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641  General CNC Chat / Show"N"Tell ( Your Machines) / Re: AL54b (lathe) project from New Zealand on: November 21, 2010, 07:06:33 AM
Thanks for the reply Dan, I don't see how motor voltage makes a difference as long as the PSU is also 50v can you please explain.
2:1 is the motor the 2 or the 1?

thanks.

Hi,

Read this guide on stepper motors: http://geckodrive.com/upload/Step%20Motor%20Basics%20Guide.pdf

A very informative one.

And yes, the motor does 2 revolutions for each revolution of the screw.

Dan
642  General CNC Chat / Show"N"Tell ( Your Machines) / Re: AL54b (lathe) project from New Zealand on: November 21, 2010, 01:44:59 AM
I will second what Hood said - belt drives are easier to setup and in my opinion are the correct way to build a good machine. I think a 2:1 reduction will work great with the motor you chose. Another thing to consider when choosing the drives is the motor voltage. The G251 are 50V, so motors should be rated not more than some 3-4V if you want to get the max speed out of them.

Dan
643  Mach Discussion / FAQs / Re: Losing steps or something? on: November 18, 2010, 05:40:13 AM
Hi Don,

Glad you got it sorted.

The PP issues still bother me though... so the problem is not fixed (nor found) Wink , but you rather found a workaround.

Dan
644  Mach Discussion / FAQs / Re: Losing steps or something? on: November 17, 2010, 04:44:16 AM
Hi Don,

Good news! And the signals look like they should be. I still wonder though why you were seeing those odd signals with the PP...

Dan
645  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
646  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
647  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
648  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
649  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
650  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
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