Inside Profile vs. Pocket

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mcromney
Posts: 2
Joined: Thu May 26, 2022 2:38 pm

Inside Profile vs. Pocket

Post by mcromney »

I'm in the process of cutting my first real project on my newly built 50x110 unit. I've built some clamps and carved a simple sign which all came out well but this project includes cutting some dogbone slots in plywood to build a cabinet. In testing the size of the slots and the thickness of my 0.5" plywood, I've noticed that the slots come out differently if I use an inside profile cut as opposed to a pocket cut. The pocket cut is just barely undersized as expected (0.5" x 1.0" slot measures about (.490-.495)" x (.990-.995)", due to my 1/4" bit being just slightly less than 1/4", I'm thinking) but the inside profile is about 0.025-0.030" too big in both dimensions. I've looked over the Gcode and both the cuts move the coordinates the correct distance (0.25", adding the 1/4" bit makes for a 0.5" cut in the X dimension, 0.75" (+.25") in the Y dimension). Am I missing something about how these two cuts would be made? Seems to me that the only difference is that the pocket clears out the middle stock material whereas the profile leaves it alone. BTW, I ran the Square test code and it all came out looking correct, just slightly undersized by no more than 0.005" on both sides.

Appreciate any insight from the much more experienced members here!
MarkVa1
Posts: 190
Joined: Mon Aug 04, 2014 12:56 pm

Re: Inside Profile vs. Pocket

Post by MarkVa1 »

If you’re using Fusion sometimes various profiles defaults to leaving material. That is a simple check but the idea is you rough cut then do a final pass that removes any material left during the rough cut. Sometimes the preview will show material being cut that is unwanted? At least see it before cutting and measuring.

Also, if your machine is newer you can check the steps by having the machine travel a set distance, maybe 96” and then measure how far it actually travels. But if steps are off than everything should be off.

Congrats on building the big machine!
baysale976
Posts: 494
Joined: Mon Dec 31, 2012 11:07 am

Re: Inside Profile vs. Pocket

Post by baysale976 »

I envy the size of that machine!

Generate G-code for both, with just one slot. Compare the G-code details, the edges should both be the same.
If they are not the same, go to the software supplier with your problem.
If they are the same, you'll need some additional work to figure out what's not right on the machine.

Below is a G-Code file generated by Vectric V-Carve, using the same 0.5 x 1.0 rectangle in the middle of a 4x4 workpiece. Although the "Profile" starts in a different spot from the "Pocket", they both make all the same moves at the outside points (i.e., ignore lines 280 to 330, that's the 'inside' of the pocket). If my machine would cut these even a thousandth different I'd be concerned.

N90G00G20G17G90G40G49G80
N100G70G91.1
N110T22M06
N120 (1/4" Upcut Short Freud 75-103)
N130G00G43Z0.8000H22
N140S21000M03
N150(Toolpath:- Profile 1)
N160G94
N170X0.0000Y0.0000F55.0
N180G00X1.8750Y1.6250Z0.2000
N190G1X1.8750Y1.6250Z-0.1000F30.0
N200G1X1.8750Y2.3750Z-0.1000F55.0
N210G1X2.1250Y2.3750Z-0.1000
N220G1X2.1250Y1.6250Z-0.1000
N230G1X1.8750Y1.6250Z-0.1000
N240G00X1.8750Y1.6250Z0.2000
(New Path = Pocket 1)
N260 S21000M03
N270 F55.0
N280G00X1.9950Y1.7450Z0.2000
N290G1X1.9950Y1.7450Z-0.1000F30.0
N300G1X1.9950Y2.2550Z-0.1000F55.0
N310G1X2.0050Y2.2550Z-0.1000
N320G1X2.0050Y1.7450Z-0.1000
N330G1X1.9950Y1.7450Z-0.1000
N340G1X1.8750Y1.6250Z-0.1000
N350G1X1.8750Y2.3750Z-0.1000
N360G1X2.1250Y2.3750Z-0.1000
N370G1X2.1250Y1.6250Z-0.1000
N380G1X1.8750Y1.6250Z-0.1000
N390G00X1.8750Y1.6250Z0.2000
N400G00Z0.8000
N410G00X0.0000Y0.0000
N420M09
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