Heated Bed Discussion


#1

Several folks have been kicking around the idea of adding a heated bed to the FLUX. The small air gap between the bottom of the build plate and the rest of the machine is the #1 thing that you’d have to go to battle with to make it work, in my opinion.

A thin film heater, like the kapton heaters available from several sources is what makes sense to me. Anything thicker, even the silicone pad heaters, probably wouldn’t fit without making your own custom bed plate to provide the extra clearance. The next trick would be to find a temperature sensor that’s similarly thin, because I think the thickness of a thermistor would be too much…

Anyway, I haven’t started anything yet, I’m not even sure if I will, but that’s the direction I would go in. Share what you’ve got!


#2

Why does it need to be thin? The heated bed could be an inch thick without a problem if it just replaced (or went under) the build plate. There is supposed to be a z_offset setting that we can use for the height difference.


#3

Very true, yes. I’ve thought about that as well. You lose build height, but that would rarely matter. I wonder how much play there is in the probing routine and how much extra thickness you could get away with that way?


#4

My idea is to completely replace the build plate with the one I was planning on making. Integrated circuit board with glass on one side and PCB board on the other. I just need the build plate to gather the measurements and then I’m going to start experimenting.


#5

I’m definitely no electrical engineer, but I think the most important thing would be to try to insulate the base of the Flux Delta from the heat the bed would generate. Other than that, I would say, make it as thin as possible.


#6

Foil insulator is the thought on the heat transfer issue. I just need the machine here so I can really look at it.

What are the ideal bead temperatures that I should shoot for? I can make it variable controlled.


#7

The plate is 2 mm thick (using a caliper) and 225mm across (using a fabric tape measure - flat edge to flat edge)


#8

I would machine the bed out of this:

http://www.ebay.com/itm/Single-Copper-PC-Board-12-x-12-Inch-Single-Sided-Printed-Circuit-Prototyping-NEW-/272032912496?hash=item3f566cd470:g:RWIAAOSwLVZVumG~


#9

Remember that the bed needs to be rigid enough to support the probe routine. Not sure that FR4 will be enough in that size.


#10

I was planning on laminating it with something (glass, carbon fiber, aluminum, etc.). Let me play with it when my FLUX gets here. I’ll keep you all in the loop.

What temperature range should I shoot for?


#11


#12

As others have mentioned, I think the hard part will be not cooking the rubber pressure sensor pads and/or the camera, rotating stage, and lasers of the scanner. You may need to do some kind of standoff:

===================   <-- heated bed
||       ||      ||   <-- standoffs / air gap
===================   <-- base plate to transfer probe loads to pressure sensors

#13

One design consideration to keep in mind… The traces actually need to be slightly closer together towards the outside instead of the other way around. Since area increases at the square of the radius times pi, the traces need to be closer together the farther out you go.

You can’t see it very well, but that was the main design change between the Onyx V2 and V3, and it did a great deal to even the heat out.

For temperature, I run PLA around 40c, Nylon around 60c, and ABS between 90 and 110c depending on how temperamental it wants to be.


#14

Thanks Jim,

I’ll rework the design.


#15

My suggestion would be to re-use the base plate for the heated bed. As long as the bottom of the heated bed mod is flat, it shouldn’t have a problem with the pressure sensors.


#16

You might check these out if you end up needing a thin temperature sensor.

http://www.minco.com/Sensors-and-Instruments/Products/Thermal%20Ribbons


#17

Great find! I’ll have to check those out.