Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: guido666 on February 25, 2015, 01:07:13 PM
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I just added a PWM spindle to my machine (Mach3 > SmoothStepper USB > Gecko G540). Now it runs, but with some very odd symptoms:
- The spindle gets up to speed quickly (1sec?), but then slowly drops in speed... from 2500 RPM initially, down to <100, then stall, over the course of 2-3 minutes.
- If I check voltage across Ground->Speed pins at the spindle, I can watch it correspondingly drop slowly from 5V down until it stops, in tiny increments.
- Power cycling the spindle or Gecko G540 does not fix it.
- Stopping and restarting the spindle from in Mach3 does not fix it. In fact, if I stop the spindle, and restart it, it continues at whatever slow speed it was stopped at, and continues it's slow decline to stall.
- Changing the spindle acceleration in Motor Tuning of Mach3 has dramatic effects. A setting of 1 gives the "slow decline" behavior above. A setting of 5 causes the spindle to start, then stop within about 1-2 seconds. A setting of 10 causes the spindle to start accelerating and then decelerate to a stop before it even reaches full speed (<1sec), then it will do the same thing when the spindle is stopped in Mach3.
- Closing, and restarting Mach3, without turning off or resetting anything else, will reset the problem... resetting the spindle to its full speed, to start a new slow decline.
- Also, not sure if this is important, but I'm typing 2500 into the spindle box, Mach3 is showing 2500 in the sVo box, but the RPM box always shows less (~2415).
I'm thinking that since the problem persists until Mach3 is reloaded means the problem is likely in there somewhere. Anyone have any ideas?
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Vfd settings?
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Sounds like the VFD speed reference input is setup for 4-20ma instead of 0-10Vdc. Reading voltage of 5Vdc to ground is typical of 4-20ma... (1-5Vdc across the drive's internal 250 ohm resistor = 4-20ma). Typically there is a jumper on the VFD that has to be moved and then the VFD's speed reference input has to be programmed for 0-10Vdc so the rpm scaling is correct.
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Vfd settings?
They aren't really set to much. I enabled the spindle PWM, and set it to 50Hz in Mach3, and then enabled the spindle and set it to 50Hz in the SmoothStepper (USB) Mach3 plugin. The spindle's motor tuning settings are currently set to 5000 steps, 60, 1 accel... no real reason why, except playing with it from the 1000/60/1 settings I've seen recommended elsewhere.
Sounds like the VFD speed reference input is setup for 4-20ma instead of 0-10Vdc.
Is this a setting in software or a physical switch somewhere?
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Both are VFD specific... should be in the VFD user manual. The drive parameters have to be setup correctly. THEN the setting in Mach 3 have to be setup correctly. Just playing with the Mach setting alone will not fix the VFD problems.
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Unless I'm misunderstanding what I have (not impossible, though maybe unlikely) I'm guess that isn't it then.
This is the spindle controller... http://littlemachineshop.com/products/product_view.php?ProductID=4213&category=
The instructions ( http://littlemachineshop.com/instructions/4213CNCSpindleControlUpgradeKit.pdf ) include a wiring diagram to the G540 (page 8 ), and I have it set up as described. There are no jumpers, DIP switches, or other adjustments on the board (besides a potentiometer for speed adjustment, which I've tried in many positions with no change in effect, besides top speed). I know what they say about assumptions, but I'm taking this to be an indirect confirmation that it's known to work with the G540.
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Contact the seller and ask for help. The wiring diagram shows a AC motor and connection but it's labeled as a DC motor?? The specs also state DC brushless motor control?? Which is it AC or DC?
Good Luck...
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Is there a reason you think it would be on the spindle or spindle controller side of things? If I wire the spindle controller up manually (e.g. just jumpered, not connected to G540) it runs fine. The speed voltage signal from the G540 drops slowly over time, and since it resets happily when Mach3 is restarted it seems logical that the "issue" would exist in Mach3 or the SmoothStepper plugin for Mach3. Do you disagree? Why?
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The seller has a 800 number to call.... best bet is contact them for help. One issue I see (and it may not be an issue) is the controller is 0-5Vdc where as Mach 3, ESS and Gecko 540 are all 0-10Vdc speed references. Could be a scaling issue. What I read is this is for a DC brushless motor??
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I really can't understand how it would be the spindle, since the spindle runs perfectly if manually connected (not to the G540). I called them anyways... and they had nothing to offer. They said if it works when wired up manually ("simple connections" in the manual), then their side of things works... which sounds reasonable.
I understand what you're saying about 10V vs 5V, but then it should run at 1/2 speed at least.
I'm waiting to hear back from SmoothStepper support too.
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Gecko 540 0-10V output is voltage sinking which means it has to have a external power source... in this case the speed controller's power supply. Its a long shot but the power supply for the controller may not be capable of providing enough current for the Gecko. Could test the Gecko by using a 9v battery (Terminal 9+ and 8-) in series with a multimeter and see if the voltage drops. This will eliminate the speed controller's 0-5v.
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Good idea, I'll try that when I get home!
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I'm still going to try it, but now I'm skeptical it will work. Anything that fixed it would need to explain why restarting Mach3 fixes the problem, and is the ONLY thing that fixes the problem, plus the acceleration issue.
Any problems in the the spindle, spindle controller, or G540 should be able to be fixed by restarting those, and unaffected by restarting Mach3. That's obviously the opposite of what's happening. That really only leaves the SmoothStepper USB, the SmoothStepper USB plugin for Mach3, and Mach3 itself. Which of course is why I came to post on these forums in the first place.
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Can't you just follow the voltage level feeding the controller. Check the voltage level feeding the Controller. IF the voltage level is not constant follow it all the way back to the source. What is feeding the logic to control the speed in teh G540 is it step/dir or PMW. Check those levels coming out of Mach3 to the G540. I can't see that being able to droop to zero. (But never say never) The G540 just takes those values and converts to 0-+10 which is feed from the controller. The controller seems to be the culprit Check for a steady level voltage that feeds the G540 . IF the voltage level at that point is steady then it points to the G540 ?
Just a thought,
(;-) TP
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I can see the PWM feeding the G540, and it seems ok, but I don't have an oscilloscope to see what the PWM signal is doing. The way I understand it, the G540 is looking at the duration of the PWM pulses, whatever percentage of the pulse cycle is high (say, 50%) it then makes an output voltage that is also that percentage of the input voltage (such as 2.5V is 50% of 5V input).
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OK then Check the output voltage from the g540 to the controller while running IS it drooping as time passes or does it remain steady ?? IF drooping then check the out voltage from the controller to the G540. It is steady or drooping. If steady then the problem maybe G540 IF drooping it maybe the controller Power supply drooping under load. IF needed install an outside PS to power up the G540 VFD voltage input. Wallwarts are cheap. Just make sure it has enough capacity so it does not droop.
Follow the voltage trail,
(;) TP
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I just checked, and the spindle controller supplies a solid 5.01V the whole time, it doesn't drop. The G540 output voltage to control spindle speed drops slowly (e.g. 5.00V, 4.98V, 4.95V, 4.94V...).
So it looks like the spindle and spindle controller can be excluded as the cause.
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Can you check the PMW with a volt meter ?? The higher the % the higher the voltage ?
(;-) TP
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Not really, I'd need an oscilloscope.
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Have you tried it ?? Do you have another PC to test with or another lpt port ?
Just a thought, (;-) TP
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It's a USB SmoothStepper, but yes, I could probably get another computer into the garage tomorrow and try it.
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IF it is a SMOOTHSTEPPER then forget the spare PC as the SS does all the PMW ouput work not the PC. Just check the output from the SS.
(;-) TP
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Does the SS have it's own +5 volt power supply or is it using the USB port power. The USB port may not be capable of powering the SS. There are a few postings about the PC's USB port +5v power problems with USB SS.
I have a Ethernet SS with a Gecko 540 controlling a VFD (0-10V) without issues. However, the ESS has it's own +5v supply.
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The SS does not have it's own power supply.
I plugged it into another computer, this time a desktop instead of the regular laptop, and used the same Mach3 .XML profile. The same thing happened, and is oddly still affected by the spindle's acceleration setting.
I also tried both the .24 and .30 USB drivers, and the 17F and 17FE Mach3 plugins. Same results.
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I dought that this is a sotware problem it is very much like a hardware problem Sagging power. Using a SS it was not usefull to swap PCS as the PC does not control the PMW to the Spindle controller the SS does. DID you check the incoming voltage to the SS. You have very limited power from the PC's USB port. Try supplying power to the SS with an outside power supply.
Have you talked to Greg over at Warp9 to see what he thought ?
(;-)TP
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I emailed Greg, and he responded that he wouldn't be able to respond until Wednesday (4 days ago), and I haven't gotten a response to any of my emails after that. I'm hoping he'll have something insightful, once he gets a chance to respond.
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An external 5V power supply didn't change anything.
I did flip the Active Low for the spindle step pin back off, because speed was operating in reverse (higher setting got slower speeds). I can get constant spindle RPM now, but it's way off "specified" value.
Some questions...
1. When I set the speed to 2500, Mach3 fills in the "S-ov" field to 2500, and RPM gets something value that winds up to about 95%, such as 2377. See attached picture. What does "S-ov" mean? Is this RPM value being off normal? I have a pulley ratio of 1, so shouldn't it just be 2500? Why does the RPM value ramp up, then stabilize?
2. I checked everything, and the spindle is providing 5.01V, and getting back 3.58-3.70V at 2500 (of 2800 MAX) RPM. This happens repeatably regardless of which of the two computers I hook to, and whether I use USB 5V or external 5V. So it seems like it's happening on purpose.
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Also, can someone explain the spindle motor tuning settings, as they pertain to PWM spindles, better? The Mach3 manual does not provide very thorough explanations, and I'm pretty lost.
1. Steps Per: What does this do? (I know what it does for a stepper, but how about here?) I've tried settings from 100 to 20,000, and all it seems to do is change how fast the spindle speeds up. Smaller settings result in smaller speedup, so 200 takes like 2 minutes, and 10000 takes like 10 sec. Does this have an effect on the problem posted above, where RPM never reaches the speed I set, or the voltage being less than max at full speed for the pulley?
2. Velocity: What does this mean for a spindle? Does it affect maximum speed? Nothing I change in here seems to affect anything obvious. Also, sometimes Mach3 forcibly sets it to something I can't change, I'm guessing based on my Steps Per and Acceleration values.
3. Acceleration: What do I want to put here? Obviously bigger numbers seem to result in faster acceleration, but how do I computer/know what it should be? Is it related to Steps Per and/or Velocity?
4. Step Pulse / Dir Pulse: Do settings here have any effect on PWM spindles? Changing them doesn't seem to have any effect.