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Shape dimensions not being cut as expected by xcarve

I’m posting this under the Easel tag because I’m unsure if the problem is related to user error, software, or the machine. I’ve generated a shape in Inkscape and imported it into Easel as an .svg file. Based on the measurements, the bit size (1/8" upcut), and choosing for the path to cut outside the shape, I’m expecting the protruding rectangles at the top of the shape to be 3/8" wide, with 3/8" wide spaces between each. Using digital calipers, I’m measuring the rectangles from .362 in to .367 in, and the gaps from .393 in to .397. All of the measurements should be close to .375 in. The difference is a problem because this piece is to be part of a box joint jig for a single-blade table saw. I’ve attached (I hope) the .svg file. Any help is appreciated, and please let me know if I’m not providing enough or pertinent info. Thanks!

three_eighths_box_joint_jig

Can you post the Easel file here. Also have you calibrated your machine and measured the bit?

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Perhaps you need to fine tune the steps per mm? That would be $100 and $101. There is a calculator here:

http://www.designsbyphil.com/x-carve-tips.html

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Sounds to me like your bit is smaller than 1/8" or deflection is causing pockets to be undersized.
If you take you under and over and then average them it is real close to the .375 you expected.

First of all, use a closed design-CNC work flow and make sure your $100 and $101 values are as good as you can measure.
Carve some test pieces in Easel, designed in Easel.
Do a 2" square, a 4" square and a 10" square.

If the discrepancy is the same for both axes (X&Y) then its mechanical, a combination of machine flex, tool and backlash factor.
If the discrepancy is consistently different in X-direction vs Y-direction you have rigidity difference between the two causing the bit to “drag behind” during X/Y-transition/gradient.

If the discrepancy grow at the same rate as the design its steps/mm value ($100 and $101 for X/Y)