the voltage and or current until commanded by the BOB to go. The other test would be to check the currrent coming out of the power supply, but that will be a little more tricky.....

[Torchhead]

Motor drives move for one reason. They are getting a signal into the Step & Dir inputs that "tells" them to move. Noise on the power supply will not make them move. With no signals to the drives (from a lower impedance source like a buffered parallel port) they may be picking up noise but should never move when you have everything hooked up and no signals being sent.

See, chopper drives use a method called PWM (pulse width modulation) it turns the windings on/off at some higher frequency (16KHZ for the drive you have). It is at high current. Move a signal across a wire at high current and turn it off and on at a frequency and it forms (drum roll) a transmitter. The signal can feedback and effect parts of the logic. I have seen the signal get back into the PC and parallel port. The fact the DRO's in MACH do not move shows MACH is not sending the signals. Noise is funny stuff. It will travel down grounds and cross talk between conductors running in parallel.

Part of the design process in power electronics is to understand the paths for noise transmission and deal with it with proper layout. The input circuits need a level of noise immunity.

I can't tell if the inputs on the drive are opto isolated. If they are not the drive motors, drive components and low level logic all share the same ground path. That can be problematic if grounding is not done correctly.

Your BOB could be at fault but it would be unusual for it to produce crosstalk at logic levels. If you have your BOB mounted close (in the same case) as the motor drives try taking the BOB outside the case and running it that way. The PWM from the motors may be getting into the low level inputs of the BOB. Make sure your BOB is a power version and has bufferes on the step & dir lines. Better yet that it has opto isolation on all of the INPUTS.

TOM CAUDLE
www.CandCNC.com
Totally Modular CNC Electronics.

[corrie]

Thanks for the replies gentlemen. While no P.C was hooked up I turned on the controller briefly but left the P.P cable attached to the B.O.B and all axes moved.I did this agian without the P.P cable attached and the axes still moved but there was a five second delay before they moved. The B.O.B is in the same case,yes.I may have to get a larger case and reconfigure the internals.I,ll post a pick as I can giving a closer view of part placement.Thanks to you both for your replies.

[corrie]

Hello folks, thought I would chime in with the latest news. The owner of Durham robotics came over today and installed a revamped B.O.B. Also, we tried out some Gecko 203v,s and I gotta tell ya what a difference. The Geckos were mounted to a large piece if 3/4 aluminum with heat sinks on opposite side and mounted on edge, will post pics later. I,ll run some code tommorrow and let you all know how it turned out.Thanks for the help Gary, I appreciate it. Also thanks to the good people here that chimed in with their thoughts,thanks.

[corrie]

Good day all, thought I would post a pic of a carving I did yesterday with the new setup. Eagle dimensions are 3x1.125x .093. I used a 30 degree v-bit .015 and I think it was around 8% stepover or less at 100 I.P.M. Compared to many other carvings the new setup proved out well.

[trubleshtr]

Ahh finally someone with some electronic background....thank you Tom.

[trubleshtr]

Hey look at that, good job! Thanks for posting your results.
So in the end it was a new drive set-up and a new BOB?...I suspect your old drives were damaged?

[corrie]

Hello Shooter, not sure if it was the drives or not ,but I would put my money on the BOB. Garry will fill me in on that. But none the less the gecko,s realy rock.garry must have spent a better part of that day helping me out,good guy.Maybe if Garry gets any info on the culprit he may chime in on this thread.I,m still running some test files and see how things progress. Will take a picture of my setup latter,cheers.

[corrie]

Here are some pics of what kind of accuracy my machine is up to after installing the Gecko,s and rebuilt BOB,cheers.