Idea: Hot-pressing the print for strength and surface finish

Hi everyone,

Here's a suggestion for a possible method to improve strength and surface finish of prints. It may also have the added benefit of reducing warping by relieving thermal stresses.

The idea is, during the print after one or multiple layers have been set down, to "iron" the top layer, basically using a second heated bed but flipped upside down and coated with a smooth non-stick surface like PTFE or HDPE. This plate could be attached to Mendel's Z-axis. As necessary, the plate would be heated up, and brought down to press the newest printed layer to an exact height, creating a smooth glossy surface. Then the plate is cooled and disengages from the print, and the next layer is created as usual.

This could be done just on the top layer of any visible surfaces, to create a smooth glassy surface finish. But it could also be done intermediately, to help print roads bond to each other, enforce dimensional accuracy, and (in the case of PLA), help create fully transparent parts.

By requiring multiple heat/cool cycles, it would add significantly to the build time, but in situations where print quality is the primary concern, that could be a worthwhile tradeoff. A low thermal mass in this plate would be important.

Small perforations might help trapped air bubbles escape the printed part, which would be useful if trying to create fully solid prints.

... this could be add to the nozzle as cooled collar around the tip, so it's symmetrically to all moving directions - then the 'ironing' wouldn't consume extra time ...

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Viktor
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Top surfaces already come out pretty smooth though. This would be more useful if it could be applied to vertical surfaces, or even angled/curved ones like the inside of the y-bar clamps. You could press any angled surface if your "iron" was a free spinning ball bearing that could just be rolled against a surface. Unfortunately because you're not pressing against the bed, any pressure to the side is likely to detach the piece from the bed.

how about a heated cylinder that could be lowered down 10 mm below the nozzle. after it prints 10mm, the cylinder drops down and rolls along the the perimeter.

Maybe a servo that swings the cylinder down, or a rack and pinion salvaged from a CD player, and a resistor heater inside a ptfe cylinder. of course you'll need to edit all the software to make it work, too. and it would only work on flat vertical sides.

not a good ideia. wnat what then? the printed piece gets lowered by pressing, and the nozzle will print as it was the same height.

are you saying that the nozzle will ooze while you are doing the smoothing pass? That could definably be an issue if doing smoothing while printing.

oh and jsadusk, i didn't read your whole post but you had the same idea as me and beat me too it :-)

no. i'm saying, if you press it, the whole part will go down. and the extruder will print the next layer, assuming the height of the part hasn't changed.

That's why the press plate is on the z-axis, and only lowers to the exact height that the surface is supposed to be.

it would fatten the walls. not precise. i dont see it as a good ideia. but try it