clear path causing weird vibration?

[shadetree]

Good day,

I have converted a 4' x 4' router with 3KW water cooled spindle from NEMA 23 steppers to Teknic Clear Path CPM-SDSK-2341S-RLN motors trying to get more speed and power. Running a Masso HTG5A1S with Software v3.44 .

All went well but I have a weird vibration or shutter in the machine that only shows up in portions of the run. These are "air" cuts so there is no load on the system and always in the same spot in the GCode and it was not there with the old steppers? I'm wondering if its a programming issue?



Any help would be appreciated.

 

[cncnutz]

Hi @shadetree

Your acceleration is a bit high. CNC machines are like cars. You don't go 0 -100 instantly and you don't stop that way either. This is how you have it set at the moment. It will cause huge inertia changes when the gantry starts and stops and unless your machine is very rigid indeed you will will get vibration and put high loads on the machine. If you manage to hit the resonance frequency of the machine it will amplify the issue even further.

For example my maximum feedrate is 600ipm but my acceleration is 16ipm.

Each machine needs to find it's own values but I would dial the acceleration back myself.

Masso uses exact stop machining instead of constant velocity so curves in your Gcode need to be made of circular arcs and not short lines. Exact stop machining is more accurate than constant velocity because the machine does not take shorcuts and make up the toolpath as it goes. Exact stop follows the Gcode exactly.

Hope this helps

Cheers Peter

 

[segoman-designs]

Like Peter says your acceleration is a bit hi,drop it 50% and try it again. Is you machine rock solid stable? Any wobble or backlash will throw the auto tune values off. I had a similar issue of low speed chatter until I did a live tune with Teknic now all is great, I'm getting a traverse of 1140 IPM on a 375 lb gantry.

 

[shadetree]

Thanks

I have lowered the acceleration down to 20 and I do still get the issue.

Could pulses per Revs have anything to do with this? I'm not real sure what this actually does.

Its just strange that it was not there with the steppers?

 

[breezy]

Quote from Shadetree on March 31, 2020, 2:50 am

Could pulses per Revs have anything to do with this? I'm not real sure what this actually does.

Its just strange that it was not there with the steppers?

Pulses per Rev is the number pulses required to move the servo one revolution.

It is there for steppers as well!

PPR and Distance per revolution (DPR) are used by MASSO to calculate how many are required to move the commanded distance.

As Segoman suggested have you tuned the servos?

Just a curious question why do you have the Minimum Travel set to -3000, this will defeat the soft limits on the negative side of your machine.

Regards,

Arie.

 

[evermech]

I agree with the tuning suggestion also. Might be an idea to check the setting regarding position accuracy too. It's called following error sometimes. If the setting only allows for a small tolerance from the commanded position it can sometimes dither as it struggles to maintain the position, allowing a little more room for error will have it relaxing a bit in between moves

Guy