Heat bed options for Prusa, some advice please!

Hi,

I am sourcing parts for my Prusa and I am looking at what to buy / make for my heatbed.

I am looking to buy a heatbed MK2a with the three hold mounting for easy levelling looks like a good idea.

First of all, it says use M2.5 screws but a guy on ebay who sells heatbed kits includes M3, so will M3 fit ok?

Secondly, I have a friend who can get the bed and base plate machined for me but I am not sure what materials are best, some sell aluminium for the build plate and plywood for the build base, others sell acrylic for both.

Am I right in thinking Aluminium would be best for both or have I missed something? Please explain what you would use for each part and why?

Also, I can't find any design files for either anywhere. Does anyone know where I can get the designs for these parts so I can get them machined? Preferably they would also have the extra hole required for the new heatbed pcb (i.e. the hole that allows three point levelling), although I could easily drill this myself later.

Thanks in advance guys!

Oh, also, what sort of wire should I purchase for connecting it? I.e. what gauge and also, what sort of thermal properties and thickness of the insulator should it have as a minimum?

I just built a new printer and used the Helios heat bed from panucatt.com. It's a great design and it's working really well. The board is twice as thick as the MK2, and comes with its own insulating material. I purchase a 230mm by 230mm by 6mm aluminum plate from speedymetals.com, drilled through it in the appropriate places, and mounted the bare Helios with springs and M3 bolts (it actually even came with the bolts) right above it with no intervening layer. I'm very happy with it and I highly recommend the board.

I am confused, look at this:

[www.ebay.co.uk]

and then look at this:

[www.nextdayreprap.co.uk]

Which is right?

Nextdayreprap has a sturdy aluminium base on which the linear bearings for the Y axis are attached. Then a set of bolts with springs for levelling to a heat bed plate onto which the pcb and mirror are mounted directly.

The guy on ebay sells to plates but has the pcb extended another layer higher, i.e. has two sets of bolts raising the bed? Why? you would only need one right? to lift the hot part from the carriage plate, but he has two layers, is this because acrylic would melt? If so, why not just have the pcb rasied directly off the acrylic carriage plate at the bottom and make it abit wider? I guess this guys method gives you less build height and a less stable bed

What does everyone else do?

Your thoughts please, also as before, where can I get the design files to get them machined?

Cheers

Yes, the acrylic will melt (I'd bet it'll eventually buckle even with those standoffs).

You can use M3 bolts on a MK I/II heated bed. I mounted mine directly to a piece of 12mm MDF. Works great.

I second the Helios - looks really nice, better than MK II.

But as for wiring I use 16AWG speaker wire. Overkill though.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

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