Why do my jobs seem to take so long?

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atrueresistance
Posts: 151
Joined: Thu Feb 07, 2013 6:20 pm

Why do my jobs seem to take so long?

Post by atrueresistance » Wed Dec 31, 2014 3:09 am

I don't know if anyone else uses autodesk fusion 360's cam feature here. Can someone tell me why the estimate is so far off from actual run time?

http://imgur.com/a/EXDTT

Fusion 360 says 30 minutes and my shapeoko has been running for 1hr 30 minutes. . .
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tbfleming
Posts: 89
Joined: Sat May 31, 2014 12:04 pm

Re: Why do my jobs seem to take so long?

Post by tbfleming » Wed Dec 31, 2014 5:09 am

What do you have your machine's x, y, and z speed limits set to? If they are less than 1524 mm/min then it will cut slower than the gcode tells it to. Also, Fusion probably assumes machines can rapid faster than what most configure their Shapeokos to do.

Edit: fixed units. I wish gcode operated in seconds instead of minutes; minutes isn't metric.
Last edited by tbfleming on Wed Dec 31, 2014 5:45 am, edited 1 time in total.

tbfleming
Posts: 89
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Re: Why do my jobs seem to take so long?

Post by tbfleming » Wed Dec 31, 2014 5:17 am

I just noticed from your screen shot that you're at 9600 bps, which means you haven't upgrade GRBL. That can make a huge difference. Here's what you can do with Fusion + GRBL .9g:


atrueresistance
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Re: Why do my jobs seem to take so long?

Post by atrueresistance » Wed Dec 31, 2014 5:45 am

I'll have to try the upgrade. I was planning on a laser upgrade in the future that would require .9. That machine sounds visious and I wouldn't dare attempt that with a SO1. 1524mm/sec seems insane, I think you mean per minute which imperial is around 60"/min. I'll update and post back as I have to cut the inlay from cherry in a few days. Hopefully with good results.
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Hans
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Re: Why do my jobs seem to take so long?

Post by Hans » Fri Jan 02, 2015 7:21 pm

I see in your latest posts with the final product that it wound up taking an hour and 44 minutes to machine this. Did you get the latest grbl working? The toolpath doesn't have a whole lot of rapids so I doubt that's your problem. When I do V-carving, the machine doesn't go at nearly the programmed feedrate because the intricate motions don't give it time to accelerate to full speed. You might try testing just how high you can set acceleration without your motors missing steps or the belts slipping, then setting it back by 30% or so for safety. Grbl .9g will be important because it lets you set a separate value for the Z axis, which will probably need to be much slower. While you're at it, test how high you can push your feed and still get good results. Even with the tiny endmill you're using, FSWizard suggests 59 ipm slotting at .03" depth and 78 ipm at .06", 40% stepover.
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aam
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Re: Why do my jobs seem to take so long?

Post by aam » Sat Jan 03, 2015 11:37 am

atrueresistance wrote:I don't know if anyone else uses autodesk fusion 360's cam feature here. Can someone tell me why the estimate is so far off from actual run time?

http://imgur.com/a/EXDTT

Fusion 360 says 30 minutes and my shapeoko has been running for 1hr 30 minutes. . .
Fusion 360 doesn't consider your acceleration settings on your machine. The estimate is based on the defined feedrate, but depending on your toolpath and geometry, your machine doesn't reach those feedrates because of the acceleration (and deceleration) after and before corners or stops.

Try a very simple shape, let's say a circle profile cut with some simple plunge step-downs and you will notice that fusions estimated time is much closer to the actual run time.

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