I first tried ABS onto double sided copper clad FR4 taped to a bed at 120°C. The ABS stuck well enough to extrude the first layer of a 20mm square, but when it cooled down it had no adhesion at all.
PLA at 55°C did exactly the same, but PLA at 130°C stuck very well, so well in fact that I can't get it off with my fingers (the blob was where I aborted the print after the first layer).
Maybe ABS would stick in the same way at an even higher temperature, but maybe not as it is less like glue than PLA. The 120°C / 55°C temperatures are what I use for Kapton, which is why I used them as the starting point.
An interesting aside: I had to measure the PCB to work out the z-height. It is only 1.4mm thick, whereas a standard PCB is 1.6mm. You can also see the grains in the FR4 showing through the copper. This means the board I bought in Maplin for home PCB use is actually the same stock material that they use for the first part of a commercial production process, but when they plate thorough the vias they increase the thickness of the copper all over to get the standard 1oz/inch2. I don't know if this is always the case, i.e, that all home made PCBs have less copper than a production one, or whether you can get bare board with 1oz on it already.Anyway a good result, assuming PLA will resist PCB etchant. Also, it seemed like a potential bed technique. I.e. do the first layer onto hot copper and then cool it to about 50°C for the rest of the object. I tried it with this butterfly: -
It worked perfectly. After the first layer I blew it with a fan to cool it down to 50°C. It took about four layers to get down to that temperature. Since I added the insulation under the bed it takes longer to cool it than it does to heat it.
After it had finished and cooled down to 40°C it was still firmly attached, so I removed it by flexing the PCB.
The base of the object is perfectly flat.
I think for PLA this might be a better technique than Kapton. I can't imagine the PCB wearing out. It could also be self heating with a serpentine track on the other side. I don't know that just taping it down would be strong enough for making large objects. I could solder fastenings on the back if not.
I don't know if there is anything special about copper and PLA, or whether other hot metals and plastic would work . I tried similar things with ABS on AL, but may not have had it hot enough.
During our SpoolHead tests, we found that PLA adhered extremely well to various metal wires, including copper and steel. It makes sense that it would also adhere well to sheets.
ReplyDeleteYes although you could imagine it contracting around a wire and gripping that way, i.e. mechanically, but with a smooth flat sheet it must be some form of adhesion.
ReplyDeleteHehe, my "serpentine" pcb heat bed is beeing manufactured for few days and should be done next week. I'll share design if it will work well :-) It can be used with 12, 24 and 48V, 20cmx20cm heated area, 120W :-)
ReplyDeleteGood findings :-)
ReplyDeleteHowever I prefer use 55ºC instead 130ºC. Less power, shorter times to heat and cool, more safe.
I think I even prefer PLA instead of ABS because of the 120ºC for ABS. I think I just need ABS for parts that get hot like the ones in contact with stepper motors and extruder PTFE barrel.
NopHead, what if we put that copper board after a flat glass, and put power resistors on the cooper, on the sides?
ReplyDeleteWould it get hot in the middle and could we print on it, suing or not kapton tape?
Could you please test this idea?
I think it would probably work but the temperature in the middle would be a bit less than the edge. Using the copper on the bottom as the heating element would be cheaper, more even and easier to make.
ReplyDeleteI haven't had chance to blog it yet, but for PLA on my Mendel I put some resistors around the edge of the underside of the bed, which is Dibond, heated it to 50C and used blue tape.
Each surface of the Dibond is 0.3mm AL. The temperature in the middle of the side with the resistors was about 10C cooler than the edge, but on the top side the difference is only about 5C, which I think is near enough when using blue tape as it sticks well even when cold, so not critical.
Dibond seems to come very flat and is light and easy to cut and drill. It also heats about the same speed as my extruder when I put 120W into it.
For detaching, could you try cooling-spray
ReplyDeleteto rapidly cool down the copper instead of flexing it?
In theory it should work perfectly well but
I´m eager for test-results.
I don't have any freezer spray so it will have to wait until I next order something.
ReplyDeleteI don't see how freezing it quickly will make much difference though. The thermal expansion coefficient of metals is an order of magnitude less than plastics.
Casainho,
ReplyDeleteI forgot to say, but my Mendel motors don't get hot enough to soften PLA. I use 0.75A for X&Y, 1A for Z and 1.5A for the extruder.
Vik and Nopehead,
ReplyDelete>>>Anyway a good result, assuming PLA will resist PCB etchant.<<<
A better way to go might be to just make a UV electronic "mask". Not sure but black or other color might work to block the UV exposure prior to etch.
Would be cheap enough to make one or two test masks. Once a mask is of good enough quality, the same mask can be used over and over again for production.
Isn't that what a 2d printer and some transparency is for? Don't reinvent the wheel.. Printing the mask straight on the copper saves on UV chemicals and the UV equipment, but if you're going UV, just print a mask, optical methods will always be more accurate than mechanical positioning.
ReplyDeleteAnonymous,thought the ideas was to let the RepRap print out a pcb board? I prefer no UV chemicals at all, but if you want to use transparencies then just have the pcb's made professionaly with "real" negatives at a pcb processor!
ReplyDeleteabsolutely, but print a one-time mask, don't try and print a re-usable one and then go through all the UV hassle.. For homebrew I use the iron on mask stuff, it's not as accurate as UV, but for convenience, it's excellent.
ReplyDelete