Layer adhesion problem

I’ve been having a tough time with layers separating on some prints (really anything taller than a few mm). My current project is a planter that is tall with thin walls (about 2mm thick).

I’ve tried nozzle temps of 225, 230, and 232. Temp doesn’t seem to make a significant difference.
I’ve also tried slowing down (esp. on the perimeters). Again not significantly better.

The whole gcode is 62MB, but here’s the top part:

; generated by Slic3r 1.0.0RC2 on 2014-03-16 at 09:03:33

; layer_height = 0.2
; perimeters = 2
; top_solid_layers = 4
; bottom_solid_layers = 3
; fill_density = 0.2
; perimeter_speed = 80
; infill_speed = 100
; travel_speed = 120
; nozzle_diameter = 0.35
; filament_diameter = 2.89
; extrusion_multiplier = 1
; perimeters extrusion width = 0.35mm
; infill extrusion width = 0.50mm
; solid infill extrusion width = 0.50mm
; top infill extrusion width = 0.35mm
; first layer extrusion width = 0.70mm

G21 ; set units to millimeters
M107 ; disable fan
M190 S85 ; wait for bed temperature to be reached
M104 S232 ; set temperature
G28 ; home all axes
M203 X192 Y208 Z3 ; Speed limits to minimize skipped steps when moving really fast courtesy of user 1013
M109 S232 ; wait for temperature to be reached
G90 ; use absolute coordinates
G92 E0 ; reset extrusion distance
M82 ; use absolute distances for extrusion
G1 F1800.000 E-1.70000 ; retract
G92 E0 ; reset extrusion distance

ABS has an inherent tendency to warp when cooling. The larger of an object you print the greater the effect. An enclosure would help, to lengthen the part cooling time (similar to tempering). Printing with HIPS or PLA may be easier, as they do not warp to that extent. A tall skirt may help hold in heat around the outside of the print. You can find that setting in Slic3r at Print Settings > Skirt and Brim > Skirt > Skirt height: and change to ( model height in mm / layer height).

Thank you for the reply. I have more information to report. It appears as though I’m having a feed problem. Anything faster than 100mm/min feed rate is backing up. Even at 100mm/min, I don’t get quite as much extruded as I expect. If I print at 200mm/min, I get very little output, and what does come out is in a tight corkscrew:

it’s hard to see, but the output isn’t the smooth flow I’m used to seeing.

I tighten the tension screws down to about 3.5mm between the washers (very tight), and it didn’t help. I thought I might have a problem with the nozzle, so I swapped the stock .35 with a brand new .50 - same result. Could I be having a problem further up the nozzle? What do I try next?

The hobbed bolt did have a bunch of junk in it after these experiments. I cleaned it out and tried again. Same thing. Feeding with nozzle temp at 237 improved things a bit. Here are some feed rate tests at 237:

20mm @40mm/min = 20mm actual feed
20mm @100mm/min = 19mm actual feed
20mm @300mm/min = 17mm " "
20mm @500mm/min = 16mm " "

check the idler bearing in the extruder. Mine jammed so bad it would barely move one time but the machine would still print, just not well. Also check that the small gear on the NEMA motor is tight and not just kind of moving.

Those are both great suggestions! But alas, the idler bearing (and the hob bearings) moves freely, and the gear is tight on the motor shaft. Also, the gear assembly moves smoothly; no catching of teeth or anything.

If it’s not mechanical. maybe it’s the heater core or the sensor? if the machine thinks your hot end is operating at a higher temperature than it actually is, that could do the trick. Only other thing I can think of is if the hot end itself got hit and is offset to one side or the other now and binding the filliament where it exits the hobbed bolt and goes into the lower extruder hole and enters the hot end. You could be able to see that from the top though, and that would be a bit of a long shot as a problem.

When I had this problem it was partial obstruction of the filament due to cheap quality filament.

You can at times purge the hot end melting chamber by bringing the hot end to temp, allowing it to cool slightly and with the hinged idler open, pull out the filament. Do this a couple of times and see if any other colors/materials show at the end of the filament.

Piercet, you might be on to something. My laser thermometer show 210C when the hotend thinks it is 230C. Admittedly, the beam on the thermometer is a bit wide, so it’s accuracy is questionable, but I went with the highest temp I could measure when aimed at the heater block. Is there a calibration procedure for the hotend temp? If I raise the temp 20C based on my laser thermo, and it’s wrong, then I’ll be melting the PEEK isolator.

I could try to replace the thermistor (100k Honeywell Axial Thermistor, I believe), but I would need to calibrate it.

Orias, I tried your procedure, and nothing apparently off came out. Still, I’ll try another test print to see if it made a difference

ThecallmeJohn, what did you do to clear the obstruction?

Anyone know what a typical feed rate range is during a print? I mean I used 500mm/min in one of my feed rate tests, and that was way off, but perhaps I shouldn’t care because it’ll never use rates so high during actual prints.

I’ve actually never attempted calibration of hotend temperature. There’s a procedure to do so here: which makes sense and I believe could be done safely. The runny liquid point of ABS would be lower than the melt point of the PEEK insulator, though not by much. If you take it slow, you would probably be ok, but there is a risk of damage.

That being said, it makes sense to me that a thermistor that might be starting to fail would return a reading indicating that the temperature is higher than it actually is. The Thermistor works by changing the level of electrical resistance across the material in a linear manner, increasing as the material inside the thermistor gets hotter. if it was starting to break down it would show more resistance than it should, making the machine think it was operating at a higher temperature than it actually was. If that is the case, it may not be safe to go much above 230 because the resistance change may be intermittent or it may be failing in such a manner that higher temperatures may not return a linear value. You might believe you are increasing the temperature 5 degrees but actually increase it 30, etc.

I’d get a second opinion before you actually swap it out, but that’s probably where I would lean going eventually.

This is similar to the temperature cycling method (which never works right for me.) Lets call it the heat gun method.

  1. Let the extruder totally cool to room temperature.
  2. Loosen the springs so the filament is could be pulled out freely and is no longer bearing against the hobbled bolt.
  3. Elevate the nozzle up off the build surface.
  4. Set you software to display the the temperature curve. (Apparently powerful heat guns can melt critical componets)
  5. Start heating the nozzle tip with a heat gun.
  6. Apply consistent but firm pulling force on the filament. (I use pliers but I do it in a way so so its only pulling against the extruder assembly. (i.e. Not bending the rods)
  7. Continue to pull on the filament and heat the tip of the nozzle with your heat gun.
  8. It should pop free soon giving you a nice clean plug.

On a side note, I do not work for Lulzbot ( :cry: ) and I take no responsibility if you damage you printer in some way. I just know this way works the best for me.

It would be much safer and more controlled to simply set the temperature in Pronterface or on the Graphical LCD controller.

If you think the thermistor or the heater resistor is not working correctly, you can test them with a multimeter. With the printer turned off and unplugged disconnect the hot end from the wiring harness and test hot end for the proper resistance. The smaller orange wires are for the thermistor and should read ~100k at room temperature. The larger red wires are connected to the heater resistor and should read between ~4-7 Ohm.

Once you safely bring the hot end up to temperature, steps 6 and 7 are great, just avoid the heat gun.

Well my only issue with that is that that method is that the heat radiates towards the nozzle from the heater block and though the aluminum extension. This results in the plastic in the extension softening and by the time the nozzle gets heated to the point the plastic can break free.

I know other people have success with the method Orias recommends it just doens;t work for me.

Thanks guys. I’ll try those ideas.

I can certainly check the cold resistance of the thermistor. Am I assuming that if it is good (100k) at room temp that is should be good at extrusion temps? Does anyone know of a cheap/easy/accurate tool to measure temp at the nozzle?

If I do run the temp up too high and damage the nozzle, is it just the PEEK isolator and PTFE tube I need to replace, or is it a bigger deal than that?

you can use an instant read contact thermometer, or a type-k thermocouple (some meters have a plug for that). For most room temperature measurements, the resistance of the orange wires on the hot end (thermistor) is around 100k. If it reads appropriately at room temp, it should do so at extrusion temperature.

If you do damage the hot end by exceeding the recommended 240C, the PEEK insulator is the typically damaged component.

The thermistor reads 131.9k at room temp. I think we’re on to something there. What’s the resistance suppose to be when it’s up to temp? I could heat it up, disconnect, and test again.

Either way, a new thermistor is cheap - so a replacement is on the way.

The thermistor on the Budaschnozzle is a 100k Honeywell thermistor, so on average, it should read around 100k at room temperature. Before you change anything on the hot end, if your replacement thermistor is another 100k Honeywell, compare the resistance reading.

Good call.

After re-considering my previous question, I realize it was a foolish one. If I heated the hotend to what it thinks is 230C, it would obviously show the correct resistance. I have no way to heat it to an actual 230C to check the resistance.

I’ll see what happens when the new thermistor gets here.

The new thermistor reads 101.8K at room temp, and at the same time the old one shows 111.1K.

Anyway, after screwing around for a long while with this, I finally gave in and just bought a whole new head assembly figuring I could then dissemble the old one at my leisure and figure out what’s happening with it. Besides, then I’d have enough parts to make a dual extruder setup. :slight_smile:

Now, the new head won’t heat up at all. Nothing. I checked the resistor, and it’s measuring 4.6Ohm at the connector. It does give me a temp reading so I knew the connector is connected correctly (it’s keyed anyway). I traced the problem back to the board, and now it looks like I have a blown fuse! ARRGHH frustrating. :imp:

The blown fuse is a tiny little rectangular one that looks like it’s a 5A. It’s about 6mm long and 2mm wide. Anyone know where to get these?