Aluminium Bed Thickness

Hi everyone, I've just signed up and hoping someone can give me a bit of advice.

I'm designing and building a printer from scratch and am wondering how thick my print bed should be. The bed will be 330x330 mm cast aluminium tool plate with a 300x300mm 750w silicone heat pad stuck underneath. I can get tool plate from 5mm thick and was thinking of going for 6mm as this should give me enough thickness for mountings threaded in around the 15mm border and I can also drill recesses from the bottom to mount thermistors in several places to check even heating.

Obviously thinner plate is cheaper and thicker plate will be more rigid and will give a more even heat but will take longer to heat and cool



What do you all think?

I want to try lots of different materials and have a very versatile printer with a build area 300x300x450mm so a decent size as well

Cheers
Ian

Welcome to the forum!

IMO 6mm would be a good thickness. You could go a little thicker, but I suggest you don't go thinner.

750W is somewhat over-powered for that size bed. A power rating of 0.4W per sq cm will be sufficient to heat up the bed quickly, unless you go to much thicker aluminium. That works out at about 435W. With this amount of power, the bed is still likely to reach more than 200C if you leave the heater on at full power.

Edited 3 time(s). Last edit at 10/07/2017 05:49AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi, thanks for the reply.

I can probably go to 8mm thick plate. My print head can reach about 345x345mm so I could extend my build area slightly and go for a plate 350x350x8. I would then have a 25mm area all round the edge not directly heated and I suspect the mat heating element stops a few mm from the edge as well.

I'm probably not going to need the extra build space but it's always nice to have as long as it doesn't drag down the temperature on the 300x300mm area I need.

Edited 1 time(s). Last edit at 10/07/2017 05:52AM by Dwarfer.

I used a 425mm round Mic6 disk 8mm thick. Heater is 120V, 500w. Print area is around 320mm. I wouldn't recommend thinner plate for a bed this size.

when i was building my big mendel i ordered a 8mm 280mm x 350mm . It was a 6061 aluminum sheet ( i have a hard time finding cast aluminum here) . When i got it on my hand and felt how heavy it was i then realized once more what an a*** i am .

I went down to 6mm then and because on my previous mistake getting me out of the budget i got the simple aluminum ( just aluminum) . I am very happy with that although now i 've ordered one more i ordered it 5mm .

On my first contact with aluminum sheet was a smaller one for my second mendel (250mm * 250mm) which i 've bought it 8mm for milling it down to 6mm . Finally i got it 5.4mm due to a mistake i ve made during the milling but at that moment i realized that a 60 series aluminum would be more than enough if it was 4mm and the more expensive of all could easily be 3mm.

All of this are personal thoughts and experience. I also aggree to dc that it is overpowered. in the big one i have a heater of 600w main power and i am getting the bed the last two days i got my printbite sheet at 120c in a (couple of minutes)² :-) .

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Delta Printer
Duet 0.8.5 firmware 1.19

Will the bed be moving, and if so in what direction? A bed moving in the X or Y direction needs to be kept light in weight. A bed moving in the Z direction, or not moving at all, can be heavier.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The bed will move on the Z axis with two 12mm linear rails and a 8mm lead screw on the rear and another two lead screws one on each side near the front.

The bed heater will be pid controlled so I am not worried about it being overpowered. I can always reduce the on time if the bed temp spikes.

I have a 750 watt heater on the 300x300x8mm bed in my printer and it heats to 105C in 4.5 minutes. You don't need multiple thermistors to check even heating. It will heat evenly- that's why you're using aluminum. Adding a thermal cutoff is a good idea for safety. See [drmrehorst.blogspot.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]