Extruder not heating up?

[Julio Ibarra]

I was in the middle of a print this morning when the printer stopped.  I canceled the print and went to start again.  After uploading the gcode, the printer seemed to start calibrating then stopped and showed "Idle."  Thinking maybe this was a jam (hadn't had one yet) I clicked unload filament.  The window popped up showing that the extruder was heating.  However, it stopped about two thirds of the way and claimed it was done heating.  

I decided this was a jam and not wanting to open the printer I ran out and bought a 65w soldering iron to perform the clearing described in another post.  I was able to remove the filament and went to again load.  The process started but again the "heating" stopped at slightly past half (see attached).  It then claimed the filament was loaded without prompting the load procedure involving extruding a bit and pressing the front panel.  

I felt around the extruder and there didn't seem to be any heat coming from the hothead.  I touched the tip itself and it was completely cool.  I don't know what might be happening here but it seems that the printer is not heating.  Anybody have any idea how to fix this?

[ajf]

First thing I'd do is email NewMatter and describe the problem, hopefully they'll send you a new hotend.  Last I heard it's going to take 2-3 weeks until they have hotends in stock to ship replacements.

If it'e an intermittent issue, then it's likely a short in the wiring. Check to make sure the connector on the hotend is firmly plugged in and that the wires going into the connector aren't damaged. The wires are crimped on to the pins in the connector housing and sometimes a bad crimp will damage the wire.  

[Julio Ibarra]

Thank aj I just sent them an email.  At least their support seems be pretty timely.  I'll check the wires and see what's up.  Man, I wish I would have done a bit more research before backing the MOD-t.  Great idea, but I probably would have been better off building my own machine.  I was actually printing the first parts for another printer when this issue came up.  Maybe it knew it was going to be replaced!

On Friday, January 1, 2016 at 3:29:58 PM UTC-7, ajf wrote:

First thing I'd is email NewMatter and describe the problem, hopefully they'll send you a new hotend.  Last I heard it's going to take 2-3 weeks until they have hotends in stock to ship replacements.

[AlanZ]

Maybe a coincidence, but I could not print today because the hot end would not heat at all.
I am awaiting a new hot end for another reason, but this one has never failed to heat up before.

Strange.

[ajf]

Alan & Julio,

Which firmware version are you using?

[Julio Ibarra]

Alan

That's kind of weird.  It may just be coincidence but at least we're in this thing together!

AJ

I just checked, I'm on 0.7.0.  I haven't had any issues with the firmware at all until today.  Recently I started using Slic3r to print multiples of parts together.  I had never done that until yesterday.  Could that have caused an issue?

[ajf]

I have been running 0.5.3 because 0.6.0 and 0.7.0 weren't behaving well for me, for unrelated reasons.

No, putting multiple parts together shouldn't effect anything. Slic3r nor the robot (MOD-t) care what you are printing, they just output and execute respectively. It is possible to turn off the hotend with gcode mid-print, but Slic3r (or any other slicer) will never generate that code, it would have to be inserted manually.

Most likely, there's an intermittent short in the wiring, perhaps at the thermistor which is a rather delicate component. I don't have access to the source code for the MOD-t, but a basic feature of every 3D printer firmware I have seen is to disable power to the hotend if there is a failure to get a reading from the thermistor. It would be insane to do otherwise, as it would result in continuous heating of the hotend which would result in temperatures sufficient to melt aluminum...

[AlanZ]

I have been usin 0.7.0 since it was released.

[Kraig McLaughlin]

Same thing has just happened to me.  Printing great, from the web store/slicer.  My last print stopped after about 20 min and I could tell the head was not moving and was stuck in the building blob of pla.  Immediately unplugged and manually raised the head.
After that, the hot end will not heat up.  Everything else functions normal, but no heat.  Unload filament goes through the motions, but hangs at the heating.  Hot end is always cold.
I have had this happen 2 other times, and New Matter sent me a new hotend.  When I changed it, it worked again.

Don't know if there is something inside the replaceable hotend that is frying/shorting?

Hopefully we can figure this out.  I am using firmware 0.7.0 and have been printing fine until now.

[ajf]

Hi Kraig,

Do you still have the old/defective hotend? If so, would you be willing to send it to me? I'm waiting on a replacement myself, but it sounds like it's going to take a few more weeks and I'd like to put together a guide on rebuilding the hotend.

[Kraig McLaughlin]

Hey ajf,
I do have the original hotend that stopped working.  I was hoping someone could figure out the problem.  New Matter didn't really say much as to what the problem might be, they just set up a replacement order.  I can totally send the defective one to you to tinker with.
I'm in Los Angeles.  Let me know.

[ajf]

Cool. I'm in the Bay Area. Will email you my address,I'll paypal you for shipping, and will also send you a couple of laser cut acrylic replacement beds, which should improve print quality.

regards,

aj

[Kraig McLaughlin]

Perfect.  I should be able to get that out end of the week.

[Julio Ibarra]

Man am I glad we've got AJ here to keep us sane! Thanks a lot for dedicating some time to helping some fellow MOD-t users!

[Ran Sagy]

Hear, Hear. Color me impressed already :)

[AlanZ]

My hot end is out of commission, and it may be 3 weeks before the redesigned hot ends are available.
I am looking forward to getting the MOD-t up and running again.

The MOD-t has kickstarted my interest in 3D printing, and I intend to start printing prosthetic hands for the Enable project.
I explained to my wife that our MOD-t is our "first" printer.
I am taking the downtime for the MOD-t as an opportunity to build a new printer, a SeeMeCNC Rostock MAX v2 delta style printer... Should be quite the experience building this machine.

[ajf]

Awesome!

I've bought some components from SeeMeCNC, specifically their PCB heatbeds and the EZstruder. I like the beds a lot (aside from the silkscreen;-), and the EZstruder was a step up from printed extruders, but could use a stronger spring or a tensioning mechanism.

I also bought an assembled Onyx delta a couple of years ago, unfortunately I had to return it due to a weird problem neither I nor SeeMeCNC support could resolve. I've made some suggestions on alternate printers here, might be of interest.

[Christopher Leger]

Alan, I've just completed printing first Enable hand with the MOD-t.  I am currently waiting on the "extra parts" to assemble.

I can tell you that I'd be climbing the walls if I had to wait 3 weeks to print now that I've got the bug.

Good luck!

[Derek Schulte]

The hot end contains a thermal fuse.  Initial production hot ends have a tendency to prematurely function (go open circuit), and NM has only recently started shipping replacements that fix the issue.  These can be distinguished by looking under the black rubber insulator and noticing that aluminum is removed in the vicinity of the thermal fuse, but frankly, unless you've received a replacement very recently, you don't have the revised design.  NM will generally replace hot ends of the original design that have prematurely functioned.

If you want to do the repair yourself or rebuild the hot end, this is generally possible, but the very high temperature thread lock and thermistor potting compound make things difficult.  Bypassing the fuse is dangerous:  cartridge heaters can exceed 800 degrees C, above the temperatures required to melt aluminum, burn organic materials, start fires, make noxious fumes, etc.  Replacement fuses can be found on eBay and Digikey.  The part in the MOD-t is marked as an SEFUSE SF240R, and Cantherm makes a similar part that is distributed by Digikey.  Don't solder the connections, use crimps as they don't melt.  You will need some high temperature fiberglass sleeving to insulate things, and be sure to check that the heater and thermistor circuits are electrically isolated from each other and from the metal parts of the hot end or the MOD-t controller can be fried.  Always unplug the MOD-t power when disconnecting and connecting the hot end.  PTFE-insulated wire is probably smart due to it's higher temperature rating than PVC insulation.  Also be aware of the glass bead thermistor potted in the grey adhesive.  It is possible to crack/compromise the thermistor by clamping across the adhesive.

Suitable PTFE tubing, potting adhesive, and threadlock are available from McMaster-Carr.  

When the fuse functions, it can either be a strictly one-time event, or it can oscillate open and closed as the temperature goes up and down, eventually going solidly open.  This can make it look like the hot end becomes hot, but not hot enough to print and/or exhibits strange behavior until it stays open.

The threads in the hot end are M5x0.8, which is VERY close to a #10-32 thread for cleanup.

The original aluminum hot end block can be easily modified into the revised design if you have access to a metalworking mill.  It is possible to do this on original-design hot ends.

On Saturday, January 2, 2016 at 2:41:56 PM UTC-8, ajf wrote:

[ajf]

Derek, 

Thanks for all the info! Could you provide the spec on the thermistor? I'm going to break that for sure. I'm assuming it's an EPOCS 100k at the moment. 

regards,

aj

[Derek Schulte]

It is generally the thermal fuse in the hot end that is functioning prematurely.  It escaped the early design validation testing due to a late design change in the hot end.  NM is typically replacing the hot ends when they blow with the same parts until new parts recently became available.

NOTE: because it is a thermal fuse, exposing the hot end to temperatures above standard operating temperatures (limited to 220C by firmware) are likely to cause the fuse to function (open).  E.g. don't use a blow torch on it.

Operating without the fuse is dangerous --- in the event of a mosfet fault or FW failure you don't get flames, but a LOT of noxious and toxic smoke.

On Saturday, January 2, 2016 at 2:14:43 PM UTC-8, Kraig McLaughlin wrote:

[Julio Ibarra]

So the issue has reared its ugly head once again.  This was on the replacement hotend that NewMatter sent me.  Apparently, I either received another of the old hotends or the "new redesigned" hotends have the same issue.  In any case, I contacted NewMatter support, and they will be sending me a replacement hotend.  Unfortunate timing since my friend's birthday is tomorrow, and I wanted to print something nice for him. Oh well!

[JP]

I've got to call nm, my 2nd printer (after Rma) had its hot end stop heating. Cold to the touch.

Aj, did you find out if there's any user serviceable parts in the hot end we can replace ourselves?

[ajf]

JP,

As Derek noted above it's probably the thermal fuse which has functioned and it's not settable.  You can replace it pretty easily and the part is very inexpensive.  Just have to be careful not to damage the wires, etc... You will also crimp ferrules and high temp fiberglass sleeving, unless you can manage to salvage the existing. Take note of the other tips and precautions Derek provided.

Now, it is possible to simply eliminate the fuse altogether and, in fact most hotends used in DIY/kit printers don't have one. But, as Derek mentioned, when a mosfet fails it sometimes/often shorts, meaning that it will continuously power the heater cartridge... This is bad.

regards,

aj

[JP]

howd you peel off the rubber coating on the hot end?  And it's just the one fuse?  Is there a 2nd in that bottom chamber?

can I purchase replacement sleeving just in case as well?

it looks like it's just soldered in-line in that wire, seems like a simple fix to get a spare hot end, and well hell, mines already shot...

[JP]

found the sleeving on amazon as well, sleeving measured 6mm on mine and that was losely with the calipers...think something like this would work or do I want smaller?

http://www.amazon.com/Fiberglass-Insulating-Sleeving-Sleeve-Pipe/dp/B007PENCSQ/ref=sr_1_4?s=industrial&ie=UTF8&qid=1457489258&sr=1-4&keywords=fiberglass+sleeve

[ajf]

The rubber insulator can be peeled back pretty easily, just go slow so you don't start a tear. You actually shouldn't need to remove it to change the fuse.  The bottom chamber is the ceramic heating cartridge, and it's cemented in place, don't try to remove it... 

You can get replacement sleeving, but I don't think the one you linked on AMZN is sufficient @ 120ºC... I can't find any on AMZN with higher temp, but this from McMaster is the stuff you want. (Teflon (PTFE) tubing will work too.) I actually have a bunch of the high temp fiberglass stuff salvaged from old halogen light fixtures and have never had to buy new.  You might try contacting local appliance repair shops to see if you can get scraps for cheap/free.

And, it's not soldered in, it's crimped with copper/brass ferrules. Solder may melt.

[JP]

ok I see the crimps..are those just regular brass hose crimps or specific ones for electronics?  My search on amazon returns a ton of pneumatic hose parts..

Good call on the appliance repair place, ill see what they've got

[ajf]

I think they're brass and probably custom cut for the application. Think these would be suitable, but they come in packs of 100.  I generally use whatever I have on hand that will work for a particular application, sometimes the crimp part of a MOLEX/whatever crimp pin, other times a piece of brass tube cut to length. You can get brass tubes at any hobby shop (K&S usually, and the adorable little cutter) or maybe even Walmart or something like that...

[JP]

well i picked up a bag of these, I have some in the workshop but they were far too big, looks like the wire size is about 1mm (+/- a bit) and that equates to about 18AWG based on what I found 

here: http://www.engineeringtoolbox.com/awg-wire-gauge-d_731.html

might e a bit longer than needed, but it's worth a shot..i do have some small brass tube laying around as well I'll take a look at that...

the connectors and the new thermal fuses should be here tomorrow...

[ajf]

The leads on the fuse are 18AWG, I think the wire is 22AWG (0.65mm bare). So, if figure a ferrule with 1.8-2mm ID.

[Derek Schulte]

Folks:

Here's a variety of information that may clarify things.

I am under the impression that NM service has been replacing failed hot ends with hot ends of the revised design WHEN AVAILABLE.  When not available, the old design has been sent, as it should get the user back up and running for some period of time.  The original design is known to prematurely fail.  Exposing the hot end to very high temperatures, e.g. above 220C will cause the embedded thermal fuse to blow and is not covered by warranty.  They also need to verify that a hot end has blown before sending out a warranty replacement (they aren't just sending them out as soon as anybody asks for one).

I don't know the current status/ability of NM to fulfill non-warranty requests for replacement hot ends.  

If you wish to attempt your own modifications or repair to the hot end, your hot end will obviously not be covered under the warranty.  However, if it has failed during normal use and before modification, I don't personally see why NM wouldn't honor the warranty if the dialog with NM Support is started before modification.

Things to keep in mind if modifying the hot end:

• The cartridge heater is pressed into the manifold.  It is not removable without drilling it out.
• The nozzle and the threaded barrel are retained with a very high temperature threadlocking compound that also seals the interface between them.  They are generally not removeable without potentially damaging or even sometimes shearing the barrel.  There's also a very small brass washer hidden between them.  Heat and/or solvents are very unlikely to weaken the threadlocker.  The brass washer is precisely located during assembly.  In short, don't mess with the nozzle and barrel or you may regret it.
• There's a PTFE sleeve in the top of the hot end.  McMaster-Carr P/N 5335K18 is probably a reasonable replacement.  it needs to be cut square and flush, for example, by dragging a sharp razor blade across it.
• The thermistor is a glass bead unit that is potted in the large groove with another very high temperature adhesive.  In addition to the glass bead, the 30GA dumet leads are fragile.  Handle this one with care:  clamping across the groove can crush the glass bead.
• The wires are insulated with high temperature fiberglass sleeving of various sizes.  Teflon tubing will work in some places but your mileage may vary.  It is important that the heater-fuse circuit and the thermistor circuits are isolated from each other as well as from the manifold/ground.  An isolation failure can easily cause the heater to run in an uncontrolled fashion and/or overload the temperature sensing circuit on the controller, irreversibly bricking your MOD-t's controller board.  This is also why it is important to unplug your MOD-t before connection or disconnecting the hot end.
• The wires have been crimped with a production band/strip crimper during production.  Soldering is not recommended when the connections are near the heater or manifold as these exceed the melt temperatures of many common solders, but your mileage may vary.  Brass tubing can be used.  The crimp portions of some crimp terminals can be used, or even crimp splices designed for hand crimp tools can be used, for example, TE 62759-1 and TE 61769-1 (although those two in particular may require a LOT of force in most common hand crimp tools as they have fairly thick walls).  Sleeving may not slide as easily over conventional crimps.  The fuse leads are close to 1mm diameter.  The heater and wire leads are closer to 0.7mm diameter.  The wires have PTFE insulation/jacketing as lower temperature materials could melt.  
• The electrical connector is from the Molex KK series at 0.1" pitch.
• If you tear up your black silicone rubber thermal insulator, plumber's PTFE tape (aka "dope tape") works fairly well, it's just isn't pretty and doesn't hold up for all that long.  Just wrap a bunch around the hot parts:  you want to thermally insulate the hot end from the part you are building as well as reduce how much energy it takes to heat the hot end.
• The threads are M5x0.8.  M5x0.8 is very nearly a #10-32 UNF thread.  M5 threads are also found all over bicycles/cycling equipment.
• The "nut" in the bottom of the perforated carriage heatsink plate is internally retained with a spring wave washer and a push-on retainer.  If you rotate the nut, it can become loose.  When the nut is loose, it does not make good thermal contact with the heatsink.  You can tighten up the retainer with some carriage disassembly.  In general, the nut should only be rotated after screwing in the hot end (via the barrel), in order to align the harness with the carriage's connector.  The nut has flats that are just under 10mm.
• If you want to unscrew the threaded rod, it has an 8mm hex at the top.  It has been threaded into a "deformed thread" "nut" in the base.  Be careful to NOT bring the consequentially deformed threads at the tip of the rod back through the Z-axis drive gear in the carriage as you may damage the gear's internal threads.

--Derek

[JP]

oh man good information for us armchair engineers (at least myself, I'm not sure on AJF's background but he is definitely more knowledgeable than I) 

I was able to use the replacement thermistors I ordered from Amazon and the old hot end has been brought back to life..The butt connectors I used were a bit long, I was able to hand-crimp them with my tool but looking at it I would probably be better off having used shorter length tubing.

As it is with most of the wiring being so short on the hot end, I don't think I could get more than one or two repairs out of it before the whole hot end goes kaput.

I asked the tech if NM was planning on selling hot ends, she did indicate that was something that has been discussed, I eagerly await that day :)

I wouldn't mind purchasing a new carriage plastics as well, I have some plans to hack mine up, and my attempts at modeling a new one didn't turn out that well (mostly because the NM can't print the size needed to replace it lol)

[Henrik Sozzi]

Ok, I'm into the club :'(

I was printing and, midway the print, MOD-t stopped. From that moment the hot end doens't go over 150-160 celsius degrees. It's going up and down in the range 110 - 160 for some cycles during the warming phase then printer stops going idle.

I was struggling to understand what happened when I remembered this thread :) I don't think I'll try to repair as I'm waiting the new revised hot end (thanks to New Matter!)

[Derek Schulte]

The temperature oscillation is a tell-tale sign of premature thermal fuse failure.  While the oscillation doesn't always occur, if it does occur, then the fuse is almost always the culprit.  Revised/new hot ends should not exhibit premature failures.

If your hot end fails, contact New Matter tech support at he...@newmatter.com.

--Derek

[Anthony VanVolkinburg]

i know this is an old post but did you ever figure out what the actual part is for the thermistor? I'm looking to buy a new one online.