Tina2 Malfunction – Bed Levelling [SOLVED]

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Tina2 Malfunction – Bed Levelling [SOLVED]

Post by CrazyIvan »

Starting off a print today, I aborted straight away because the first layer seemed to be printing in mid air. Everything has been great up 'til now, so that's weird...

Trying to diagnose the problem, I went for the Z axis offset calibration, which performs a bed levelling first. The bed levelling process lowers the nozzle in the left front corner until the proximity sensor triggers, then lifts and moves to the right front corner, then the right rear corner. Except that's not what happened.

Instead of lifting, traversing, lowering until sensor triggers, it lifted, traversed, then lifted again! Why would it do that? The amount of lift must have been limited by software, because (of course) the sensor didn't trigger, but it behaved as if the sensor did trigger. Then the same again in the right rear corner. As a result, the nozzle is miles off the bed when it settles for user adjustment of offset.

I did not try adjusting the offset, because clearly there is a malfunction. For some reason the Z stepper is being spun the wrong way, but not when doing the initial slew!

I've tried power cycling, I've tried the restore defaults operation, I've even tried pressing the (apparently undocumented) reset button at bottom left of the display panel. And the same with the SD card removed in case something on there is corrupting it.

Now, I might have a suspicion what has caused this, although I can't explain why (and I might be completely wrong, but I don't accept coincidences until all other possibilities are eliminated).

I've done quite a few prints, all fine up until now. This print is very similar to one I did yesterday, except that because it has an irregular base surface I decided to raise it off the bed so that there is 5mm support structure (minimum) under it. This I did in Cura 5.3.0 with "Entina Tina2" set as the target printer and "Generic PLA" as the material.

Has this offset somehow corrupted the Tina2's code? I don't see why – the preview in Cura looked correct, and it would still be sending a series of layers in the gcode starting at the adhesion layer. Nonetheless, something has happened and (pending further research for a cure) I'm currently stuffed.

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Re: Tina2 Malfunction

Post by CrazyIvan »

Ignoring the "Cura gcode corrupted the firmware somehow" hypothesis (flimsy at best), all I can come up with is a NVR failure which has specifically corrupted the bed levelling code. I wonder whether I can re-flash the firmware...

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Re: Tina2 Malfunction

Post by Antipodean »

CrazyIvan wrote: Mon Jul 31, 2023 2:18 pm Ignoring the "Cura gcode corrupted the firmware somehow" hypothesis (flimsy at best), all I can come up with is a NVR failure which has specifically corrupted the bed levelling code. I wonder whether I can re-flash the firmware...
One of the links you sent me had a firmware download available.
Would possibly be worth a try.
Hmm, the Tina2S firmware is available, but not the basic ... :shock:

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Re: Tina2 Malfunction

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Antipodean wrote: Mon Jul 31, 2023 2:41 pm Would possibly be worth a try.
Only as a last resort, I'm still putting feelers out for advice.
Antipodean wrote: Mon Jul 31, 2023 2:41 pm Hmm, the Tina2S firmware is available, but not the basic ... :shock:
I don't think it will matter which brand of firmware I use, so far as I can see they only differ in the splash screen. That's presuming I can find a suitable firmware at all of course.

If I can't find a way to fix this, I'll treat it as an opportunity to fit a third-party controller. That might then lead to using the Tina2 parts to build a bigger printer...

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Re: Tina2 Malfunction

Post by Antipodean »

CrazyIvan wrote: Mon Jul 31, 2023 4:02 pm I don't think it will matter which brand of firmware I use, so far as I can see they only differ in the splash screen. That's presuming I can find a suitable firmware at all of course.

If I can't find a way to fix this, I'll treat it as an opportunity to fit a third-party controller. That might then lead to using the Tina2 parts to build a bigger printer...
One of the links has the GPL source code, which also appears to contain non-GPL link modules. There also seemed to be a set of instructions on how to do the compiling.

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Re: Tina2 Malfunction

Post by CrazyIvan »

For reference, here is a link to the Weedo version of the Tina2 firmware: http://www.weedo3dprinter.com/doku.php/firmware/tina2

...except the download links don't seem to work!

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Re: Tina2 Malfunction

Post by CrazyIvan »

I've found the problem.

I was playing with the "move axis" controls (Prepare menu), and reproducing the motions of the "level bed" operation, which worked fine. However, in the process, I noticed the light on the proximity sensor was not coming on when it should, except when the head was on the left, as per the first stage of bed levelling.

I have waved a screwdriver under it, and released the sensor from its mounting, and this seems to be a broken wire in the sensor cable which only loses contact when the wire bends as the head moves to the right.

I presume the head raises instead of lowers (during bed levelling) because the firmware has somehow detected the anomaly (or maybe just got confused by an unexpected reading). My guess is that it's the power wire which is broken, so the sensor looks like it's sensing when it isn't (when the wire loses contact).

Anyway, I am confident about this because I cut a wire tie to reduce the stress on the sensor cable, and bed levelling now works correctly (and waving a screwdriver under the sensor lights the LED wherever the head is).

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Re: Tina2 Malfunction

Post by Antipodean »

CrazyIvan wrote: Tue Aug 01, 2023 7:17 am I've found the problem.

I was playing with the "move axis" controls (Prepare menu), and reproducing the motions of the "level bed" operation, which worked fine. However, in the process, I noticed the light on the proximity sensor was not coming on when it should, except when the head was on the left, as per the first stage of bed levelling.

I have waved a screwdriver under it, and released the sensor from its mounting, and this seems to be a broken wire in the sensor cable which only loses contact when the wire bends as the head moves to the right.

I presume the head raises instead of lowers (during bed levelling) because the firmware has somehow detected the anomaly (or maybe just got confused by an unexpected reading). My guess is that it's the power wire which is broken, so the sensor looks like it's sensing when it isn't (when the wire loses contact).

Anyway, I am confident about this because I cut a wire tie to reduce the stress on the sensor cable, and bed levelling now works correctly (and waving a screwdriver under the sensor lights the LED wherever the head is).
Ah, sigh of relief then. My unit has arrived, but haven't fired it up yet, might have a look to see if the cable to the level sensor needs some strain relief in the same manner as yours before i try and do active things with it.

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Re: Tina2 Malfunction

Post by CrazyIvan »

Antipodean wrote: Tue Aug 01, 2023 2:34 pm Ah, sigh of relief then.
Huge sigh. I was really rattled. Not just an intermittent fault, but a systematic intermittent fault – if there's anything to drive an engineer around the bend, that's it!

However, the silver lining is that we have an excellent data point on the Tina2 hardware/firmware (and I presume is common to printers in general, I imagine many of them run from forks of a few base code sets rather than re-inventing the wheel): if the head retracts immediately, we now know it thinks it's detected the bed even if the sensor LED hasn't lit up.

I guess the real experts would have known that, I'm having to start again because they don't seem to be around.
Antipodean wrote: Tue Aug 01, 2023 2:34 pm might have a look to see if the cable to the level sensor needs some strain relief in the same manner as yours before i try and do active things with it.
I'm not sure how much I might have been to blame for the fault. The sensor itself went faulty originally, and I replaced it, and judging from the "cure" for the wire break (I cut a cable tie) the break is where the tie was (I will try to confirm). I would not have said the cable (within the sheath, with the cable tie around the sheath – not the cable itself) was under any undue strain or flexure.

Image
(Click through to full size image)

I shall disassemble this whole area, partly to investigate an upgrade to the cable management, but mainly out of curiosity. For example: how does the fan blow onto the extrusion? There must be a duct.

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Re: Tina2 Malfunction – Bed Levelling [SOLVED]

Post by CrazyIvan »

Hmm. Tests indicate the break is about an inch nearer the sensor than where the cable tie was. I'm not sure there's enough lead left – I think I need another new sensor!

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