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Here's a sneak peek at my DIY heated vacuum dryer. I still have to run some more tests but so far the results are promising!

I have about $75 into it so far. I already had the vacuum pump for recharging air conditioning.

[img]https://lh4.googleusercontent.com/-k8NF ... 130_153631[/img]
[img]https://lh4.googleusercontent.com/-zJOE ... 130_153228[/img]
[img]https://lh4.googleusercontent.com/-kSvJ ... 130_153439[/img]

I use the same paint pot for pressure testing dive equipment! Great for equivalent up to about 60 metres before the seal starts to let go. Nice alternate use

This is awesome! I love printing nylon but I hate drying it in my oven at 100C for several hours at a time so much that I basically never use it.

Got a link to that paint pot? HF paint pot is surprisingly expensive.

http://m.ebay.com/itm/261259886334

Looks like he has 3 more. I offered $55 and he took it.

I bought mine on eBay then found them ten bucks cheaper at one of the local discount car part / tool places.

That is super cool.

rpress, can you tell us how long you let it heat, at what temperature before you draw the vacuum?

I let it sit for a couple hours and it's 32C inside. At that temp, the vapor pressure of water is 4800 Pascal, and my pump goes down to 10 Pascal.

rpress wrote:I let it sit for a couple hours and it's 32C inside. At that temp, the vapor pressure of water is 4800 Pascal, and my pump goes down to 10 Pascal.

Thanks for the response because I have one similar to yours that I have not had a chance to use yet.

I've been scheming about this too. Great design, I love it!

Thanks guys. I have a hygrometer data logger on the way, so I can see how long I need to vacuum it down for. Hopefully the logger can handle the vacuum. http://www.perfect-prime.com/temperatur ... ogger.html

My idea is to come up with some timer so it will sequence the heater and pump and shut off when done. If not I'll probably forget and leave it running for a day... I ordered a couple of these, I think I can hack them into submisson. http://www.amazon.com/Belkin-Conserve-S ... B003P2UMS0

Where did you get the connector to attach the R134a hose to the pressure pot?

I've been printing a lot of parts with nylon lately. The dryer works great, and the prints look smooth and lay down with no steam. After about 4 hours of the filament exposed to the air the prints start getting a milky white texture and the extruder steams a bit. The RH is around 80% lately, so this shows that the dryer certainly works well, and also if I want to do a longer print I need to make a dry box for de-spooling.

This brings up another question. The perfectly dry filament makes smooth prints with shiny finish and nice color. The wet filament has inconsistent white spots and the finish isn't smooth. But, the wet filament has much better layer bonding! I think the steam causes small fractures in the layer surface, allowing the next layer to hook on. I'm printing at 245C which seems reasonable, but I will try a bit higher and see what happens.

Dry = smooth finish, nice color, weak layer bonding
Wet = milky inconsistent finish, strong layer bonding

rpress wrote: I'm printing at 245C which seems reasonable, but I will try a bit higher and see what happens.

What kind of nylon?

If you are talking about blue trimmer line nylon, that's significantly lower than most people use. I use 260-280C for it.

0110-m-p wrote:

rpress wrote: I'm printing at 245C which seems reasonable, but I will try a bit higher and see what happens.

What kind of nylon?

If you are talking about blue trimmer line nylon, that's significantly lower than most people use. I use 260-280C for it.

Yes it's the blue trimmer nylon from Amazon. 280C seems awfully high, have your checked your hotend accuracy with a thermocouple? Mine is pretty close. Do you know anyone else running from 260-280C? I've seen temperatures used from 235-255C, but who knows... I'll dry it again and run it at 260C and see what the layer adhesion is like.

I just found this on google, looks like others are seeing what I'm seeing about a little moisture helping the layer adhesion:
http://www.tridimake.com/2014/01/how-to ... -line.html

As an aside I kept pushing the retractions up and up. Finally no strings! Only took 18mm length at 160mm/s, heh.

Rhere was a thread recommending shorter and slower for PLA. You may want to have a look.

rpress wrote:Yes it's the blue trimmer nylon from Amazon. 280C seems awfully high, have your checked your hotend accuracy with a thermocouple? Mine is pretty close. Do you know anyone else running from 260-280C? I've seen temperatures used from 235-255C, but who knows... I'll dry it again and run it at 260C and see what the layer adhesion is like..

I have not verified my hotend temp with a thermocouple, so any temps I claim may be off, but there are others that print at 260C and above. Personally I usually set it to 270C for my 0.4mm nozzle E3D V5. All the below quotes come from this thread... http://forum.seemecnc.com/viewtopic.php?f=36&t=2356

Cope413 probably has more experience printing with blue trimmer line nylon that anyone on here and here is what he says...

I set my hotend to 265 for the first layer (at my print speeds, it holds at 260-261), and then drop it to 260 for the rest of the print (it stays between 255-258).

Below 255 and you're not going to get optimal layer adhesion. As long as you don't push it to 280C, the nylon will be fine.

and in response to one question I posted

Nylon needs to print at 260-265 to get good layer adhesion.

Also, Generic Default says...

I just switched to the E3D hotend because 240 degrees is about the minimum temperature you can print nylon without serious delamination. 260 degrees makes extremely strong parts; I can't pull apart a magnetic arm cup joint with pliars.

I highly recommend trimmer line if you have a hotend that can print over 250 without melting its own PEEK.

and

I did notice a difference in layer adhesion when I switched to a tiny nozzle. You can print at 245 to 250 degrees with a large nozzle and get good layer adhesion; if you use a 0.25 nozzle you will need to go 260+ degrees.

Thanks for digging those up, appreciate it. I'll try 260C with dry filament and let you all know how it goes.