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Made one! It works really well..

http://www.thingiverse.com/thing:661143

All you have to do is pull the bars out of the existing mount and put them through this one.


I found some strange behavior, though.

I set the z height and went from home to x0 y0 z0, and got 0 on the dial indicator.
I went back to home, and then went to x65 y-35 z0 (Y tower) and got +39 thousandths.
I went back home, and then went to x-65 y-35 z0 (X tower) and got +60 thousandths.
I went back home, and then went to x0 y65 z0 (Z tower) and got +65 thousandths.

I repeated that 10 times for each step and had consistent results.

I went back home, and then went to x0 y0 z0 and got 0 on the dial indicator.
I then moved to x65 y-35 z0 (Y tower), and got -48 thousandths (the pin moved out 52 thousandths)
I then moved back to x0 y0 z0 and got +2 thousandths (the pin moved in 52 thousandths, and then an additionall 2 thousandths)
I then moved back home and back to x0 y0 z0, and got 0 on the indicator.

This also happens on the other towers. Seems that returning to x0 y0 z0 is only accurate when moving all steppers down at the same time.

That is because you're likely changing the geometry of the machine by using that effector. You want to mount an indicator to your existing effector.

That could be true... I modelled mine based on the dimensions of the original. I also observed this behavior with the original effector, but wasn't able to measure the difference accurately.

The cheapskate on the Y tower is markedy more difficult to move than the X and Z towers, but I'm not sure if that would have anything to do with it or not.

For mounting it to the effector that came with the Orion, would I do that by using the hotend adapter or just the effector?

Have you calibrated horizontal radius, etc?

I had not until today. With the indicator mount on I disabled heating the nozzle and extrusion, and sent my circle print to the orion and saw what was described in the manual as all towers lowering. I tweaked the hr a bit and saw less of that. Gonna switch back to the factory effector, recalibrate it in a bit and see how it goes.

Not sure what to try next...

I have the towers leveled, but I can't seem to get a uniform z height around the build plate. Even when adjusting the horizontal radius, all that does is offset the pattern.

e.g., if z at X, Y, and Z are a little lower than z=0 , and z at X!, Y!, and Z! are a little higher than z=0 -- with Horizontal Radius of 75.2 (default),
then increasing or decreasing the HR will increase or decrease, respectively, the value of z at any of those points.

I forget the link to an image of the pattern, but you've probably seen it.

It's a heat map of some sort, indicating (I think) z height at various points along the build plate. As you approach a tower, the z height lowers, and as you move away from a tower, the z height increases.

I mean, I can make some pretty good prints, but I'm trying to eek every last bit of precision out of this thing. What sort of tolerance should I expect with respect to minimum and maximum z height vs what it's supposed to be?

Currently I'm looking at (Z) = Z +/- 20 or 30 thousandths of an inch for the edges of things about 4 inches in diameter.

Also seems to make it rather difficult to print a long, thin cylinder with a (reasonably) consistent diameter.

Sounds like this http://forum.seemecnc.com/viewtopic.php?f=37&t=4868

Yep.

That's the thread where I saw the map.

So from what I've learned, errors in geometry will result in this issue.

Should I take down the machine and look for things that are out of spec?

I haven't measured yet, but the arms of the X tower, with the axes homed, at the end closest to the hotend, extend a little further toward the build plate (maybe .65-.8mm or so) than the others. I suppose the length of the arms is one of the most critical dimensions in the process, along with the effector dimensions, heated bed -> base squareness, buildplate -> heated bed squareness, and tower alignment.

On the build plate: I take care to place all the clips in the same place every time, and I have noticed that clip placement alters the shape of the build plate slightly. I don't really know of a good way of measuring how level the build plate and heater are with the base of the machine.

Out of curiosity, there is a dimple in the center of the heated bed. When I travel to X0 Y0 Z0, the extruder nozzle is on the right edge (side opposite of the arm I think is a little longer than the others) of that dimple, toward the Y tower. It's been that way since I first set up the printer, so I assumed that was normal. Is it?

Note: I do find my attempts to solve this problem to be really entertaining. I've had a big interest in learning how to be precise for a long time, but never really had anything capable of being all that precise. Kind of makes me wish I had bought a MAX kit instead of the Orion, if I'm going to be (re)building a machine anyway =)