GUS Red build log (aka SpiderPig)

GUS Red build log (aka SpiderPig)

Postby brandonh » Sun Dec 08, 2013 8:22 am

Today's progress:

IMG_20131207_234212_small_2.jpg
IMG_20131207_234212_small_2.jpg (165.67 KiB) Viewed 15967 times


Successful prints of most of the extruder pieces, minus hub_bottom, which popped off with maybe 20% of the print left. I did all prints on a Kossel Air with no heated bed, using Aqua Net for extra adhesion; I wanted to see how far I could go without a heated bed.

The good news:
- These parts are strong! The aborted shoulder print is completely rigid. 20% infill with 3/4 perims feels right. I ddi 60% for hub bottom but probably 40% would be fine. Slic3r fills in the threaded cylinder part anyway.
- Amazing fit. FWIW, I calibrated the flatness of the Kossel Air to within ~0.02mm for both flatness and bed height and to ~0.2% for length. The extra 0.1" slop built into the Inventor files was perfect for me, with a tight slip fit to the 6702 bearings. I just pushed hard on a table and they popped into place, no oven required. They're in there tight but I could probably still get them out. Absolutely no cleanup or drilling required for any of the holes, too, with an equally perfect loose slip fit on all bolts. Printer tuning FTW; really, I probably just got lucky today.

The problems:
- Unprintable overhang in hub_center: a rounded end can't be tangent to the build plate, or it will exceed the printable overhang threshold. As you'd expect, the filament printed in air and fell to the bottom for the first few layers. It's ugly but I can have it face downward to hide it somewhat.
- Excess slop in hub_bottom. The sketch shows 14.7mm for a 15mm bearing hole. Yes, with the lock nut clamping down, this may not matter in practice, but I'd rather not have this slop, especially when it's 3x the slop for the 6702 bearing ODs. I'm going to modify mine to be 15mm, knowing it will print slightly smaller.
- Curling with the shoulder parts; I gave up on this print when the bearing side had lifted up maybe 4 mm, to where the bearing would never fit. Need a heated bed upgrade.
- Adhesion: the hub_bottom popped off with 2" of height, but was doing great until then with no curling. Again, heated bed. Adding a heated bed fixed adhesion problems on my Printrbot Jr that had prevented me from printing Kossel parts.

Looking forward, I can't imagine how hub_bottom will not melt without some kind of fan. Since I have to print a new hub_bottom anyway, I plan to add a small hole to form a 3mm thread near the flat face on the end of hub_bottom that is farthest from the arm attachment screw. A single screw looks perfect for a diagonally-mounted 40mm fan to hang down. I'll probably add a small flat face below where the hotend-holding screws go.

The hard/fun stuff is all left to do.
brandonh
 
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Re: GUS Red build log (aka SpiderPig)

Postby Nicholas Seward » Sun Dec 08, 2013 8:43 am

I just pushed a more printable version of the HUB CENTER.

Thanks for sharing. Looking good.

I would normally under size the shaft to 14.8mm to get a slip fit. After a lot of sanding on a few of mine I dropped it to 14.7 to same me time. It also makes the nut easier to put on. I made a branch with a bigger shaft for the HUB BOTTOM. (14.85mm)

You don't need a fan for cooling but angling it down to cool the print would be handy. I am considering putting mounts for a LED ring and a downward facing fan. (For now, I am going with the bare minimum to keep from getting bogged down.)
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Re: GUS Red build log (aka SpiderPig)

Postby brandonh » Sun Dec 08, 2013 9:02 am

Nicholas Seward wrote:I just pushed a more printable version of the HUB CENTER.

Thanks for sharing. Looking good.

I would normally under size the shaft to 14.8mm to get a slip fit. After a lot of sanding on a few of mine I dropped it to 14.7 to same me time. It also makes the nut easier to put on. I made a branch with a bigger shaft for the HUB BOTTOM. (14.85mm)

You don't need a fan for cooling but angling it down to cool the print would be handy. I am considering putting mounts for a LED ring and a downward facing fan. (For now, I am going with the bare minimum to keep from getting bogged down.)


Both of those would certainly be cool. Some options for the interface:
- two vertical through-holes parallel to the hotend body but just clearing hub_center (so no real changes, just a single negative extrusion)
- a circular flange at the bottom of hub_bottom with through holes and a bit of clearance. Keeping compatibility with the Kossel would be awesome here; the interface is just 6 holes on a circle, which enables you to use hotend clips, hotend clip / fan combos, fans, and auto-probes. I'm realizing you could get j-head compatibility with a simple spacer and hotend clip. Examples:
j-head retainer
auto-probe example
fan mount
The GUS parts are a bit beefier so I'm not actually sure this compatibility is practically feasible.
brandonh
 
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Re: GUS Red build log (aka SpiderPig)

Postby Nicholas Seward » Sun Dec 08, 2013 9:57 am

Want to give this a go. I added the Kossel Flange. I hope it works. I also increased the shaft size for this version since I figure you will be the only tester for a while.
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Re: GUS Red build log (aka SpiderPig)

Postby brandonh » Sun Dec 08, 2013 7:21 pm

Thanks, Nicholas. I'll print it out now, also with a narrower bowden tube channel. Playing with some printed Kossel effector pieces, the Kossel auto probe won't fit, because it wraps around three screws and assumes a ~16mm dia inside, which clearly doesn't leave space for a Ubis-style hotend. But, whatever, I'd rather have probeless leveling anyway:
Probeless auto-bed leveling
draft Kossel probeless probing
Yes, I would like to add the second style, but flipped around so the rotation is on the bottom. The top part of the interface doesn't matter and you can do something prettier and stronger like a tapered cylinder above to intersect with hub_bottom. Hopefully I'll get the chance this week to try it out.
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Re: GUS Red build log (aka SpiderPig)

Postby brandonh » Sun Dec 08, 2013 10:41 pm

Printed Nicholas' flange mount hub bottom (see branch KOSSEL_MOUNT) and posted pics in a G+ post:
https://plus.google.com/104919785646757 ... jkMtFqodxP

Most pics have comments explaining what you're seeing.

Here's a single pic from the album:
GUS Simpson Red build - 8.jpg
GUS Simpson Red build - 8.jpg (76.07 KiB) Viewed 15935 times


I have a complete hub assembly now. Works great with my J-head and a printed clip:http://www.thingiverse.com/thing:107890

The flange helped the part stay attached to the unheated bed, with only a tiny bit of curling.

Ideally you'd also put in a spacer where the Ubis would usually go to fully lock down the J-head. Easy enough.

My Ubis is 3mm so this saves the me the $$$ of buying a new Ubis.

I think I may try another should mount, but really slowly and with extra Aqua Net, and see if that doesn't curl.
brandonh
 
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Re: GUS Red build log (aka SpiderPig)

Postby Nicholas Seward » Sun Dec 08, 2013 11:36 pm

KOSSEL.png
KOSSEL.png (91.65 KiB) Viewed 15930 times


As per your suggestions, here is the new experimental hub bottom.

You will need to replace the M3x20 bolts with M3x25 bolts.
Last edited by Nicholas Seward on Mon Dec 09, 2013 5:31 am, edited 1 time in total.
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Re: GUS Red build log (aka SpiderPig)

Postby brandonh » Mon Dec 09, 2013 5:06 am

Nicholas, that looks great! Looks stronger and easier to print.
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Re: GUS Red build log (aka SpiderPig)

Postby brandonh » Mon Dec 09, 2013 6:13 am

Latest part: shoulder. This one completed with about 1/16" of curl at both ends. I think it's still usable. 0.16666 infill, 3x 0.4mm extrusion wall, 0.25 layer height, 3 bottom/4 top layers, printed slowly (mostly 60 mm/s).

https://plus.google.com/104919785646757 ... T6yZDv5PYN

My Kossel needs a bit more calibration, as on one side the hole is 22mm and the other, it's ~21.7mm. Same difference measuring the beam thickness from one side to the other. I have no idea how to fix that one, so I'll just live with it.

You could argue that none of the ugly part errors really matter, as long as I can insert the bearings where they need to go. But, it would be nice if they weren't there out of the box.

Nicholas, would you be able to convert the angled tunnel to hex or octagonal "holes"? When the top edge of the slightly angled tunnel in the should joint is flat, it should print much better than when it's an extreme overhang.

This part seems beyond the limit for an unheated bed. That's up next. Then, time to get the big-size Kossel Mini running to print the gear arms (it has a 10in printable diameter, with 300mm arms rather than 240).
brandonh
 
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Re: GUS Red build log (aka SpiderPig)

Postby Nicholas Seward » Mon Dec 09, 2013 6:49 am

See if this version of the shoulder is better. If it prints better then I will consider making this the new norm.
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