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Prints stopping mid-print when printing from LCD via USB stick

SystemSystem Posts: 13Administrator
This discussion was created from comments split from: MKS LCD: Flashing, Firmware Modifications, and Logo/Icon customisation.
Post edited by Samuel Pinches on


  • FlatwoodsDadFlatwoodsDad Posts: 3Member
    So I got and A5 this week.  Printer was stopping mid print.  Upgraded the firmware as per this forum, just mainboard Marlin not the MKS TFT28's.  Still fails mid print. I noticed when this happens the display's E1 and Bed temp readings start screwing up and the display still thinks it's printing.  I caught it real fast last time turned off power to reset and it came back with resume print menu.  But when resumed it began printing a layer or 2 up on the Z axis,  This leads me to think the LCD which is acting as it's own computer is losing serial com to main board?  Has anyone tried changing (lowering bauds) in Marlin and in config file on LCD?  Thought I'd throw it out there before going any farther.  I'm not so worried about flashing Marlin but the LCD requires opening the printers case.  Anyone tried this? 
    Pardon the long post but this is also how I kinda work theories out in my head.
  • Samuel PinchesSamuel Pinches Posts: 2,060Administrator
    edited January 20
    Hi @FlatwoodsDad, sorry to hear that your having random failed prints, that's one of the more frustrating things that can happen...
    Some people have had similar problems with failing prints, and changing the baud rate helped (115k) reduce error rates, but it didn't work for all people, just some. If the problem is fluctuating temperature readings, then I'm not confident that will help.

    You can verify if it is communications issues between motherboard and LCD by connecting via pronterface and enabling marlin's debug mode. Then you can monitor any errors, while still printing from the USB stick.

    You can flash the LCD without opening the case if your fingers contort enough... I found it easiest to unplug the USB cable plugged into the LCD board first, and then try to wrangle the SD card in there (with the firmware copied on) afterwards.

    I made a blog post about examining this issue here:

    One of the main advantages to upgrading the firmware, is when over/under temperature errors occur (and cause the mainboard to reset for safety reasons) the LCD will now display those errors too, and stop trying to send data to the mainboard regardless....
    Post edited by Samuel Pinches on
  • FlatwoodsDadFlatwoodsDad Posts: 3Member
    Yeah the LCD doesn't show any errors when this happens even with the Marlin update.  Your suggestion about pronterface was going to be my next step.  I ran a print last night with it tethered but it completed the print OK.  Kinda making me suspect the com error even more.  Was going to keep printing this way with larger files tonight.  I only have 1 laptop and I hate tying it up all day.  I'm not familiar with the main board but saw no postings about it having this problem.  Found ton's about the LCD failing.  I'm not discouraged yet.  Still seems to me this printer is pretty well made.  But that said I want to solve the issue.  Thanks for the reply I'll also check my finger contorting abilities a little before opening the housing :)  Oh yeah I was going to ask.  Do you get any real tech support from the company via Email?  Don't know how many printers they sell but they must be hearing and trying things to address this stuff.
  • Samuel PinchesSamuel Pinches Posts: 2,060Administrator
    edited January 20
    Most people seem to have a good experience from what I've seen. Just be patient as they are not always instant with their replies.

    Regarding the LCD problems -  yes, I think they are probably aware of the issues but I am not certain. It certainly looks like it - on the A5S they ditched the MKS motherboard (which was ok) and the MKS LCD (which was trash), and replaced it with a bare LCD, and a custom 32bit motherboard. This brings pros and cons... but at least reliability is fully in their control, so they are not dependent on a third party.

    @FlatwoodsDad - I'm just going to separate out these comments into a separate thread.
    Post edited by Samuel Pinches on
  • Enrique RiriEnrique Riri Posts: 37🌟 Super Member 🌟
    My thoughts regarding the suddenly random stop printing:
    I noticed that with 1 of my A5. I tried to source exactly where the problem comes from and nothing really accurate from my side. 

    After some investigation, seems to me, the issue comes from the reading stream data between USB stick and LCD board. I suspected first the stick, replace it and same results. 

    What is strange, when I tried to stop and launch again the printing process: message "no file found". Like the USB port was suddenly not responding and active. Unplug and plug again the stick and all seems to be OK. But for small time.

    I replace the LCD and flash with new firmware: Again same random issues stopping printing in the middle. Suspected the Motherboard, replace it and same results.
    Replace the ribbon cable between mother board and LCD = same

    So at this stage, the only last suspect: USB cable could be the issue ?

    Very, very difficult to source the internal black cable USB from LCD to chassis plug where we connect the stick. I didn't source it anywhere.

    Here, I add external SDcard slot reader (from MKS)and connected it to LCD mother board and for moment seems to work correctly. I didn't spend too much time here for moment.

    But again, in // I have working replacing stepper drivers, customization, etc... so too much things at same time on same machine to allow me to source exactly the issue. Can be also temp issue somewhere , as failure happens only after xx time running?

    I'll need to take some time to advance more on this issue.

    Feel free to contribute here if you found 
  • FlatwoodsDadFlatwoodsDad Posts: 3Member
    For me this was caused by a few issues.  Garbage in the ribbon cable and a marlin setting.  I updated firmware on mainboard and front display.  Changed the baud rate on both to 115200.  On display config make sure last line to show error messages is enabled.  Got a lot less garbage but still had some.  I broke the ribbon cable out of the printer harness folded it over itself wrapped it in 2 layers of foil then enclosed it in a layer of duct tape.  It came out looking good and no more garbage.  I think this fixed the issue between the display and motherboard but sometimes the printer would stall "Freeze" and the display would give a min temp err.  I changed line 87 in Configuration_adv.h from 20 to 40.  It's been printing darn near 24/7 for a week now.  This is just to give you some ideas of what to look for.  might be one, might be all.  Good Luck.
    Thanked by 1Samuel Pinches
  • Samuel PinchesSamuel Pinches Posts: 2,060Administrator
    Stepper motors produce a lot of electrical noise - I had problems with stepper motor wires causing noise in the endstop lines on one of my other printers. I think @FlatwoodsDad 's suggestion to use foil is a good idea. You can buy copper or aluminium shielding foil specifically for this purpose, but good ol' Al foil and duct tape is a nice kitchen hack I admire.

    I tried the 115200 baud rate on another A5 that was having problems, and it did not solve it, but perhaps it reduced the frequency of random stopping, so this also supports the theory that this is an electrical noise issue.

    The communication between the LCD and main motherboard is all verified using checksums - what was strange was occasionally the data gcode command was so badly corrupted that the checksum was actually correct, causing the printer to do weird movements!
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