Today, we're going to be revisiting the whole subject involving solid bed mounts because
one type of bed mount that I did not use before due to certain technical difficulties was the
aluminum bed mounts. The thing about them is that, yes, they are machined to a point where
their variances between each other are very small, within the hundredths of a millimeter, making them
perfectly suitable for solid bed mounts. You would think that with them all being the exact
size you need them to be, that you would just put them in place, tighten down your nut here
for the screws for the bed, and call it a day. That is not the case because when you install
these aluminum bed mounts, one thing you have to take into consideration is the Y-axis carriage
itself is not nearly as flat as the hotbed that you're printing on. It's not built to the same
tolerances. Even though the aluminum bed mounts are perfectly machined and are sized just the way
you need it, they will not be perfectly level. In fact, you're going to be very far off because the
Y-axis carriage is just not flat and it was never meant to be super flat. It was meant to allow you
to adjust the level of the bed with something like this, a metal spring so that you can
fix the uneven nature of the bed. That being said, there is a solution. I had
waited for a long time to get it because it comes from AliExpress. My solution are shims. These are
M4 x 8 shims, meaning, their internal diameter is 4 millimeters, their external is 8 millimeters.
They are what I use in order to relevel it out. Instead of adjusting a spring up and down,
what I do is I put these aluminum bed mounts in, do a bed level test with my ABL
using the OctoPrint Bed Mesh Visualizer, see what part of the bed needs to be raised up or--
Well, you can only raise it up in this case, and put shims on those spots to flatten it out.
Now, what we found is in place of these shims, you can use razor blades.
That's what we're using on here. This was our testbed.
Believe it or not, it worked out quite well. That being said,
the razor blades actually are not as thin as my shims. This razor blade is slightly thicker
than 0.1 millimeters and we measured that with my digital calipers. That's pretty good, but
they're not consistent like the shims are. These shims are always consistent. Now, you would think
that at this point, all you have to do is raise up the corners that are too low, the shims,
put your nut back on the screw here with a little wheel, and you're good to go. Well, no,
you're not. Actually, you've got long ways to go. It's a bit of an annoying process,
but it is worth it once it's done. You see, the problem with shims that are this
thin, and these are measured at 0.1 millimeters exactly, is once you compress these shims,
meaning, when you screw this nut back on the bed and screw, that 0.1 millimeters becomes
slightly thinner. You can do a measurement before compressing them with these little wheels
and you think, "Aha, I got a perfect bed level. Everything is super, super flat,"
but the moment you screw everything down nice and snug, your bed level is no longer a level.
It can get pretty wild pretty quick because some of these bed mounts needed
more than just two or three shims in order to get them to a point where they were the same
height relative to each other after shimming. The thing you have to do is not only do you have
to shim it, but you have to compress it, then measure and then reshim after that measuring,
then compress again, and then measure again until everything is perfect. Yes, it's way more tedious
than I initially imagined it would be because you would think, "Okay, if there's 10 millimeters all
exact on these and there's maybe 0.2-millimeter difference here, 0.1-millimeter difference there
or something, yes, you put two shims there, one shim there, and you're nice and flat," but
that's just not how this works. On top of this, there is another very important point to note.
These shims are quite small. I could not find anything with the M4 internal
diameter with a wider external diameter. Unfortunately, these are as big as they get
for the purposes that I ended up using them for. Because of that, if you put the shims
above the spacer, what you've essentially done is you've created a point that was
nice and big before and made it really small. The problem with that is you go from a large flat
surface to a very small flat surface, and this small flat surface essentially makes a point.
If you make a point, then you might warp your bed a little bit. That's not good.
When you put these on, put these spacers so that they are touching the hotbed, but put
the shims so that they are touching the Y-axis carriage because if you don't do that, you're
going to end up warping the bed when you tighten everything down. Once you get all that done,
is it worth it? Yes, because once everything is set, compressed, and level enough that your ABL
can handle any miniscule variances, that's what the ABL is there for, and you get nice,
flat, first-layer prints, you really don't have to adjust anything else from there on out. it is set,
it is done, it's not really going to change. Even with the expansion and contraction
of the metals, because yes, your bed is touching a full metal bed mounts, I found that it's not
enough heat to transfer through this to make any real, noticeable issues. All that to say
that yes, these are worth it if you shim them properly and compress each time and measure,
compress, shim, measure, compress, or measure, shim, compress, measure, shim, compress,
yadda yadda, you're going through this process several times in order to find the perfect level.
Now, the reason I think it's important to use proper shims instead of razor blades is
that these shims are the exact internal diameter that the external diameter of these screws are.
Even though they're much, much smaller than the spacer themselves, because that internal
diameter on the shim is the same as the external diameter of the screw, they will not move. They
will stay in place regardless of the fact that they are different sizes. It's not as simple
as I was hoping it would be, but it is still very much doable. It's just really tedious.
Hopefully, that helps if you are considering going this route.
Again, it's worth it if you're already the kind of person who's doing stuff
like linear rails on every axis, you know how tedious getting those are,
to be perfect as it can be and these are the same. It's the same concept. You've got a solidified
system that is not going to change once it's put in place, it just takes a while to adjust.