PLA Heat Creep - SOLVED

Help with printing with specific plastic filaments.
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CoParaTech
Posts: 202
Joined: Thu Dec 17, 2015 6:09 pm

Re: PLA Heat Creep - SOLVED

Post by CoParaTech » Fri Apr 29, 2016 6:40 pm

I just got 100% reinforcement that the fan replacement works. I had printed out Billy D.'s fan shroud and put a cheap 25mm fan on it and it did indeed cure my clogs and filament stripping. Then a few days ago I got a clog again. I thought, now what? After close inspection I found that the fan was not turning as fast as it did when I installed it. In fact it was rotating at less than half speed, hence the clog. I spent a few extra bucks and ordered a 25mm Orion fan from Mouser Electronics and boom, problem solved again, but for good this time. Moral of the story, do yourself a favor and get a decent fan or you will be replacing it again. I wonder why this fan upgrade isn't stock on all Lulzbot printers.

KelVarnson
Posts: 65
Joined: Thu Dec 03, 2015 10:03 pm

Re: PLA Heat Creep - SOLVED

Post by KelVarnson » Fri Apr 29, 2016 8:12 pm

CoParaTech wrote:...the fan was not turning as fast as it did when I installed it. In fact it was rotating at less than half speed, hence the clog...
Many of the fans I have seen are only rated to 70C. In fact, the Pelonis blower that comes stock is only rated to 70C, as is the 20mm Sunon fan I replaced it with. I'm sure it is a complex equation, e.g., if the fan is running all of the time, what is it really seeing? But, printing ABS with a 240C extruder over a 110C table has got to be pushing it! I wouldn't be surprised if some of these fans are wavering.

killacycle
Posts: 38
Joined: Mon Apr 04, 2016 2:14 pm

Re: PLA Heat Creep - SOLVED

Post by killacycle » Fri Apr 29, 2016 11:08 pm

All muffin fans are not created equal.
What you look for is "ball bearing(s)" or Sunon's "vapo-bearing" instead of "sleeve" bearings or no specifications at all.
Muffin fans without any bearing specifications are typically sleeve bearings, which are the least rugged, shortest lifespan, but are also the least expensive.

So far, the inexpensive sleeve bearing fans I bought on Ebay are working fine. If they give me grief, I'll replace them with more expensive ball bearing fans. Ball bearing fans will cost ~$15 each instead of ~$3 I paid, however.

I should note that it is important to leave the power on (and the little fan running) for a while after your print has finished. Let the nozzle and heater block temperature cool off to ~30 Celsius or so, then switch off the power. If you don't do this, the parts that are normally cooled by the fan, aren't, and the fan, duct, filament left the extruder, etc. can get quite toasty from the latent heat of the heater block spreading out to the adjacent parts. This might be why your fan decided not to work so well after a bit of use. Might be something caught in the fan, like a bit of hair, or some other crud. Might be simply "infant mortality."

Bill D.

KelVarnson
Posts: 65
Joined: Thu Dec 03, 2015 10:03 pm

Re: PLA Heat Creep - SOLVED

Post by KelVarnson » Sat Apr 30, 2016 9:03 am

Very good points Bill, especially about letting things cool before turning the machine off. I generally do that, but I hadn't given it a lot of thought. Fortunately for me those little Sunon fans are hanging in there, because there aren't a lot of other choices when you get down to the 20mm size.

Unfortunately they are a wee bit on the loud side, but after all the drama I went through with PLA, it's knida like music to my ears.

chazerr
Posts: 8
Joined: Sun Sep 20, 2015 3:29 pm

Re: PLA Heat Creep - SOLVED

Post by chazerr » Wed May 25, 2016 9:25 am

Unfortunately the fin cooler only slightly extended the layers before fail. I'm using this fan (http://www.newegg.com/Product/Product.a ... 6835119098) on a seperate power supply at 0.04 amp 12v.


Did you guys update your PID when after installing the new cooler?

KelVarnson
Posts: 65
Joined: Thu Dec 03, 2015 10:03 pm

Re: PLA Heat Creep - SOLVED

Post by KelVarnson » Wed May 25, 2016 10:46 am

I did not. Do you think it'necessary, and if so, why?

chazerr
Posts: 8
Joined: Sun Sep 20, 2015 3:29 pm

Re: PLA Heat Creep - SOLVED

Post by chazerr » Wed May 25, 2016 10:54 am

from my understanding, the PID calculates the amount of energy to apply to the hotend, so it could be the direct cause of heat creep (the fan being can only cool so much when heat is simultaneously being applied).

I'm really at a loss on how to fix this...

So far I have calibrated E-steps (about 30+ added to get 100mm extruded accurately)
Calibrated bed, and also countlessly played with first layer height

Currently: Trying different low temperatures (on stock PID /Firmware)

Have not done in a while: Disassembled the toolhead >> hex tool re-assembly

ttabbal
Posts: 298
Joined: Wed Nov 11, 2015 4:20 pm

Re: PLA Heat Creep - SOLVED

Post by ttabbal » Wed May 25, 2016 1:20 pm

I used a 25mm Sunon fan from Digikey. It works great, though is a fair bit louder than the stock one. I don't mind it though.

259-1569-ND is the part number, $13 shipped to me.

PIDs are a complex subject... The basic idea is that they calculate times on/off to compensate for overshoot and maintain a stable temperature. You shouldn't need to mess with them unless you directly change the thermal conditions of the hotend or bed. As we are working on the heat-break, I don't expect it would affect the thermal performance of the actual hotend enough to matter to the PID controller. If you watch a graph of the temperature, it should look about the same as stock, it does on my mini anyway. If you see larger fluctuations, you might want to recalibrate.

With fans that move a lot more air, should that air hit the nozzle or heater block, it could cause an issue. If your hotend fails to maintain temp, that could certainly contribute to the filament stripping.

chazerr
Posts: 8
Joined: Sun Sep 20, 2015 3:29 pm

Re: PLA Heat Creep - SOLVED

Post by chazerr » Wed May 25, 2016 1:39 pm

3.0 CFM fan.. nice! I will give this a shot.

Until that arrives, I'm going to level my frame and disassembly tool head... :?:

killacycle
Posts: 38
Joined: Mon Apr 04, 2016 2:14 pm

Re: PLA Heat Creep - SOLVED

Post by killacycle » Wed May 25, 2016 5:33 pm

Look at hotend temperature on the LCD display. If it is getting to temperature OK, maintaining temperature OK, and not overshooting by more than a couple of degrees, then the PID control needn't be adjusted. If you notice a problem, then there is an "autotune" feature built in that will adjust the three PID parameters, Proportional, Integral, and Differential, to close to what they need to be. Here is a link to a guide on the Marlin software PID autotune:
http://reprap.org/wiki/PID_Tuning

I haven't felt the need to change anything about any of the three (four?) PID temperature control loops in my firmware. Seems to be doing exactly what it is supposed to be doing. I tend to follow the old adage: "If it ain't broke, don't fix it."

Bill D.

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