Dibloff's Build Log

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Re: Dibloff's Build Log

Postby roberlin » Thu Feb 28, 2013 1:35 pm

If I remember correctly you are using the qu-bd hotend.

There are numerous reports of issues extruding PLA with this hotend (I have one that works but I had to drill out the filament barrel).

I switched to a j-head (from hotends.com) and it has never given me a problem. If you go that route, be advised that they you can only count on them being in stock on Friday afternoons.
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Re: Dibloff's Build Log

Postby Zat German » Thu Feb 28, 2013 1:38 pm

Blue painters tape on a cold bed for PLA works best for me. I just make sure to get good adhesion on a squashed first layer. As far as jamming the extruder, you need to make sure that that fan is running full speed to prevent the PLA from creeping up the hot end. It's possible you need cooling a little lower too, on the part of the nozzle between the bottom of the carriage and the heater block. That could be where the PLA is creeping up and cooling down. Your heated chamber might be contributing to this too, since the fan is just going to be pushing around warmer air than an unheated chamber.
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Re: Dibloff's Build Log

Postby SystemsGuy » Thu Feb 28, 2013 1:44 pm

I do 3M blue painters tape and heat the bed to 55 if the ambient temp is around 20, then drop to 30 after the first layer. I print PLA fast and hot - so 100mm/s and 200-220c depend on the PLA. I had horrible luck with my QU-BD, and went back to a j-head, and am loving it. I also usually start cooling as well after the first layer - again, this sorta depends on the model.

I don't "squash" the first layer, and run it at 50% of my normal speed.
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Re: Dibloff's Build Log

Postby dibloff » Fri Mar 01, 2013 3:46 am

Thanks all for the suggestions. I'll try those. Looks like switching between ABS and PLA will not be as easy as I thought.
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Re: Dibloff's Build Log

Postby dibloff » Fri Mar 01, 2013 3:49 am

Back to the ABS. Not sure if this is still the Hadron built, but I think somewhat it is. Because the FDM technology has its drawbacks - especially in my case the lack of support – will make me think a lot when building some specific shapes.
A sphere, in this case. 8 mm dia. I need a perfect sphere. Actually 20 of them, for this large ball bearing. The main problem is that the sphere has a real small initial contact with the bed, so when it’s halfway built it’ll roll off, while the extruder is still building it.
I tried to have a small patch underneath, I tried to build it on a pedestal etc. None of those worked.
I ended up building half spheres with a 1.7 mm hole inside, then I cut small pieces of filament and used it as a pin to locate the halves relative to each other. Later I used some abs diluted in acetone to glue them together.
2013_0228_Hadron 001.JPG

2013_0228_Hadron 009.JPG

Here is the end result.
2013_0228_Hadron 005.JPG

And here is the finished bearing.
2013_0228_Hadron 013.JPG
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Re: Dibloff's Build Log

Postby fma » Sun Mar 03, 2013 8:54 am

I recently made a large ball bearing, as yours, using airsoft balls. They are not expensive and very well calibrated. The bearing works fine.
Frédéric
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Re: Dibloff's Build Log

Postby dibloff » Wed Mar 13, 2013 11:51 pm

FMA. Thanks for the advice. I obtained some Undead Apocaliypse Airsoft Defense Zombie Antidote... :) They all mesure ~5.89-5.91 mm. I redisigned all my bearings to use this ball size, and they work flawlessly.
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Re: Dibloff's Build Log

Postby fma » Fri Mar 15, 2013 5:56 am

How do you insert balls in your bearing?
Frédéric
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Re: Dibloff's Build Log

Postby dibloff » Sat Mar 16, 2013 7:39 pm

Hi FMA. Here is how I build my bearings:
The inner and outer races are built in the same print. I use the 6mm balls mentioned in the earlier post. I also print a cage. This will prevent the balls getting to the same side and falling out.
Here are the parts before assembly
2013_0316_Hadron 002.JPG

Balls are inserted
2013_0316_Hadron 003.JPG

The balls are arranged
2013_0316_Hadron 004.JPG

Cage before insertion
2013_0316_Hadron 005.JPG

Completed bearing.
2013_0316_Hadron 006.JPG
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Re: Dibloff's Build Log

Postby fma » Sun Mar 17, 2013 8:06 am

Ok, I understand. The fact that you have a few balls, and not all over the perimeter allows you to insert them! Then, the cage maintains them... Very nice design!

I guess you made a few tests to find the correct dimensions, to avoid having the balls too much tighten, or too loose?
Frédéric
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