Heated Bed Questions

[mikegrundvig]

So how does this heated bed thing work? I bought the one as part of the Azteeg electronics but I'm not quite sure the proper process. I assume the heated bed is offset from the aluminum Y carriage of the Hadron and I need to be able to level it as much as possible. Or do I bolt the heated bed right to the surface of that carriage? Shouldn't insulation be used on the back of the heated bed to keep it from dissipating into the air from both sides? Finally, what about the glass on the surface of the bed? How thick/thin should it be? Thanks!

-Mike

[cozmicray]

When using ABS you need a heated surface for the extruded plastic to grab on to
and also keep part from warping. (so I've read)

I have a heated bed plate I got from supplier of my RAMPS 1.4.

I plan to make a sandwich of thermal insulator (bottom), heater,
aluminum face plate (top)(good thermal conductivity)
and attach this to plate, perhaps with spacers, but not too thick to keep max z-axis print distance.

Some people sell borosilica glass (pyrex) to use on top. (glass is considered a thermal insulator)
Some people use regular window glass.
Just something to hold Kapton/blue painters tape on top of all of it.

How to attach it? Can't drill thru heater so I'm going to have to use clamps around edges.
Spring ACCO clips may work very well. But don't know if insulation material will be stiff
enough to bolt thru to plate?

I was thinking about looking around a kitchen supply place for a nice thing
that you put down before you put a hot pot on a table.

Anyone got suggestion for a stiff insulator.

Tnx
Ray

[royco]

Mike,

You are correct, the heated bed attaches with an offset( usually with springs) from the aluminum plate. On the Helios heated bed the heat traces are on the top and requires a flat top material( usually glass as cozmicray suggested, usually 3mm thick). The Helios heated bed kit comes with mounting hardware(except for the springs) and strips of adhesive-backed woven ceramic insulator that you stick under the bed.

[mikegrundvig]

Thanks for the answers! Why springs? Seems like leveling the PCB is nasty hard. Also, what dimensions X/Y should the glass be? Finally, doesn't the glass need corners cut out because of the screws/bolts holding the PCB?

-Mike

[blah_59]

Roy,

To follow on Mike's questions so you can answer them at the same time, what kind of springs are best to use?

Thanks,
MC

[royco]

The springs were originally used to protect from the head crashing on to the bed. Here's how its usually installed.
http://www.nextdayreprap.co.uk/build-heated-bed-assembly-reprap-prusa-mendel-3d-printer-manual/



The bed has an 8x8 build area(approx) so you need a slightly larger than that for your glass. It is commonly secured by clamps on the sides.

The helios heated bed uses countersunk screws to keep the top surface clear of obstructions for the glass.

Here's an example of the spring, others have used springs with higher compression force to keep the bed from wobbling during fast moves.
Mcmaster 9657K155

http://www.mcmaster.com/#catalog/118/1220/=jek560

[cozmicray]

Silicone insulation?

How important is it too insulate bed plate from bed heater?
I don't see much about insulating the bottom of a heater bed
and protecting the bottom maker slide from the heat.

I was walking thru a kitchen gadget place and saw a silicone pot holder / trivet.
Pad of silicone 7"x7' -- 1/2" thick says it is good to 530deg F
I got a red one (Red -- HOT) but there was blue ones.

Lots of cavities in it and will squish down some

It will become my bed heater insulator some how.

I will let you know if it oozes out under use.

[canadianavenger]

It won't ooze out, the silicone mat is good for 400+ degrees. I did the silicone mat thing for an original makerbot at my local hackerspace. I used a flat sheet cut from a silicone tray. It isn't really needed, but it doesn't really hurt either.

[orcinus]

The springs were originally used to protect from the head crashing on to the bed.

You come to appreciate the function of the build platform springs *immensely* the first time you issue a G1 command instead of a G92

(brainfart while zeroing the Z-axis)