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Circles Bigger Than Expected

Ok, I’ve drawn out my design using Inkscape and trialled out some shapes to get to grips with the machine.

For some reason, it seems most of the cuts are coming out too big. I have tried different profile options with inside and outside, I am using a 6.35mm bit.

A circle that’s meant to be 353mm is coming out at 363mm. Any help is always appreciated!?

How are you generating the gcode? Is this using MakerCAM?

You may need to change the resolution under Edit -> Preferences -> Svg Resolution to 96…at least that’s what I had to do to make MakerCAM generate parts the correct size

I am using MakerCam for the gcode.

I did see another post whilst searching through the forum where you suggested Svg R to 96 but it didn’t appear to make any difference.

I will have another play around with it this evening.

The circles and squares are being cut to the correct shape and all look great, if I can iron out these little issues, I’ll be over the moon! It’s an amazing machine.

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Fantastic!

I’m 99.9% certain that the scaling issue is cropping up somewhere in the gcode generation process. A quick way to check is to create a 100x100 rectangle in MakerCAM and see if it looks the same size as one which is imported from inkscape

Sorry I should have remembered this! I did draw a square in MakerCam to see if it would draw the same size.

My square was 118mm squared. I drew this in MakeCcam at 4.65 inches and they did appear to be the same size. So it does seem to be importing in to MakerCam correctly?

Thanks so much for all your help so far. I’m itching to get back to it after work!

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I suggest that you create a rectangle in makercam, do the cut, and then share the resulting measurements and the gcode you created with us.

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So I’ve just created a rectangle in makercam.

The dimension 118mm by 118mm (so square). The actual cut it’s left me with is 129mm.

Can you post the gcode.

Sure, here it is. z66.nc (367 Bytes)

Well, this is not a scaling issue. But what size bit are you using? 1/4 inch?

And you are measuring the distance of the inside edges of the cut, correct? not the outer edges…

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Oh no, I think you’ve hit the nail on the head. How stupid I feel. I’ve just measured the inside edges and they are in fact 117mm close to 118mm. Stupid question, but I want the overall outline to be 118mm, so do I need to calculate the bit in to this? Essentially so I can place a component inside this 118mm section on the project I’m building, if that makes sense?

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Sorry it is a 1/4 inch bit.

There are three functions you can use to generate contours… inside profile, outside profile, and follow.
I’ll see if I can find a writeup on the three, but in general… follow puts the router bit exactly at the 118mm point (so half the bit is inside and half the bit is outside). Inside profile offsets the bit inside so that the outer edge of the router bit is at the 118 mm point. Outside profile offsets the bit outside so that the inner edge of the router bit is at the 118 mm point. Let’s say you want to cut a 5-inch hole in something. Draw a 5 inch circle and use an inside profile. The hole will be 5-inches but the piece you cut out will be 3.5 inches (because the router bit cut 1/4 inch all the way around), but who cares, you wanted a hole. If you want a 5 inch circle cut out, draw a 5 inch circle and use an outside profile. The circle that you cut out will be 5 inches, but the hole in the board will be 5.5 inches but who cares, you wanted the circle. Follow is usually used to do engravings of the board.

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Draw the 118 mm square and then use an outside profile.

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Thanks so much for that, I should have noticed this!

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It’s a learning process. We’ve all been there.

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Thanks so much for you help, all my speaker boards are cut perfectly!

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Nice!

Great work!