Silicone Heated Bed

DocTrucker

What controls have you got for the environment of the machine? Enclosure or is your machine made out of a low thermal expansion material? With a linear thermal expansion rate of 23.1 * 10^-6 for Aluminium I work that as a 0.23mm expansion per metre of extrusion for a 10C temp change.

There's something to be said for a slow warm up as it gives the rest of the machine a chance to warm up and settle before the bed probe. The expansion itself isn't so much of a problem - you can tune / change procedures to account for it. What is a problem is the bits closest to the heat sources get hot first, then conduct heat away taking a while to reach equilibrium, geometrically changing the chassis in a non-linear manner over a longer period of time than it takes to heat the bed.

I've been meaning to ask if there is feature request for some sort of average duty report on the heaters or a warning of under powered heaters for the chosen set point. Having whinged about the negatives of big heaters I have to conceded my bed heater is lacking.

dc42

@doctrucker said in Silicone Heated Bed:

I've been meaning to ask if there is feature request for some sort of average duty report on the heaters or a warning of under powered heaters for the chosen set point. Having whinged about the negatives of big heaters I have to conceded my bed heater is lacking.

See the M573 command.

DocTrucker

@dc42 Thanks.

In the python coding world this sort of thing was referred to as Guido's time machine! I've still many tricks to learn with the V0.6 boards. Watching the RTOS updates for the Wifi/Ethernet with interest.

peter247

@3dpmicro In the end I went for a 300 watt heater which for my 70c max looks to get the job done.
But will have to try a external Thermistor because it gets upto temperature quickly , BUT 55c is 48c and it get 55c I need to set it to 70c , using a IR gun on the print side of a 6mm bed on tape.

3DPMicro

@peter247. Awsome. I switched back from aluminum to glass bed with thin adhesive backed fg/foil insulation on the back of the pad. Small cutout in insulation to expose thermistor so its not insulated. Surface lags about 10 deg behind thermistor on heat up then catches up within a few degrees after a couple minutes.

peter247

I've had problems, never getting the bed level , which was killing the nozzles very quickly .
Today after various mods , rebuilds , and resigns to make it stronger I've found the problem I hope !!! , with the aid of a new straight edge ? , my aluminum 6mm bed is bowed at the corners , YES , ( how do you bend a 6mm plate ) the centre looks level but not the edges , so I`ve edited my bed level macros which now levels 50mm from each corner.
All I need now is a 410x410mm glass bed to level it off ?.

3DPMicro

@peter247 the 6mm Mic 6 tooling plate I was using is in the annealed state and very easy to bend. Identifying exactly where the bent areas are, marking those areas then clamping to a table and carefully working out those areas might be possible. Are you using bed leveling?

peter247

@3dpmicro said in Silicone Heated Bed:

Are you using bed leveling?

Depends on what you mean bed leveling ? , I use dual Z and auto level them , But my bed leveling is via a macro to the bed corners and some paper.

3DPMicro

@peter247 I basically do the same thing you do. Seems mesh bed leveling with a probe is all the rage these days. Great first layer even with warped bed. I'm probably going with 8 standoff adjusters on the next machine. Adjust it flat

peter247

@3dpmicro said in Silicone Heated Bed:

I'm probably going with 8 standoff adjusters

Wow , that is a lot of adjusters ?
I was thinking of getting a bed leveling probe , but can`t find how to mount it anywhere near the nozzle ( titan aero ) .
Now I've come to the opinion the best way is thin aluminium plate 3 or 4mm and flat glass / shims , what is the point of a heavy plate if it bowed ?

3DPMicro

@peter247 said in Silicone Heated Bed:
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Now I've come to the opinion the best way is thin aluminium plate 3 or 4mm and flat glass / shims , what is the point of a heavy plate if it bowed ?

@peter247 sounds like a great idea. I didnt like the aluminum bed because of the weight and because 40% of it is outside the printable area. Not an efficient approach in my opinion on a machine that moves the bed in x or y. A lot of wasted energy. I here many claim the poor thermal conductivity of glass as being the reason for aluminum but the glass is thin (relative) and has a high rate of heat flow even though it is a poor conductor.
If you ended up with a flat piece of aluminum you may be able to plop it down on a layer of PVA glue and call it a day bypassing the shims