Short version: the simple fix that the Printrbot folks shipped for the Metal Plus works a a treat. You may still want to preheat your bed a bit.
Originally shared by paul wallich
Yesterday I took off my cobbled-together insulation and installed the simple fix that Printrbot sent out — thank you! Since part of the installation process involved running the bed up to 100c to get the thermal expansion right for tightening the rails, I…
http://invisibleturtles.org/2015/02/14/less-is-more
Can you give us pictures of printrbots insulation. I would like to do something like it to my Simple.
@Thomas_Cox
Not sure I can do that now it’s installed. But I think it’s going up in their shop. It’s a little square of aluminized plastic, but heat-resistant so it won’t melt (the regular bubble-wrap stuff melts about about 85C) and with some kind of embossed pattern so it doesn’t lie quite flat (because then it would pass heat by conduction). It’s really pretty impressive how straightfoward it is.
@paul_wallich I just found one for the simple and ordered it. It also comes with some delrin rails to space off the wings.
@Thomas_Cox
Yep. Alas, the wing attachment for the Plus is different, with the wings attached to the rails and butted up against the sides of the heated bed. And the fix instructions warn you against unscrewing the wings (I would guess because it could muck up Y tension and linear-rail alignment, which are nicely dialed in at the factory.
Hmm. @Brook_Drumm once the heated bed is tightened back down, do you think it could be ok to loosen the wings and use the tolerance in the rail holes to move them out just far enough for a little thermal break? As it stands now you can almost get a 7-mil sheet in there, but not consistently along the whole width.
Yes, you can safely remove the wings if your rails are tight to the heatbed. You may be able to force a gap between the wings and the heatbed. The only other thing we could think of, but haven’t pursued, is to find some tiny nylon washers to put on each screw that attaches the rails to the heatbed. Those screws do make a thermal transfer for a little heat to transfer to the rails . Plastic screws may do it too. Our fix is sufficient, since we don’t promise a short length of time for heat to get to 100c, we just know that it does work.
We have a beta test heater PCB in our shop that has a hole drilled to allow the thermistor to come in contact with the metal print bed for more accurate measurements during heat up. Carl tells me a bit of high temp silicone will hold the thermistor in place, but we have only tested polyamide tape (kapton). More testing is needed but it does seem to work well. It reduces heat up time slightly.
Brook
Tried it this morning. It’s a wash, as far as I can tell. Actually took longer to report 100C on the thermistor (9 minutes) than before, but bed temp was higher (60C at 10 minutes). At longer times (20-30 minutes) temperatures were the same, give or take exactly where I pointed the thermometer.
And yeah, putting the thermistor in contact with the bed will speed up heating a little because the firmware isn’t fooled into turning down the heat… Could you enlarge one of the pockets around the edges/corners of the bed and put the thermistor there, or would that screw up the build?
This may actually be important for some people, because with other machines (e.g. my jrv2) it mostly works to just start printing as soon as the bed and extruder claim to be at temp.