Bridgeport Interact - TNC151B programming

[mwoodard]

I have been trying out 3d contouring with my mill and notice very jerky motions when in the XY plane. It has me scratching my head. First some background.

When using canned cycles in either conversational or iso modes, the circular interpolation is smooth as butter. All seems smooth when doing helical motion (movement in three planes simultaneous) while in ISO mode. When I use a cad/cam program to create code to cut circular contours and pockets (2d) without using canned cycles the machine appears to be in exact stop mode.

I have experimented with MP91 (constant contouring speed on corners) by setting it at various points in the range from 0-179.99 degrees. The default was 10 when I got the machine a few months ago. *At slow feed rates, the motion seems to improve as I increase the value. *But at speeds above 50ipm no setting is usable.*

Is there a MP that I am overlooking to take this out of exact stop mode?*

Is this motion common for these controllers?

I have discovered that the Heidenhain gcode implementation is no longer (if it ever was) compatible with the current standards. *Has anyone uncovered an English version of the Heidenhain ISO programming manual for the TNC151/155 control? *The Heidenhain site has a couple but none in English.*

I have a home brewed CNC router running Mach3 doing 3d contouring in wood and aluminum with ease. *Since 3d contouring with the mill is a must for me, this behavior has me contemplating a retrofit. *I will likely move to LinuxCNC so I can maintain much of the electronics and a closed loop servo system. *

Any thoughts or suggestions are welcomed.

Mark*

[gus]

Since it can do canned cycles just fine, it is probably not a parameter, rather your CAM program is chopping the moves into tiny little moves, and it is trying to accelerate at every corner rather than a smooth calculated arc.

50 ipm is pretty fast for that era servo amp. The control doesn't care but the servo amps cannot always do it. You could up the accel decel parameter, but if the canned cycles work, that really isn't the issue.

[mwoodard]

The CAD/CAM program is definitely outputting very short line segments. My experience with how Mach3 handles extremely short lines is different. Mach smoothes them out unless you have the control in exact stop mode. In exact stop, Mach exhibits the same behavior as I am seeing in Heidenhain. I was expecting the TNC151 to work the similarly. I agree that it isn't the drive being incapable. The control is interrupting the motion at the end of each line of code. Almost like there is no look ahead.

Mark

[gus]

I lookd through some old posts but found little helpful, I was sure someone had this problem and overcame it.

http://www.cnczone.com/forums/genera...ng_issues.html

I have alot of manuals but no ISO manuals, have no use for 1940's programming language.....

Are you doing actual 3 d contouring or just 3 axis machining?

[mwoodard]

I had not run across that posting. Thanks. My manuals don't show an M90 listed as a valid code but the MP60 "speed pre-control" is a possible change. Mine is set to 0 and I will try setting to 1.

I did find this which makes me wonder.

iTNC 530 Post

I am really doing 3d contouring and not 3 axis milling. I am working on an artsy wedding gift. It is an organic shaped bowl cut from a black cherry burl. Bowl made on my router. My intent was to form an aluminum stand on the mill with the top the same surface as the bottom of the bowl.

Mark

[mwoodard]

I just had to go try this. It sure is nice having a job where I can work from home.

I first reset MP60 from 0 to 1 which had no effect. I hand edited a few lines of test code that I have been using to understand the effects of various changes. I added an M90 at the end of a series of short line segments. The control didn't object to the M90 but I was still cautious.

I ran the program with one hand on the estop in case M90 was the command to rapid and axis past the soft limits. My fears were unfounded. I did notice an improvement in the motion. Still jerky but less so and not optimal. I expect the finish to reflect the motion.

I wonder what that M90 does in a TNC151B... I'll research that a bit.

Thanks for the assist.

Mark

[gus]

There is little you can do without getting crazy with parameters that will blow things up. This control is smarter than many made today.

Try playing with the parameter 91 now. One machine i retroed i always had in a state where If I programmed a fmax into another move it would error, but it ran well otherwise.

Try making the cam program produce fewer steps at least for a rough pass.

playing with the accel ramp and ramp kink point parameters might get you somewhere.

It is possible you may want to change parameters for this type of work that are not suitable for simple drilling work

[mwoodard]

Or I can swap out the 11uA encoders, buy a couple of MESA boards and take the control to LinuxCNC and the new millennium.

Thanks Gus. I appreciate your assistance. I was hoping it would be something simple. i don't think changing MPs accomodate what I am trying to cut is something for unranked amateurs like me. I am barely able to make good parts without the extra drama.

I'll have to think about my next move.

Mark

[gus]

here's the problem: you will still have the same servo amps, you have no 100v supply for different amps. More money.

I think people do what you want with that machine, so hopefully one of them will come along. People do this with steppers for gawds sake.