How hot should the V3 bed get?

[timskloss]

I can't seem to get the bed above 85C on our new V3. It is in my basement that is continuously 65F (19C). I put baffles around the printer and added insulation to the bottom of the plastic bed support. The insulation got me a few degrees warmer but it really helped even out the temperature across the bed. I was seeing significant cooling from the power supply fan when it turns on (it's automatic in the V3). There is significant drop off at the edges a few cm from the outer white ring.

I confirmed the MAX PID drive for the bed is 255 in EEPROM.

Code: Select all

<-EPR:0 106 1 Bed Heat Manager [0-3]
<-EPR:0 107 255 Bed PID drive max
<-EPR:0 124 80 Bed PID drive min
<-EPR:3 108 87.860 Bed PID P-gain
<-EPR:3 112 3.010 Bed PID I-gain
<-EPR:3 116 641.820 Bed PID D-gain
<-EPR:0 120 255 Bed PID max value [0-255]

How do people get more heat? I have read about bigger power supplies and solid state relays but could not find info about voltages, amperages or wiring diagrams to the RAMBO.

[Noircogi]

It sounds like your performance is pretty nominal considering the ambient temps. If you put a towel over the bed, it will heat faster.
If you turn the adjustment potentiometer on the stock PS up to 13.5V or so it will probably hit 100C reasonably.

If you put a 600W 24V PS in the base it will hit 110C in 3 minutes or so.
Details of what I did to mine are here: http://forum.seemecnc.com/viewtopic.php?f=35&t=10904
If you do that, make sure you get the Auber or Crydom SSRs, others are likely to be counterfeit, fail in the on state and a real fire hazard.

[timskloss]

Thanks for the piece of mind on the nominal performance. It is good to know ours is not too different from what other people are seeing out of the box. I'll also try the towel trick to get going faster.

Thanks for the info on the 24V upgrade. Not sure how I missed it in my search of the forum. I would like to add thermal fuses(s) under the bed to kill the power if it overheats. Instead of fusing the heating current directly as is done in the hot end, I was thinking about the thermal fuse operating the coil in a mechanical relay in series with the SSR [http://www.digikey.com/product-detail/e ... ND/1095333]. The only trick is what temperature to pick for the fuse???

Adding the mechanical relay and thermal fuse is cheap insurance. I have seen too many automated heating systems fail closed and overheat.

[geneb]

Note that to print ABS, you really don't need more than 80C anyway.

g.

[Xenocrates]

Thanks for the piece of mind on the nominal performance. It is good to know ours is not too different from what other people are seeing out of the box. I'll also try the towel trick to get going faster.

Thanks for the info on the 24V upgrade. Not sure how I missed it in my search of the forum. I would like to add thermal fuses(s) under the bed to kill the power if it overheats. Instead of fusing the heating current directly as is done in the hot end, I was thinking about the thermal fuse operating the coil in a mechanical relay in series with the SSR [http://www.digikey.com/product-detail/e ... ND/1095333]. The only trick is what temperature to pick for the fuse???

Adding the mechanical relay and thermal fuse is cheap insurance. I have seen too many automated heating systems fail closed and overheat.

I've been playing with that. a 140C fuse seems high enough to not open under load while at printing temperatures up to 100 (It probably would work for 110 too, but I haven't ever seen a need to test it). I found a 25A DPST relay (These may be called contactors, depending on your supplier), with a 12VDC coil. The amperage is low enough for the fuse to handle well, and the fuse itself is embedded in the bed insulator and potted in a (Non-conductive!) thermal paste to bond it to the bed thermally. I've had some trouble with getting the relay to close properly on start up (I find I need to tap the test button to get it to close, however I believe that's an issue with my Vsense connection on an ATX supply.) Once it closes, it stays closed until the printer is power cycled (I am debating connecting it to 12V standby on my power supply, so that it will remain powered until the printer is unplugged.). With a V3, I would probably use 2-3 thermal fuses in series, spread around the bed, so that if one decouples, or the bed heats unevenly (Somewhat common in a short), you're still safe. It's harder on a V2, as they have very little accommodation for wiring to different areas of the bed.

Another thing to keep in mind is that the contacts on the relay can be welded or otherwise fail. Where practical, use over sized relays (There is safety factor there already on constant duty relays, but more is better), and switch the lowest practical amperages. I would recommend killing the AC side where at all practical. (Mine isn't, as I have an internal and external power supply that either could drive the bed).