Problems with printer hot bed not being consistent

Had this printer for about two years. Did some long prints after not using it for about 6 months. The prints came out perfect on maybe 10) 6 hour prints. Now the printer stops about 30% into an hour print.
I changed out the ramps board 1.4. Changed out the power convertor both with new equipment. I flashed the board with the old ardruno software I got from Sintron when I bought the printer. I used two flies not sure which one I used the first time. So I flashed it with Marlin_v1 for the lcd 2004 board. It printed for about an hour like it should of. Then it quit about 30% into the print again.
I then flashed it with Marlin_v1 for lcd 12864. I have the 2004 lcd screen reader.
One thing I did notice on the old ramps that I replaced on the board after I examined it, was the lead contact to the hot bed was corroded off. The solder joint crystallized and caked some filament on the end. I brushed it down and re soldered it back on.
I am thinking that doing those 6 hour prints may have been too much for this little printer.
Now I am back to square one where it stops in the middle of a print about 30% in. Even with fast print settings. Any ideas where else to look? I am thinking it could be software related now.
My hot bed is set too 70 degrees on the first two layers. Then it drops to 60.
My hot end is set too 210 on the first two layers then sets back to 200. Using hatchbox pla. It is good filament.
The picture is the same model I have from Sintron.
All of the replaced parts are from the same company.
Thoughts?

Edited 1 time(s). Last edit at 05/06/2017 08:48PM by cadcygnus.

Did some test.
Printed it from the laptop with the usb cable. It was 50/50 some prints would work some prints would not let the bed heat up.
Did a full reboot.
Then printed a test file cube from the sd card. Again the results where hit and miss. Now I am thinking it might be the sd card reader. So I am using a new sd card on this next test.
I did learn that if I printed for a half hour instead of 3 it would print the part. I also learned that doing multiple prints was prone to causing it to stop in mid print.
This printer is 2 years old now with a new ramps, new power supply, and one new stepper motor. Any ideas at all?
I plan to post the g code as I monitor this next test.
Now it wont heat up past 50 degrees when I printed from the sd card. Now to print from the laptop and copy and paste the g code here. I am using simplfy 3d for my slicer.
Need some ideas here people.

Could it be the thermistor on the hot bed?
But how could it be the thermistor if the room temperature is being read correctly?

This is the g code from the laptop usb connector.

The next g code got up too 69 then backed down from there. I need to hit 70 for the next step of the extruder to kick in

What could be causing it too work and then not work? I did resolder the connections to the hot bed.
Should I try a print without the hot bed?.

Edited 7 time(s). Last edit at 05/06/2017 08:50PM by cadcygnus.

It may be a bad PID setting. Did you save your old PID values anywhere before flashing new firmware? Wrong PID values may cause heating taking ages or not reaching the target at all, and a mix of both - especially when combined with some fresh air from an open window. Maybe you should save or write dowm your PID values and try auto tuning.

It has been printing flawlessly for two years. I did contact Sintron and the great customer service said they had the same issues with the LCD screen card reader not compiling the g code correctly after much use. Sintron did give me a new Marlin updated software with new PID settings, I think the damage is done, and I may likely have to replace the LCD screeen or the hot bed. I have been searching you tube videos to show how to use a multi meter with the right settings for checking the resistance. I am a design engineering and not very familiar with electronics like using the right settings for a meter.
I can get by with videos or a good step through tutorial. You would not happen to know a good vid or walk through to using a meter to check the hot bed would you?
Since I did flash it with the new marlin and the hot bed only heats to 37 degrees then steps down from there by the usb cable, I am guessing it must be the reader screen. I did not change out the hot bed, I can't find one the same thickness as this one I received from Sintron. This bed is 4mm thick and the replacement I bought was only 2mm, bent like a pretzel before I able to use it.
Let me ask you this, Can a hot bed say with a bad contact or line wire cause a drop in the hot bed during heating? The screen does not show any errors, just when I shut it down it shows bed heating still and still counts down to room temperature.
I guess I could edit my process settings in simply3d and not use the hot bed at all and test it out that way. I just hate to use hair spray and elmers contact glue sticks.
Thoughts
and thank you for replying.

Update.
I disabled the hot bed and it is printing so far like it should. I am thinking it is more a filament wire in the bed itself now. Can a shorted out wire cause it to turn down from a certain temperature and not heat up to full power?

Edited 1 time(s). Last edit at 05/07/2017 12:48PM by cadcygnus.

Yes, a broken wire to the heated bed can cause similar problems. At the beginning the bed may be ok, starting to heat. During the print, while the bed is shaking, the wire may loose contact, and the bed will stop heating. With a multimeter you can check your bed - disconnect the wires, and check the R with your multimeter. A 12V or 24V bed would have a few Ohms, a mains power bed will have more - probably something about 50-200. From the picture your bed looks like 200x200 mm^2 - out of the head:

R = U^2 / P

So with a 12V 75W bed it should be around 12*12/75 = app. 2 Ohms. The exact values vary somewhat, by production and by temperature. On your multimeter, the correct range for measuring low resistor values like this, the lowest scale will be the right one. Check for something like R, Res, Ohm or the Greek Omega sign.

Yep its the hot bed. I am printing fine with no hot bed and just using the elmers xtra tacky glue with blue tape.
So on the meter it is a cen tech electronic. I put the dial on the resistance symbol (upside down u). I have a zero setting, and the highest is 2000k. Measure the leads on the bed (not attached to the ramps)
I should get ..02 ohm reading?
I am sorry but I never learned how to use a multi meter in my field of work. Here is a picture of the meter. Yes the bed is 200mm x 200mm x 4 mm thick. I am having a hard time finding another board this thick. This one is 4mm and the newer boards are between 2mm and 3mm.

This littel thing will do perfect for this. Just turn it to the left 2 more, so it points at 200 Ohm (this is the Greek Omega, the upside "U"). When you connect the test wires directly it should read 0 or a very small number. If you connect your bed to them the number sould be somewhere in the range 1.2 to 3.something, probably. If you have less than 1.0 or more than 5, the wire or the bed is probably broken. The "1 ." on your photo says "infinity", so nothing connected at all. If this is what you see when your bed is connected, there's something wrong.

Took it off the power board, measured the contacts with no power, set the meter to 200 ohms. Read zero resistance. No symbol for infinity just 0.00.
Does that mean the bed is bad?

I can print on a cold bed without any delays or stopping points. So I know its not the ramps board. It still could be the lcd 2004 reader or the hot bed or both.
I am thinking.
Thoughts?

Edited 1 time(s). Last edit at 05/08/2017 02:11PM by cadcygnus.

0.00 is indeed a very low value. I almost can't believe this is true. Normally the measuring lines itself will have some 0.02 or 0.1 Ohm resistance. Do you have any chance to check if your multimeter may be broken? You got a spare 12V light bulb, maybe for the car or some halogen room light? Or check your extruder heating? A 40W 12V heating cartridge should have about 3-4 Ohm.

Sorry I am back again.

I just installed the new PCB MK2 bed I bought from amazon.
Before I put it in I measured the bed and was getting 3.8 ohms of resistance. I know its not the board. The thermistor is reading 60 degrees so its not the thermistor.
I have been able to print,(pretty good too) with just the plate glass with blue painters tape and rafting the object. So I know it is not the ramps board when it comes to everything except the hot bed.
Some questions?

Can it be the yellow fuse? Can it blow and still heat up to 35 degrees then back down?
Can it be the LCD reader? I know lately it has been messing up my g code when reading from the sd card so I have been only printing with the laptop and my slicer program.
The Sintron machine I prusia prints good on a cold bed. I just want to get this working again.
Can it be something on the ramps board 1.4 I have not covered?
The symptoms are it heats to 35 or 40 degrees then it backs down and counts down from there. The hot end and the tip the feed all work fine.

bump

3.8 Ohm is a reasonable value for the bed, this seems to be good. These nasty polyfuses do behave very strange sometimes, but it doesn't sound like a polyfuse problem. Is your bed loosing the voltage and stops heating, or is your RAMPS shutting down the heater for any reason?
In your test print logfiles from May 7 I can see the bed temp is set to 70 deg, then reaches 69.something, and then drops again for no reason I can see. On the RAMPS board, there is a LED to show if the heatbed is on or off. Do you use a PID regulation for the bed, or just bang bang? Does the LED start to flicker or go off when the temperature drops? Can you put your multimeter in parallel to the bed when heating up? DCV 20 will be the right position to check the voltage of 12V. If the LED is on, your multimeter should display something close to 12V. If you use PID, and the LED is flickering, your multimeter can't keep up, so no worries.

[www.dropbox.com]

[drive.google.com]

[drive.google.com]

Here is my marlin software. I uploaded. The bed heats up with it hooked to the power supply. I only did this for a test. So its not the bed.
Here is what I am thinking it might be. When I took off the old board and replaced it with the new ramps, I noticed on the back of one of the yellow fuses a bad solder joint broke loose. I thought this may be the problem. I did re-solder it after cleaning it up it had some crusty stuff on it. It is possible it could be happening again to this new board. I have not taken a look yet. I would have to completely dismantle and reassemble the boards to know. What can cause one of the solder joints to break loose? Could it have been those long prints? This is the only time it has happened.

Edited 2 time(s). Last edit at 05/16/2017 08:52AM by cadcygnus.

Hello Bill.

it’s the heated bed resistance problem.

it needs to be around 1.4 ohm . then you can heat it up to 100c.

and now it’s 3.8 ohm . that’s why you can’t heat it up .

did you try to solder 2+3 together first ? ( if there’s this option )
if you don’t do this , then the resistance would be high .
after you do this , the resistance should be around 1.9 ohm i suppose.
but still a little bit high .


regards

james.


This is the response I got from Sintron.

Would this fix my problem?

[reprapchampion.com]

Installing a mosfet to a separate power supply and running the lead from the ramps into this for monitoring?

Quote
Inhumierer
3.8 Ohm is a reasonable value for the bed, this seems to be good. These nasty polyfuses do behave very strange sometimes, but it doesn't sound like a polyfuse problem. Is your bed loosing the voltage and stops heating, or is your RAMPS shutting down the heater for any reason?
In your test print logfiles from May 7 I can see the bed temp is set to 70 deg, then reaches 69.something, and then drops again for no reason I can see. On the RAMPS board, there is a LED to show if the heatbed is on or off. Do you use a PID regulation for the bed, or just bang bang? Does the LED start to flicker or go off when the temperature drops? Can you put your multimeter in parallel to the bed when heating up? DCV 20 will be the right position to check the voltage of 12V. If the LED is on, your multimeter should display something close to 12V. If you use PID, and the LED is flickering, your multimeter can't keep up, so no worries.

LED light goes out at 27 degrees no flicker. I don't understand bang bang or pid unless this means software settings in the firm ware.
When you say hook up parallel do you mean, un connect the positive line and use the multimeter as a wire to finish up the connection?
There is no flicker from the LED light when I try to heat up.

FIXED IT.
Soldered an XT 60 to the back of the connector on the board. Those cheap clone ramp boards have faulty connections. Now it heats up and prints like it is suppose too.
So in case anyone else runs into this problem check your check connections and if they are weak. Then soldered the leads connector like a deans, tamiya or XT 60.
Good thing I build these drones and have a ton of parts to choose from.

Good you solved it. Anyway, if the LED went out when the bed had 27 degrees, and the bed was still heating up, you probably watched the wrong LED.