Rostock Max V2 Hot end won't hold temp - Jams.

[Doug68]

Hi All,

I needs some pointers on trouble shooting my issues I'm running into...
So the printer was running fine and I'd been doing big prints like this:

[img]https://c3.staticflickr.com/8/7457/26884134890_df8098d0fe_k.jpg[/img]DSC_0274 by Doug Clark, on Flickr

But then I went and moved country, so I'm now working on getting the thing up and running again after it being shipped, also in that process the machine is now being fed 230v instead of 100v (yes I moved the switch on the PS).

To the issue, which is persistent hot end jams happening an hour or 2 into the print.
I've think this is happening as the hot end is not holding temp, I've read the Repetier logs the temps but I've yet to work out where they are or how to see what its logging, any advice on that?

But what I've worked out so far...
1. The reported temp and the actual hot end temp are very different, set at 210c the measured temp was 180c to get 210c I've had to set a requested temp of 245c.
2. I can see in use the reported temp drops slowly (the target temp stays the same), my belief is that after an hour or two, its got to the point it jams due to not being hot enough. I've yet to catch it in the act though, by the time I get there the extruder motor has given up and the temp has climbed back to where it should be.

On the last couple of attempts I've run blue tape so the bad heater has been off, so there should be no shortage of power.
I've run the "M303 S200" routine and reset the values, clean out the hot end etc.

So where to go what to try next any advice?

[IMBoring25]

It is possible to have a shortage of power, especially if you have the old ATX power supply, but if it's capable of maintaining the temperature you actually want when you use a higher setpoint, your first stop will be reconfiguring the PID settings.

[Turpinator]

Check the resistance of the resistors on the hotend. Should be ~4.5 ohms. If its 9ish, one of the resistors is bad.
I had a similar issue with maintaining temp (mainly when printing fast or long) and thats what it turned out to be.

[Doug68]

My machine has the ATX type power supply in it. Are these known to die?

[Doug68]

Check the resistance of the resistors on the hotend. Should be ~4.5 ohms. If its 9ish, one of the resistors is bad.
I had a similar issue with maintaining temp (mainly when printing fast or long) and thats what it turned out to be.

Thanks, I'll check that.

[Xenocrates]

My machine has the ATX type power supply in it. Are these known to die?

The original ones were known to die semi-frequently, although it was a bit of a bathtub curve type thing. I recently serviced a V1 which had the original power supply (And as it was a V1, was several years old), which had only just failed. I would recomend that if you haven't got anything connected to secondary rails (5 or 3.3V), you buy the new industrial power supply kit from SeemeCNC.

However, as a caveat, the ATX supply should actually perform better on 230V (Almost every one has higher efficiency running 230Vac as a source than 120V). So it may well be a bad PID value due to different air currents/temperatures, an intermittent open on the heating circuit, or a dying resistor.

[geneb]

..and if it's in your budget, get the replacement arm & carriage kits.

g.

[Turpinator]

I may have been wrong on the resistance value. Either way, if its <5, youre good. If its >5, its the resistors.

You can disconnect the heater circuit from the board and check its resistance. The original V2 hot end uses two 6.8-ohm resistors in parallel, so the circuit should have a resistance somewhere near 3.4 ohms. If it's significantly different from this, something may be wrong with the resistors.

http://forum.seemecnc.com/viewtopic.php ... 933#p96803

I don't know. Mine (purchased oct 2015) had two 9ish ohm resistors. I think. At least, that's what one of them shows now (while the other shows a few mega ohms).
At two 9 ohm, its ~30w heating, at two 6.8, its ~40w. And if you've only got one of those resistors, its half as much. I actually had to disconnect my peek fan otherwise it couldn't maintain temps.

[Doug68]

Update...

The hot end resistors measure 4.6 ohm, there's 2 in parallel. (I think these values are ok?)
The thermistor is reading 77.4k ohm at 30c

I think maybe the root cause of the issue was me being ham fisted when tightening up the hot to stop in wobbling around in the plate.
Probably I've dislodged the thermistor along the way.

Next to re-seat it all and bail it up in more kapton tape for another go...

[Turpinator]

Resistance seems fine. Maybe you just need to redo the pid autotune for the hotend?

As for

I've think this is happening as the hot end is not holding temp, I've read the Repetier logs the temps but I've yet to work out where they are or how to see what its logging, any advice on that?

You mean the repetier firmware? *shrugs*
I used repetier host (controller software) and it logs it in that. Not sure if matter controller does, but I haven't seen it. If using repetier host, its a tab at the top of the display window, I think.