Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: homersimpson on August 09, 2011, 04:21:46 PM

Title: sin/cos velocity profile control
Post by: homersimpson on August 09, 2011, 04:21:46 PM

I'm new to this forum and am using Mach3 with my homebuilt CNC routers.  I am writing to ask if Mach3 supports anything other than a trapezoidal velocity profile.  With the standard profile, even though I've decreased my accelerations significantly, I still experience a fair amount of jerk (2nd derivative of velocity) that could be reduced alot with a simple sin/cos (S-shaped) velocity profile.  Does anyone know if this is possible with Mach3?  I've searched google, and these forums and haven't found that it does so thought I'd pose my question directly.  If not, how do I go about requesting this feature?
Thanks.

Title: Re: sin/cos velocity profile control
Post by: Hood on August 09, 2011, 05:07:04 PM

No not with Mach, there is Quantum but it was just a project for Art to  see how things worked. It is useable but does have limitations so best check out that part of the forum for details.
Hood

Title: Re: sin/cos velocity profile control
Post by: ger21 on August 09, 2011, 06:01:50 PM

The test version of the Tempest Planner does as well. I've found it to work extremely well for 2D cutting, but it's rather limited, with no pausing or FRO.
http://www.machsupport.com/forum/index.php/board,83.0.html

Title: Re: sin/cos velocity profile control
Post by: Hood on August 09, 2011, 06:21:41 PM

Just a thought though, are you using CV mode or Exact Stop? If you are in Exact Stop mode it will make things worse.
Hood

Title: Re: sin/cos velocity profile control
Post by: homersimpson on August 11, 2011, 11:43:40 PM

I am in CV mode.  I loaded Tempest and tried that.  I'm using the same g code file that I have motion problems with in the standard Mach3, which is in mm, but when I bring it into Tempest, it runs really slow.  I've brought in my profile and have tested that the steppers are running per the velocity profile in the motor tuning screen using the up/down arrows.  Any suggestions on why it runs so slow?  I've tried setting the default units in Mach to both IN and mm to no effect.  Until I can get it running the right speed, I can't test if the S-shaped velocity profile works.

I still need to test Tempest.  Thanks.

Title: Re: sin/cos velocity profile control
Post by: homersimpson on August 12, 2011, 10:07:20 AM

sorry, i meant that i had tested quantum and was having those problems, not tempest.

Title: Re: sin/cos velocity profile control
Post by: homersimpson on August 12, 2011, 04:35:50 PM

I've tried Tempest now.  That works MUCH better.  Why isn't velocity profiling available in the standard version of Mach?

Gerry, I downloaded your router screenset.  I love it.  Thanks!  Only one question.  Is there a button for online/offline, so I can turn the holding current off when my motors are sitting around for a long time?  If not, can I add one fairly easily?  Thanks again for the tip on Tempest.
Stan

Title: Re: sin/cos velocity profile control
Post by: BR549 on August 12, 2011, 04:50:31 PM

For some machines the S curve improved the process in many more cases it made it worse.

(;-) TP

Title: Re: sin/cos velocity profile control
Post by: ger21 on August 12, 2011, 05:39:55 PM

For 2D routing, Tempest kicks Mach3's ass! But it can be slower for 3D cutting.
Brian has said that we'd be able to use Tempest (and other Planners) in the next version of Mach3. I'm not holding my breath.

I don't believe there's an offline button in that screen. Sorry.