Common problems/Tips and tricks

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gfeliksdal
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Common problems/Tips and tricks

Post by gfeliksdal »

This topic addresses common problems that happen during operation of the printer. Also some important tips and tricks are described here to have an optimally working Felix printer. This will be continuously updated. If you have any additions, please let us know, we will add it to the list.

Why does the filament not stick to the bed?
Please check the following
  • Distance between bed and nozzle is the same at every x,y position
  • Bed is degreased. Even a small fingerprint could potentially ruin your print.
  • The temperature of the bed is sufficient. 60 degrees is sufficient for small prints, but 65 degC is more reliable for large
  • prints.
  • The print speed of the first layer must be slower than the rest of the print. This will make the filament stick better to the bed.
  • Is the nozzle temperature enough? Try increasing it 5 degrees.
The part sags after a few layers.
This happens mostly to smaller parts with thin walled features
  • The temperature of the filament is way too high
  • Slow down the print speed.
The quality of small parts is really bad.
Even though the fan-airduct, cools the filament relatively fast. It could still not be fast enough for small parts to print with reasonable quality.
Solutions.
  • decrease temperature
  • slow down speed.
  • print multiple parts in the same print. Use the multiply plugin in SFACT/Skeinforge
The filament is not consistently extruded, resulting in sparse prints
The most common reason for this is the extruder tensioning mechanism is not tensioned enough. Increase the tension by tightening the nuts on the bolt which hold the curly washers on the extruder arm. When tightening make sure the bolt is not turning along. Fixate that with a nippers.

Recommended hot-end nozzle temperature
For small detailed parts I print as cold as possible, but for my production prints I print close to as high as possible (200-205 degC), because that increases strength of the parts.
Higher temp is possible but you will suffer from bad quality prints because you will see big blobs at the start of perimeters, if I see that I lower the temp 5 degC.

Recommended way to change filament
It is possible to change filament in the following ways.
  1. Retract/Replace. This is the safest way to change filament.
    • Retract the old filament at a high speed, 1000mm/min for 100mm. The high speed prevents development of a long string which can potentially jam the hot-end.
    • Now extrude the new filament 50mm at a time at low speed 200mm/min, until filament comes out of the nozzle.
  2. Feed through. In this method filament is cut off near the extruder.
    • Cut the filament off as straight as possible. The new filament will push it down, and if cut of scew, the new filament will slip of the to be pushed filament resulting in a extruder jam.
    • Extrude the filament long enough at a low speed 200mm/min. When the filament is just cut off above the extruder entrance, 50mm should be sufficient to push the new filament into the hot-end.
    • Again extrude it 50mm to flush out the old filament.

Solving extruder jams
Causes.
  • Wrong feed-through of filament
  • Bad filament quality. Sometimes bad filament, can have high tolerance on filament diameter. The nominal value recommended value for the filament for the printer is 1.75mm with a tolerance of 0.15mm. On a filament roll I once bought I experienced a diameter variation of 1.5mm to 2.1mm.
    • Too thin filament results in that the molten filament creeps up to the hot-end barrel.
    • Too thick filament will obviously not go through the nozzle barrel.
  • The hot-end parts are not assembled good enough.
  • When the temp is too hot. So filament can creep up the barrel.
  • The three hot-end parts were not fabricated perfectly, the holes didn’t align well and caused the filament to get stuck behind the peek part.
  • Contaminents inside the hot-end. They somehow create a thermal barrier and prevent heat to go into the filament fast enough. Only way to prevent it is to redrill the hole a little.
  • The fan on top stopped working, This got the top part very hot and filament started melting too fast.

Solution:
If for some reason a extruder jam happens, I follow the next procedure.
  1. Cut of the filament just under the filament guide above the extruder wheel.
  2. Unscrew the hot-end M8 bolt
  3. Slide out the hot-end.
  4. Try to pull out the filament, if the hot-end is cool, that probably doesn't work. The cut the filament as straight and close to the hot-end top part as possible.

Elongate the lifetime of the hot-end
The hot-end is robust, seldomely have I experienced a jam or failed operation. But when printing 24/7 I've experienced that the hot-end stopped working after 2-3 months. The reason for that is a contaminated hot-end.
Ways to prevent this from happening.
  • Make sure the filament enters the hot-end is clean from dust. Do this by letting it run through a piece of sponge before it enters the hot-end. You will be surprise how much dust there will be there after a 5 hour print. That would of all entered the hot-end and form a layer of contaminent, which isolates that heat. from going into the filament
  • Do not use too high temperatures. This will make the filament decompose and contaminate the inside of the nozzle.
  • Do not leave the hot-end heated for hours. The filament might decompose after leaving it at high temperatures and this will leave a layer of contaminents behind in the hot-end nozzle
Optimize x and y-axis sliding bearings.
Minimize friction and chance of vibrations.
Vibrations in the sliding bearings are caused by the stick slip effect of the contacting elements, this effect can be amplified when the friction coefficient is higher than it supposed to be. It seems that the production process of the bearings can somethimes vary, as some sliding elements seem to have slightly more friction than others. To overcome this problem, PTFE/Teflon spray is advised by the manufacturer. It can be obtained from any bike or car store.

First clean the bearings with alcohol or some detergent. Then spray a little PTFE/Teflon on a q-tip and rub it against the rail where the rail makes contact with the sliding elements.
Note1: Do not use any oil based products, those will only work for a short time because they will catch dirt and eventually increase the friction coefficient.
Note2: Do not spray it directly on the rail it will make a big mess.
After applying this the bearing rail should move a lot smoother than before and the friction is a lot lower.

Minimize play in sliding bearing
Before the kit is sent out to the customer, the sliding bearings are tuned to have virtually no play. It might happen that it is not done correctly. It is however a relatively easy procedure to tune it yourself. See the tutorial in this post how to properly do it.
http://www.felixprinters.com/forum/view ... ?f=14&t=10

Reduce/eliminate Z-wobble
Several users have reported z-wobble, this results in banding on vertical walls of printed parts. From my experience it is because of the following causes:
1. Wrong assembly of z-spindle
2. Z-spindle is not straight
3. Too much play in z-axis bearing

To eliminate the wobble I try to find to solve the causes from 1 to 3.
  • [1] Wrong assembly of z-spindle:
    • Make sure the curved washer is mounted at the bearing on top and also underneath the bolt which is there to fix the coupling. This will compensate for any imperfections of the bolt. I experience that the top or bottom surface of the bolt is not always perfectly flat. When you tighten the bolt against the coupling you are forcing the coupling a little out of line. Don't over tighten it, because that will loose the compensation effect.
    • Make sure the top part which holds the z-axis spindle is mounted firmly. Any deformation or imperfection on the top part is transmitted to the bed.
    • Make sure the spindle isn't screwed in to the coupling fully. Screw it all the way to the end of the coupling en then turn it back one turn.
    • Loosen the setscrew which locks the coupling slightly, do it in such a way the coupling can slide over the shaft of the coupling but when rotating the motor schaft will still turn along with the coupling
    • Now when you rotate the coupling by hand, you will notice that the motor will wiggle a little bit. The goal is to reduce the wiggling to a minimum.
    • keep rotating the coupling and try to reposition the z-axis motor including bracket in such a way that the shaft will get more in-line with the z-axis spindle
    • Keep doing this until you think it doesn't get any better. Now carefully fix the setscrew, without forcing it out of line.
    • Print the following test piece.
      test_thinwall_export.gcode
      Part sliced at 0.1mm layer height to better see banding effects
      test_thinwall.STL
      Hold it against the light and if you don't see any banding you got it tuned perfectly.
    [2] z-spindle is not straight.
    Remove the spindle from the printer and roll it over a flat surface. Ideally it should look straigt, but a slight deviation of 0.1mm should be acceptable. If deviation is too much you could try to bend it back, but it is almost impossible and you need to get a replacement.
    [3] If the z-spindle is straight (enough) and you mounted the z-axis assembly correctly than there could be too much play in z-axis bearing. During production the bearing is tuned to have no play, but it could happen that it is done not properly. You should be able to feel it if you exert some back and forth force on the big fork. If you can feel some significant play, you can do the following steps:
    • Lay the printer on the wide beam of the frame.
    • Remove the z-spindle and put the z-axis assembly in the middle of the guide
    • Unscrew the four bolts (button-head screws) which hold the z-axis rail to the beam.
    • Rotate the whole z-axis assembly in such a way, that you can slide off the z-axis guide.
    • Remove the plastic sliding parts from the z-axis parts from the z-axis.
    • Put some extra kapton or other thin tape on the spots where there already is some tape.
    • Move the rail on the slider and check if it can still slide smoothly. Otherwise remove some tape again.
    • Iteratively check to get it right. As low possible play with acceptable friction.

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gfeliksdal
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Post by gfeliksdal »

Reserved 2

Kjetilei
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Location: Stavanger, Norway

Post by Kjetilei »

It would be nice with more tips and tricks/procedures for fixing extruder jams.

I have some troublesome filament that has been difficult to handle. The problem is that this is my main batch of filament (1kg spool) and all the other PLA filaments I have are small samples so I have been "forced" to using it anyhow.

The filament is nice when it prints but I could not let the hot-end cool down with the filament inside since it would then clog and the regular retract-procedure always led to jams since the filament did not "break" nicely but formed a long string that clogged the hot-end.

My solution when a print was finished has been to cut the filament and feed some of the good sample filament I have from Ultimachine (and 1 sample delivered with the printer) to purge the hot-end for the troublesome PLA.

And the 3-4 times the hot-end got jammed with the filament (before I learned about the troublesome filament behaviour), I always managed to ram the hot-end open by forcing good filament with high stepper speed down the extruder with the hot-end set to 210-degrees (not particularly elegant/smart but it worked).

Last night I started a print that failed once due to the hot-end jamming while printing. It had printed for several hours before and the filament most likely "backflowed" up the hot-end. I managed to purge the filament and restarted the job and went to bed. This morning I came down to a partially printed model and a major hot-end jam.

My normal ramming procedure did not work on 210-degrees and 230-degrees. So in "desperation" I turned it up to 250-degrees and waited for 5-10 minutes for the remaining filament to hopefully melt all the way. Luckily this helped and the hot-end purge blackish discolored filament with some white puffs of smoke when I fed good filament into the extruder.

This time I really thought I would have to learn how to disassemble the hot-end so I looked into the tips and tricks section and saw that nothing is written about solid hot-end jams where a disassembly is needed. I hope I will not need such instructions in the future but you never know...

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

A little update.

Guillaume sent me thè instructions below on how to securely disassemble the hot end to remove the filament that was clogging it. It worked :)

I was a little more anxious about disassembling the hot end than I normally would have been since that is one of the few parts I didn't assemble myself originally and therefore never had studied the internals properly before... For those of you who assembled the hot end by yourself it most likely is a no brainer to disassemble it for the first time ;)

Instructions:
Untighten the m8 bolt which fixates the hot-end to the extru_base part. Slide the hot-end out, this can be a bit fiddly, but should work.

When hot-end is out:
Grab the hot-end with a pliers at the peek plastic part. Unscrew the top part with a 13 or 12mm wrench. With the top part off you should definitely see what's clogging it. If there is something in there pry it out with a small allen key or if it is really stuck carefully drill it out with a 2mm drill.

mcole254
Posts: 18
Joined: Sat Jun 02, 2012 12:42 am

Post by mcole254 »

I've been having problems lately printing structures containing thin walls (1-3 layers wide). After a few layers the print would no longer be smooth, it would extrude the path kinda squiggly. I first noticed this happening on just the support material in a few spots, it would work through it after a few layers. Heres and example of what I mean.
Image

However I've notice this happening more often and its getting worse and no longer with just support material. Here's an example on a 4 layer wide part.
Image

I thought that perhaps that as the print moved in the z direction it would wobble, however other sections that are unaffected by this still have smooth straight walls. I can no longer even do the 40x10 calibration print (which I have never had a problem printing this before).
Image

Any insight or help would be greatly appreciated.

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gfeliksdal
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Post by gfeliksdal »

I think this could be the reason:
- Too high temperature, lower temp.
- filament slips onto the extruder wheel. Try to put more tension on the extruder arm
- Hot-end nozzle is blocked a little, maybe by hitting the table or some dirt came into it. Carefully use a 0.35mm drill to clean out the nozzle exit.

I hope these tips help.

HLA
Posts: 73
Joined: Sat May 05, 2012 11:35 pm
Location: Vienna, Austria

Post by HLA »

Hi,

I had exactly the same problem because the extruder-arm was not tight enough.

However, if this does not solve the problem and the extruder motor is skipping steps, then this could be related to the bearing (i.e. the bearing that pushes the filament against the hobbed gear of the extruder motor) touching the filament "guide-part" (i.e. the plastic part where you feed the filament through in the extruder). I have cut around 2mm off the bottom of the filament "guide-part" and the issue was solved.

Hope this helps :)

mcole254
Posts: 18
Joined: Sat Jun 02, 2012 12:42 am

Post by mcole254 »

I've solved this issue by cleaning the nozzle with a .35mm drill bit. I printed one piece, now it jams every time I try to print. I've disassembled it may times and cleaned to hot end to no avail. I'm at my wits end of why this is all of a sudden happening. I've been using the same filament, temp, tension and extrude speeds that I've had no issues with before.
Also, is it possible to replace the heating resistor, one of the wires broke from all the times I've disassembled the hot end.

Thanks

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gfeliksdal
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Post by gfeliksdal »

How does it jam?
a. After a couple of layers of printing?
b. Can you keep extruding 1 or 2cm but you have to wait for a couple of seconds to get some filament out.
c. Or in a different way?

Things you could try:
1. From my experience it sounds like you didn't reassemble the hot-end top part not firmly enough into the peek part. But not sure if you disassembled the top part. The peek part acts as a thermal isolation between hot and cold part of the hot-end, but it is also a seal. If the top part is not tightened enough onto the peek part, melted filament can go in between the gap and clog the hot-end. When you want to tighten it more, don't overdo it. Peek is very strong but still not metal.

2. You could also check if the hot-end nozzle is becoming hot-enough. When you press a piece of filament against the hot-alu heated nozzle does it melt? Maybe the sensor is defect.

3. If you only drilled the nozzle with a 0.35mm nozzle from the bottom, there is a slight chance that the dirt is pushed inside the nozzle. So when you start extruding again, it could still block the nozzle. You could try to drill out the 0.35mm hole from the top.

4. It could also be that the inside walls of the nozzle are contaminated, which prevent proper heat transfer from the alu part into the filament.
You could fix that by clearing the inside walls with a 2mm drill, And also use the 0.35mm drill to post drill it from the inside.

Some other questions to better diagnose the problem.
Did you also let the filament run through a piece of sponge or something to remove dirt when it enters the hot-end?
Did you leave the hot-end at elevated temperatures for long periods of time?

It is possible to replace the heat resistor, it is glued in there with heat resistant silicone kit, so easy to pull out.

mcole254
Posts: 18
Joined: Sat Jun 02, 2012 12:42 am

Post by mcole254 »

I can only print for a few min if that before it jams, when it does the stepper motor will click and not turn (if I have the tensioner any looser it will just grind through the filament when it jams).

It could be possible that the last time I reasembled it, it was not tight enough, however all the other times it was for sure, I never had any plastic between the metal and the peek.
I'm pretty sure it was getting hot enough, any filament residue that was on the tip of the hot end was always melted and I would be able to scrape it off with tweezers.

I have always had a sponge, piece of foam or paper towel cleaning the filament before it goes into the hot end, and never left it heated very long unless I was printing (at least not recently).
Could you tell me which heat resistor I can replace it with.

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