err: MINTEMP BED

[TMeeks]

After printing very successfully for days an error popped up.

Err: MINTEMP BED

PRINTER HALTED
Please Reset

Until the error appears the D9 LED is on. Then it starts to blink and finally the D9 LED goes off and the error appears.
Another sign of the error is that the LCD reports -14 as the bed temperature.

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MinTemp Error.JPG (188.54 KiB) Viewed 8450 times

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Any help will be appreciated. Fortunately, I have another A10 that is waiting to be built during our teacher training, so we're not dead in the water. But, we need to know everything we can find to keep these printers up and running like we know they can perform when healthy.

Tom

UPDATE #1: After restarting several times. The after leaving it on for a bit, the -14 went away and it started showing the expected bed temperature. My first guess is that this either indicates a wiring issue or a bad thermistor.

UPDATE #2: With the LCD reporting Bed temperature as expected, a print was started. D9 glowed solidly as the bed reached 60C of 60C. The, as the nozzle started heating D9 blinked furiously until the nozzle temperature reached 210C of 260C. At the moment the bed started to move D9 went dark and the MINTEMP error popped up. From this it makes it all the more likely that the problem is at the bed end of the circuit and possible a cold solder joint.

[TMeeks]

I think I have narrowed down one path to follow in debugging the issue I'm having.

I am going out to buy some polyimide tape and clips to replace the ones I had tried previously, which I think are shorting through the existing tape.

I had tried some slightly smaller clips than those supplied with the printer and they were (1) a bit smaller and (2) uncoated. I will replace the existing tape holding the heater to the bed with new polyimide tape and try clips that are the same size and type as those that came with the printer.

To come to this conclusion, I had removed the bed and checked the solder joints and continuity through the wiring. I also tested the thermistor. I did not have a multimeter; but, did have a voltage/continuity meter. Continuity was fine.

But, I did notice some chafing of the tape from the clips. I'll know in an hour or so when I put everything back together again.

Sometimes we are our own worst enemies when it comes to 3D printers.

But, this also points out the wisdom of putting together a "first aid" kit for our new printers that would include extra thermistors (bed & hot-end), polyimide tape and other accessories to help us get back up and running quickly should we need to do some quick repair. The beauty of the architecture of the A10 and A20 series is that every possible replacement part is available and access to parts is relatively easy. No matter what the final answer turns out to be the cause of this issue, it is clear that nothing we run into is permanent nor catastrophic in the long term. And, that makes these printers a very good investment from a price/performance point of view. And, that is our primary criteria for these printers in our system.

A lot of people may feel that a very low cost printer is going to be more trouble than the most expensive printers. In addition to needing a number of low cost printers, we are also considering a MarkForged Onyx Pro and possible Fusion3 F410 and Fuse1 to meet our educational goals for the at-risk students we serve. Based on all of our experience with every price level of 3D printers, I do not expect them to be any more free of issues than the A10s and A20s. ALL 3D printers have issues.

[TMeeks]

What I did:

Working on the theory that the bed clips may be shorting the heater board, I replaced the Polyimide tape with new tape and doubled the layers on the underside where the clips might touch. I also went back to the original clips.

Outcome:

Sadly, while it initially seemed to work, the error showed up again. At least this rules out the clips shorting something as a cause.

At this point, it appear that it could be one of three things:

• Bed Heater
  GT2560 V3.0 board
  Cable harness

Unfortunately, this happened in the middle of the Chinese New Year, so it may be difficult to get replacement parts quickly.

Fortunately, however, we have another unboxed A10. So we will raid that one for parts. We'll first swap out the bed heater and if that does not work we will swap out the GT2560 V3.0 and, finally, the harness so that we can try to pin down the culprit.

The other good news is that we have 3 more A10 printers on the way; but, probably not until after the Chinese New Year. This will allow us to see how things go over several printers.

[_kaktus_]

Hello.

Very good deduction.

Do one test.
Disconnect the thermistor and check the temperature indication on the display.
Perhaps, as you wrote in your deliberations, the culprit is a poor quality connection, in a measuring electrical circuit.

[TMeeks]

Hi _Kaktus_,

I have really appreciated reading your posts not only to myself; but, everyone. You are very valuable around here.

Once I found that I could still function by disconnecting the heated bed altogether I decided against raiding the other printer. And, can simply wait for the end of the Chinese New Year and order some extra parts.

In the meantime, I want to try to work on getting the smoothest print out of the printer. I have what appears to be a slight Z-Axis wobble that I believe was NOT there earlier. I think I failed to tighten some of the rollers when I adjusted them. I am actually happy when these things come up because it helps me to help our teachers later when I am able to identify and solve issues.

Our A20M is suppose to arrive tomorrow. And, we have the A10 that has yet to be built. This is a good start for our teachers when they arrive for training next week. Even the fact that my heated bed is not working will allow them to see how to keep printing should the same thing happen to them.

As soon as the Geeetech staff is back from holiday, I will order the backup parts and follow your advice. Thanks!

[soularb]

Hi how are you? I have exactly the same problem, what did you do to fix it

[William]

Hi how are you? I have exactly the same problem, what did you do to fix it

Hi, When you turn on the printer and the temperature is as shown above,

You can check if your hot bed line is fully connected to the motherboard.

The resistance of the hot bed is then measured and the hot bed may need to be replaced.

I hope this can help you.