Slow control question

[MBX5]

I am a bit of a noob, so please don't flame me if this question seems stupid...

I am running HSMWorks in Solidworks, and am doing a pocket cut w/ a 1/4" ball end mill... For roughing I used Adaptive Clearing w/ a 3/4" flat end mill (SGS S-carb) - and was running about 200ipm....hogging it out quite well... for finishing I used a 1/4" ball mill.... the pocket is a simple flat surface w/ a 3/8" radius transition from flat to vertical walls..... I picked a scallop tool path for the finish, and my stepover was tight... On the straight cuts I was able to run 100ipm as called for, however on my circular transitions and along the radius the machine slowed to probably 2-3ipm but still showed 100ipm on the monitor....this happens throughout the process...also it seems to "machinegun" a bit at times - gets real jerky and watching the code I can see g1...g2...g1...g2...g1....g2...etc... So it seems to be interpolating the toolpath as splines? Is the CNC88HS control not so "HS" or am I doing something wrong?

I am feeding the control via DNC....

Any ideas on what I could be doing wrong? It takes FOREVER to cut these pockets - cant be right??

I have a 1995 4020HT with CNC88HS control in format 1.... Is my control too slow to handle the circular/linear interpolations any faster?

Thanks for any insight~~

[DareBee]

I have a 1995 4020HT with CNC88HS control in format 1.... Is my control too slow to handle the circular/linear interpolations any faster?

Yes it is.

Couple things to try that may give slight improvement.
1) Run your DNC at the highest baud rate (38400 I think). If you are running 9600 your DNC is starving the control.
2) Turn off acceleration (G8). If you have hard corners this may hammer.
3) The very best thing to do (especially with " a simple flat surface w/ a 3/8" radius transition") is to change the toolpath from linear segments into circular interpolation (1 line of code instead of 1000). I do not know the capabilities of your CAM, but this is always my priority with my programs and doable within my CAM. It also has the benefit of often making the program small enough to be run from the control. It is amazing how arc fitting can change 80,000 lines into 12,000.

The control will not show actual feed only programmed feed.

[Neal]

If you are using cutter comp make sure the M97/M96 code is turned to M97. M96 will add arc moves when CRC is used and you don't need it in this case.

Neal

[MBX5]

Thanks for the suggestions!!

I ran a G8 on my 3d paths and adaptive clearing...for now just a manual add to the G code but eventually I'll modify the post....I also raised baud to 19200...HUGE difference....machine gunning gone, smooth transitions.... also did some smoothing selection on the toolpaths (within my CAM).. I am new to using HSMWorks - so I need to do some asking to find out about their method of "arc fitting" but I am pretty sure its possible...

Thanks again!

[Neal]

If you use arc fitting do the following:
1. Set tolerance level in CAD/CAM to it lowest possible setting
2. Make sure G8 is in effect
3. Make sure M97 is default in SETP

The reason for arc fit caution is that when CRC is used, if there is ANY geometry breaks CRC can go nuts and make a very undesirable tool path.

Neal

[DareBee]

My CAM has always done perfect Arc Fitting.
No concerns here.
If you set the CAM to the lowest possible setting it won't fit any arcs at all. I am sure experience will differ between software.