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Messages - TunerTom

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31
General Mach Discussion / Re: Really need help
« on: August 12, 2009, 04:52:10 PM »
Hood,

I will gladly buy the SS if someone thinks it will help.
If there is some glaring error in my present setup, I hope somebody will tell me...


Tom

32
General Mach Discussion / Re: Really need help
« on: August 12, 2009, 04:35:58 PM »
I'm in Massillon, Ohio, USA

Are you near Loch Ness?

33
General Mach Discussion / Really need help
« on: August 12, 2009, 03:57:58 PM »
I see the Smooth Stepper discussion area is not taking new posts.

I have been working with Mach3 for about three months now and am convinced that this application is working well for most of you, but I continue to have problems with instability (losing steps) and am curious if anybody thinks adding a Smooth Stepper card might help me.

Right now I have a PC running Windows XP dedicated to this project.  I have run the System Test and it reports the system tests OK, and the "spikes" are nice & short... I have also uninstalled all programs from that PC except for Mach3 a G-Code editor, a file comparison utility, and a Parallel port monitor (none of which which are running when Mach3 is running) I have the graphic toolpath display turned off.

My PC inputs data from LPT1 to a Probotix PBX-RF RF Isolated CNC Breakout Board (and a Probotix relay board for spindle on/off) and tailstock (extend/retract).  The oputput ot the RF isolator is wired into a Slo-Syn SS2000-DP4 drive and two Slo-Syn KML092F07 Stepper motors.  I'm using Mach3 Turn. Everything works, except that the stepper motors (particularly the Z-Axis) fail to return exactly to their starting points, as My g-code calls for at the end of a run.

I have shielded cable from the output of the Probotix card, but the card itself is not installed inside a grounded metal enclosure. The output of the drive connects to the stepper motors using shielded cable. The shield is tied to earth ground. There is a splice at each stepper motor, and from there the wiring is exposed. The shield is tied to earth ground. The exposed leads are about 3" long at each motor. The Z-Axis motor is particularly unstable; it misses the home position most of the time and the error ranges from (say) three or four pulses to maybe 25 pulses. Once in a "blue moon", Z will return to zero. X is the other way. X might miss 1 or two steps "once in a blue moon" but returns exactly to zero, most of the time.

I have tried numerous settings of maximum speed settings in Motor Tuning; I have tried numerous settings of Accel/Decel to no avail.  I have tried using the Sherline 1/2 step mode, which helps occasionally. I have turned Sherline off and tried pulse widths as high as 14. (I read that 15 or higher can cause the system to lock up). A max speed of 300 mm/min would be nice to obtain.

I wrote a simple G-code program that exercises the saddle in the Z-Axis back & forth at full speed (G0) for 50mm four times... then the X-Axis in/out 50mm four times at full speed (G0) four times.  This profile NEVER MISSES! The problem seems to show up when curring curves and both motors are running simultaneously at varying rates...

There has to be an answer to this problem.
Is there anything wrong with my choice of the Probotix RF isolator?
Would getting a Smooth-stepper card help?  If so, does the Smooth Stepper provide the necessary isolation? Should I then install a simple breakout board on the Probotix's place?
I'm going to go to the shop tomorrow and run through the procedures in your report to optimixe Windows... Maybe that will help.

Any suggestions or answers would be greatly appreciated.
I like the idea of the Smooth Stepper using the USB port and that it's parallel pouts are probably more stable than the PCs LPT1 port.
It even suggests that we might be able to use a laptop at the lathe... Another plus for us...

My sincere thanks for any advice you might be able to share...

34
Thanks...

35
Thanks for your help.

One question...  Since this all seems to have to do with timing issues. Are there advantages to increasing thw kernel speed  (currently at 25000).
That would mean recalibrating the motor speeds again (sigh) maybe, I should simply leave well enough alone.

Thank God, it doesn't appear I need to rewire the stepper motors...

Tom

36
I think I have found the problem.
I have turned "Tool Path" off, in Debug, and I reduced the Accel rate for the "X" motor from 100 to 75.

I have run the complete profile four times on the plotter and the pen path has superimposed itself exactly on top of the previous drawings and both the "X" & "Z" handwheels have returned to their starting posiitions every time.

37
I have a mark on the handwheel that I line up when I begin the process. If I plot the entire profile including the curves, the marks do not line up at the end of the run. It takes two single-step clicks to get the marks to line up on the X-Axis.  The DRO is showing the correct number at the end of the run. After I correct to get the marks to line up, the DRO is off by two 0.04mm... or 0.08mm repeatedly. I have to re-set the DRO. Once I line the marks up again, re-running the profile does the same thing.

If I'm doing this with the pen plotter, the second (and third) retrace sits exactly atop the previous provided I adjust "X" before re-running.

I've played around with motor tuning and acceleraton to no avail...

If I skip the curves, the plot returns exactly as it is supposed to... over & over.

I have other profiles that do not have curves. and they also work just fine.

If the problen has to do with electrical noise, it seems strange to me that the tathe and the plotter would act the same. They are in different electrical environments.

I must tell you, that the stepper-motor wiring is not shielded. The cables are relatively short but they pass through a pair of DPDT 5toggle switches.  The switches allow another computer to connect to the systems that runs DOS (and profiles written in Microsoft Basic).   This was intended to be an intrim hookup that would allow the older PC ro turn parts until we get the new system debugged.

Is that a mistake to even try?

38
I have a "Home-Brew" lathe fitted with SloSyn SS2000-DP4 drive and a Probotix PBK-RF isolator.  The Mach-3 software is licensed. I also have an XY plotter at home, I use for debugging profiles.  I have been running profiles on the lathe that consist entirely of straight lines and the lathe will return to its starting point, precisely and exactly... ready to start another piece without any compensation, over and over...

I am running Mach-3 Turn, in the Diameter mode.

I am having trouble running profiles that contain arcs.  At the end of a run, the X-Axis returns short of its starting point by two pulses, repeatedly. Motors are 200 pulses/revolution... 50 pulses/mm. In Diameter mode, the X-Axis in incrementing in 0.04mm steps; the Z-Axis (of course) increments at 0.02mm/step. So my "Return to Zero" is "dead on" for the Z-Axis, but 0.08mm shy for the X-Axis.  If I remove the "curves", thus skipping over them, the cutting point returns to zero, every time.

My question is...  Do you think the intermediate calculations for the curves seek points beyond the resolution of my stepper motors? Could this be the source of my problem?  I can control the end points of each line in the G-Code, to make sure the value for X divides evenly by 0.04mm, but I have no control over internally-calculated values for X when the curves are plotted.

I DO have "Steps Per" set to 50 in the X-Axis motor Tuning.  Could there be something else I am missing?



39
I was told on an earlier post that Mach-3 Turn has some bugs in the Front-Tool/Rear-Tool definitions, and tht I should list both tools as (say) Front-Tools and use the X-Offset for the Rear-Tool to declare the distance between them.

OK... I have a turning stock chucked up...
   Diameter  27.92 mm
   Radius    13.96 ..

Start the spindle...
Select Tool #1 (front)
Jog the front tool forward until is just touches the turning stock
Set the "X"=DRO at 13.96
without changing anything, Jog back until the rear tool just touches the back side
Make note of the "X"-DRO...  72.28 and we are at -13.96 for Tool #1 (we still have Tool #1 selected)
So add 13.96 to 72.28... The X=Offset between the tools should be 86.24
Set the X-Ofset for Tool #3, (my "Rear-Tool") at 86.24  (see attached screen shot)

Now with Tool #1 selected...
T0101
G01 X13.96  F150.0
should position the front tool, just touching the front surface, which it does.

Then enter...
T0303
G01 X-13.96  F150.0
should position the rear tool, just touching the rear surface of the turning stock, but it does not.
There must ba a 20 mm gap between the Rear-Tool and the Turning Stock.

Am I doing this incorrectly?

40
General Mach Discussion / Re: Problem with Jog Step Mode
« on: May 31, 2009, 11:48:08 AM »
OK,  I am not at the lathe this morning, but I see what you are saying.  I did not realize what the "Steps Per" did. I will try this at work tomorrow.

Thanks for sharing...

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