A different multi-extrusion approach - UM tool / printhead changer

[ultiarjan 1,223]

I'm sure planning on picking this up for the UM2, but with the little spare time I'm having It can take a while :(

I ordered a few different magnets to play with, also tested an idea (picture) to use a "slide" movement to unlock the magnets, but the force of the magnets is much to big for this. So I will go for a smaller version of foehnsturms wig design.

I hope to be able to do a test setup based on the original UM2 head soon, but this will be very bulky. I want to stick to a design with fans, but changing a complete head including fans seem not the best option. It would be nice to be able to mount the 2 side fans separately, so only the hotend part+3th fan can be changed. Think the hotend + 3th fan part could be made a bit smaller then it currently is, as only 1 hotend is needed, but this will take a while if I come to it at all... but if anyone has a good address for small parts aluminium milling just let me know (the Netherlands preferred).

 

[macua85 52]

I tried my design tonight. There is too much play with the bowden tube exerting force. Also too much flex (the e3d bearing had a lot of play, and the e3d module I designed need more support. I've spend the evening deciding how to proceed, and whether to give up or not! I'll try one more design now I know where the problem spots are. Only annoying thing is i've got to rebuilt my printer back to original now to print the new designs!

 

[macua85 52]

I think a flex3drive would have similar problems too as its essentially the same as a bowden. Hmmm, one more go, then its off to a dual e3d print head design.

Foehnsturm, out of interest, how do you hold your magnets in place?

 

[foehnsturm 969]

Macua85,

Do I understand correctly that there is some play when the two parts should be locked together?

Do the magnets really touch each other?

The magnets will only act against forces which try to break their connection. They will not sufficiently inhibit lateral movement. That's the job of the cones.

It should be impossible to move the two parts against each other except tearing the magnets apart.

In other words: It's all or nothing. There shouldn't be any play at all as long as the print head doesn't fall down.

 

[duesentrieb 0]

Absolutely awesome & impressive!!! Big thumbs up! Looks like dual extrusion in good quality with an Ultimaker is in reach... I´d love to build one of these. Will get another printer soon, so I will have my Ultimaker free for fiddling around with this. But don´t have the time right now... Hmpf... So I will have to wait a little.

 

[macua85 52]

Foehnsturm, yea with me design I left a 'skin' in front of the magnets (0.3mm), and pushed them in from the back. The idea of this was to make it so that they could be easily removed and no need for glue. Have you just made yours a tight push fit?

The bearings seems to be the biggest area of play, very disappointed with those. I guess I'll have to use the oem UMO ones; I was trying to avoid ripping the original print assembly apart incase this doesn't work out. Anyone know where I can buy either oem or good quality replacements?

[aviphysics 9]

Foehnsturm, yea with me design I left a 'skin' in front of the magnets (0.3mm), and pushed them in from the back. The idea of this was to make it so that they could be easily removed and no need for glue. Have you just made yours a tight push fit?

The bearings seems to be the biggest area of play, very disappointed with those. I guess I'll have to use the oem UMO ones; I was trying to avoid ripping the original print assembly apart incase this doesn't work out. Anyone know where I can buy either oem or good quality replacements?

 

Were the ones you bought from robotdigg?

 

[macua85 52]

No the ones I got were from e3d. Recommend the robotdigg ones?

 

[foehnsturm 969]

The 0.6 mm (0.3 on each part) will make a huge difference.

I made a tight fit and used a drop of super glue. But you're right, if you want the magnets back you have to destroy the printed part.

Linear bearings of lower quality can have horrible play in my experience.

 

[ultiarjan 1,223]

Luckily it was raining all weekend..... finally time to copy foehnsturms design to the UM2...

I'll call it a partial success, but am satisfied I came this far in a weekend

 

 

Pick and place works fine.... as long as there's no tube/filament, then the pressure gets to big for the magnets.

 

printing also works fine, as long as you stay in the center to have minimal force from the bowden. watch the spectacle at the end :(

 

 

The UM glass is strong, dropped the head at least 4 times today :oops:

 

Im a bit in doubt on the next step.

Option 1> place the feeder motor different to get les force on the bowden

Option 2> use stronger magnets.

I think I'll try option 2 first. I used 10x5x2 mm magnets this time, but also ordered stronger 10x5x4mm. FYI I used "magnetenspecialist.nl" they deliver quickly.

 

And some pictures; Unfortunatelly the design of my modular printhead forced me to use support on this print.

 

[macua85 52]

This is the problem i foresaw, which is why i have so many magnets. seeing how well it holds with just those, i'm pretty confident if I get rid of the 'skin'on mine, I should have no problems. then its just a case of the linear bearings and getting some good quality ones.

Great progress for the UM2 group there though for sure!

 

[ultiarjan 1,223]

Some more info;

The 10x5x2 magnets I used are rated with a holding force of 1.5 Kg.

The 10X5X4 I'll try are rated 2.4 Kg.

No idea what it means or if there good or bad ... but they are N52, NiCuNi ...

And I just figured out I forgot to tighten 2 screws on the fan mount... that will explain some noise in the videos

 

[foehnsturm 969]

Time for a short progress report.

Spring steel strip to block the nozzle: bad idea

Too weak to prevent oozing -> filament gunk conglomerates -> nozzle finally sticks to it -> disaster

Rotating hotend in the groove mount to adjust height: good idea but with severe side effects

The whole hotend assembly is not exactly centered -> adjusting height changes x/y offset of nozzle tip

-> adjustment workflow turns into a serious nightmare

Spring steel strips to push cartridge back into holder: brilliant idea

The parked cartridge might start to move back a little (due to some force applied by the filament ...). If it moves too far the arm will hit its corner before picking it up -> disaster

In the video you can see tiny spring steel strips which gently push the cartridge back into place before the arm arrives to pick it up.

Direct drive and 3mm retraction when changing extruders -> no more oozing

Next step:

Adding small fans at the parking position. Right now there is less cooling airflow there -> PID lowers heating power -> when the hotend is picked up and moved into the cooling airflow the temperature drops some degrees -> the opposite is intended

 

 

[ultiarjan 1,223]

Spring steel strips to push cartridge back into holder: brilliant idea

can you share a close up picture ?

 

[foehnsturm 969]

It's running at the moment, difficult to take a picture. This is from the video.

 

[foehnsturm 969]

The new tool holder. Printed with PLA and FlexiFil.

It can bend a little, as the orthogonality of the x/y axes is already overconstrained which may produce additional friction IMHO.

 

[ultiarjan 1,223]

looks like a cute little animal :eek:

I assume you used a material that's not too flexible? I like the idea, curious about the test result ....

 

[aviphysics 9]

No the ones I got were from e3d. Recommend the robotdigg ones?

I don't know. Robotdigg just often gets recommended as a source for cheap parts. No idea how good their linear bearings are.

[foehnsturm 969]

The connection is 2.4 mm wide, 2.2 mm long, 15 mm high, FormFutura FlexiFil. It just bends. Stretching or lateral movement is virtually impossible.

 

[macua85 52]

That new design looks like it does away with the modular system you were using before?

[foehnsturm 969]

Yes, but I didn't install it yet.

My modular system was designed for easy hotend change and the magnetic mount does this as well. So some space is occupied by a part which realizes a feature which is already there. If the magnetic mount proves its reliability I'll install the new part. But of course I'll keep the tried and tested modular printhead in reserve.

 

[aviphysics 9]

What layer height do you typically print the hot end mounts at?

[foehnsturm 969]

0.15 mm most times, 1.2 mm shell, 20% infill

 

[ultiarjan 1,223]

finally, repeated foehnsturm's repeat accuracy test

redesigned my head a bit, made it a bit smaller, with a bit better weight balancing, and added the bigger magnets (only in the head, not in the pickup, will maybe do that later)

 

sorry for the long video, just skip the first 2 minutes or so..

 

 

Now I dear to call it a bit of a succes...did a little print with a head parking every layer, so in total 147 times.

 

The print in itself is ok, just the stringing caused by the retraction is ugly. If you look at the back of the print the accuracy is fine. Did a print before this one without retraction and that was better, but not good enough.This failed because a magnet got loose (the loctite didn't work that well, now use bison).

 

@foehnsturm > do you use any retraction during parking? What settings?

 

I'm also not totally happy with the parking, although it went ok for 147 times, it just does not sound good, will try to make a little more accurate parking dock.

 

Asked UM support for extra parts to build a 2th head, but no reaction sofar... think this might delay my progress.

 

[foehnsturm 969]

Regarding the (pickup) sound:

Greasing the wedge shaped part works wonders! I used "Titanfett".

Retraction:

One of my two (supposed to be identical) hotends shows almost no oozing / stringing with a retraction of 2 or 3mm (direct drive!) when parking. No idea how the 2 or 3mm translates to with a bowden.

The other one oozes with the same settings. :???:

Congratulations for accomplishing this with an almost original UM2 setup!