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641  General CNC Chat / Show"N"Tell ( Your Machines) / Re: AL54b (lathe) project from New Zealand on: November 15, 2010, 01:22:47 AM
Good project and very interesting thread to follow.

I must say that you're making progress faster than I am able to read Wink Keep it up!

Dan
642  Tangent Corner / Bargain Basement / Re: Back Covers For Stepper Motors on: November 13, 2010, 12:52:26 PM
Hi,

Just a follow up that the first batch of 60mm covers is finished. See here for details:

http://dyengineering.com/60mm.html

Thanks,
Dan
643  Mach Discussion / Mach SDK plugin questions and answers. / Re: Impact engraving plugin on: November 10, 2010, 02:17:17 AM
Hi Andrea,

Sorry, didn't had the time to read through your post, just saw a familiar photo and thought that impact engraving could do this.

Anyway, just read through your posts and I find your approach for driving the magnet very interesting. However, I wonder why can't one use a MOSFET to switch the magnet? Isn't it fast enough?

Also, if you increase the kernel speed, can you go faster than 300mm/min? Or is it a hardware (magnet) limitation?

I've seen on a few occasions impact engraving letters and lines with Mach, but this kind of work is just incredible! Thanks for sharing your results!

Dan
644  Mach Discussion / Mach SDK plugin questions and answers. / Re: Impact engraving plugin on: November 09, 2010, 02:19:04 PM
The third picture in the first message - isn't it Tweakie's laser engraved image? Looks exactly the same:

http://www.machsupport.com/forum/index.php/topic,12444.msg110555.html#msg110555

Dan
645  Mach Discussion / FAQs / Re: Losing steps or something? on: November 09, 2010, 12:51:08 AM
Hi, Again.  First, Duh!  The 1Volt O'scope readings are my fault.  The variable gain on the scope was set.  Now the traces show 3V logic for everything. 

Glad you discovered it, Don. Was actually hoping you'd find a similar fault of yours with the direction pulsing issue Wink

Hi, again Dan.  It appeared after I installed the dwell in the program that the offsetting went away except at the extremely slow acceleration rate of 0.5...  Why would very slow accel. cause the steps/direction signals to malfunction?

Have got no explanation to this at this point.

The fact that sometimes the pulses are leading vs. lagging bothers me a lot.  I would expect that the direction pulses ( if they are supposed to be pulses) wouls stay in the proper timing sequence.  The two O'scope pictures show clearly a timing difference, sometimes during the same line  of code execution. 
Thanks for the help, Don

This is something to be worried about indeed. Absolutely not the way it was meant to be.


I just tried the jog mode.  Set the Dir Pin to Pin 2 hooked up the scope to pin 2 and ground, terminated the pin with a 4.7k resistor to ground, and set the jog rate to 30% feedrate.  Note that the little ticks on the lower part of the trace are the screen reticle.  The timing of the direction "Pulses" seems to be varying, even across the screen.

Again, this needs to be investigated. Have never tried to look at the Mach signals with a scope, but I do know that I can measure the direction state with a voltmeter and it would show 5V or 0V depending on the direction. Could be Brian has changed something in last versions...? Don't think so. But would be nice of him to chime in here and confirm this.

When I ran jog at 100%, the trace was jittering and flickering.  Not steady.  It is definitely not setting a steady state!

A symptom of a not perfect driver test, though yours looks good (if the picture shows the worst case).

Dan
646  Mach Discussion / FAQs / Re: Losing steps or something? on: November 08, 2010, 04:45:50 AM
Hi Don,

That is a nice debugging feature of the PMDX that you discovered. It proved what we had already been guessing - that everything after the Geckos outputs was fine. The problem is somewhere between Mach3 and Geckos inputs.

So are you saying that the offsetting disappears at higher acceleration rates? Interesting... if so you have the solution now, but don't know the cause yet.

Anyway, I really don't like your pictures of the signals. Something is surely wrong there. Can you connect the scope in exactly the same manner to the PMDX outputs while it's set to demo mode? Would be interesting to see the signals. For some reason, I am thinking your scope is not set right. Can you just use one channel and look at the direction signal? Just set the scope to DC mode and jog each side. I am pretty much sure that the direction is a state and should look like a DC line on the scope.

Dan
647  Mach Discussion / FAQs / Re: Losing steps or something? on: November 05, 2010, 01:33:11 AM
Yes, those pulses ARE strange. The direction line is a state and shouldn't be pulsing! The way it looks I am amazed your motors were rotating anyway... Are you sure the scope is set up correctly?

Dan
648  Mach Discussion / FAQs / Re: Losing steps or something? on: November 04, 2010, 02:43:52 AM
I would like to note that it is not as easy as it may look trying to capture the timing between the step and direction signals using a plain scope. Thing is there is also the motor acceleration factor and the step pulse stream is not going to be constant frequency. One could probably try a very slow speed and VERY small acceleration and even then it's not going to be easy.

May be you could try in Incremental Jog mode, defining ONE motor step there...? But don't know if your scope can capture a single pulse.

Dan
649  Mach Discussion / FAQs / Re: Losing steps or something? on: November 03, 2010, 02:30:44 AM
Hi Roger,

The Step Pulse parameter is how many micro-seconds are added to the base step pulse width (don't remember what it is). I think the label is wrong and it would accept values 0-15.

Dan
650  Mach Discussion / FAQs / Re: Losing steps or something? on: November 02, 2010, 10:22:17 AM
Hi Roger,

I was talking about the Dir setting under Motor Tuning. The value there is how many micro-seconds before the first step in the opposite direction, the Dir pulse changes state. You are correct about the direction line that its Hi or Low state essentially defines the direction of the motor rotation. But the timing is critical here. Change it too soon and you lose one step in the current direction, too late you gain one.

Yes, the SS and the BOB were screwing the timing. It was an abnormal condition that was fixed with a new plugin for the SS. The opto-isolators on the BOB also were changing the timing slightly, but the change was so small that with the perfect timing of the fixed SS plugin it had no effect on the operation, but with the (rather "not perfect") timing of the PP it was adding up to a more substantial change that was affecting the operation.

Dan
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