Lower corner accuracy issue

No Judgement
1

I, like so many others, have not built my machine yet. I have been reading quite a few posts in the last couple weeks, and especially interesting is the accuracy issue and proposed solutions for the lower two corners.

It occurs to me that if you were cutting an entire 4 x 8 sheet, you could use a strategy to cut all the parts in the top half of the sheet, then stop the machine, invert the sheet, re-orient the Maslow, and continue cutting the rest of the sheet.

I think this would work even for parts that go all the way across the 4 foot width of the sheet if you plan your SVG and G code properly.

Yes, you would need to start your Masllow and align it twice for each sheet, but then you don’t have to worry about all of these accuracy issues.

Is this possible? From everything I see and read about, if you set up your G code properly I think it is.

Obviously not as good as a fix for the lower corners itself, but a possible workaround in the meantime.

What do you guys think?

2

It occurs to me that if you were cutting an entire 4 x 8 sheet, you could use
a strategy to cut all the parts in the top half of the sheet, then stop the
machine, invert the sheet, re-orient the Maslow, and continue cutting the rest
of the sheet.

I think this would work even for parts that go all the way across the 4 foot
width of the sheet if you plan your SVG and G code properly.

Yes, you would need to start your Masllow and align it twice for each sheet,
but then you don’t have to worry about all of these accuracy issues.

Is this possible? From everything I see and read about, if you set up your G
code properly I think it is.

Yes, this is possible, the same approach can be used to cut on both sides of the
wood.

the problems you run into here are:

getting the alignment exactly correct when you move the workpiece (“is the sheet
of plywood really a rectangle, or is it a trapizoid by 1-2mm?” for example)

designing the CAD so that it does the right thing.

one trick that people do is that they drill holes through the workpiece (ideall
in an area that doesn’t make it into the final product) and then when they move
the workpiece, they put pins/dowels into these holes so that the piece is in
exactly the place they told it to be (not resting on any edges or anything).
Positioning these holes and making the CAD work properly can get “interesting”

People do this.

I cut a 6’ long shelf side on a CNC with a 2’ long bed by doing a cut, moving
the router (via the g-code) to the right place, then moving the wood until it
was against the router bit (turned off), and then turning it on and let it cut
the next part of the shelf. It worked very well and everything was exactly
consistant.

avoid doing anything that requires you to precisely measure a position, always
make it so that you are pushing your material against something (pin, edge, etc)

David Lang

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3

Thank you for the explanation. I will use that when mine is built.

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