Build Bed Platform question

Just finished building my oversize MendelMax 1.5, and am looking a an easy to adjust bed.
I have a 3mm Alu sheet that has had the edges bent 90degrees so its pretty straight. I have glued resistors underneath, and it heats up pretty nicely.

Question is what I should mount this on top of? I have this Y carriage by Tommy C
[www.thingiverse.com]

I searched around, but all I see is the MDF that some people are using. Is this the way to go?


Thanks

Jonas

Why not I use MDF and it works really well

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Experimenting in 3D in New Zealand

I've used both dibond and laminated (mainly mdf) floor boarding with great success.

I suggest you ditch springs and level the bed using washers as shims.

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-Nudel
Blog with RepRap Comic

I found MDF warped and the bed would not stay level from one build to the next. Dibond is much better.

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[www.hydraraptor.blogspot.com]

I use printed Y-carriages. Some consider them a waste of plastic, but they're light, accurate, everything is in one piece, they don't need any extra drilling or parts...

ttsalo Wrote:
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> I use printed Y-carriages. Some consider them a
> waste of plastic, but they're light, accurate,
> everything is in one piece, they don't need any
> extra drilling or parts...

Me too, on my last two printers, the printed Y carriages have been excellent, using Di-bond above the Y carriage, and the heated bed PCB on top of the Di-bond supported by 3mm metal Hex stand-offs, cardboard and foil thermal insulation under the PCB and 3mm Mirrorglass on the top, bulldog clipped front and back.
It's all very light-weight and can move very quickly with high acceleration.

Don't use any springs or anything that can move, Once you have it level, it will stay that way. Not a single adjustment in over 2 months now.

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[richrap.blogspot.com]

richrap Wrote:
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> Me too, on my last two printers, the printed Y
> carriages have been excellent, using Di-bond above
> the Y carriage, and the heated bed PCB on top of
> the Di-bond supported by 3mm metal Hex stand-offs,
> cardboard and foil thermal insulation under the
> PCB and 3mm Mirrorglass on the top, bulldog
> clipped front and back.
> It's all very light-weight and can move very
> quickly with high acceleration.

I have the aluminium build plate bolted to the printed Y carriage with sunken head bolts, and four power resistors bolted to the build plate, also with sunken head bolts. There's just the carriage and one plate. Simple and easy.

richrap Wrote:
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> Don't use any springs or anything that can move,
> Once you have it level, it will stay that way. Not
> a single adjustment in over 2 months now.

If you don't mind me asking, how do you level it and keep it there while it gets fixed? By level I'm assuming you mean parallel with respect to the XY axes.

I'm very dependent on getting the print nozzle right down in there and using a feeler gauge and adjusting the screws on my spring-mounted bed to bring it up and down in very tiny increments. My bubble level can't tell the difference between a quarter turn too low on one corner versus level but my prints sure do make it known!

I screw the Y carriage down tight, and the Di-bond sheet also nice and tight. I use 5 x M3 Hex PCB spacers on a Prusa MK2 heatbed.

The hole in the middle of the bed is countersunk and a M3 x 6mm countersunk screw is tightly screwed into the middle pillar.
This stops the PCB from warping and also gives you a fixed centre point.

The four corners are then adjusted to be flat and tightened down after the rest is wired up and assembled with the glass on top.
My mirror-glass plate is 200 x 200 with rounded corners, so the mounting corners of the PCB are accessible while the glass is on top.

On the last machine I did fine tuning with kapton tape on the top side of the heated PCB. As I'm using a mirror-glass with a black-silver backing it does not seem to make any difference to the temperature if some Kapton tape is used as a shim on one section.

I'm happy to take some photos and post if that would help?

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[richrap.blogspot.com]

richrap Wrote:

> I'm happy to take some photos and post if that
> would help?

I think it might. I tried catching a glimpse on your videos but it isn't really a focus point.

I read:
> The four corners are then adjusted to be flat and
> tightened down after the rest is wired up and

and visualize those screws going into fixed PCB Spacers but the board just laying on the spacers due to gravity and the screws just holding it from sliding around. Then I read shim and wonder if your measuring then undoing that same screw, siding tape under, and inserting the screw again through the tape or something?

I just use hexagonal pillars in the four corners, tapped into the Dibond carriage. Twisting the pillars raises or lowers the corner and the screw in the top locks it and holds the PCB down.

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[www.hydraraptor.blogspot.com]

Mazaw Wrote:
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> and visualize those screws going into fixed PCB
> Spacers but the board just laying on the spacers
> due to gravity and the screws just holding it from
> sliding around. Then I read shim and wonder if
> your measuring then undoing that same screw,
> siding tape under, and inserting the screw again
> through the tape or something?

I'll take some photos at the weekend, and post them.

I'm doing it exactly the same as nophead, I just also have one in the middle that I do not adjust.

The Kapton shim is only as a last resort, this is just stuck on the top of the PCB, under the Mirror-glass to lift it ever so slightly.

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[richrap.blogspot.com]

nophead Wrote:
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> I just use hexagonal pillars in the four corners,
> tapped into the Dibond carriage. Twisting the
> pillars raises or lowers the corner and the screw
> in the top locks it and holds the PCB down.

How often do you have to re-level? Does the vibration loosen the pillars or is there also some Loctite or glue on the threads?

I don't do it unless I change the glass or move the machine. They don't shake loose. A spring washer might be a good idea but I have the glass too close.

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[www.hydraraptor.blogspot.com]