Messages

11

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 03:51:18 PM »

 I'm not sure exactly but it seems to be about 1.5:1 or so. The timing index to spindle is 1:1 and I have confirmed that only 1:1 should be entered in the pulley ratio box.

12

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 03:14:02 PM »

I did. The minimum and maximum seem to define the 0-10V relationship with the S word in the Gcode and within the screen input DRO. Beyond that they don't have any effect.

13

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 03:03:28 PM »

Full speed as defined in the pulley ratios tab by the maximum RPM outputs a 10V signal and half speed represents a 5V signal. Likewise, when 5V goes into the VFD I'm getting 30hz out, 10V  = 60hz. The pisser is that the motor isn't connected to the spindle w/ a 1:1 gear ratio. This is why I originally thought setting the pulley ratio would be ok, but that effects the index pulse ratio and thus throws off my IPR calculation. Brian obviously acknowledged this issue since there is the auto spindle calibration function.

14

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 02:51:37 PM »

 Been there done that. The spindle motor tuning tab doesn't seem to have any effect on the relationship between the 0-10V output and the RPM actually commanded. I wish there was a way to manually set the modification values which the auto spindle tune is coming up with.

15

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 02:34:20 PM »

 The VFD is being controlled through the C32 breakoutboard via analog 0-10V PWM. Using the auto spindle calibration feature in Mach did work, it just isn't as accurate as I'd like. I can manually tweak the voltage signal on the BoB to tune in a particular setting, but if I get 500rpm right on, 1000rpm is compromised. It seems like the auto calibrate routine should work better than it does...

16

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 14, 2013, 09:15:57 AM »

SOLVED:

I was able to turn some very nice threads last night after figuring out the last of my issues. As I mentioned above the error between the two slots in my timing disc was the source of the inconsistent pitch issue. I suspect this particular problem was rather unique to my system since my index wheel rotates at exactly 1/2 the speed of the spindle. I have two slots on the disc so that my timing index still reflects a 1:1 ratio. Most people would have one slot because they are running the disc at the same speed as the spindle.

The problem with the pitch being wrong was also related to ratios. At first I thought maybe my Z axis calibration was wrong but it was spot on. In my pulley setup screen I had modified my pulley ratio to make the VFD and the RPM readout match. This was WRONG. The pulley ratio will reflect the ratio between the index signal and true spindle speed. I could have used this to keep just 1 slot on the disc with a 0.5:1 ratio, but instead I had the ratio set to 1.5:1. I only realized this error when it occured to me that the pitch I wanted was exactly 2/3rds of what I was actually cutting. Well, guess what 1/1.5 is? ) 0.667. When I changed my pulley ratio to 1:1 it cut a perfect 8tpi thread.

Since I changed the ratio on the pulley the VFD and the RPM readout were now significantly off. I fiddled with the rather miserable automatic spindle calibration function in Mach3 for an hour before I got the numbers somewhat close. They still are not the same (500rpm setting reads 460, 600rpm setting reads 600, 1300rpm setting reads 1100) but at this point I don't care much.

17

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 13, 2013, 02:41:38 PM »

OK. I milled two precise slots with the CNC mill and eliminated the shift in the signal between slot 1 and 2. I turned the index debounce to 0. As a result the threading cycle seems to be working significantly better. It seems to want to cut an 11 pitch thread instead of an 8 pitch thread but I think I need to go back and revisit the Z axis steps per inch calibration since it seems to have also cut another surface on the component at 5.95" when it should have cut it to 6.00". I also need to go back and read the threading manual again. I'll report back once I have these last few bugs straightened out.

Thanks for the help.

18

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 12, 2013, 07:49:32 PM »

Its actually backwards from that. The spindle rotates twice for every 1 disc rotation. I thought about tuning it back in the ESS dialogue but then I'd have half the threading resolution and I already consider 1 tick per revolution to be barely adequate. The slots in the disc are hand ground. I'm going to throw it in the mill and cut two precise slots to get rid of that differential you saw in the scope on the video. Do you feel like that is the core problem here?

19

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 12, 2013, 05:50:50 PM »

http://www.youtube.com/watch?v=eCZo9f5JKRg

Have a look at this folks and let me know what you think. My only thought is the timing pulse disc might need some tweaking on the slot timing.

20

General Mach Discussion / Re: Mach Turn Index Pulse and IPR question

« on: January 12, 2013, 02:20:30 PM »

I thought about the refresh of graphics now allowing the LED to keep up. This would make sense to me if I was dropping visual index pulses @ 1000+ RPM but even when turning it by hand at maybe 40 RPM I lose LED pulses on the diagnostics page. I'll get the "tick tick tick blank tick blank tick tick tick". At 500RPM I can see the LED's on the C3 and C32 flickering at approx. 8-9hz...clearly visible. The Mach LED's should be able to display consistently at these low frequencies but they are not. I'm headed out now to check out the circuit with the scope and will report back.