Inter-layer planing tool

[Whosa whatsis]

Ironing works pretty nicely for smoothing a flat top layer, but it can take a while, and I've seen some issues resuming extrusion on the next layer after using it, since the plastic is sitting hot in the nozzle without moving for so long. Either it oozes during the ironing and there isn't enough plastic in the nozzle when the next layer starts, or heat creep causes a partial jam. It usually doesn't cause a complete print failure, but sometimes a little skipping as the next layer starts.

There have also been proposals for a separate ball-ended tool to re-melt the plastic for smoothing, but if this idea was simplified to only serve the function of ironing, you could design a tool that would work on the entire layer in one pass. I'm imagining a heated rod or roller, or a taut piece of nichrome wire like in a hot wire foam cutter might work. It would span the build space parallel to the platform, and you would run it across the top each layer.

You could even mount such a device to one of the printer's existing axes, mounted a little above the height of the nozzle. You would then move the nozzle to one side of that axis and drop the Z to allow the smoother to make contact. You wouldn't be able to do it on the first few layers this way of course, and you would be narrowing your printer's usable area a little if you want to use it, but it might be a worthwhile tradeoff (and you could still use the full width if you don't use the smoothing tool. You probably couldn't toolchange this device, but if you left it permanently attached and above the nozzle height, you could use it while no tool is mounted (which would happen between layers anyway).

Working this way, the tool would also work on the support surfaces in contact with the bottom side of the print, so soluble support prints would, in effect, be ironed as well.

[Ryan Carlyle]

Wonder what kind of wire diameter you would need for nichrome to smooth and not just cut?

Also: I wonder if we could just put a ring of PTFE around the nozzle that would plow into still-warm plastic right after the strands go down, and not have to worry about heating. 

[tray]

If your ring could cool the plastic past Tg, maybe it would help reduce curling by holding the plastic down as it stiffens.That would need a flat-bottomed ring with rounded edges.

[Sjoerd Fruijtier]

During Formnext a company called Essentium3D showed a similar (contactless) approach with plasma, mainly to improve interlaminar bond formation, without a heated chamber. It would be interesting to know if this would have a positive effect on surface roughness / optical print quality as well.

See:

• https://essentium3d.com/flashfuse/
  
• https://patents.google.com/patent/US20190344502A1/en?assignee=essentium&oq=essentium
  

[Ryan Carlyle]

Stratasys has a patent (iirc) on microwaving parts printed with conductive fibers to internally heat them and improve bond strength. The plasma technique sounds similar. You could probably use a lot of different heat sources that are composite-selective and leave the resin more or less alone, like an induction coil with metal powders.