Fuel Vapor Separator - Design Opinions Wanted (2 Viewers)

[Andrew S]

Very cool, I should buy one for the inevitable failure of my own vapor separator.

Easy option for tapping straight is to print a quick guide block with a clearance hole for the tap. Since you've already modeled your part-to-be-tapped, you can make the guide block fit snugly to the part body wherever you need it to be.

Another option is to model the threads and let them be printed. Then just run the tap through to clear out any flashing.

 

[procomsignathid]

Update:

3D printer is set up. Have a dedicated space now, plus a filament drier (the large dehydrator), a dry box for a 5KG roll of Nylon, and we're off to the races. Kids are enthralled:

Working on dialing in print settings for nylon... Aborted the first print after 15 or so layers as the edges were curling. Here's what that was looking like:

Knocked down the fan speed to keep temps up and the current print is looking much better thus far, but I can tell I'll need to be dialing in surface finish. Here's the current prototype:

They said Nylon is a PITA, and it seems to be living up to the reputation, but I think it will be manageable.

 

[charliemeyer007]

I have read that you need to dry the nylon filament to get better results.

 

[procomsignathid]

That's right, I dried it for around 6 hours at 70C / 160F, but after this print I may do a full 24h and see how that goes.

 

[procomsignathid]

The 3D-printing saga continues, but is starting to bear fruit:

In short, nylon is annoying to print, but I'm figuring it out. It wants to print super hot, and super slow compared to PLA, but I'm now starting to get surface quality I'm happy with. That said, the prints are taking awhile, the current one is about 4 hours into a 16 hour print. The wall thickness of the chamber is way too much material, so I'm going to thin it down from about 5mm to 2.5-3mm. That should hopefully speed up print time and use less material.

For those who want to delve into the madness of 3D printing, here are my attempts up to now:

1. Stopped this print after seeing poor surface quality and lots of curling. This was due to poor bed adhesion (didn't properly clean the bed first) and too much cooling in the print chamber.
2. This print failed around 90% through, likely also due to poor bed adhesion (still hadn't properly cleaned the print bed). Quality is pretty rough on the sides, only recently learned this was mostly due to under-extrusion (print speed too fast)
3. This print completed successfully, but still terrible surface quality, and some pitting/holes due to under-extrusion. I hadn't started slowing things down yet. There also may have been too much moisture in the nylon. I did use supports for this print, although they did not break away cleanly and left a terrible surface finish on the bottom. Thanks to a properly-cleaned print bed, it took real effort to remove it.
4. Turned off all cooling for this print, played around with support settings. Surface quality was not looking great still, and I noticed on the infill sections it was god-awful. This was the ah-ha moment, as the infill sections print much faster than the walls. Still can not remove the damn supports, leaves a lot of artifacts.
5. Slowed things down from ~200mm/s print speed to ~100mm/s. Quality notably improved, but not there yet. Played with support settings again, but still too much adhesion.
6. Slowed down to ~60mm/s, and now seeing much better quality. I had resolved to let this print continue, but there was a filament tangle in the dry box and it failed. I am still seeing minor curling on the overhangs, so I will play with even slower speeds or perhaps some cooling for those parts. Ditched the supports, but added a brim (much easier to remove)
7. In progres... Added some cooling to the overhangs, looks good so far. Wall quality is great. We'll see tomorrow how it looks, hoping to have the first nylon print I can pressure-test.

Circles in red: curling on 1, stuck supports on 4 and 5. Also note how thick the walls are on print 6. Aside from meat where brass threads are going, I think the walls can be half that thickness and still be plenty strong. The next photo shows more detail on the surface quality for overhangs. Left to right: first print, curling. 4th and 5th prints, stuck supports. 6th print, getting there but not there yet (no supports).

Under-extrusion (looks like scratches) due to print speed too fast:

Here's print #7 in-progress, so far so good. We're in "functional but not pretty" territory now, I still want those overhangs looking nicer. You can see the brim printed around the first layer to reduce curling/warping:

 

[procomsignathid]

Print #7 is a success! Seems to hold air pressure (very un-scientific "plug holes and blow into it" method), but good enough to test drill/tap etc. I'm still not satisfied with the overhang surface quality and the top of it is a bit rough too, but this is leagues better than prior prints, and without supports as well (which is how I designed the part). I'm doing more iterations to test overhang surface quality next, and I'm going to make some design tweaks to slim down the ridiculous wall thickness.

Lastly, I have a new build plate on order which will provide a smooth finish to the bottom of the separator. This may require PVA glue for bed adhesion, we'll see.