orgizmo

Thank you all so much for the quick and helpful replies, very interested to see a picture amano =] What are you using for a heatshield between the acrylic UM plate and the heat sandwich? With the thicker sandwich what does your maximum z travel become? Thanks again =]

We have recently built our UM and now we're looking to upgrade to a heated bed for doing larger parts. I have a few questions and would appreciate any help anyone can provide =] We have a MK2A PCB (http://www.geeetech.com/wiki/index.php/PCB_Heatbed/Aluminium_Bed_Mount_Plate/Borosilicate_glass) as the plate is designed for the reprap prusa the aluminum plate will not quite reach between the bolts that normally hold the acrylic print bed on the UM. I've seen people using plywood/MDF as a base to mount the heated bed to the UM. Has anyone had experience with using these materials for this purpose? Any feedback on the pros/cons of using plywood or MDF would be appreciated. All the build logs I've been finding have used either the aluminum plate (x)or the glass plate, I've yet to find one that uses both. Should these boards be mounted: Glass ---------- <BullDog Clips PCB ----------- <Bolts/ (Spacers?) Aluminum ----------- <Bolts/Spacers MDF/Plywood Base Would I be better off have spacers between the aluminum, the PCB and the Plywood layers? Or do I only need spacers between the aluminum and the wood? From what I've read either nylon or PTFE washers would be sufficeient to withstand the heat involved. Any thoughts? I have a PSU harvested from one of my parts computers that can supply 350W, 17A @ 12V, my PCB has a measured resistance of 1.8Ohms which means I should be getting a cold start draw of 6.7A... is this going to be sufficient for doing ABS/PLA or should I upgrade to a more powerful 24V supply? With the 4.7kOhm resistor going to the UM electronics will a 1/4W resistor do the job or should I get a higher wattage resistor? I'm not in any particular rush to get the heated bed up and running (slow and steady winning the race and all) so if there's anything I've overlooked in all of this please let me know. I love our UM and would perfer not to see it burn/explode