Vcarve not properly ramping into corners for some custom par

Vcarve not properly ramping into corners for some custom par

Postby Customizeddesigns » Wed May 11, 2016 4:24 pm

This has been a problem for a few versions now but I figured I'd make a post about it finally. Sometimes when we create custom parts with sharp, or even soft 45 or less degree angles, vcarve won't properly tell the machine to ramp into these corners (slow down) and will hit them at full speed which at the minimum will destroy your entire sheet or at the worst damage your CNC which is what just happened to us moments ago.

We were just cutting a sheet that included the part in the attached file. When it hit the top corners, it was moving so fast it tried to make the corner but couldn't and continued along the X path and took out our tool holder. It's probably not a common problem because I doubt most people are running their machines as fast as ours (8 in/second) but it's a pretty big problem for machines running this fast and you'll never know until it's too late.

Perhaps it's isolated to the Multicam .cnc output but it should definitely be looked into.
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Re: Vcarve not properly ramping into corners for some custom

Postby ger21 » Wed May 11, 2016 5:46 pm

Afaik, V-Carve doesn't have the ability to slow down at sharp corners.
This is an issue with your machine controller.
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Re: Vcarve not properly ramping into corners for some custom

Postby Rcnewcomb » Wed May 11, 2016 6:05 pm

This would be handled by the machine controller. It may be referred to as look-ahead. Check the manual for the Multicam controller. I came across this in the Multicam marketing material:
Controller
© 2006 MultiCam L.P. All Rights Reserved.
The MultiCam Controller is a powerful, stand-alone, 32-bit, simultaneous 4-axis CNC system using 64-bit motion algorithms that give our CNC machines unsurpassed high-speed performance. Our controller operates on industry standard M & G codes and can interpret HPGL (Hewlett Packard Graphics Language) as well. Features include 12 MB of program memory coupled with standard DNC, a 1,000 line program look ahead and unlimited file size.

Our Controller has the most user-friendly interface in the industry. It includes our easy-to-use keypad interface and our exclusive Productivity Software Suite (PSS). The PSS offers everything you need to
transform your ideas into results including DNC, Job Editor, Job Reporter and Motion Mechanic software programs. Extend the capabilities of the MultiCam Controller by adding the optional Advanced Graphical CNC user interface. This option gives the machine operator more control at the machine including real time graphical feedback, advanced file editing and optional parametric macros.
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Re: Vcarve not properly ramping into corners for some custom

Postby Customizeddesigns » Wed May 11, 2016 6:39 pm

We've had our multicam for 5 years and haven't had this problem until recently.

It has something to do with creating shapes with the cutting tool. I drew that shape from two boxes and two separate lines and then cut away the excess. If you trace over that shape with a single closed polyline then the problem disappears.
Additionally, if I draw a box around that shape and then use "Keep overlap of vectors" it ramps in those corners the way it should. If the problem can be fixed in Vcarve then it's safe to say the problem is with Vcarve itself.
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Re: Vcarve not properly ramping into corners for some custom

Postby Adrian » Wed May 11, 2016 6:56 pm

I cut at those sort of speeds quite often and with similar shapes and haven't seen a problem like that.

I don't see how it can be VCarve at fault as it doesn't generate code to slow the machine down for corners. That's the job of the controller software.

I traced over the shape as you suggested and created two output files, one for each shape in the same position, using the Multicam PP and both files were identical.
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Re: Vcarve not properly ramping into corners for some custom

Postby Customizeddesigns » Wed May 11, 2016 7:06 pm

Just did and they're identical. Very strange indeed.

I put an email into Multicam to see what they think it might be.
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Re: Vcarve not properly ramping into corners for some custom

Postby ger21 » Thu May 12, 2016 1:29 am

It has to do with how the MultiCAM control handles the g-code.

On our Morbidelli, if a corner has a very small radius in the toolpath, it'll try to go around that corner as fast as possible, which can be very violent. But if there's no radius, it'll smoothly decel into the corner, and accel out.
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Re: Vcarve not properly ramping into corners for some custom

Postby GF357 » Sat May 14, 2016 6:17 pm

Mach3 has constant velocity settings, does the Multicam have something similar, or would issuing G09/G61 before the corner and a G64 after the corner work?
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