Problems with heating the Bed (JGA A5, M 1.8. C)

Samuel Pinches

Quote:

medicusdkfz 

6 hours ago 

Hello community,

whenever I want to heaten up the Hotbed over 90°C it stops heating at about 89°C, the temperature freezes in the Display and it cools the heatbed down. I thought that the max. temperature is at 105? With this behaviour I can't print ABS...
Maybe I get some help in this Forum?

Thank you very much,
Pierre

Samuel Pinches

Hi Pierre,

Yes, you should be able to get it up to over 100C. 
Does your printer have 4 cables or 6 cables for the bed?
Has this problem always existed?

Cheers,
Sam

medicusdkfz

Hi, Sam,

it's really nice of you to want to help me. My heating bed has 4 cables. The heating bed heats up to a maximum of 90 degrees and then the display stops and the heating bed switches itself off. In addition, the system freezes and I have to trigger a reset (on/off-button).

Do I have to make any settings in the firmware? I've only known the problem since I wanted to make high-temperature prints. PLA can be printed without any problems. It seems, that there ist a thermal protection...

Thank you so much,

Pierre

Samuel Pinches

Hi Pierre, the problem is the 4-wire connector. The connector is unable to carry the high current, and so the connector starts to overheat. You need to either, replace the bed heater and the bed heater cable with a 6-pin bed, or, to solder the 4-bed wires directly to the 4-pin bed.

Samuel Pinches

Also, does your A5 have a drag chain for the bed cables? How long have you had your A5 for?

Cheers,
Sam

medicusdkfz

Hi Sam,

I didn‘t install a drag chain for the cables. I think that I solder thicker cables directly to the bed... Thank you for the valueable hint... I've been using my JGA for a month now. Is there a possibility in the configuration.h to use a higher temperature at the nozzle as 250 °C?

I made several and useful updates:
- TMC2130
- custom Marlin
- mesh bed leveling
- IR auto leveling (in a dark room it works fantastic)
- 2 seperate Mosfets (for secure reasons) -> I’ve had the problems already before... 
- new fan duct
...

Your support is fantastic and thank you for your generous help.

Cheers, Pierre

medicusdkfz

I soldered the cables directly to the heat bed and I will install and test it this evening. 

Samuel Pinches

Hi Pierre, looks great, nice work! Lets hope it improves the bed heating now.

The reason I ask about the drag chain, is the early A5 came with a drag chain from the factory. It was not well engineered, and it actually caused the cables to fail early. So it is good if your printer did not come with that.

The problem with higher nozzle temperatures, is that the material inside the heatbreak is PTFE. The heatbreak is designed to keep the hot end away from the rest of the x axis - the cold end. This means the heatbreak is exposed at one end to the full 250C of the nozzle. Above 250C, PTFE starts to break down more rapidly. Yes, there are brand names that claim that theirs is resistant at higher temperatures. But they all bogus. They all still warn about having pet birds in a room with a printer about 250C, because the fumes from PTFE are toxic, and extremely toxic to birds in particular.

If you want to print about 250C, it is difficult. You need to use an all-metal-heatbreak. This is hard to find, as the inside needs to be precisely machined, in order to have a very smooth surface. I have not yet found a compatible part for the A5 hotend dimensions unfortunately. Some people have replaced the whole hot end with a standard E3D v6 system, on the wiki under the A5 modifications section, I have linked to a collection of thingiverse parts - hopefully if you explore those, you will get some inspirations.