Corner spacers and shimming the bed level

[Glenn Beer]

Ezra, I'd recommend for the next version, the corner holes in the Al
bed be tapped instead of clear holes.

I wanted to have my glass top surface just above the tops of all the
corner blocks. That meant shimming for level needed to be done under
the blocks. Loosening and tightening the screws and nuts with the al
bed mounted is awkward.

Fortunately the existing holes are just right for installing M5-0.8
heli-coils. I installed a set this morning.

FWIW: my shims ran 0.000, 0.004, 0.011, & 0.019"

[Josh S]

Glenn, what did you use for shims?  Can you take a picture of how you set it up?  And how did you measure it?  I got myself a dial indicator but I don't know how to rig it to the machine.  

[Glenn Beer]

That post was primarily about adding the the heli-coils.

But, I used a variety of shim materials. 

Some .032 thk aluminum sheet, Measures 0.84mm   K&S brand purchased at local hdwr store (OSH)

Some aluminum tape, the kind used for sealing ductwork Measures at .09mm 

Some Scotch clear packing tape 0.07mm thk.

Cut from the aluminum sheet,  4 squares 20mm x 20mm

    Used squares between blocks and head spreader, this gets the top glass surface just above the tops of the corner blocks. Squares are taped to bottom of heat spreader w/alum duct tape. http://www.flickr.com/photos/gkbeer/8486269263/in/photostream/lightbox/

Used layers of Scotch on bottom of blocks to get uniform bottom of bloc to top of glass measurements. 

From that start, I made further adjustments adding alum tape to bottom of corners of heat spreader. 

[Glenn Beer]

measurements were taken with a pair of digital calipers. 

On Monday, February 18, 2013 1:11:38 PM UTC-8, Josh S wrote:

[Dave]

Has anyone considered sanding down the blocks to get the bed level?  Might be neater. 

[Jonathan Shapiro]

Dave:

As a naive beginner, I'd worry that shaving down the originals would leave me SOL if I got it wrong.

Something that I haven't seen here:

If I have a bed that is *close* to level, and a dial indicator, is there some way to print new brackets that will get it *closer* to level? How close does the initial bed leveling have to be? Is there some spec beyond which I can't converge iteratively?

[John Stevenson]

With all the shimming and leveling, does anyone think the A1 would just be better off with adjustment posts built in like all the other printers? I know the idea was "shim it once", but it seems like there would be less hassle if it just had the adjusters.

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[Rick Zehr]

I was contemplating that yesterday, and I'd agree, particularly since any shims that stay in place with adhesive will become thinner over time as the adhesive drys out or squishes thinner. 

[Dave]

If you're willing to print new brackets (on a "close to level" machine) that are merely better (but not perfect), why not print a few spares right off the bat for sanding down?  Once you get them dialed in, you can't beat properly-sized spacers: no shims to lose, no adhesive to dry, no screws to slowly turn against their springs, and all the rigidity that molded PLA can provide. 

Personally, I intend to level the aluminum X-plate first, ideally using the four machined spacers I made.  Once that's square, I know I have a good foundation for a glass or garolite plate on top, ideally supported by 4 identical corner brackets.  

Presuming, of course, that I don't just replace the slide with a THK truck...   but that's a way down the road. 

Dave

[John D]

:-)  I think the answer is "it depends".  The A1 frame should be solid enough that you only have to go through this once.  If that's not the case, then we have other issues as well...

[Glenn Beer]

Agreed,  about the plastic tape not being absolutely stable.

That earlier post reads like I chose the plastic tape deliberately over the aluminum tape.
I'd forgotten I had the aluminum tape initially. I didn't want to use the Scotch near the Heater and was searching for a suitable alternative, stumbling on the aluminum tape during that search.