Drying Times and Temps in Dehydrator  

RE: Drying Times and Temps in Dehydrator

I got one of those SUNLU dryers and have a reverse bowden setup so have the tube sticking into the dryer. I did a 12 hr print with some old PETG and it came out as well as I could have expected, no stringing, no zits and no blobs, this was some semi white filament which prints best at 245 deg C.

All worked nicely and the dryer / heater shut off automatically.

The only issue is that it is a bit of a faff getting the filament threaded into the reverse bowden tubing.

RE: Drying Times and Temps in Dehydrator

Posted by: @dragon1291

Just got and modified this guy off of Amazon: https://www.amazon.com/gp/product/B07MPC7C8G
Figure for $50.00 with a digital display and 48H Timer, it was the best bang for the buck.  The modification is a bit more permanent (have to cut out the grills) but I have no intention of ever using it as a normal food dehydrator. Works great, can hold up to 2 Spools plus any random non spooled bits that you may have laying about.

I purchased another device from Amazon that was cheaper, claimed it could do 155 F, claimed to be 280 watts. Those were lies. The fan used 20 watts, and the total wattage of that unit was 260. So it's a 240 watt heater. The CCD100W6 is not suitable for drying PETG. It simply doesn't get hot enough. I set to 135 F which worked fine, but setting to 155 (the maximum) yielded basically the same result

The CORSI unit has no problems hitting these temperatures. The unit claims 450 watts and it consumes 460 when in heating mode (about 20 when fan only).

(all temperatures are in F, regardless of what the display says)

You can pretty easily see that the unit has no problem getting to a 150 F set point.

In fact, in general, the temperature is always about 3F to 5F higher than requested. It has no problem hitting (and exceeding) 165 F.

The upward tick above 170 F made me wonder what the long term regulation was like, and it's pretty good.

In this picture, I took the temperature down from 170 and tried to hit 130 F.

Again, it sits 3-5 degrees above the set temperature.

So I left it sitting there for some time, and the long-term temperature regulation appears pretty good.

It continued to be pretty good.

I also checked the temperature with a NIST-calibrated device (Thermapen) and it was providing similar readings.

All in all, I'm pleased with the temperature control on the unit so I plan to proceed to modification.

RE: Drying Times and Temps in Dehydrator

I bought a set of scales and now weigh the spool after printing and write it on the box so I can weigh the spool before next print to see if it has increased with moisture and would benefit from drying before I start.  I don't live in humid climate and not necessary for the usual filaments but think useful for Nylon and such.

RE: Drying Times and Temps in Dehydrator

@technogeeky

Well I'm glad someone was able to confirm that the unit I bought had solid temp control. haha. 
Where in the Dehydrator did you measure the temperature at? I'm wondering how much of a delta there is from the bottom to the top. 

RE: Drying Times and Temps in Dehydrator

Posted by: @dragon1291

@technogeeky

Well I'm glad someone was able to confirm that the unit I bought had solid temp control. haha. 
Where in the Dehydrator did you measure the temperature at? I'm wondering how much of a delta there is from the bottom to the top. 

I measured it down where I expect the bulk of filament in the first roll would sit. Having said that, it seems pretty consistent in all positions except the ouside edges where it is a bit warmer.

I actually finished my testing yesterday with a few 1 hour setpoint tests. As I mentioned before, the unit has about a 5F offset (which grows to about 6F at the highest settings).

I wanted to confirm that temperature regulation was good at various temperatures (not just that it is powerful enough to hit 80 C) - or more specifically that temperature regulation is consistent across the whole range (e.g. it's linear but with an offset). This is the case.

1. I set it to the lowest temperature supported, 95 F or 35 C. This isn't perhaps useful for filament drying, but if it doesn't have any flaws at the low end it could build confidence.

Very good regulation, it stays about 5 F too high.

Then I transitioned to the temperature we'd probably use for PLA, but in this case I went ahead and compensated for the 5 degree offset. So I set it to 144 F expecting to hit 149 F (or 65 C). You can see it doesn't overshoot:

And finally we can see a full hour at this temperature (again, set to 144 F expecting to regulate at 149 F (65 C)):

And here we see, again, good temperature regulation. There is a bit of upward drift - by this point it looks like the offset might be a full 6 F (which matches the offset at max temp).

I would trust this unit (I misspelled it CORSI, it's COSORI apparently) across the whole range as long as you measure the offset of your unit first. If there's a way to trim it out, that would be nice but since it's linear it's not really critical to me.

edit: Man, the image settings on this forum are really bizzare. It looks like it hard resizes the maximum dimension to be 500px and ignores constraints.

RE: Drying Times and Temps in Dehydrator

So we're looking at a +3.03% to +5.25% Variance here with nothing going below. Honestly, more than acceptable for me. Makes one wonder how bad the "knob" style dehydrators can be off by. Super happy I made my purchase on a whim. haha

RE: Drying Times and Temps in Dehydrator

3-5% could be a big deal in the filament print quality.  

RE: Drying Times and Temps in Dehydrator

@bunny-science

Thank you so much for doing the work. 

I have a question-do you cool the filament before bagging it, or put it into the bags right out of the oven?

RE: Drying Times and Temps in Dehydrator

FWIW, I notice CNC kitchen got his best results from heating up the filament in a dehydrator and then putting the filament into a vacuum chamber:

RE: Drying Times and Temps in Dehydrator

@dimprov

If Swiss_Cheese could still be here, he would be Proud of you.

RE: Drying Times and Temps in Dehydrator

Posted by: @snuffleupagus

@dimprov

 

If Swiss_Cheese could still be here, he would be Proud of you.

What happened to him?

RE: Drying Times and Temps in Dehydrator

 

Posted by: @bunny-science

My temperatures and processing times

TPU 129F (54C) x 10 to 24 hours -- low temperature means extended drying time. Still stringy even when dry.

Hi Bunny-Science,

in very short, your TPU is "still stringy even when dry" for a specific reason: it's not dry.

54C is way too low of a temperature to dry it.

TPU absorbs moisture almost as fast as Nylon and is almost as vicious.
Saturated TPU will NOT be dry even after 24 hours at 70C.

Lightly moist TPU might benefit from staying at 54C for 24 hours IF THE AIR IS VERY DRY IN YOUR LOCATION.
Most places, though, are not bone dry as the air from desert locations and if your relative humidity hovers around 55% at 20C you WON'T BE ABLE TO DRY TPU EFFECTIVELY EVEN AT 70C in your oven.

The only effective way I found, is to place TPU in the aerated oven at 100C for at least three hours. Of course, you need to reinforce the spool with wood plates. The filament won't warp at 100C, but the spool will certainly warp otherwise.
I now use cardboard spools, these hold 100C indefinitely without warping.