MK8 on UM2 ?

[jtschichold 0]

Hi,

I have read that some users on this forum have successfully switched to the MK8, may I know if you are using the stock feeder or a modified version ? or if you are using specific settings (lower speed, ...) ? other tricks ?

I have installed it and I can't achieve a reliable extrusion, the filament is slipping inside the stock feeder.

Thanks,

luigi

 

[gr5 2,172]

Is it the filament that is slipping or is the feeder turning backwards?

Check that there isn't ground up PLA in the teeth of the mk8. More information here:

http://umforum.ultimaker.com/index.php?/topic/6720-test-report-testing-different-feeder-wheel-grip-patterns/

You might want to stick with the original feeder sleeve.

 

[Blizz 53]

I am using the MK8 gear but I'm using Roberts feeder.

If it just appears not to get a grip on the filament (as in: you barely see teeth marks in the filament) it might be that you have to up the tension (there's a small screw on top of the feeder for that).

But like gr5 said: Make sure its not grinding or that there is something else wrong (ie if you hear a "ploing" sound once in a while it's the feeder skipping backwards because of too much pressure)

 

[sebastian 0]

Did you adjust E-Steps to 365?

 

[Blizz 53]

Yeah I did indeed.

Although depending on the print I sometimes have to modify the material flow to 99% for a bit because of very slight over-extrusion. But it works correctly more than not, so I guess 365 is a good value for me.

I saw that EldRick is using 340, don't know how that is working for him.

 

[jtschichold 0]

Thanks for your replies.

@gr5: the filament is slipping, I know the noise of the feeder turning backwards and it doesn't happen here. Thanks for the link to the report, I'll take a look at the report. I could go back to the stock kurled wheel (I am pretty happy with it after the last firmware upgrade), but I like experimenting :-)

@Blizz: I'll work on the feeder screw to see if I can increase the pressure of the spring. Thanks. I set my E-Steps to 365 but the printer was overextruding and I lowered the value to 335. I'd try the Robert feeder, but the first time I printed it the arm broke while I was trying to insert the nut.

I'll let you know how it goes.

Thanks !

 

[flashp0int 0]

I use a MK8 with E-Step set to 300.

The difference with you guys look weird to me, I'll do the tests again as I have the software installed on the laptop now.

Yet I did not suffer any underextrusion lately. But mostly doing small prints these days with a lot of filament changes for testing.

Thanks for sharing your E-Step values! :ugeek:

 

[Blizz 53]

jtschichold: I've had the same thing happen to me, lookout for version 5, Robert improved a lot on that one.

The arm is now printed lying down, which makes the seams go over the length and rendering it a lot stronger.

Been running the new version since he posted the link to the testing version without issues.

 

[eldrick 65]

Update - I've been working upward from e-steps=340 with the MK8 - currently at 354.

 

[Blizz 53]

EldRick: care to share your diagnostic method? I'm curious to test it here too. Have had nearly no issues with the calculated value of 365. Only with white 123inkt.nl filament I've experienced slight overextrusion. Setting 98% material flow during printing works but that might just be the filament, as the rest is ok.

[flashp0int 0]

Indeed, if filament diameter is smaller or slightly larger, you might experience slight differences.

I did a lot of PET and Nylon tests lately.

While the feeder works great with PLA, my impression is that has not enough pressure for PET and Nylon. Hence the new slightly longer yoke I am testing.

@Eldrick: Thanks for the tip. I'll definitely retry extruding 100mm with Pronterface.

 

[gr5 2,172]

I haven't adjusted steps/mm on UM2 but I did it on UM Original - the procedure is simple. Take filament half way out (just pull with head at 90C) and then cut it off 200mm below the feeder. Measure the position of the end hanging down and then move the filament 100mm. Measure the actual movement with caliper. If it moves more than 100mm say 105mm then reduce the steps/mm by multiplying current value by 100/105. If it moves not enough, say 90mm then multiply by 100/90.

Or you can do different distances other than 100mm.

 

[jtschichold 0]

Blizz: I have used the little screw on the feeder to increase tension and now the extrusion is much more reliable. Thank you.

For the E-steps calibration I have followed the procedure here http://reprap.org/wiki/Triffid_Hunter%27s_Calibration_Guide,%20except%20for%20the%20E-Steps%20fine%20tuning%20part%20where%20I%20have%20created%20some%20gcode%20in%20a%20rather%20perverted%20way%20to%20check%20for%20the%20

Thanks,

luigi