Clearance for plastic hinges

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Numonic
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Clearance for plastic hinges

Post by Numonic » Fri Nov 16, 2012 10:38 pm

Anyone know a good clearence number for parts that move with the printed plastic? As far as hinges?
Ball joints seem to work well on my end no probs with that but when Ihave the pin inserted into some of the loops the outter area cracks.

eyUP
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Re: Clearance for plastic hinges

Post by eyUP » Fri Nov 16, 2012 11:23 pm

The Up printers are pretty good on finished sizes but I've found all FDM printers tend toward smaller holes than designed. I'd always expect to drill or ream out pin / screw holes before fitting so as not to strain and crack the model.

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Numonic
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Re: Clearance for plastic hinges

Post by Numonic » Sat Nov 17, 2012 4:41 am

I was thinking about having my figures use 2mm diameter metal dowels, so I'm guessing I should make the holes and just drill them with a 2mm drill bit if that even exists?

odiegel
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Re: Clearance for plastic hinges

Post by odiegel » Sat Nov 17, 2012 6:13 am

Yep. 2mm drill bit is pretty common.
But, if I were you, I would try to avoid drilling if you can. It's just an extra step in the process...
It's just a matter of experimenting a bit. I would start off with a 2.2mm hole (as EyUp said, FDM typically makes any internal hole dimensions smaller than designed), so you will probably end up with a decent/tight fit around a 2mm pin. If you want a looser fit, you might go as high up as 2.5mm. From 2.2mm just increase in 0.1 increments until you get the tightness you want. Obviously try to have those holes printing vertically so they are as 'round' as possible.
Cheers
Olaf

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Numonic
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Re: Clearance for plastic hinges

Post by Numonic » Sat Nov 17, 2012 6:35 am

Sounds really good to me wasn't really in the mood to drill but would have done it if need be. Your right the pieces are tight and split for some reason, I have found twisting it like a screw slowly gets the part it but when making holes I might make it .1 larger so when I make the part it's fine. I'm thinking of going with metal pins this time instead of printing them. Doing it Takara Tomy style and Hasbro ;) . That method hasn't failed them and it might do me just as well smaller holes is better looking anyways. Thanks for the helpful hints will do them when I get the printer.

roller
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Re: Clearance for plastic hinges

Post by roller » Sat Nov 17, 2012 8:44 am

I would simply create a test piece with a range of holes in 0.1mm increments ranging from 0.5mm under to 0.5mm over the size you want. Then you can see which give you the pin clearance you desire. It's a quick simple print and is a handy reference.

Be aware that changing the layer height may give slightly different results in hole sizes (this may not be true for Up software but it's true for reprap). Also version changes in software may have an impact on the result.

walter
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Re: Clearance for plastic hinges

Post by walter » Sat Nov 17, 2012 8:42 pm

yeah, I've definitely noticed changes with layer height. The type of plastic sometimes makes a small difference as well (some of them spread out a bit more than the OEM filament), so I usually do the test prints with the same settings and same plastic as the final piece. Sometimes you can reinforce holes by putting really narrow cuts around it, forcing it to print extra material around the hole.

roller
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Re: Clearance for plastic hinges

Post by roller » Sun Nov 18, 2012 1:37 am

Indeed some plastics flow more but often the difference is the variation in filament diameter. As we can change the feed ratio in UP software we cant compensate for over or undersize filament. That said if you can find thicker filament 1.77ish mm you will get a stronger part (I presume genuine filament is 1.75? I've never measured it)

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Re: Clearance for plastic hinges

Post by odiegel » Sun Nov 18, 2012 2:30 am

If I remember correctly, the technical spec for the filament dimension is probably be 0.07" (from the Stratasys Dimension spec) which is 1.778mm.
Cheers
Olaf

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