i'm about to tune my extruder with a axe!

i'm going to chop it in 1000 pieces,
then i'm going to burn it death,
and then i'll chop it some more.

so the question is,
can a direct extrude work or is it just fairy tails and do i really need a wade gear one?

i have a mendel v9 one, and because it skipped sometimes i now changed the copper gear to a good quality MK7 style steel one.

result: it skips even more, and a lot now.

what i want is an extruder that works.
always
all the time

after trying a lot of things i assume reprap just isn't ready for something reliable yet, that is fail proof and easy to install and calibrate.

thanks for listening to my frustrations, but it was posting here or trowing a lot of things to my printer.

i know the feeling...

i was skiping a lot at the beginning... on my first few prints.
it turned out that the extruder was not calibrated and was extruding 140mm when i asked for 100mm. this created a bit of noise of the clamp during higher speed extrusion.
Calibrated it and slightly under the 100mm extrusion... Et voila! no more skiping or noises!

Quote

so the question is,
can a direct extrude work or is it just fairy tails and do i really need a wade gear one?

i have a mendel v9 one, and because it skipped sometimes i now changed the copper gear to a good quality MK7 style steel one.

Put away the axe. There's still hope.

The answer is yes, it works. But it doesn't work very well with a MK7 drive and a NEMA 17 motor. The large diameter reduces the force on the feed. I use something equivalent to a hobbed 8 mm bolt with a 5 mm hole to fit over the motor shaft.. I've been using this direct drive design for more than a year. It's been very reliable!

There have also been a lot of designs lately using geared stepper motors. People still call that direct drive, but I don't see why since it's being driven through gears. It's just that they're hidden from view.

The hot end is also very important for a direct drive extruder since you don't have much torque to spare. I think the J-Head MK-V is the best choice to day. I can extrude 3mm ABS through a 0.35 mm nozzle at up to 160 mm/min using my direct drive extruder with this. Another one that I've been successful with is the Budaschnozzle.

Anyway, with the Mendel90, there's nothing wrong with using a geared extruder. You have plenty of room for it.

Edited 2 time(s). Last edit at 03/07/2013 12:42AM by brnrd.

You sure it's not skipping from being under-driven? (current too low)

Yes. I can hear it when the motor skips somewhere above 160 mm/min. I have the current set to around 1.25A (Vref=0.5V) and I have a fan blowing on the filament drive and motor to cool it.

Edited 1 time(s). Last edit at 03/07/2013 12:29AM by brnrd.

160mm/s you mean 160mm/minute? about how many steps per second?

Yes. Corrected to mm/min. The e steps per mm is 144.627. So, that's 385.673 steps/s.

Edited 1 time(s). Last edit at 03/07/2013 12:37AM by brnrd.

the axe is gone.
the small hex key is back!

i never realized that it could be the torque of the motor that was the problem.
with my wade gear i had the problem with the M8 bolt i made all the time.
it just ate away in the pla without pushing it.

thats when i went for the direct drive with a machined piece instead.
since i saw that "slip" as well, and found on the mendel parts forum people using the MK7 instead i went that route.

so this morning, after much needed sleep i changed the mk7 for the copper mendel parts again, put my e-steps back at 141,
and instead slowed down my printing from 30mm/min to 22mm/min
result was a perfect printed shot glass 50 mm high and not a single skip.

so for the moment i'm going to keep printing slow,
and in the future i think i'll design the extruder i want:
-mendel part hotend V9 (i've become a expert in destroying hot ends, and this one is the only one that keep just going, i love it)
-mendel-parts thick alu design base with fan to keep everything cool
-a wade type gearing 5/1 reduction to produce more torque
-a 5mm bolt so i can use the MK7 filament driver on it
-a duct fan near the nozzle for good bridging.

in my mind, it's going to be perfect, good, reliable, fast and not to forget imaginary.

thanks

The MK7 filament driver is actually not considered to be good by by a lot of people in IRC. The ones available from trinitylabs.com or from arcol are much better. And trinity makes one with an 8 mm hole so you don't have to do too much redesign of the Wade or Greg type extruder.

I think most of your problem is likely to be your hotend. It shouldn't require that much for to extrude.

Edited 1 time(s). Last edit at 03/07/2013 03:03PM by brnrd.

just to mention it could be temp table are wrong and your filament it not melting enough so its harder to push down.

also i had the exact same problem with my 1st 3d printer build for months and months. turns out it was the extruder i had had printed ! when i printed my own out (gregs)it got a lot better now i have no problems at all.

i was the same back in the day i used to print everything at 20-30 mm/sec as it worked but sometimes solving the problem is worth it.

what you need to do is keep measureing extrude 5mm and see what you get put a bit more temp then try again i do this at around 60mm/sec as this is what i generally print PLA at

there is a sweet point for pla where it melts like butter but does not crystalize. can't say for sure i know what that temp is.

I have a direct drive extruder on thingverse which has proven to be quite reliable,
Search for " JGR direct drive extruder"

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