Yes, a top beam, and I’m just working on the mountable/demountable doodah!
Had a look at my measurements and it turns out I was right first time. So starting Calibration again and will go the full mile…
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Okay, I’ve measured everything with squares and tape, and have run the calibration sequence.
I’m using the latest versions of everything, and have a studwall frame that I labouriously mortised and tenoned together to ensure a rigid and non-flexing top beam. My tape and square measurements:
Motor Spacing: 3079mm
Sled Mount Spacing 139.5mm
Vertical Offset: 468mm
GC measurements:
Motor Spacing: 3073.37mm
Sled Mount Spacing 139.5mm
Vertical Offset: 479.08mm
I hit the tighten chains button many times and used a finger to raise the sag as doing so.
My motors are not dead centre to the board in the x-axis, but I figured that’s irrelevant at this stage, just that my board is offset right by 4mm.
So, GC is measuring the Motor spacing as over 5.5mm out of whack. and the dist to top of the workpiece as 11mm different.
All procedures have been followed to the letter and my frame is as rigid as is possible using wood. Motor mounts, albeit a bit of a hack together, are very solid and not subject to any flexing during operation.
As such I’m stumped. Going to procede to see where it leads me and hope it’ll reveal some glaring error on my part!
And tips or advice gladly received.
Cheers,
Miles
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It seems appropriate to continue the ramblings of my calibration issues here instead of starting a new thread.
I’ve just run calib again, and this time have GC measuring the motor dist as 3073.03, so pretty close to the first one today. And, the vert offset as 479.67, again not bad consistency with the first calib.
Oh, I’ve just noticed that it’s gone and set the sled to 125mm, and I have no understanding of why it’s done that.
I also got as far as the test cut pattern, my sled merrily started making it’s way to the top left of the board, with a sharpie in it, and it stopped about 230mm shy, the GC pops up a message asking me to set the z-axis at a different depth, I ignore this and try to restart the cut pattern and it won’t do it, just popped up another z-axis request, this time a +5.00, but I’d previously skipped the z-axis bit, and had it switched off.
I suffered a moment of major retardation earlier and instead of playing out the left chain first at step 7, I played out the right chain first, only to discover that it then screwed up the whole process as it wouldn’t then allow me to play out the left! So, I started again. May i suggest a greyed out Extend Right Chain button until the left has been done, or render it so that it makes no difference which you extend first. Apologies if this is just me being retarded, it happens! ;¬)
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Have just found that the power supply tripped causing the test cut to fail. The ATX was doing so well! May have to purchase a for-purpose PSU this week.
I’ve rebooted and set the sled back to 139.5mm dia, and have altered the vert offset to a manual measurement. I returned to centre and I’m 4mm low and 7mm from the dead centre of the board as measured with laser. I had previously laid a laser diagonally over the 8x4 board to find the exact centre. NB, this relies on the board having been manufactured square, but I think is good enough for this purpose, within a mm) Accounting for my not perfectly central motor mounting (to the workpiece) this resolves essentially as a small inaccuracy from the vertical I reckon.
This has left me wondering if the small discrepency in my Motors Dist figure could account for the sled hanging 4-5mm low. I’ve played around with it adding a mm at a time and it appears to have very little bearing on the movement of the sled when I hit Return to Centre - odd!
Is it poss to run the test cut pattern again without going all the way through the calib process?
M
Cheers,
Miles
Yes, that’s what I do. Just skip past all the other steps until you choose ‘triangular’.
The motor spacing measurement is very important. Using the Actions/Advanced/Simulator will show how much a few mm. can change things. It’s a great way to learn about how different settings affect things.
One way to check frame stiffness is to make a measurement between the motor mounts without and then with the motor tension. Pick a spot that won’t be blocked by the tightened chain, but which would move the most if the chain pulled the sprockets together. I measured between the outer corners of my motor mount blocks. On my original frame I found as much as 10mm of flexing. I was quite surprised.
That said, the auto cal. steps are and aid, not a requirement. I never cared much for the original motor height auto cal., I always skipped that step and used my own value. The new ‘triangular’ cal. step does a good job at it now, though.
When using a pen instead of a router, I add weight to the sled to simulate the weight of the router. It took some adjusting and rigging to arrive at a pen holder that moves with the z-axis, applies slight but firm pressure toward the surface, and doesn’t rock sideways at all. Not pretty, but works. I tape butcher paper to the worksurface to get nice crisp lines.
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Okay, I’ve measured everything with squares and tape, and have run the calibration sequence.
I’m using the latest versions of everything, and have a studwall frame that I labouriously mortised and tenoned together to ensure a rigid and non-flexing top beam. My tape and square measurements:
Motor Spacing: 3079mm
Sled Mount Spacing 139.5mm
why do you have sled mount spacing instead of rotation radius? that seems like a
significant problem.
Vertical Offset: 468mm
GC measurements:
Motor Spacing: 3073.37mm
Sled Mount Spacing 139.5mm
Vertical Offset: 479.08mmI hit the tighten chains button many times and used a finger to raise the sag as doing so.
My motors are not dead centre to the board in the x-axis, but I figured that’s irrelevant at this stage, just that my board is offset right by 4mm.
So, GC is measuring the Motor spacing as over 5.5mm out of whack. and the dist to top of the workpiece as 11mm different.
I think we need to figure out hy the motor spacing is off like this. I think
that’s causing the other errors
can you try using your other chain for the motor spacing measurement (and/or
compare the two chains and see if one is a few mm longer than the other)
When doing the calibration, a tiny error in the measurement (even off by 1 mm)
can cause several mm of error in the result.
Is there a way for you to set the motor spacing and then to the rest of the
calibration?
Hmm, yes, that sled mounting thing irked me, but I think it is hangover from me messing around with the last GC version, before realising there is another field for it. I just left it s I figured selecting tri-kinematics would just ignore those fields.
Chains checked and fine, they were a single length split in two.
I’m unsure about what you mean with your last sentence, do you mean plug in a manual motor distance and then run calib again?
Hmm, yes, that sled mounting thing irked me, but I think it is hangover from me messing around with the last GC version, before realising there is another field for it. I just left it s I figured selecting tri-kinematics would just ignore those fields.
we’ve seen some strangeness happen when this is set, try clearing your config
file and try again.
Chains checked and fine, they were a single length split in two.
ok, just trying to make sure the chain we are using to measure didn’t get
stretched or something.
3079mm is almost 500 links, an error of 4mm is <0.01mm per link. It’s possible
that this is in the relm of expected error/play in the links. If you change your
link size from 6.35mm to 6.36mm per link, that may make the measurement come out
correctly, and if we are off like this everywhere, it could be a source of
position error elsewhere.
I’m unsure about what you mean with your last sentence, do you mean plug in a manual motor distance and then run calib again?
yes, run the calibration with a manually entered motor distance and see how
close to accurate you are.
and then try the link size change I mention above and see if it makes a
noticable difference. A 0.1% error isn’t much, but multiplied over the distances
we are talking about here, with the accuracy we are aiming for, we may have
eliminated enough other errors for this to start showing up.
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