1 Topic by heychris

  • heychris
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  • Registered: 2012-11-28
  • Posts: 20

Topic: My Silicone bed/ PCB bed experiences

I wanted to share some of my experiences with different bed options.  I currently have a silicon mat from QU-BD.  Additionally I have a makerbot replicator PCB bed.  My print surface is glass that has been lightly sand blasted.

If you compare the different solutions.  The resistance of the heating element is pretty critical.

Standard issue resistor - 3 ohms
Standard replicator pcb bed - 10 ohms
QU-BD Silicone Bed - 1.6 ohms

Please note the resistance was taken with care using a fairly new Fluke 87V.  For readings that low I'd be more comfortable with a milliohm meter, but don't have one close by.

Some interesting thing happen with the different beds.

The replicator uses a 24 V power supply.  I happen to have an extra old laptop power supply that seemed to do the trick for me.  I first tried a relay.  I need to put in a diode as a flyback as the relay clacked on and off.  Ideally a solid state relay would do the trick.

Using Ohms law I see the following  (P=V^2/R)

24V with 10 ohm bed yields  57.6 watts
12 V with 3 ohm resistor  48 watts
12 V with 1.6 ohm resistor 90 watts

I did the math from the reprap bed page.  They figure 120 Watts is ideal.  http://goo.gl/k5nEa

I think having a second power supply becomes pretty necessary.  The 7.5Amp draw of the silicone bed is a bit much for my taste.  It seems to me that the ideal way to go is to follow the PCB design, but rebuild it for 12V and 150mmx150mm.

I designed a bed, but got delayed on the production.  This is good, because I'm thinking an adjustment of the traces is necessary.

Is there any interest in a group buy on PCB beds with a second power supply input/ solid state relay board?

2 Reply by devilman2075

  • devilman2075
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  • Registered: 2012-08-21
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Re: My Silicone bed/ PCB bed experiences

If you are designing something like that and want a lot of interest from here itd be nice to have it designed with the solidoodle in mind as far as mounting goes.  Not a necessity but itd probably help those on the edge get one anyways.  I know is be interested. I have a silicone mat but unsure if that's the route I truly want yet

3 Reply by heychris

  • heychris
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Re: My Silicone bed/ PCB bed experiences

Here are a couple photos of my solidoodle with a cut down replicator bed.  I designed holes in the pcb  for the solidoodle bed.

It works well with a 1/4 birch plywood piece to replace the aluminum.  You'll notice the bumpers on the side to hold the glass in place.  I have a couple clips to keep the glass held down tightly.

With an extra laptop power supply attach via relay and flyback diode, it heats up reasonably fast.  Typically I turn on the printer  and load the file.  By the time I have the slicing done, the bed is up to 65 degrees or so.  I find that the bed is much more evenly heated.  I print with abs at 70 degrees.

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