Why the huge difference in Machine Time given by F360 vs the time machining time executed by Win-PC NC?

[Anonymous]

Hi There,

our studio we are using a new CNC machine. Haase AL1290. We use Win-PC NC as post processor. But are having a major issue with our workflow, since, for example, when generating the tool path in F360, the machine time given is 28 minutes. But when we run our nc/gcode in Win-PC NC that runs our machine, the machine time happened to be 4 hours (8 times more). Any clue why this happens and how to have clarity of what is generating such difference? or if there is a way to edit parameters and preven it?

Many thanks to everyone willing to guide us!

Esteban

[seth.madore]

I'm betting that you are on a Personal License?

There were some changes made a few months back to the Personal, removal of rapid feedrates and tool changes being the notable CAM related ones.

[Anonymous]

Thanks @seth.madore for this info! Yes, I am on a Personal License. Do you mean that the removal of rapid federates feature, makes Fusion 360's Machining Time estimates highly inaccurate? and therefore not reliable?.

Thank you! 

[seth.madore · Accepted solution]

That is correct. The estimated machining time is based on a machine with rapids. The removal of rapids on Personal translates into all rapid moves being done at the last cutting feedrate. So, if you've cutting at 10 inches a minute, that's going to be your "rapid" feedrate as well.

It's an unfortunate change that really had to be made. You can read more about it here

[Laurens-3DTechDraw]

Not sure that under any circumstance would cause it to be 8 times the suspected time.

[seth.madore]

Without the file, it's certainly hard to tell. I assumed that there was a low feedrate and large distance involved

¯\_(ツ)_/¯

[Anonymous]

@Laurens-3DTechDraw I do agree with you. A 800% machine time deviation is excessive and unbearable for project planning. I was expecting a 20-30% machine time deviation as tolerable. 

@seth.madore, actually the model is not that big (ca. 56.5 cm x 21.5 cm x 5.8 cm), and the cutting feedrate was set at 6000 mm/min. Our machine is able to cut up to 9000 mm/min. I attach some screenshots of model and tool path settings. Also .nc file (oler files, if helpful, can be shared). So I am still sceptic that a 800% time difference is due to the removal or "rapids" in F360.

We are testing on styrofoam. 

Any further insights will be very appreciated.

Regards,

[seth.madore]

I guess the first question is:

Is your machine actually feeding at the rate it is supposed to? Do you have any means of getting a rough idea? At 500mm/min, how long does it take to traverse your machine travels?

When I run this through a backplotter (HSM Edit), I get an estimated machine time of 1hr 45 min:

 

[Anonymous]

@seth.madore,

- it seems this issue was due to a group of factors and settings. i.e.: very low tolerances (0.001, and smoothing toolerance: 0.0001). Also there is an option in the winpc-nc post processor setting when generating the gcode, which states the built-in feedrate. Changes on these setting seem to generate faster response of the machine.

This makes sense to you? 

- On the other hand, is there any tool that you can suggest us as a more reliable way of estimating (or double checking) machining time? Right now we experience a 2-3X difference between F360 estimate and the actual time spent by the machine. At least much better than the 8X we had before. Still, would be great to double check the machine time.

- another question. You mentioned that tool change was also removed from personal license? Therefore is not possible to program multiple toolpaths with tool changes in between processes?

Thank you!!