Sunday, February 28, 2010

Rep strap Mini/Micro Mendel Heated Bed using Fire Glass

Building Mini or Micro Mendel for the show I don't know where I can get Aluminum sheet easily so I had an odd thought on Saturday when passing a Glass supplier so popped in to see if I could get some heat resistant glass 140mm x 138mm to use as a heated bed.


I was told I had to buy fire glass it can take up to 600C. I got lucky they had an off cut so I had two cut for £11 note this is good price as its usually £100 Square Meter. 


It has a slight yellow tint to it but as its not for looking through who cares.


Here are pictures of my attempts to get the element right using 50ohm per meter nichrome.

  

Note as I re-make them I start using much less Kapton tape  

  


The last attempt was the best achieving 100C in 6 minutes



Then 110C  in 7 minutes. I'm running from power supply no temperature control yet..





So resistance of final solution is about 20 ohms based on a 30.5 voltage and current of 1.5A total wattage is about 46 W. 


The original attempts were mounted on Plastic chopping board using bulldog type clips as the wattage went up the Plastic started to smoke so the final version has 3mm MDF bulldog-ed to the Fire Glass. I removed the two silver levers on each of the bull dog type clips.



I just need to figure out how to mount a Thermistor then I can add PID or Bang bang control of temprature using an extruder controller.


The nichrome has a 30mm spacing the other attempts were 10mm, 15mm, 20mm, 25mm to fit a 100mm x 100mm central print area.
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