tag:blogger.com,1999:blog-4339813531032979196.post7223301974556123178..comments2024-02-28T07:32:59.864+00:00Comments on HydraRaptor: Hot bednopheadhttp://www.blogger.com/profile/12801535866788103677noreply@blogger.comBlogger23125tag:blogger.com,1999:blog-4339813531032979196.post-49883783146522475952011-12-05T19:18:23.869+00:002011-12-05T19:18:23.869+00:00I can be thinner but thinner AL plate isn't gu...I can be thinner but thinner AL plate isn't guaranteed to be as flat.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-36183658350389977392011-12-05T17:50:10.821+00:002011-12-05T17:50:10.821+00:00Does it have to be 6mm or can it be lower?Does it have to be 6mm or can it be lower?Simone Iannuccinoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-7869198191179535642010-09-24T15:57:09.408+01:002010-09-24T15:57:09.408+01:00Many thanks for the detailed calculations :))) Now...Many thanks for the detailed calculations :))) Now its possible for me to build my own, based on a PC-Powersupply and NiChrome Wire .... I know its not the best solution, but it will produce some heat :)koallalaysnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-23905472219930876012010-02-03T03:37:06.483+00:002010-02-03T03:37:06.483+00:00I have made some silicon that I showed to NASA (th...I have made some silicon that I showed to NASA (they were unimpressed) where I took an oxy acetylene flame, for 30 seconds to a 1/4" 4"x4" piece I cast for them. It glowed red and chuffed off white powder (probably quartz), at a 1/4" radius where the flame point was the center. That was read on a thermal imager to be 4500°F at the center radiating out about 1" diameter to 800°F and at the edges at room temperature. I wanted to cast a giant sock for them at the underside of the space shuttle. It remains flexible and does not crack. When the flame was shut off it quickly went to 800°F all around the piece and slowly cooled.<br /><br />It is not an inexpensive solution but you could mold the entire undercarriage with this. It will eventually come up to temp but with your balsa wood idea there should be enough insulation to limit the heat soak. I can make some up for anyone interested or simply go to Home Depot and they have a fire stop from Dow Corning that is similar but very expensive.<br /><br />Another thing to consider as far as heat capacity of your metal. Yes Aluminum comes up to temp quick and evenly but it also like copper will heat soak in areas creating cold spots in others where the cold is more prevalent. One problem seen on the stove top, hot in the center cool on the sides. Trying cast iron, once it is up to temperature and it stays there with little power needed thus no cold pots. Just look a fajita pan for proof. The whole pan comes up to temperature(350°F) and keeps hot cooking the food off the burner for a long time. Metals all come up to temp with everything else being equal the same. It is how long they stay hot after the power cycles off that I think you are looking for. Aluminum and Copper cool off too quickly. I think what is happening here is your efficiency through the aluminum plate. The bottom is very hot, heat rising up through it, and constantly hitting cool air; and what does aluminum like to do? Act like a heat sink and it does just that. So you have to dump a lot of power all the time. With cast iron, you heat it up, it is hot all over. Much more efficient, because cast iron makes a terrible heat sink. Problem is you have to make a sand cast and cast your own bed. It can be surfaced but does not hold a screw well. Sorry, I don’t have a very good answer on that one for you.<br /><br />BTW, Be very careful with your PTFE. At about 350° F it out-gasses hydrogen fluoride gases. Extremely toxic. Honestly I would cast up a nozzle for you out of my silicon before using PTFE. And after all wouldn't you like the ability to run higher temp materials like casting aluminum?Watergroovenoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-37392967183834905582010-01-08T20:31:41.537+00:002010-01-08T20:31:41.537+00:00@nophead
If you use an oversized one it actually ...@nophead <br />If you use an oversized one it actually gets hotter then using a "correct size one" for a given tank.<br /><br />Plus thats just one example.. Forgotten where but they do make a variable heat one.<br /><br />drakeDrakenoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-21570781163883523922010-01-08T18:33:12.722+00:002010-01-08T18:33:12.722+00:00@Laslo,
6mm was about the thinnest that I could ...@Laslo,<br /> 6mm was about the thinnest that I could blind tap to leave a flat surface. Some of the back of the plate could be milled away in between the resistors leaving some ribbing for strength perhaps.<br /><br />@Drake,<br /> They are limited to ambient plus 20C, so only about 40C which is not hot enough.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-63546124681026620932010-01-08T18:12:05.558+00:002010-01-08T18:12:05.558+00:00Another possibility is use what reptile pet owners...Another possibility is use what reptile pet owners use on their cages for heating up them up. They come in different sizes for various sizes of "tanks" and have a sticky side that you can peel and stick to the underside of the plate.<br /><br />Just an example, <br />http://www.tinyurl.com/ycud9qb<br /><br />DrakeDrakenoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-77693931590135255432010-01-07T12:31:26.982+00:002010-01-07T12:31:26.982+00:00For lowering thermal capacity, you could go with a...For lowering thermal capacity, you could go with a thinner sheet of aluminium.<br /><br />Needs to work out the fixation though. Like soldering aluminium rods to the sheet, and cutting thread on it. Soldering aluminium is tricky...<br /><br />LaszloAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-63439156079630751072010-01-06T10:23:37.128+00:002010-01-06T10:23:37.128+00:00I didn't notice it warp. I expect that since i...I didn't notice it warp. I expect that since it is such a good conductor both sides will be very similar temperatures, so both expand together.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-42065986597694737012010-01-06T08:13:31.068+00:002010-01-06T08:13:31.068+00:00Does the aluminium plate warp when heated to 230de...Does the aluminium plate warp when heated to 230degrees?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-33975159607104650862010-01-04T23:56:52.402+00:002010-01-04T23:56:52.402+00:00Actually the silicone ones look a better bet. They...Actually the silicone ones look a better bet. They seem cheaper, are available for 230V and just about reach soldering temperatures.<br /><br />http://www.omega.co.uk/ppt/pptsc.asp?ref=SRFR_SRFGnopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-83804754289851763552010-01-04T19:09:23.399+00:002010-01-04T19:09:23.399+00:00Hi Shane,
Yes they are quite a nice solution, an...Hi Shane,<br /> Yes they are quite a nice solution, and we can get them in the UK, but they are still 115V only for the bigger ones. I would have to get two 3" x 6" and wire them in series. It then gets expensive ~ £70. The economics are a lot better in the US as I could use one 6" x 6" and they are a similar price in dollars as they are in pounds here, so considerably cheaper.<br /><br />Also they are only rated at 200C. That is fine for plastic extrusion, but my original intention was to also solder SMT which is why I chose resistors that I have previously used at 240C. If I was aiming for plastic extrusion only then a PCB with a zig-zag track would be my first thing to try.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-10611909186504567132010-01-04T13:34:31.210+00:002010-01-04T13:34:31.210+00:00Bad Link in my above post - sorry! Here's the ...Bad Link in my above post - sorry! Here's the correct link:<br /><br />http://www.omega.com/pptst/KHR_KHLV_KH.htmlShane Wightonhttp://www.mechanicallyinclined.netnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-6857533540316437212010-01-04T13:30:51.522+00:002010-01-04T13:30:51.522+00:00An alternative to power resistors for the heating ...An alternative to power resistors for the heating element is a kapton heater - they are basically a thin heating element sandwiched between two pieces of kapton film. They provide very even heating, are available in many sizes, shapes and wattage ratings. They even have models that can be run off mains voltage. The other percieved advantage I see is because of the low profile of a kapton heater you would have more room to install an insulator.<br /><br />(www.omega.com/pptst/KHR_KHLW_KH.html)<br /><br />I don't know how available they are outside the US but I can testify that they work very well!Shane Wightonhttp://mechanicallyinclined.netnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-87497946479174424832010-01-03T15:10:19.559+00:002010-01-03T15:10:19.559+00:00@Enrique,
Yes wool looks ideal, thanks for that. ...@Enrique,<br /> Yes wool looks ideal, thanks for that. I had no idea it could stand high temperatures.<br /><br />@BodgeIt,<br /> PEEK is not that good an insulator compared to air. I think most plastics are ~ 0.17 compared to air ~0.02 and wool ~0.04.<br /><br />I doubt balsa would burn at 100C, especially as it would have about 1mm air gap between it and the resistors. It may warp though and not as good an insulator as wool.<br /><br />Even with a bit of warped foamboard it seems to work, i.e. my XY table stays cool when the bed is 100C. I should really have covered the top side of the foam board with AL foil to reflect any radiation.<br /><br />I didn't try it with just the 15mm air gap. It may well have been fine like that.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-35265913561113387832010-01-02T22:43:32.335+00:002010-01-02T22:43:32.335+00:00Hi Erik,
Yes I think nichrome and Kapton on AL wi...Hi Erik,<br /> Yes I think nichrome and Kapton on AL will work but I think you need to pick the length and gauge carefully. You can work out the total power from 1Kw/m^2 plus some margin. But then you need to distribute that amongst enough nichrome so that it does not get hot enough to burn the Kapton. Might need some trial and error as it depends on the thermal resistance between the nichrome and the AL.<br /><br />If you don't have the correct guage then you might need to use parallel loops.<br /><br />That is why I went for resistors, more expensive and more work to mount them, but somebody elae has worked out the nichrome length and guage and how to electrically insulate it but thermally couple it.<br /><br />TO220 style resistors are probably a better choice in this low temp application, IIRC they are good up to 150C. Slimmer and easier to mount.<br /><br />I have also been thinking about a jet of hot air around the nozzle. Same temp as the bed, fast airflow to cool the filament to below Tg quickly, but concentrated so as not to waste too much energy.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-21418900720043801992010-01-02T22:08:36.154+00:002010-01-02T22:08:36.154+00:00Wow, I know how much time and dedication can go in...Wow, I know how much time and dedication can go into such thorough blog posts! I always look forward to them :)<br /><br />But back on topic. I also have plans for a heated bed for a while now. Maybe you can comment on its viability. I hope to use two 2mm sheets of aluminium with kapton taped (and insulated) nichrome between them. Just need to find time to cut the sheets. Wanted to put two 6mm sheets of acrylic around that, to balance out the warping force from the temperature gradient. Together the sheets will probably resist a substantial amount of force from printed object, so much that there will be no cumlative bending.<br /><br />I may also try a 90'deg air feed. Already built it, just need a proper way to affix it to the X carriage of my darwin and still be able to direct the airflow properly.Erik de Bruijnhttps://www.blogger.com/profile/09433438819279256757noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-41834451285631713882010-01-02T09:06:31.295+00:002010-01-02T09:06:31.295+00:00Thanks for your great heated bed article.
Another...Thanks for your great heated bed article.<br /><br />Another insulation option is wool. From the "Wool Burns" page at:<br />http://www.strobel.com/wool_burns.htm<br /><br />wool has an ignition temperature of 600 C, higher than other common textile insulators like cotton at 255 C or rayon at 420 C.<br /><br />Besides buying wool at a clothing store, you can also get wool insulation batts, like Heatkeeper in the UK:<br />http://www.heatkeeper.co.uk/insulation.html<br /><br />or Sheep Wool Insulation in Ireland:<br />http://www.sheepwoolinsulation.ie/about/Enriquehttps://www.blogger.com/profile/09426013757234244524noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-29586613158138227302010-01-02T01:35:25.902+00:002010-01-02T01:35:25.902+00:00Hmm I'm not sure if fiberglass gives off any n...Hmm I'm not sure if fiberglass gives off any nasty gasses tho.. I have seen it used for heat insulation thouAnonymoushttps://www.blogger.com/profile/11790019375326311849noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-85978682410986285352010-01-01T23:02:35.435+00:002010-01-01T23:02:35.435+00:00Balsa will also burn but you could get a sheet of ...Balsa will also burn but you could get a sheet of peek as an insulator.<br /><br />or<br /><br />To cut up into strips to make a frame with two central dividers between the resistors to restrict any air movement within the frame.<br /><br />Or you could make a fiberglass cover. I believe that fiberglass epoxy resin is OK up to 150C I think.Anonymoushttps://www.blogger.com/profile/11790019375326311849noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-3339192298410143232010-01-01T18:51:05.499+00:002010-01-01T18:51:05.499+00:00The aluminium looks very sexy.The aluminium looks very sexy.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-86864520071379586782010-01-01T18:18:37.679+00:002010-01-01T18:18:37.679+00:00The foamboard had a small gap between it and the r...The foamboard had a small gap between it and the resistors but it seems to have buckled on its excursion to 230C. I have some ceramic wool which is a much better solution but I don't like the fibres it gives off. I would have to seal it in well. I may just go with an air gap for simplicity or perhaps a sheet of balsa.<br /><br />I think that the thermal conductivity of aluminium 6mm thick is so low that temperature will be pretty even, but I have no evidence to back that up.nopheadhttps://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-4339813531032979196.post-9407754792627365272010-01-01T17:58:02.301+00:002010-01-01T17:58:02.301+00:00This looks like a very neat solution a couple of q...This looks like a very neat solution a couple of questions tho.<br /><br />Will the foam in the foam board melt?<br /><br />Will you get hot spots where the heat is radiating out from the resistors making much hot areas at the center point of each of the power resistors?Anonymoushttps://www.blogger.com/profile/11790019375326311849noreply@blogger.com