How well does abs print onto cold, smooth abs? I’d like to print one or two layers onto an existing piece of injection-molded abs, which I can’t really heat up throughout. (I may be able to heat the top surface with a hot air stream.)
Thanks for any advice.
I have had some luck pausing abs prints overnight. Expect the line to be visible tho.
I doubt it will work because printers and software assume your printing on a flat surface, and that nothing is pre existing. Your trying to do an overmold with 3d printing, but that’s just not possible to do with existing tech. Over molding even with conventional plastics is very difficult to match up. The best you can do is get a dual head printer, so both objects are molded at the same time. That’s your best bet.
Maybe enclose the printer and heat the air inside it. The part will warm up to that temp and it might be enough.
Print the extra layers and then stick them to the original using acetone?
@MidnightVisions : I’m presuming I will have to write my own gcode rather than using a slicer, but that’s okay. I can map the surface with a touch probe.
It should stick, but there will be a lot of warping stress (and thus risk cracking or loss of strength) at the hot/cold join. Printing very hot (like 250C maybe) will help it stick. Preheating the part a bit (like in an enclosed chamber) will help enormously, just like any other ABS printing.
@John_Bump That still won’t work because the head of the extruder can’t go into crevises, and it can’t inject, it can only go flat across a surface. Anything that is protruding will only be an obstacle to bump into. What you are thinking just can’t be done with 3d peinters. A multiple head printer, printing everything together at the same time is the only way to achieve what you want.
@MidnightVisions We don’t really know what kind of surface/contours he’s expecting. I’m assuming it’s flat enough that the nozzle can reach most everything, and simple enough that hand-written gcode is viable. In that case, it should work. The first layer can always be over-extruded like a raft to deal with minor contour matching errors.
Handwritten gcode can certainly handle non flat surfaces. And a delta, for example, can move in Z just as quickly as in any other axis.
What I’m planning is inlay: mill a 0.15mm deep channel in a surface that’s as flat as a plastic injection molding machine can make it, then come back and fill it with a contrasting color. It’s for a very niche application. My expectation is that I’d z up to a safe height, g0 over to the right x,y position, z down to the point where the nozzle is essentially against the plastic surface (that might be a problem: it might mark up the surface as it traverses) and then put down a 0.175mm thick layer, then z up to safe height after each pass. I’ve written post-processors to edit g-code and add in z moves, so that part’s not a problem. I’m mostly worried that it simply won’t stick. I might end up having to pre-ink the milled channels with acetone, but if I don’t have to do that I’d really prefer to avoid having any acetone involved.
@John_Bump can you do a colored epoxy pour in the milled channel rather than extruding?
Yeah, I could, but I really would prefer to have this all automated. Another possibility is using a paint pen as a tool in the cnc mill. If I cut deeper I could possibly use a paste dispenser to fill the channel and then wipe it with something like a soldermask squeegee, but in my experience that provides a lot more avenues for variation.
Depending on the complexity of your desired engraving, might consider hot stamping. Makes a permanently bonded second color marking. Good for making text stand out and could be done in a pinch with an alphanumeric set meant for metal marking.
As I think of it, if you used an abs film of your desired color and a small-tip solid nozzle you could hot stamp a dot matrix pattern. Particularly if custom g code is in your skill set.
If the part you are printing on is flat you could flip it over and let it warm up on the bed. Then an enclosure should keep it warm enough.
Extending on the paste dispenser direction, you could make an abs/acetone paste.
@Jason_Burton : I was thinking about that, but am worried I’ll end up melting through the part if I’m not careful. Maybe print fast and then hit it with lots of air to evaporate the solvent.
How thick are the parts to be marked?
Not very, like about 1.3mm. That’s one reason I’m trying to find a process that can just barely cut into the surface.