I am confused. I dried some off-brand PETG in my new AMS-HT recently and found it ruined; filament sticking to itself and breaking repeatedly. My guess is that it was overheated by the AMS-HT. Yes, it was probably of poor quality and should have been dried to a reduced temperature which I have done for subsequent spools. But, it made me wonder about the quality of temperature control in the AMS-HT.
So, I made up this temperature monitor device which uses a digital temperature sensor (18B20) which I have found to be accurate +/- .5c. FWIW, I tested in boiling water at 100m above sea level here. So, reasonably comfortable that it is close to showing the correct temperature. The device writes to a data file which I show in the photo. Iāve placed the sensor through the TPU port with a fitting and located it near the bottom of the spool well.
It looks to me that my AMS-HT is underheating by 5c at 65c and underheating by 10c at 85c. The good news is that the heating is consistent. Yes, this finding is contrary to my off-brand PETG problem but I can manage around that. But, the underheating is my question. Maybe my unit or a product design feature?
I have documented this very early on and Iām very disappointed at AMS HT as well.
The problem is that they measure the air temp at the hot air output exhaust instead of the cold air intake. AMS HT is a cycled dryer, it has the hot air end and the cold air end. Most cycled dryers would either measure temperature in chamber or at cold air intake end. But AMS HT is doing that right after the air has been heated up, which IMO is very stupid.
The solution for common materials would be to dry longer or manually set temps higher by 5-10C. Essentially itās a 70C dryer in winter.
Thank you hotellonely. Iām measuring right at the bottom of the spool well. Is that where the hot air exits? My measurements show 75c achieved with a 85c setting. My PETG test was closer with, just 5c colder than the setting. Have your heard a response from BL? Iām thinking to submit a ticket to determine if it is a sensor problem, a software issue or a heating capacity issue. Yes, disappointing if it is not fixable.
Nice data! I havenāt tested my HT, though Iāve suspected as much based on empirical evidence (my hand). But my AMS 2 āProā under-heats, maybe as by as much as 10Ā°C when set to 65Ā°. My temperature measurements arenāt anywhere as precise, but when 3 other thermometers, all different, consistently read within a degree of each other but way lower than what the AMS reports, one has to wonder.
When I still used them for drying, I put a thick rag/towel over the top of the units when drying to help trap the heat. Making sure not to cover the rear vent, of course. Definitely helps.
Bit the bullet and bought an external dryer. Though I sill put a towel over that one tooā¦ lol.
Iād be curious to know what BBL support would have to say about your findings.
Yup, I built my own filament drier a couple years ago (before all of this was available) with a solid state heater block from a cheap space heater, PC fan housing, a few temp/humidity sensors and an esp32. It has a thin plywood inner, insulation and another thin ply outer skin. The heater is below a deck with a 100mm metal chimney to a mushroom shaped diffuser which directs the hot air over the top then around the spools. Holes with baffles allow return air down below the deck for heating and recirculation. I have a 90c mechanical overtemp switch on the heater/fan assembly for safety and heat/humidity sensors everywhere. The esp32 microcontroller uses one core to control the heater to a max temp of 85c when heating is called. The other core cycles that heating cycle to reach/maintain chimney top temp to set point. I have a rotary encoder and OLED display to cycle through filament set temps and it all is available on an HTML page with regular timestamped data of everything. It has been working fine for a few years now :-). So, making it all work is not a mystery. They should have enough heating capacity; will see what they say.
Holy filament drying Nirvana! Iām sorry to break it to you, but thereās no way youāll be satisfied with the HT. Or maybe anything else on the market for < 1K moneysā¦ lol.
I had to open up my HT to replace a stuck value (āDIY warranty replacementā), and thatās what made me realize that baking these plastic things at high temperatures is just a bad idea for multiple reasons. The insides reeked of overbaked plastic and electronics, for one thing, after just a dozen or so dried spools. That canāt be healthy for the primary function of the thing, which is to precisely feed filament on demand.
Yes hotellonely heat was/is a worry. I took the cheap space heater apart to yield the solid state heating device which is basically a few plates sandwiched between a few fin sections, Then I reproduced an adaptor in PC which clips to that unit and holds a fan maybe 30mm away; allowing the fan to push cooler air through the fins. The assembly then fixes to the metal 100mm chimney. I added a 90c electrical cutoff device fixed to the heater block to stop run-away temperatures. I was very focused on maximum working temperatures in this but still crossed my fingers in early testing. So, two checks, my heater logic maximum is 85c and the temperature cutoff is 90c while the PC housing is said to be good to 110c. The heater logic has code to minimize temperature over-shoot.
The hot air comes out at the front vent I believe. It would not surprise me if measuring at the bottom of the Ams ht is lower as there is really no insulation.
since reel can be rotated while drying, the localized spot on the reel near this vent is dried at the higher temp
Iāve seen some solutions where the packaging that the Ams ht came in is used as insulation and I think there are some covers on makerworld.
I have replaced failed vents on two separate Ams ht units and I agree long term this might not be a robust unit at its highest heating temp.
user_3535829363 FWIW, I moved the sensor around inside the AMS-HT and found the temperature to be highest in the middle of the bottom of the unit. I guess that Iām left with the questions of āspecification accuracyā and āfit for purposeā. That said, I have another functional dryer so Iām good and still see the AMS-HT good for filaments that can be dried at lower temperatures and a stylish single spool AMS. So, life goes on .
I measured the hottest spot right at the air outlet at the back (I was wrong about which was the intake and outlet). it was still low about 10C, reading 75C when set to 85C
That is right next to one of the vents which is open so I donāt think it will ever reach 85C inside where the spool is with those vents open and without any insulation.
The air coming out of the vent would have to be much hotter.
Unfortunately my thermometer was having some issues and it stopped working before I could explore it anymore.
Yup. I am seeing the same thing. Set to 85c, no place it higher than 75. Which would not be a bad thing if the display showed 75. But it displays 85-86c Reminds me of the speedometer in my VW, reading 100k/hr when my gps was showing 95. Had to get into the computer and change the tire size setting.
Or maybe anything else on the market for < 1K moneysā¦ lol.
Theyāre not designed to sustain that temperature.
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