From the weekly newsletter it is good to know you are working on the calibration and accuracy testing. I’ve had to give my Maslow a rest due to other projects, but one of the last things I was doing is running a series of batch jobs that would drill holes in a test sheet at 6" intervals in a grid. I retracted the belts between runs to see how consistent it was shelf to table. Between runs I zeroed it in 1/4 inch from the last starting point. I was going to look for zones with the greatest amount of drift. I didn’t finish this work, but wanted to share my thoughts and methodology.
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I think that is an excellent system to check.
We’re testing with 600mm squares (although to let us fit more tests on the same sheet we just cut the corners of the squares). 600mm squares are nice because it’s big enough that it’s easy to measure with a tape measure, but small enough that we can do multiple on the sheet to test in different areas
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Bar wrote:
I think that is an excellent system to check.
We’re testing with 600mm squares (although to let us fit more tests on the same sheet we just cut the corners of the squares). 600mm squares are nice because it’s big enough that it’s easy to measure with a tape measure, but small enough that we can do multiple on the sheet to test in different areas
I would suggest doing a test based on making a MFT table.
a MFT table has 20mm holes spaced every 90mm in a grid. There are a HUGE number
of accessories designed to attach to such tables (search for 'dog hole
accessories), and ‘cheap’ pre-made tables are several hundred dollars. Just the
templates to make such tables yourself commonly run a couple hundred dollars
If you cut 20mm holes, you can use 3/4" PVC pipe to make pegs to go in them. If
you just do 1/4" holes, you can use extra router/drill bits.
For testing, just do the 1/4" holes as they will be faster, you can put tape
over them and offset slightly to repeat the test with a different calibration on
the same board.
If you can find a local machine shop, have them make you a few pegs that have
EXACTLY half of the peg machined away on one end so that you don’t have to
account for the thickness of the peg in your measurements (or you can look at
the tape measure vernier that I posted several years ago to read more accurately
from a tape measure, it includes 1/4" pegs and it wouldn’t be hard to make a
version that had 20mm (aka 3/4") pegs instead.
David Lang
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I am very interested in accuracy when using the entire range of Z like in a deep foam surfboard carve.
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gazinux wrote:
I am very interested in accuracy when using the entire range of Z like in
a deep foam surfboard carve.
If your Z offsets are good, using the entire range of Z should not be a problem.
The maslow takes the Z distance into account when calculating the belt length.
Just make sure that you calibrate with the Z all the way down, and that you set
this frame Z=0 once in a while (which is different from bit Z=0)
@bar, @anna what’s the best way to differentiate setting the two different Z=0
points?
David Lang
Good to know that in theory it will be accurate and thanks for the tip–appreciate it! Cheers.
I first tried squares but then I thought I would be measuring on potentially non-parallel sides of a rectangle so I went to holes to insert pegs and measure from peg to peg with calipers- what you were describing in the MFT description. Most of my 3D work is metric, but my woodworking is stuck at Imperial sadly. Thanks for the replies!
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