Top Beam Tilt Correction Pull-Request

Software
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21

(comments out of order)

Have you done anything like this in the development of the Maslow?

No, there have been no tests like this in the past. When Bar developed the
Maslow he had a much simpler model in mind, the community has added many things
he didn’t think of at the time, and Chain Sag and Tilt are the two most recent

Chain Sag experiments. Thinking that if you put the sled at 0,0 about,
(center of board), and took the bricks off. Assuming that the motors paid out
the equal amount of chain on both sides that would put the sled at 0,0 (I
would eliminate the current chain sag corrections from the program for this
experiment.) without any sag corrections, it would sit somewhere above the 0,0
point on the y, and hopefully ok on the x since both chains should be the same
length.

With the bricks removed, the sled assembly with the router weighs “x”, say 7
pounds for discussion. With your new optical measuring cameras, is there a
way to lock in on that point, and then record the sled movements as weight is
added to the sled up to the brick weights, or even more for the experiment.

The optical tracking should be able to see a difference.

I would not expect much difference at the top of the board, and more at the
bottom.

They can even do this test in the bottom corners, to see how much a variation in
weight between the ~min 10 pounds to something overly heavy like 30 pounds
affects the location.

One problem is that we don’t really know how heavy the sled is (and it actually
varies depending on how much vaccuum hose it’s lifting)

It’s impossible to get the sag to zero, but what we are trying to do is to
figure out of our calculation can properly model the sag.

David Lang

22

What advantage does this offer over a decent spirit level and some level adjusting devices (I like carriage bolts and t-nuts, with a jam nut to prevent slippage). Put the level on the top beam, adjust the adjusters until the bubble’s centered, lock the jam nuts.

2 Likes
23

“Any problem has hardware solutions and a software solutions…”.

This would be the hardware solution. In this instance, the simple and elegant one as well.

24

For me, my frame is on casters that don’t have a level adjustment and its my shed that the Maslow is in that’s out of level the most. So I’d have to change out the casters I got (which is not going to be an easy task) to ones that have adjustment and make sure the maslow is pushed back to the right spot for it to be level again. The best spirit levels, according to one of the manufacturers, are accurate to about 0.3 degrees. That’s about 1.5 cm difference in height between the motors. My hope with Holey Maslow was to be able to determine the amount of tilt to use to arrive at a better calibration rather than to manually measure it.

1 Like
25

This doesn’t actually correct for the entire machine being off like that, this
only corrects for the top beam being tilted compared to the workpiece.

But if it did, the advantage would be that if you have your machine on wheels,
it could correct for it.

David Lang

26

@dlang It would seem that another advantage is that the frame does not have to be made super precisely or kept from warping over time with the top bar and bottom tray perfectly parallel.

27

the answer here is a water tube level, a plastic tube from motor to motor with
some water in it (ideally to the level of the bottom of the top beam for easy
reference?)

1 Like
28

Machinist level . That’s a cheap one, good for 0.0002 inches over 10 inches. A Starrett on Amazon claimed 90 seconds.

A water level (clear tubing) would get you better than 1.5cm over that distance.

I’d use shims under the wheels, or make adjustable mounts for the castor’s. How’d the shed come through the hurricane? Imagine it’s gonna settle as the ground dries out.

29

You can fix a racked frame, starting with measured diagonals and ending with that same level.

I’d think that having the bottom support out of level would only put a little tilt in the plywood, not as important as having the top beam level. Cuts would still be straight, just off kilter like old moose.

Here’s another research project, after the other errors are figured out start testing the effects of tilted beams. Wonder if I can get a sine bar and a set of gauge blocks past Mrs. Moose. Be able to wring more than just my hooves then, although Mrs. Moose might try and wring my neck

30

I hear what you are saying, but shimming is a pain considering how much I move the frame and it’s heavy as heck since I store all my plywood off the backside (my shed is very small, so i have to be very efficient in using the space).

Also, one of my theories is that a component of “poor” calibrations that some people are experiencing is that their top beam is not perfectly level with gravity, even though they think it is. I incorporated it as an adjustable value in holey maslow calibration and it did help reduce the error of the current model.

The shed survived well, no issues… it rains so much here in general that I don’t know if there is a constant settling amount.

31

We’re leaving Tuesday for Bokeelia, expect I’ll get to learn about all that raining and settling first hand, er, hoof. 1800 miles hauling a trailer behind a Subaru, we’ll see if U-Haul is right about towing capacity or if there’s a happy transmission shop owner in Cape Coral

1 Like
32

Looks like the robot went ahead and merged this. I guess the vote is counted 48 hrs from when the PR is originally opened, not when it was re-opened.

I think we either need to upvote the GroundControl PR so it also gets merged OR we need to revert this PR from firmware. One doesn’t make sense without the other.

2 Likes
33

I think some silly people (like myself :roll_eyes:) were confused and just voted on the Ground Control PR. For some reason I had it in my head that the firmware PR was just an earlier version of the GC pr which had been closed. I reverted the firmware version while awaiting the results of the GC PR and will do something when that vote is up…so get out there and VOTE folks!

2 Likes
34

@bar
Went through this thread.

Looks like this was voted down?

35

Nope! Was deemed not useful enough for the community at large. The advice was to instead that folks should invest the effort to get their top beam level because it keeps things simpler

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36

It also wasn’t clear that this wouldn’t further confuse efforts at accuracy.

David Lang

1 Like