Messages

21

General Mach Discussion / Re: A axis rotary problem, strange stalling issue

« on: June 01, 2015, 07:35:37 PM »

This is a copy of something I posted on "Rotary Axis Feedrate Compensation" within Mach3.

It may be helpful in understanding the issue.

=========================================================================

All axis move in units per min. With a rotary axis those units are degrees.

So what is 120 ipm on the linear axis (desired speed of the tool in the work), is 120 degrees per min for the rotary.

That 120 degrees per min angular feedrate will make the tool move through the work at a speed dependant on the distance the tool is away from the centre of rotation. (in your case, very slowly)

So Mach has a feature to compensate the rotary axis feedrate, to accommodate differing radius that the tool is cutting at.

It is activated via the Toolpath Setup menu. Check "Use Radius for Feedrate" All the other settings in this box are to do with the toolpath display window.

On the Settings page there are three DROs labelled "Rotation Radius". IMO they would be better labelled "Origin Offset"

They are to tell Mach the distance that the relevant axis origin (Z in this case), is offset from the centre of rotation. (A axis in this case)

So if you are machining on the outer surface of a 10 unit diameter job and Z axis origin (zero) is set on that outer surface, then the correct value for the "Rotation Radius" DRO is 5. The distance that Z origin is OFFSET from centre of rotation.

If, on the other hand, the Z axis origin is at the centre of rotation (my preferred method for most jobs) then the correct value for "Rotation Radius" DRO is zero. The distance that Z origin is OFFSET from centre of rotation is zero.

Mach takes the Z axis DRO value and the "Rotation Radius" DRO value and adds them together to ascertain at what radius the tool is cutting at any one time. Then compensates the angular feedrate to have the tool move through the material at the desired speed.

Maximum velocity as set in motor tuning is honoured, so that will always be the upper feedrate limit.

Now there is one little "Gotcha". A zero value in the "Rotation Radius" DRO will automatically disable the entire feedrate compensation feature. This is a known bug and is being addressed by Artsoft at this time. Hopefully it will be fixed soon.

The workaround for this, is to use a very small value (eg. 0.001) in the "Rotation Radius" DRO when zero is the correct and desired value. Small enough to have no measurable effect on feedrate, but not zero.

22

General Mach Discussion / Re: Rotary carving skewed

« on: April 26, 2015, 10:28:59 PM »

Sounds like losing or gaining one  or more steps on every reversal.

As TP said, check your signal polarity against drivers specs.

23

General Mach Discussion / Re: 4th Axis Right hand rule question

« on: February 13, 2015, 06:36:54 PM »

Explaining a visual aid with words is easy to get wrong or be misunderstood

Example, I quote from the first paragraph of the link posted above

Hold up your right hand with the index finger extended and the thumb up, like you're simulating a gun.
Now extend your second finger at right angles to the index finger.
Those three fingers are now pointing in the directions of positive X (second finger), Y (index finger) and Z (thumb).

Do the action as described and it becomes obvious it is incorrect.   

I prefer pictures.  Maybe I am just a visual sort of person. 

Here is one that describes all axis.

24

Mach3 under Vista / Re: Aspire file to Mach3

« on: August 12, 2014, 02:28:27 AM »

Glad you found it.  I no longer have it on hand. 

Would have had to search as you have done.

Greolt

25

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 25, 2014, 09:23:00 PM »

OK I jogged from the darwin driver.

Movement was definitely smoother but not as good as Mach3

Then it crashed my computer.

It is my better half's birthday and I must now go and do what dutiful husbands must do and stop that infernal fiddling with stuff in the shed.

Greolt

EDIT:  I am going to assume that adding a video card is not going to miraculously transform my meagre computer into a Mach4 power house.

26

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 25, 2014, 08:48:12 PM »

Ger

It is only running to about 25%

Mach4  Ver 1914

Greolt

EDIT:
That was jogging one axis.  When running a three axis file it goes up to about 40%

However one of the four graphs (cores?) goes to 100%

27

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 25, 2014, 08:24:49 PM »

Art

I have two computers happily running Mach3 on XP. 

Both would be considered under spec for Mach3 but have been doing a great job for some years (and continue to do so).  Very smooth reliable movement.

Both have on board graphics. (no video card)

One will run Mach4 with rough and unreliable movement.  The other will barely move an axis.

I have gone through all the things you have recommended to try. Pulse widths, kernal speeds etc.

Have come to the conclusion that the computer is too far under spec to ever run Mach4 and to chase it further is just wasting your time.

So my question is, do you think there is a chance that adding a graphics card would make any substantial difference.

I have never got as far as seeing if toolpath display is OK or not.  I will worry about that after getting smooth movement.

Thanks for all your help.

Greolt

28

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 20, 2014, 05:26:55 PM »

Greg:

 So in version 1900 in metric it sounds smooth? Is that the upshot?
That's an important thing to know I think, it would tel me that something in your CPU
is being dragged down by M4 in terms of having enough time to properly function.

Sorry, my poor explanation.

Metric weirdness seems fixed but smoothness is not discernibly different.

Greolt

29

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 19, 2014, 10:39:01 PM »

  If this doesnt fix roughness its OK, what I need to know is , Is it Smoother than it was..? If so Ill turn on a setting you can change to make it match your system. If indeed pulse width is the culprit, this should at very least make it better.

No I don't think it is any different in my case.  Perhaps my computer hardware combination that happily runs Mach3 is not up to the mark for Mach4.

I had Mach3 set to 3us pulses.  Only because I set it to that way back.  Set it to zero and it made no difference to smoothness in Mach3.

Mach4 again. Funny thing is sometimes an axis will run smooth and then next time rough.  Sounds like it has sand in the linear bearings.

I have gone to ver. 1900 and set everything to metric.  That seems OK now.

Spending way too much time trying to get a handle on homing with a slaved axis.  Need to stop doing that for now.  Can't make any consistent sense of it.

Greolt

30

Mach4 General Discussion / Re: Mach4 Printer Port Discussions

« on: July 19, 2014, 06:17:53 AM »

Tweakie

I will try the 'Disable VBO Tool Path' thing tomorrow.

I am in a different time zone and off to bed now. 

Greolt

PS: this is XP