Messages

701

General Mach Discussion / Re: Problems threading on the lathe

« on: March 25, 2010, 05:00:21 PM »

>>I have to link intrnet turning the ID check?

  Not sure what that question means... Id report it as an error to machsupport.com , sound sliek something is screwed up..

Art

702

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: March 25, 2010, 02:19:39 PM »

Bruce:

  Yes, since its 5th order, it can handle Gobs more...

So feel free to turn it up.. till jog starts to fumble, then back off a bit..

Art

703

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: March 25, 2010, 12:54:56 PM »

Bruce:

>>The setup of acceleration in M3 is done starting at rest.   The user tunes the acceleration based on how the machine performs in this test - with no control of jerk (pretty high at end points) as I understand the test.   As it says in the docs - the limit is set mostly done by sound and pushing to failure and them backing off.    I believe that if the setup were done with a jerk limit, the peak acceleration that the user would end up with would be higher than the acceleration you end up with in the standard test.   This is because higher peak accelerations would be possible since they would occur (in the test) when the machine was already moving.  This of course implies a different acceleration setup for Tempest M3 than stock M3.  Is that clear?

  If I understant you , thats only true in non-linear acceleration. In Mach3 ( linear accel), setting it to a jerk limit woudl reduce the end accel and speed as its that that causes the jerk in the first place, in Tempest ( sinusoidal accel), its very true that the accel shoudl be set with a jerk limit. It uses MAch3's simply because tempest is mach3 with sin accel, so I didnt rewrite the motor tuning. In fact in Tempest one shoudl set the accel normally, then increase it by about 30% as tempests use of sinusoidal accels will allow the motors typically to do about 30% better accel.

  However, since sine based accel uses about 30% more time than linear ( on average ), the end speed is then simplyequalized, not increased ( on average) by havingthe accel set higher.

 The problem in tempest is that while Gcode motions use sine accel, jog doesnt, so you have to be carefullnot to make jog too jerky when tuning. If Jog was sinusoidal as well, then simple
motor tuning by sound woudl be fine.
 I advise simply tuningmotors in jog as high as you can without losing steps.. Tempest can usually handle that high an accel..

Art

704

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: March 25, 2010, 11:24:03 AM »

REally, 2 axis is good and 3rd axis is rough?  Or do you mean your using x,y an dA for example?
Its true that using rotart is not perfect as yet in tempest, Ive focused primarily on cartesian...
but using x,y and Z should be fine?

Art

705

LazyTurn / Re: LazyTurn

« on: March 24, 2010, 09:20:55 PM »

Rich:

>>I would have thought that you would take the dxf info and manipulate it some .
>>What does LazyCam do to get just the profile for example? 

  The profile is easy..its just the raw dxf input.. but that has little correspondance to the finish path profiles.
Its hard to explain, but since the arcs get broken up in the calculations, they simply dont exist anymore
other than the raw dxf inptu profile, but thats useless to put out, any tool used with that would simply gough the
stock on one side of the tool or another.
   While I could put it out as a profile in GCode , I dont really see much use for it, be pretty rare Id think when it could even be modified,
because no matter how many tools you use, getting the complete profile cut with no exclusion due to tools is very rare I woudl think..depending on the profile.

Art

706

General Mach Discussion / Re: Problems threading on the lathe

« on: March 24, 2010, 08:12:28 PM »

Hard to say, is this the latest version?

   That shouldnt happen unless the license is invalid though, so Id check the license is installed
properly, and also check the "Use Spindle Feedback" option is checked.


Art

707

LazyTurn / Re: LazyTurn

« on: March 24, 2010, 07:57:52 PM »

Hi Rich:
 The problem is that there is no Arc to build from, by the time the finish is computed, with offsets and collision avoidance, all thats left is points, or small
linear segments equalk to "tolerance" distance in length. The problem occurs when trying to get arcs from such information. There is no arc in the data
at all in that case. Useing the original arc's from any loaded profile is impossibel as it hasnt been processed for anticollision or dosnt exist.

  The cad program may have used arc's in the drawing, but there long gone by the time a finish path is created. And though intuitively youd think
you could generate arc data from thsoe linear points... it aint liek it seems..

Art

708

LazyTurn / Re: LazyTurn

« on: March 24, 2010, 10:56:07 AM »

Rich:
 
   Its suprising to me how few arcs there are in the finish pass. I have found a few, and am still working on the conversion algorithm. Finding arcs from
linear segments is somewhat a difficult operation as it has tolerance issues. The techiques used conventionally are pretty bad when applied to the
linear segemnts we use. Tolerances make things a bit inaccurate and Im finding issues with cutoffs and such. Its easy to find from 3 points in the line what arc woudl fit them, but rarely is the forth point going to conform without a certain tolerance of error and that error compounds over distance and time.

  Im still unsure exactly how the arcing willwork out from the data. It may be a cas eof having to use small enough finish tolerance to get a proper
finish on those radii.

   Its the only issue im working on in Turn at the moment, as there doesnt seem to be too many reported issues other than re-arcing the output
data..

Just an update
Art

709

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: March 22, 2010, 12:19:38 PM »

>>Mach3 presently does the acceleration setup from a standing start.   I believe you can, for most machines, achieve greater acceleration from a moving start due to higher static than dynamic friction.


   I may not be understanding your intent. Its true that MAch3 applies accel from a standing start, it goes from 0 accel to max accel instantly...
Tempest applies it gradually. But both tempest and mach3 apply accel from moving start on every block as its in motion.. tempest gradually, mach3 instantly..

  Its mostly a tradeoff with any scheme, but Tempest is a test of the tradeoffs..

Art
 

710

Tempest Trajectory Planner / Re: Tempest Planning - Preliminary information and testing

« on: March 22, 2010, 10:23:04 AM »

Hi:

  >>But what are the specific ends you are trying to achieve?

 All of the things you mention really. The problem lies in the way planners typically plan a motion. When acceleration is applied, its applied fully
until the motors get up to speed, when decelerating, the decel is applied at full rate to slow down. This causes "Jerk", the immediate slowing down of mass
which causes a jerk on the motors and mechanics.
  Tempest applies the accel is a sine wave template, so its much smoother. Its an attempt to make motion in cnc more like driving a car where the accelerator
is pressed in an analogue motion dependingh on requirement.

  As the thread says though, this makes most motion take up to 30% longer.. the guy  with the binary accelerator pedal DOES get to his destination faster,
but its harder on the vehicle and brakes. The challenge usually is the small segement code, where its hard to concatenate small segments to move quickly.

 Tempest is an experiment producing 5th order waveforms instead of 3rd order as is typical. It does achive less error in the pah, smoother motion and defined
limits in mechanical stress, but at the  expense of speed. MOre work willlikely be done this summer to see what can be done to address the time compnents.

Art