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Heat bed slowing at upper limits  

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joefiorini
(@joefiorini)
Eminent Member
Heat bed slowing at upper limits

I've had my i3 kit for a few weeks now. The first couple of weeks I printed solely with PLA. Now I'm trying ABS and I'm running into an issue. The heatbed is set to 100° as it should be for ABS. In a few minutes it gets up to around 93-95°, but then it stops going up, or it slows way down. It sat at 94° for nearly half an hour yesterday without ever changing.

I'm wondering if ambient temperature has something to do with it. Its in the basement of my house and it's currently 41° F outside.

[EDIT] If I start a print and then turn the heatbed down to be just below the current actual temperature of the heatbed it does print, but nothing sticks. Not sure if that's a temp issue or a separate one.

Has anyone else seen the heatbed act like this?

Napsal : 01/03/2016 5:34 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Heat bed slowing at upper limits

Hi Joe

Yeah, you probably need to insulate the heated bed and possibly put an enclosure around the printer.

You can put a cork tile (3mm - 1/8") under the heater.

There are a couple of other possibilities. I had similar happen a couple of weeks back. The heater cable had started to fray just outside the RAMBo box due to flexing. Replaced cable and all OK. Easy way to test is to put a multimeter across the RAMBo connector and measure resistance. Should be around 1.2 to 1.5 Ohms.

Also, check the voltage across the heater when it's turned on; that should be above 11.2 Volts. If necessary, you can tweak the 12V supply - there's an adjuster under the cover on the right hand side. Turn this upwards by half a volt (the RAMBo is OK on a 24 volt supply, so you won't do any harm).

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 01/03/2016 5:43 pm
Josef Průša
(@josef-prusa)
Member Admin
Re: Heat bed slowing at upper limits

Hi Joe,

What is the ambient temperature? Did you get the testing protocol with your printer?

Founder and owner / Majitel a zakladatel
Napsal : 02/03/2016 8:39 am
joefiorini
(@joefiorini)
Eminent Member
Topic starter answered:
Re: Heat bed slowing at upper limits

Josef,

I'd say the room with my printer is usually in the 50 - 55° F (10 - 13° C) range. I am not sure if I got a testing protocol or not, how would I know? Is it something in one of the manuals?

Napsal : 11/03/2016 6:34 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Heat bed slowing at upper limits

Hi Joe

The "testing protocol" is the piece of paper showing that all components underwent proper testing prior to shipping. It is included with all printers and kits shipped by PR.

Did you follow up on any of the points I suggested (above)?

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Napsal : 11/03/2016 6:40 pm
Archania
(@archania)
Trusted Member
Re: Heat bed slowing at upper limits

I am encountering the same thing.
Printed PLA since I got it and now I need to do ABS and the heat slowly comes up. Room temp is comfortable. It is like 68F in the house.
I am going to try the cork tile, thanks Peter, and see if this helps.

Napsal : 24/03/2016 1:40 am
joefiorini
(@joefiorini)
Eminent Member
Topic starter answered:
Re: Heat bed slowing at upper limits

I still haven't tried the voltage check, but I think I can solve my issue by building an enclosure for my printer. I came to this conclusion after I had some serious layer separation issues on a number prints. From what I could find online it sounds like this was due to low ambient temperatures, and I realized that not only was my printer in a drafty basement room, but I also had an open window in the same room. It sounds like I need to build an enclosure to keep the heat in, and that should solve both of these problems. For the time being if I need to do a large print and it's cold out I'll turn on a space heater in the room to get the temperature up to around 75° F before starting to print. It still takes awhile to get the heatbed to 100° C (typically I end up printing around 90° and haven't had any noticeable issues from it yet), but I'm hoping to build an enclosure at some in the near future to fix it once and for all.

Napsal : 18/04/2016 4:29 pm
richard.l
(@richard-l)
Member Moderator
Re: Heat bed slowing at upper limits

After building a 12"x12"x16" printer with a heated bed I highly recommend moving the heatbed connections off the rambo and putting a relay in. Connect the heatbed to the relay and the relay to the Rambo and power supply.

I can heat my 12" bed up to 85 in 4 minutes where the 8" on my Prusa takes 12 minutes to reach the same temperature. I will be putting a relay on it soon. This should also help eliminate any possibility of the power connector getting fried.

Napsal : 18/04/2016 5:16 pm
Josef Průša
(@josef-prusa)
Member Admin
Re: Heat bed slowing at upper limits

After building a 12"x12"x16" printer with a heated bed I highly recommend moving the heatbed connections off the rambo and putting a relay in. Connect the heatbed to the relay and the relay to the Rambo and power supply.

I can heat my 12" bed up to 85 in 4 minutes where the 8" on my Prusa takes 12 minutes to reach the same temperature. I will be putting a relay on it soon. This should also help eliminate any possibility of the power connector getting fried.

Hi Richard,
Did you get the test protocol with the printer?
We now check every bed if it reaches the temp in decent time. The state of the heatbeds is miserable, we tried multiple suppliers including european. And 20% goes straight to trash. We will haves some changes about this in upcoming weeks and for some time we are moving the manufacturing here to czech republic.

Anyways, 12x12 bed must take some serious power, at-least 2x the normal one. Be careful your PSU can handle it!

You can definitely use relays, but use solid state ones. Regular ones will die fairly quick.

Founder and owner / Majitel a zakladatel
Napsal : 18/04/2016 5:53 pm
Josef Průša
(@josef-prusa)
Member Admin
Re: Heat bed slowing at upper limits

I still haven't tried the voltage check, but I think I can solve my issue by building an enclosure for my printer. I came to this conclusion after I had some serious layer separation issues on a number prints. From what I could find online it sounds like this was due to low ambient temperatures, and I realized that not only was my printer in a drafty basement room, but I also had an open window in the same room. It sounds like I need to build an enclosure to keep the heat in, and that should solve both of these problems. For the time being if I need to do a large print and it's cold out I'll turn on a space heater in the room to get the temperature up to around 75° F before starting to print. It still takes awhile to get the heatbed to 100° C (typically I end up printing around 90° and haven't had any noticeable issues from it yet), but I'm hoping to build an enclosure at some in the near future to fix it once and for all.

Yes, you are right. For ABS, even if the printer would reach the heatbed temperature, it would never print successfully. The print would crack very easily.
You want ambient air around 22°C or more and not moving for ABS. We will add note about ambient temperatures into the manual.

Founder and owner / Majitel a zakladatel
Napsal : 18/04/2016 6:06 pm
richard.l
(@richard-l)
Member Moderator
Re: Heat bed slowing at upper limits

Hi Richard,
Did you get the test protocol with the printer?
We now check every bed if it reaches the temp in decent time. The state of the heatbeds is miserable, we tried multiple suppliers including european. And 20% goes straight to trash. We will haves some changes about this in upcoming weeks and for some time we are moving the manufacturing here to czech republic.

Anyways, 12x12 bed must take some serious power, at-least 2x the normal one. Be careful your PSU can handle it!

You can definitely use relays, but use solid state ones. Regular ones will die fairly quick.[/quote]

I got my Prusa in Sept/Oct before you started implementing the test protocol. I haven't printed much that requires an 85 degree bed but have started.

Yeah, the 12x12 when clicking on will use 24A. I forgot to mention that it is on its own 30A power supply.

Napsal : 19/04/2016 4:26 am
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