Even to print PLA a heated build platform is beneficial. And as I had read about repairing broken plastic parts with nichrome heating wire some time ago, I salvaged it from our last hairdryer. Time to put it to use.
A thin metal sheet had to do as heatspreader, Kapton (polyimide) became isolation as well as fixation. Cork from the hardware store was used as thermal insulation at the bottom and plywood as the mounting plate. Like Airtripper suggested I crimped the connections to the wires.
The glass plate came from an old scanner and was the only flat part of the whole construction, as you can see below. 😉
Using four screws to adjust the bed leads to over-determining (and by chance bending) it, so three had to do. The TinkerCad parts on the frame were already linked here.
The heating wire was originally powered by 230 V AC, but I did not trust some thin layer of Kapton tape enough to use mains voltage. Using the 12 V rail of the old ATX PC power supply I had to raise the ante two times, however…
…until the PSU was finally exploited completely.
In the end I could heat a glass plate larger than a DIN A4 sheet to about 75 °C in about 20 min, but also powering Hot End and motors had it drop below 70 °C as a result. (And the annular nozzle fan is also unhelpful in this situation.) That limited my choice of materials.
In the meantime I had made positive experiences with BuildTak on the Sumpod. Finally this annoing corner lift and the uncertainty if the print would stick were gone. But I was too cautious and pushing the material into the first sheet hard. So it ripped apart, when I removed the objects. As you can see below I don’t care if a BuildTak sheet was meant for a Vertex K8400 or if Conrad’s in-house brand was meant to fit a Renkforce RF100. I did not even bother to remove the complete BuildTak foil – and now I can show you the disadvantage of the “Foil used on printing plate, dimension AP”: the glue sticks to the HBP, not itself. Both work, but BuildTak seems to be less unnerving.
For the Junkstrap I tried another Build Surface: GeckoTek EZ-Stik was on Kickstarter and I contributed. And it really helped my colorFabb nGen / Amphora AM3300 co-polyester to stick. In contrast to the other surfaces this one gives you a shining undersurface – but it does not feel any slippery. Feels really exceptional, actually.
And where the adhesion to BuildTak can be described as “tough” and the part can be peeled off slowly with a sharp angled spatula, the removal tool from GekoTek looks different and the adhesion feels “digital”: knock against the print several times and -after not moving at all- suddenly the complete part pops off. As I only used half the sheet I shall test it on a different HBP and perhaps with (EPR) PET in the future…