Extruder not heating  

Re: Extruder not heating

Hi Ruud

OK, one thing at a time now; process of elimination.

Can you please take out the heater connection on the RAMBo and measure the resistance of the heater cartridge at the connector. Just hold the probes onto the screws at the top of the connector.

The resistance should be around 5 to 6 Ohms.

Please post back with the results of this test, and I will be checking out the next step.

Peter

Re: Extruder not heating

Ruud

I think this may not be good news.

Firstly, check that the connector is firmly seated into the socket and re-check the heater. You can also check to see if the LED - LED02 in the corner of the board, next to the extruder heater socket - is lighting when the heater is on.

If it's still not working, we need to check to see if there is any output on the extruder heater. You need to set your multimeter to the DC voltage range turn on the heater and check the output. Please be very careful not to short out the probes when measuring the voltage. If all is OK, the reading should be 12 volts.

However, I have a nasty feeling that you will not get a reading there...

I have checked out the fuses on the RAMBo. There are 2 x 5 Amp fuses and 1 x 15 Amp fuse.

The 5 Amp fuse by itself is for the motors; I think it was the one next to the 15 Amp fuse which blew on your board?

The 15 Amp fuse is for the heated bed, whilst the 5 Amp fuse next to that is for the logic circuitry, fans and (most importantly) the extruder heater.

As your logic and fans are working, then the fuse is also now OK. However assuming that the heater itself (as per my previous post) is OK, then this does point to a problem in the RAMBo output circuitry.

Unfortunately, these fuses are not particularly quick to blow; it seems that when you plugged the hot bed into the extruder heater output, both the fuse and the output circuitry were taken out at the same time.

The simple remedy is to replace the RAMBo board, but this in not cheap. A partial solution would be to re-program the firmware, setting the extruder heater on the hot bed output. You would of course, not be able to use the hot bed.

I think you may want to contact Prusa support to see if they have any other ideas.

Peter

Re: Extruder not heating

Ruud

One more thought on this issue - I have had a look at the circuit diagrams of the RAMBo and it would appear that the output stages for both heaters are virtually identical. Therefore there appears to be no reason why the extruder output is blown.

So you need to check out my suggestions and we will see where we are then.

Peter

Re: Extruder not heating

Please recheck the fuses on the RAMBo, I never seen fully blown RAMBo from switching the heatbed and hotend outputs. Can you please make a detailed pic of the connections?

Re: Extruder not heating

Hi guys,

Thank you for helping me. It feels good to have some more experienced people to think with me. I didn't have much time last week, but now I was able to check some things.

Please note that this extruder problem existed before I switched the heatbed and extruder wires, which caused me to completely reconnect all the wires, which in turn caused the fuse to blow.

What I checked:
* checked all the fuses for continuity. They work perfectly.
* I updated the firmware successfully.
* I checked the DC voltage on the extruder output with my multi-meter. It's 11.98 V, so I guess this can't be the problem.
* I switched the MSPBE connectors from the heatbed and extruder cables, to see if the problem could be in these connectors. It doesn't make a difference.

My guess is that the extruder itself is dead, but I don't know if there's an easy way to check this.

I sincerely hope that I did something wrong with the wires though, since that'd be the easiest to solve. Here are some pictures:

The extruder (disconnected from the frame, for testing purposes):

The endstops:

The motors:

The thermistors and the fans:

The extruder and heatbed output:

The power input:

Thanks again for the help!

Re: Extruder not heating

Hi Ruud

OK, so it's good that you have a voltage at the heater output; it's therefore unlikely to be a board problem (although it might still be that).

So next step is it unplug the heater cartridge from the board, set the multimeter to resistance (lowest range if not an automatic selection) and put the meter probes onto the screws in the connector.

The heater wires should be screwed into the connector whilst doing this. Your meter should display a reading of 5 to 6 Ohms.

If the meter display does not register a reading, then unscrew the connector and take out the wires, then put the probes directly onto the end of the wires.

If this does not register a reading, then it is likely that either the heater is broken or (more likely) the crimped connections near the heater cartridge are compromised.

Please test the resistance and let us know what the outcome is.

Thanks

Peter

Re: Extruder not heating

Hi Peter,

Like this?

Ruud

Re: Extruder not heating

Yes, exactly.

OK no reading, so there is an open circuit.

The next step is to move along the cable to the crimped ferrules. Underneath the red outer sheath neat to the cartridge.

Unfortunately, you may have to be somewhat destructive here. Do you have any Kapton tape to replace the red insulation?

It may be possible to push the meter probes into the red insulation, but that won't let us see if the connections are tight.

You need to strip back the red insulation to get to the ferrules and test again there; you will need to ensure that each ferrule is properly crimping the wire for the heater cartridge and to the connector. Due to the heat, these wires cannot be soldered (it could melt), and if one of the wires is pulled, it may come loose from the ferrule.

Peter

P.S. apologies for delayed reply; trying to get family dinner prepared.

Re: Extruder not heating

Hi Peter,

Sorry again for the late reply. It's those busy weeks before christmas that prevent me from doing fun stuff. Before I'm going to be destructive on my extruder, I'm going to contact the support, since the heater has been this way since it arrived. I'll keep you up to date!

Ruud

Re: Extruder not heating

Hi Ruud

OK, probably the best thing to do.

I don't think it's a problem with the heater itself, just the wiring. But I may be very wrong!

Peter