Messages

991

General Mach Discussion / Re: BLDC Motor Control

« on: September 17, 2009, 01:36:32 PM »

Thanks for your thoughts.  I will try to bypass the internal wiring, which is all bunched together, with a screened feed.

I am not happy with the PWM frequency and the low number of speed change steps but I do not know the requirements of the motor control.

I looked at the outline spec. of a SANGMUTAN control unit on another thread and that stated 500Hz to 5kHz I think so I guess I am about right.

When I look at the PWM signal on 25 way cable, Pin 2 in my case the pulses come in blocks with gaps between.  Is this normal?

Thanks again.

No, that absolutely is NOT normal, and you should have very fine resolution on the PWM duty cycle.  I can easily set my VFD frequency anywhere from 0 to 90Hz, with 0.1Hz precision, using the Mach PWM output.

What settings are you using?  Pulse Width, Steps/Unit, etc.  Any pulleys setup in Mach?

Regards,
Ray L.

992

General Mach Discussion / Re: BLDC Motor Control

« on: September 17, 2009, 10:32:01 AM »

FWIW - I use PWM for my spindle, andit works perfectly.  Very fine resolution, and perfectly linear response across the entire range.  You really need to address that low signal level - that will never work well.  And, if you're seeing gaps in the PWM, you need to get to the bottom of that.  There is going to be some jitter, but not gaps.

Regards,
Ray L.

993

General Mach Discussion / VistaCNC iMach/iMachPro pendant Driver

« on: September 15, 2009, 07:49:26 PM »

Below is my Mach3 macropump driver for the VistaCNC iMach and imachPro pendants.  This driver exactly (as near as I can tell) duplicates the functionality of the VistaCNC plug-in driver, but allows the user to customize the functionality to better suit his/her needs. It also allows a great deal more functionality than the plug-in driver, as it supports separate actions for MPG/Action_MPG/DoubleClick for ALL modes, which amounts to about 30% more functions that can be supported. For example, I did a custom version for myself that include the following functions beyond what the plug-in supports:

Zero X/Y/Z/A DROs
X+/Y+/Corner/Z- probing
Mist Coolant On/Off
Jog Speed +/-
Jog Speed Reset

Unlike the plug-in, this driver also allows the iMach and iMach pro to be interfaced through a SmoothStepper or Modbus, with no loss of functionality or performance.

Regards,
Ray L.

994

General Mach Discussion / Re: FeedRate OverRidden

« on: September 15, 2009, 11:45:39 AM »

Guess I will have to ask my question in a different way (asked in another thread and got no answers)

As per attached files, I set my lettering in LC to be engraved at 10”/min feed rate and when the program is saved for Mach, the feed rate is changed to 0.40”/min.

When I run the program in Mach the router stays in the same place and the stepper(s) hum (cant say if it’s one motor or all)

What is the problem?

Thanks
Nicolas

I would guess your CAM program is working in mm, and Mach is working in inches.  10 mm/min = 0.397 in/min

Regards,
Ray L.

995

General Mach Discussion / Re: Kernal Speed and Chatter

« on: September 14, 2009, 02:08:05 PM »

Paul,

I am cutting .5" solid surface material.  I am using a .25" Solid Carbide UpCut Spiral O Flute Onsrud 63-775 bit.  I am cutting .125" with each pass at 90 degrees to the surface of material.  I am using a Milwaukee 5625 router in my machine and it has a standard .25" collet.  The bit has a CEL of .75" and only the cutters are showing out of the collet.  The router is set at 14,000.  The machine is a MechMate.

I think I understand and have answered all your questions. 

Thanks for you help.

Cruiser,

I am cutting with a bit that recommended by Onsrud for solid surface material.  I need to use .25" bit for details.

The little piece missing is from a tab that broke off.

You are running that very near the top end of it's recommended chip load, which will not always work well.  Also, what I see in the picture is not what I would call "chatter", but rather indications of an over-loaded tool - you're feeding too fast, and the tool is flexing.  Either reduce feed, or increase RPM, and I bet it works fine.  I'd bet going to a stiffer tool (1/2", for example) would also help, as it would increase your SFPM, and allow a heavier chipload, albeit with more spindle power and higher feed force required.

Regards,
Ray L.

996

General Mach Discussion / Re: Rotating work offsets around Y

« on: September 13, 2009, 05:41:48 PM »

Ray, are you saying that Mach can do that in realtime while interpreting a gcode file?

Randy

Randy,

Yes, it can.  And for simple transforms like that, it'll make no detectable difference in performance.

Regards,
Ray L.

Where in Mach are these transforms entered?

FunctionCfgs->Formulas

Regards,
Ray L.

997

General Mach Discussion / Re: Rotating work offsets around Y

« on: September 13, 2009, 05:05:16 PM »

Ray, are you saying that Mach can do that in realtime while interpreting a gcode file?

Randy

Randy,

Yes, it can.  And for simple transforms like that, it'll make no detectable difference in performance.

Regards,
Ray L.

998

General Mach Discussion / Re: Rotating work offsets around Y

« on: September 13, 2009, 04:30:04 PM »

This is an application where formulas would actrually work pretty well, since the transform is pretty simple, especially if the misalignment is only in one axis.  For example, if the part is tilted down by 0.010"/inch as you move in Y-, you just add a formula for Z that is a linear function of Y (assuming your Z=0 is set at Y=0):

F(x) = x
F(y) = y
F(z) = Z + (0.010 * Y)

Though you're still FAR better off simply getting the thing trued up to begin with....

Regards,
Ray L.

999

General Mach Discussion / Re: Kernal Speed and Chatter

« on: September 13, 2009, 04:18:53 PM »

Hey Ray,

Thanks for chiming in.

Perhaps I could have been more clear.  In my previous post, I was using accel being set to high as an example of how chatter could occur.

Of course software can not compensate for incorrect settings.  However, it has been my experience when Mach is runing in CV, the speed blending which occurs to create the 'Constant' somehow overides the acel parameters in tuning in its attempt to run every axis at the same speed.  This causes undesirable effects.

Yes- I could adapt my machine so that the Axis were more similar in terms of the tuning profile but, it sure would be nice (read easier) to have some more control over CV (maybe like a CV axis scalling factor) to help smooth things out.

Sid

Sid,

I don't believe that's true, and it's easy enough to test - set the accel on one axis artificially low.  I think you'll see that ALL "blended" operations slow down accordingly.  If Mach ignored the accel on even one axis, we'd having servos faulting and steppers losing steps randomly, but that does not happen, even when there are wide disparities in the capabilities of different axes.  One of my machines runs an accel of 125 on two axes, with a max speed of 270 IPM.  The third axis has an accel of only 5, and a max speed of 30 IPM, and those settings are right on tha hairy edge of what it's capable of without losing steps.  On blended moves, the thing crawls, because of the third axis, but it does not lose steps.

Regards,
Ray L.

Regards,
Ray L.

1000

General Mach Discussion / Re: Kernal Speed and Chatter

« on: September 13, 2009, 03:37:23 PM »

VMAX-

Respectfully, I have to disagree.

If you have a machine with a lot of mass and the accel rate is set too high then a rapid acel will cause your machine to jerk, then this will result in what I am interpreting as chatter.  Perhaps I am mistaken or using the incorrect terminology.  If so, I apologize in advance.

While what you say is partially true because the "chatter" it is due to the mass limitations of the machine, the software allows us to slow down our accels to a point where things become smooth.

CV takes this away from us to a certain extent because Mach now want to control velocity on it's own terms (well sort of) but we certainally do not have the same speed/accel control as in exact stop mode.  If 2 or more of your axis are dissimilar in terms of their tuning profile, you will see Mach slowing down one axis a lot more rapidily than the other in an attempt to keep things "Constant"  this struggle can result is Jerky motion (exactly what CV is supposed to prevent).  CV is a double edged sword under these circumstances.

Sid

"If you have a machine with a lot of mass and the accel rate is set too high..." - And how is that a software problem??  Is the software supposed compensate for you setting the acceleration too high?

I agree with Terry.  This is a machine problem, not a software problem. 

Regards,
Ray L.