Cut time estimate difference between CC & CM

Why are the cut time estimates so different between CC and CM?

CM is alway nearly double the time of what CC estimates.

At least it’s somewhat predictable, but seems like these apps should be in closer agreement.

You would think 2 apps from the same developers would use the same algorithm.???

It’s not rocket science (Until you start pushing for extreme accuracy with acceleration & machine parameters). It’s simply the distance moved times the feedrate.
I suppose it’s possible that CM uses the rapid feedrates set on the GRBL board, where CC wouldn’t know what those rates are. They could have an option to enter the rapid feedrates in CC settings.

Time estimates don’t usually include tool changes. Although more advanced CAM/simulation programs do let you account for tool changes. Probably not necessary here.

I did a test in NX, with a path that estimated 26:44. CM said 2 minutes, both in the preview & the run screens. It actually took 27:30. 97% accuracy. And I didn’t change accel/decel or rapid values.
I could probably get it to 99% or better, but for a hobby machine, 97% is plenty good enough.

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I don’t see it double but easily 2% more when I get to CM.

It shows the CC estimate until you actually start the job and then it jumps up.

It’s not really that big of a issue to me, but more of a small annoyance than anything. I just know when I see the estimate in CC, to just double it when it comes to cutting it.

I started using CC v757 the other day and CM v618 today and thought maybe there would have been some alignment between them, but seems about the same.

Most of the time I’m using tools I added to the library by copying and editing the hardwood equivalent size/shape from the defaults. My assumption was the hardwood settings will be the most conservative, so if I am cutting soft wood I can override the feedrate if I want to.

I usually optimize my tool changes, so unless it’s absolutely necessary for the sequence, I’m not using the same tool more than once. That includes collet changes as well.

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