Saturday, March 15, 2008
Doctor blade
After looking at the cool stuff nophead is doing, and stealing an idea from Ed, I have improved the nozzle wiping on my RepRap considerably.
The picture shows a doctor blade cut with scissors from brass shim. It has a V notch that the extruder uses to discard excess extrudate.
I have upgraded the Java code in the repository to use this type of wiper, which works better than the previous toothbrush-wiper blogged a few days ago.
Tricks: make the V angle very acute, and curl the profile down slightly so it comes up to meet the nozzle as the nozzle moves over it. Also take care to align the nozzle with the very centre of the notch when it does the wipe.
We still nead a way to clean the cleaner, I think. As you can see, lengths of extrudate build up in the notch and are going to cause trouble eventually.
Labels: cleaning, doctor blade, nozzle wipe
Comments:
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How about using a cylindrical brush (like a bottle brush) on a rotating shaft. Then as the poly accumulated and cooled the brush could turn and a beveled metal edge could scrape off the deposits from below into a recycle bin.
It looks like PCL must be a lot stickier than HDPE. The toothbrush version always clears my nozzle and the HDPE does not stick to it. The only problem I do have is that the nozzle is hot enough to melt the bristles to it is slowly going bald.
Run a small amperage through the blade to heat it enough that the poly melts and drips off. It doesnt even need to be monitered - experimentation will show the right amount of trickle current to be left on.
You could spring load an exacto blade underneath the scraper next to the V notch. The nozzle (or an arm attached to the nozzle) would push it out of the way and then after the nozzle moves away the spring would push the blade back over to slice off the deposit of plastic filament.
> The only problem I do have is that the
> nozzle is hot enough to melt the
> bristles to it is slowly going bald.
Yes - I had that problem with a toothbrush too. Tree-hugging types brush their teeth using toothbrushes with real bristles from dead things in, as opposed to nasty chemical polymer bristles. I suspect they'd go up to higher temperatures.
> You could spring load an exacto blade
> underneath the scraper next to the V
> notch. The nozzle (or an arm attached
> to the nozzle) would push it out of
> the way
Great minds etc. That's exactly what I did. See the later blog for 17 March.
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> nozzle is hot enough to melt the
> bristles to it is slowly going bald.
Yes - I had that problem with a toothbrush too. Tree-hugging types brush their teeth using toothbrushes with real bristles from dead things in, as opposed to nasty chemical polymer bristles. I suspect they'd go up to higher temperatures.
> You could spring load an exacto blade
> underneath the scraper next to the V
> notch. The nozzle (or an arm attached
> to the nozzle) would push it out of
> the way
Great minds etc. That's exactly what I did. See the later blog for 17 March.
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