Air tight / Seal a print?

[sTaLa]

I just designed and printed a tool that will pick up labels and parts in an injection molding machine.

I have three main air channels into that thing (Red, green and blue are each of the channels.)

What I was worried about happened though: the internal air channels are not air tight. When I put on vacuum, I get some succion, but far from what I should. Reading the actual negative pressure tells me that I have a LOT of internal leakage. This was bound to happen as printing is pretty much laminating with plastic... but I was optimistic.

Anyway, tonight I am printing some test channels. My first trial will be to mix epoxy with Isopropylic Alcool (70%) and then shoot it in the air channels. I hope it will help.

Does anyone have another idea?
Thanks!

[jimc]

dont bother with the alcohol/epoxy mix. you dont want to introduce solvents into the epoxy because as the solvents flash off any openings in the wall of you air channels will open up. as a solvent flashes the resin shrinks. you want a 100% solids epoxy that is thin. a nice table resin for example. then tend to be thinner so they can be spread out and self level on a table or bar top. you will want to fill the air channel completely full then let the excess drain out.

[sTaLa]

Hmmm... I don't see how I can send epoxy right to end of every channel without blocking any of them if it is not diluted, as epoxy is pretty viscous and my air channels are 0.15'' in diameter at their end.

Maybe if I put just a little bit right after I mix while it is still pretty liquid and "push" it with compressed air...

[jimc]

yeah thats why i said you need thin epoxy. solvent is going to kill it. you could add just a touch of acetone if you want but no more than say 10%. if you get thin epoxy then you can block the bottom of the channel and squeeze it in with a large gauge needle bottle.

[sTaLa]

Oh I just got what you meant I did not know thin epoxy existed like that off the shelf. I will have to look into that.

I just read that fiberglass resin could be an option
..

[jimc]

yes polyesters will work but epoxy will bond much better to petg. epoxys are available in all different thincknesses. table resin is the thinnest i can think of that would be available to you locally. you can go into prob any michaels or ac moore craft stores and get small bottles of it.

[zemlin]

I already posted this in the filament thread - but Easy Cast is a thin, 2-part epoxy you can find at a craft store. It is slow cure, but works well. I haven't tried it in small diameter passages, but I'd probably try filling them with epoxy and then blow them clean with compressed air. Pretty significant mess potential with that - probably not a good technique to try in the kitchen.

[sTaLa]

Hey thanks for all your great feedbacks!

I'll make sure to grab some table epoxy next time I go the hardware store. Easy Cast might be harder to get in my area, I'll look for it next time I go in the city.

So during the night I printed those 5 samples.

All I had today to run my first trial was 5 minutes epoxy, 70% alcohol and acetone. So I used two samples and shot them with diluted epoxy. 1st with alcohol and 2nd with acetone, both using about 2mL of epoxy and 4ml of solvent.

It turned out great actually. I was reading -59kPa and -70kPa on #1 and #2 prior to the application of epoxy. After the first coat, I read -85kPa in both instances, which is the lowest value I am able to reach with my venturi. I am curious to see how it will hold up overtime. Also, I wonder how well that epoxy solution will travel within my mandrin that has many more channels than my small test samples...

I'll see how it goes and give a try to those other kind of epoxys soon! I have three samples remaining.

I wondered: does acetone have any kind of effect on PETG? I did not find any so far.