Heroic Printing Failures with the Thing-O-Matic and MK7
Description
Either the object first layer won't stick to the HBP and it warps uncontrollably or the filament gets so warm printing large surface area objects that it melts in the extruder feed gears and then the printing stops altogether !
Despite numerous fans on the extruder motor and lots of parameter changes, there's no improvement in the ability of the TOM to make it past the first couple layers without failing.
At least the warping is reduced by adding 'mouse ears' to the object corners, selecting multiple shells on Skeinforge, better leveling of the HBP, precisely zeroing the z-stage height, cleaning the kapton with acetone between prints, etc.
Perhaps the short distance between the extruder nozzle and the extruder motor gear wheel in the Mk7 design causes the filament to melt prematurely and so the MK7 can't print objects with large surface areas.
Any suggestions on what to try next would be greatly appreciated.
( Note: Credit for the naming of this Thing goes to en.wikipedia.org/wiki/The_Book_of_Heroic_Failures ).
Instructions
2) Create the Gcode file with the Print-O-Matic settings.
3) Select the 'Build to File' function and print the s3g file via SD Card.
4) Wait until the print fails after a couple of layers.
5) Change the Skeinforge settings to adjust HBP temperature, number of shells, etc.
6) Replace the Kapton if necessary and thoroughly clean with acetone. Level the HBP and re-calibrate the z-stage height if necessary.
7) Repeat items 2) to 6) at least 16 times !
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Decrease your side and bottom wall thickness from 4 mm to between 2 and 3. Increase the number of shells such that there is no infill in the walls. You should change the wall thickness such that there is no gap between the shells.
I'm up to 3 shells currently and that seemed to really help the adhesion to the HBP.
I'll try a thinner side and bottom wall to ensure there is no infill in the walls. I'm not sure why that would make a difference. Does using no infill in the walls increase the net feed rate through the extruder ?
It would be great if there was a way to measure the filament temperature gradient a
s it passes through the extruder feed motor into the nozzle. Any ideas ?
Hi Folks,
Thingiverse is not well-suited as a troubleshooting forum. Please take this to the MakerBot Operators group: http://groups.google.com/group...
Thanks!
you might have hit upon a useful new site as honestly there is no well-suited place and thingiverse (while not perfect) provides
a) an easy way for those who are not interested to ignore the conversation - this goes to your point
b) an easy way to visualize and understand an issue
c) an easy way to transmit objects to each other
d) an easy way to locate and communicate with others who are experiencing similar issues
for mo
re complicated prints (bridging for example), it's near impossible to lasso in a group of interested people on any other forum
#reprap is a good place to hang out, but isnt a *great* place to get anything more than simple calibration help and the MakerBot Operators groups tend to be all over the ma
p
using Thingiverse seems to solve most of the issues - it's not like this conversation is gumming up the works for anyone. the only risk I see is if the site is abused....
...we really could use a 'stackoverflow' for printers :-)
Hi Schmarty,
I agree with Guest that it might be time for MBI to add a Troubleshooting section to Thingiverse to keep everything in one place and uncluttered.
I thought I could publish any object I created for my TOM, even if it was unprintable. That way people will know to avoid the mistakes I made. Are fail
ures banned from Thingiverse ? :)
With all due respect I might argue that Thingiverse better as a troubleshooting forum (far better than Google Groups or nearly all standard forum software). Where else can you upload images and attach a conversation to an image and repeat that multiple times under one over-arching problem discussion?
What temp are you running the bed at? I've kicked mine as high as 125 in extreme cases.
What really works well is to clean the bed with acetone with a bit of ABS residue, the plastic will get dissolved and smeared around on the kapton tape, forming a cemented down thin layer of ABS that the new ABS will get stuck to when laid down. When I've done this, I've had to practically chisel
the object off when done.
The HBP I have kept between 100C and 110C and cleaning it thoroughly with acetone between prints helps a lot and I'm not getting much warping with the current settings.
The main problem I have now is with the extruder motor losing grip on the filament mid-print.
I didn't want to raise the HBP temp any more than necessary in case that caused the filament to heat up even more.
After cleaning my HBP with spirit, i rub some rinse aid from my dish washer on it. I believe this helps to break the surface tension of the hot plastic. Most of the time I need a knive to remove my print.
wow, no one could say you didnt try. Please dont neglect to post the fix.
I use isopropyl alcohol to clean my kapton sheet and it seems to fix my problems. When dust or my oily finger prints get on the heat bed, that's when I seem to get problems. After printing with a clean print surface, I have to use a knife to pry my parts off since they stick so well. It's like d4ny says, it's crazy! But hey, at least it works :/
one option might also be to temperature control the full environment: make a box around your printer and close it make one opening where you place a fan that is activated when the inside of the box gets too warm. This way you can control the gradient of temperature between the top of your print and the bottom layer on your heated bed.
Wrapping is due to the top layer getting significantly cooler than the first layer.
The only issue with this solution is that you might end up with a lot of internal stress in your object.
I've managed to print a box of this size in the past, I would recommend thinner walls, lower print temps. And if possible, try printing this with PLA on blue painters tape with no heat in the bed at all.
Active cooling may help as well
Were your large box prints done with the Mk7 extruder ?
I have to use 4mm walls as the box needs to be very sturdy and rugged.
I agree with your idea about lower print temps. I've never tried printing PLA with no heat in the bed, so that's worth a try.
I'm using 3 fans on the extruder to keep it cool, but I think the heat is radiating up the filament
itself.
I feel your pain SparkySD.
The layers shouldn't be different, once you get the first layers to work, they will all work.
Try different temperatures and tweak the nozzle to bed clearance until you are happy with the first layer, then work on getting layer spacing right for the next layer, then it should work for all of them.
Your filament width and spacing looks fine.
SteveMac,
Thanks for your empathy. It helps !
Yes, I thought that if I could get past the first layers (with the extruder motor gear wheel keeping grip on the filament) then the print would could complete successfully.
Unfortunately that hasn't turned out to be the case. It seems like the if the feed rate
is not high enough, then the heat from the extruder nozzle eventually heats all the way up the filament so much that it starts melting prematurely in the extruder motor gear wheel mechanism and then the gear wheel loses grip.
I'm using 30mm/sec feed rate in the Print-O-Matic settings and I put 3 f
ans on the extruder motor to keep the temp of the feed mechanism down - the motor feels cool to the touch now. It seems like the heat from the nozzle is radiating up the filament itself, so perhaps the short distance between the extruder nozzle and the extruder motor gear wheel in the MK7 is part of
the problem.
I also tried varying the extruder motor current between 1.37V and 1.65V on the recommendation of MBI tech support, in case it was the extruder motor itself that wasn't turning. Unfortunately, that didn't help. I wonder if there is anyway to pre-cool the filament before it enters the e
xtruder feed mechanism.
What temperature do you set your platform? I use 120 degree Celcius with my TOM. Try to clean your surface by spraying rubbing alcohol on it and wipe with a Kleenex. Your prints will stuck to the surface like crazy on kapton tape,
d4ny,
Thanks for the reply.
I tried varying the platform temperature between 100C and 110C when I moved to RepOrg0027 and updated the motherboard and extruder controller firmware. The extruder nozzle I always kept at 225C. I wanted to keep the HBP temp as low as possible to minimize the temp of the fil
ament feed mechanism.
I'm using acetone and a paper towel to thoroughly clean the kapton after each print attempt and that seems to really help a lot. Printing with multiple shells and 'mouse ears' on the corners reduced the warping also. The ABS-to-HBP adhesion is now pretty good and it takes a he
ck of a lot of effort to remove the print attempt from the platform. I found that loosening the 'mouse ears' with a razor blade first and then grabbing the ears with a pair of plyers and then prying the object off the HBP worked.
Now if we could fix the problem with the extruder motor gear wheel lo
sing traction on the filament so the print would actually complete, then we would be 'cooking on gas' !
Nail varnish remover is also good for cleaning the bed. Get funny looks when at the supermarket though lol
License
More from SparkySD
I use mk7 as well, and while trying to print with PLA I ran into the same problem - extruder gets stuck. After much experiment, I realized that the plunger pushes too hard against the filament, and the friction puts too much load to the extruder motor. I removed one of the three metal washers that pushes the plunger, and that seemed to help.
I still have the same problems sometimes, but much better success rate. I believe that mk7 doesn't have as much torque as mk6 to push filament in. Increasing the feedrate, thus increasing the flowrate helps, because the faster the stepper runs the more torque it produces. I'm even thinking about changing the stepper mode from micro-stepping to power-stepping.
Don't have any issues with ABS though...
Thanks for the suggestions.
I tried removing one of the three metal washers, but that seemed to make things worse, as the print failed half way though the first layer.
When I was looking for information on changing from micro-stepping to power-stepping mode, I noticed this article which says that the MBI stepper motors aren
ât powerful enough for the Thing-O-Matic. http://softsolder.com/2011/05/...
I wonder if this relates to the Mk7 Extruder motor ?