Fernando:

  Its actually worse on some , better on others. For the better ones its typically because a Fanuc machien woudl have 1.5KW axis motors. They have very high acceleration for their weight..

Art

Thanks for the information Art!  I'll digest this, do some more experimenting, run some more parts, and after I digest some turkey  , I'll come back and post my findings.

Thanks again

I found this on another site referring to G61, G61.1, and G64....

Path Control Mode

The machining center may be put into any one of three path control modes: (1) exact stop mode, (2) exact path mode, or (3) continuous mode. In exact stop mode, the machine stops briefly at the end of each programmed move. In exact path mode, the machine follows the programmed path as exactly as possible, slowing or stopping if necessary at sharp corners of the path. In continuous mode, sharp corners of the path may be rounded slightly so that the feed rate may be kept up. See Section 3.5.14 and Section 4.3.5.3

The canonical machining functions share with the RS274 language the simplifying assumption that machine dynamics can be almost ignored. That is, in this model, acceleration and deceleration do not occur. Components of the machining center can be told to move at a specific rate, and that rate is imagined as being achieved instantaneously. Stopping is also imagined as instantaneous. This model obviously does not correspond with reality. The control modes provided here provide some compensation for this lack of consideration of dynamics.

What would G61.1 (exact path mode) be in Mach3?  Would that be the CV distance tolerance with or without CV feedrate or is that an unsupported G-code?

Thanks

Ok, I'm back again, after two very frustrating days of lost production dealing with this issue.

I understand all of what you stated below Art, but I can't seem to come up with that magical combination.  I have hundreds of files that I will eventually need to convert from .sbp (ShopBot) over to G-code.  These files were drawn as they were intended to be cut with the radius of the bit in mind.  The only way they're going to be cut that way is to run them in exact stop mode which simply won't do.  There are many short line and arc segments involved in most of them.  Many of them get an item placed inside pockets that need to be the right shape or else things won't fit.

CV on, acell up (15, tried 20 and won't again), feed at what I used to cut that at before and I get to much shake/bounce after the stop & go resulting in poor cut quality and some rounding.

CV on, acell down (10 - 13), feed the same, more rounding less shake.

Feed set slower with both the above, not much change in the rounding but now the chipload is in the basement.

CV on, acell the same, CV distance tolerance at 0.1- 0.12, the rounding is better, but small rectangular slots are still rounded rectangular trapezoids (one corner is fair and the other is rounded off more.  If the feed is kept up, it runs smoother, but if feed is lower, then it starts hesitating at each segment again (back to what acts like stop mode).

Angular check on with any setting (90 thru 180) makes it hesitate at all segments again.  If there's a line segment with a shallow flowing curve and maybe another curve in the other direction that really needs little to no slowing, it hesitates at each segment.  Take that same right angle in the example below and instead of going straight back to X0 on an angle, make it a shallow flowing "S" going back to X0.  Now, my Cam program makes that out of a couple of arcs and a couple of small straight segments.  With CV on and Dist Tol off, it flows along smoothly.  With any angular check setting, you get a stop and go situation.  With Dist Tol on and angular check off, you can make it hesitate again with too low of a setting.

CV feedrate doesn't really do anything accept cause hesitation (low setting) or is like it's turned off (higher setting), still don't know what to think about that.

I know that the older ShopBot machines have lighter gantries and are prone to some shake across the Y axis which is why I can't run at real high accel settings.  If I run with lower feedrates, then the cutters will wear out prematurely (chipload too low).

What we need (ShopBots converted over to Geckos) is an Exact Path Mode with a variable feedrate.  Decel into the corners and acell out of the corners over a certain distance at a certain speed with a slight slow down at gentle curves without hesitation at each segment. 

I want my cake (Mach3) and to eat it too (Exact Path) don't I 

In the past I have done some inlay and I'm sure that the time will come again when I want or need to.  Is there anyone that has done inlay with Mach?  How could you possibly accomplish it?  Not with CV on and with it off, you would soon smoke your tooling.  Maybe with a high acell and a low feedrate? I'd get the shakes if I tried that. 

Maybe I need to buy some kind of a big behemoth cnc router that I can cement right into the floor. NOT   

Thanks for listening to another rant, sorry.

Download the newest version and see if that helps you There is a little bug that Art found and I think it may help you.

Hi Scott:

>>>What we need (ShopBots converted over to Geckos) is an Exact Path Mode with a variable feedrate.  Decel into the corners and acell out of the corners over a certain distance at a certain speed with a slight slow down at gentle curves without hesitation at each segment. 

  Yup, thats what I get. , thats what CV does on a system that can stand acceleration.. I do think that that the Bug brian mentions may have been affecting you very badly, try the latest version.. We'll be interested int he result..
Art

Scott:

 By the way >> (1) exact stop mode, (2) exact path mode, or (3) continuous mode.

  Mach implements 1 & 3, #2 was never implemented. Thats a quote from EMC and in EMC, exact path, though documneted, was never written..

Art

wow I'm glad that my topics are so ensue...

I'll try the latest version too, because I'm so interested in something like "exact path mode".

Faby

This new version is better than before, and now the "stop cv on angle *********" function works.

I played with CV distance and max cv angle value and I found a good quality
I think that an hypothetical "exact path mode", cuold bring mach3 in the best choice for all, as me, mill 3D objects for mold industry.

Fabiano

Ok, sorry it's taken awhile to get back to this, it's that time of year again. 

I'm not real sure if it's better, I've been running some different parts lately and it's harder to tell with these.  One thing that I have noticed is that with a CV Distance Tolerance setting of say 0.10 and a feed of 100, a toolpath may execute fine, but as you take the speed up a bit, it will start to hesitate between segments again.  If you turn on stop on angle, then it will always hesitate no matter what the setting for the angle.  Take for example the right angle talked about earlier and add a "S" shaped path going back to X0Y0 with a couple of line segments at the beginning, middle, and end (Attached sample file).  The return path in the file really needs little or no speed adjustment, depending on how fast you're going.  If I ran this with CV on and no distance check, it runs fine.  With CV and a distance check of 0.12 at 120IPM, it runs ok.  Start raising the feed and it starts to hesitate between each line and arc segment on its way back to X0Y0.  Throw in a angle check of 89 and it stops CV at the right angle, but also still at each line and arc segment.  If CV distance is unchecked and angle is checked, it doesn't matter what you put in for a value (89 -270), it will hesitate again at each line and arc segment. 

What I'd like to be able to set for the many varied size and shape pockets that I make for law enforcement badges and guns, is to be able to set a distance tolerance of 0 (exact path), a low accel (no banging in and out of corners) and still have smooth non-hesitant motion between the sections of code (G01 to G02 or G03).  Many times I have to have a rectangular pocket within the main pocket and they were intended to have a radius the same as the cutter to allow for clearance for some part to drop into.  These are getting cut (with a low distance check) with a larger radius on one side of the end of the rectangle (due to rounding) and a close to normal radius on the other side, making what I can best explain without actually drawing it, a radiused trapezoid rectangle. 

On another note, correct me if I'm wrong cuz this may just be my dyslexic mind   , but on the "General Logic" page where it says "Stop CV On Angles <", doesn't that mean less than?  So If we have an angle of 90 degrees and a setting of 89, it shouldn't stop, but if it's set at 91, it should.