Cutter Compensation Question

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RJS100
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Cutter Compensation Question

Post by RJS100 »

I just converted a PM833 to CNC. I am sending one tool path at a time from Fusion 360 to Centroid to learn the process. The first facing tool path worked great. The second tool path is an adaptive tool path that runs the perimeter of the part and cleans out a pocket (see below). To test the tool path, I ran it 1 inch above the part as a sanity check. This tool path is for a 3/8" end mill.

When I tested the g-code running 1" above the part, the end mill follows the left, rear and right side if the part as intended and appear to be taking off .050 from all sides.... Perfect! But when it reaches the front face of the part end mill is inboard by what looks like the radius of the cutter. In other words, instead of taking .050 off the front of the part, it would trim off about one half the diameter of the end mill.

Is there some setting that I may have setup incorrectly that would cause the cutter to compensate correctly for the left, right and rear of the part but not the front?

Thanks... Richard
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Test Part Fusion 360 Cam.JPG
suntravel
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Re: Cutter Compensation Question

Post by suntravel »

Hi Richard,

we have a new place for things regarding machining and toolpaths:

https://centroidcncforum.com/viewforum.php?f=66

To answer your question, only the screenshot is not enough information.
Did you activate Lead-In and Out in fusion for compensation in control ?

Uwe
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Re: Cutter Compensation Question

Post by CNCMaryland »

Why not do the same thing you did, but turn off cutter compensation in fusion so that you know its not in play.
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Re: Cutter Compensation Question

Post by RJS100 »

Thanks for the tip on the new place for machining and tool paths. I was not aware of this.

I am new to Fusion 360 so I am not sure I understand your question regarding "Did you activate Lead-In and Out in fusion for compensation in control". I do have a .15" for horizontal lead in/lead out. I have attached the G-code generated for this tool path ([T2] Adaptive1).

Here is a link to the Fusion 360 file: https://www.dropbox.com/s/9eg99mlnqe6br ... 0.f3d?dl=0

On the passes tab, for 2D contour toolpaths there is an option I set to "Wear" for cutter compensation. The toolpath referenced above [T2] Adaptive1 is a 3D contour toolpath. I am not aware of where the cutter compensation is set for this type of toolpath so I cannot turn it off to test it.

Thanks again... Richard
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1002 Titan 1M Adaptive1.nc
(219.55 KiB) Downloaded 6 times
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Re: Cutter Compensation Question

Post by tblough »

"Wear" compensation means the CAM package, ie F360, calculates the cutter path based on the centerline of the tool and assumes a nominal tool diameter. If you specify a 3/8" diameter tool, F360 will offset the path 0.1875" to the side you specify. "Wear" adjustment is then performed by the offset you have programmed into the CNC controller. If your part is cutting 0.003" oversize, you would then set the tool table diameter for that tool as -0.003".

If your part is cutting correctly on three sides, but not the fourth, my guess is that your actual stock size is different than your programmed stock size, or you machine tool WCS zero is not in the same place as the F360 WCS.

The program you just posted does not use cutter diameter compensation. There are no G41 or G42 codes in the file.
Cheers,

Tom
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Re: Cutter Compensation Question

Post by CNCMaryland »

3d Adaptive does not have cutter compensation. So, that is why the G code does not have any G41/42 codes.

I am going to suspect a mismatch between the origin you have in fusion and the origin you on the machine.
The gcode shows an origin somewhere near the top left of the part, which i imagine is the hole that is there in the sample part.
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Re: Cutter Compensation Question

Post by RJS100 »

Thanks. I am going to re-check my work coordinate system and try again.
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Re: Cutter Compensation Question

Post by RJS100 »

Ok.. I setup up the part again to confirm the G54 position was correct. I entered a few MDI commands to confirm the x-0, y=0 and z=0 were in the correct location. All good so far.

I ran the G-code 1" above the part again and it appeared to be following the correct tool path. I ran it again just to be sure and it appeared to have lost the correct origin. The WCS table still indicates the correct info for G54. At this point I noticed a 452 ethernet communication error CNCPC to controller error. While I do not think a communication error would cause this problem, regardless I am going to follow the bulletin to resolve the communication error before proceeding further.

Thanks... Richard
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Re: Cutter Compensation Question

Post by suntravel »

You have set 0 in fusion on the finished part.

If you set 0 on the stock material on the mill, you will have an unwanted offset.

Better to set WCS 0 to the stock.

Uwe
Attachments
01.png
0.jpg
RJS100
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Re: Cutter Compensation Question

Post by RJS100 »

Thanks for your thoughts!

I am completely new to this (this is the 1st part I have ever machined) and appear to be doing something wrong. I setup up the G54 WCS again. Using an edge finder, I touched off the x axis, jogged in .050 and hit F10 to accept. I repeated this for the y axis. The WCS for this part is .050 inbound from the x and y axis. To test the position, I issued the command G1 X0 Y0. Perfect.... the edge finder moved what looks like .050 inbound from the edge of the part! I jogged the machine to different positions, reissued the command and each time the edge finder moved to the correct position.

I then installed the 3/8 end mill, touched off to the top of the part (this is the correct height for z) entered the tool # and hit f10 to accept this as the Z height for this part. I issued the command G1 Z0 and the tool immediately went to the correct Z height. Again, I jogged the machine to different positions, reissued the command and each time the edge finder moved to the correct z height.

All good so far! NOPE. I then reissued the command G1 X0 Y0 and the end mill moved about .8 inches to the right of the correct part 0 position. I am totally confused. Any ideas as to what is going on. Just an FYI, I previously setup the tool heights and diameter offsets for each of the tools relative to a master tool.

Thanks... Richard
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