Triple Head, Water Cooled, AutoLift (eventually)

[mikefazz]

Hi all,

So this is esentially v2 of a water cooled hot end I posed about a while back: http://forum.seemecnc.com/viewtopic.php ... 760#p42760

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With a few significant improvements:
- Switched to kraken E3D hot ends (got tired of making my own and theirs are better)
- Quick release for bowden tubing (when I get jams sometimes I couldn't get the quick release to ...release)
- Water channel around perimeter to simplify tubing (thanks to CaptainStarfish for the suggestion)
- Autolift hot ends idea stolen directly from Dglass3D (http://www.dglass3d.com/)

So what is probably most interesting is the autolift feature. This so far doesn't work properly. When cold I can move the hot end up and down with the extruder but my springs are too stiff and the lower point doesn't have a clear end (other than the spring bottoming out). I have plans for an updated version which I hope to resolve this. When I cut the spring to reduce its strength it would lower during printing but since it was around the extrusion force the position could vary with extrusion rate or time so obviously my spring is still too strong. I basically want a spring which is just strong enough to lift the weight of the hot end and resist any friction as well.

Just wanted to put it out there and see what people think.

[dtgriscom]

I'm wondering about the mass added by the water cooler, hoses, and the contained water. It might really slow things down. ("Might.")


Dan

[Nylocke]

It can't have much of a greater mass than the Kraken, can it? I have one, and I print at 50mm/sec with 4000 acceleration. I think it should be alright.

[Eaglezsoar]

Great job in creating this and I am also curious about the weight.
Perhaps mikefazz can get back to us and answer the how it prints with the weight.

[mikefazz]

Hi all,

I have been using something similar for quite some time on a couple delta printers and I don't think the weight it an issue. As Nylocke said it isn't much different from a kraken (never used one myself but the volume of aluminum and water is pretty similar from what I can tell, and theirs is also made from aluminum so I would estimate a very similar mass. Now I am not printing at any crazy speeds eventually the weight would be a problem but extruders I have used aren't really there yet.

Whenever I get the springs sorted and working I'll put up the files and such.

Mike

[Captain Starfish]

That's looking pretty tidy, Mike!

[McSlappy]

Impressive. How heavy is it and does it affect your print speeds? Love these awesome envelope-pushing mods!

* oops, look like my question was asked just before this

I suppose having the upgraded arms would counteract the extra weight also.

[mikefazz]

So I have made some progress. With an updated design and very specific and kinda pricey springs I have a functioning autolift hot end.

https://www.youtube.com/watch?v=ELL2_QI ... e=youtu.be

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A couple issues I still have:
1. It can tend to stick sometimes mostly due to the hole in the water block being a bit big. I drilled it a bit bigger to give good clearance but probably made it too big allowing too much slop
2. The heat transfer seems to be a bit worse now that there is so much slop, a longer PLA print clogged...

Also the lifting seems to work a bit better when printing faster... So in general a little more care when I make my next water block, it may be time to look into getting it machined with a CNC.. I may also try a thermal grease but it would need to act as both a good heat transfer and lubrication...

For those wondering about the weight I weighed a similar water block of mine and got 105g. This doesn't include the hot ends, water, plastic parts and fittings but gives a rough idea.

[Generic Default]

This thing looks pretty cool, especially the lifting during retraction. Not so sure about that calibration piece, though!

From my experiments with my own hotend I found that having Z flatness and nozzle rigidity makes a huge improvement in print quality. If you stick with circular holes and cylindrical heat isolators (the part that moves up and down) I recommend you ream the piston hole to less than .001 larger than the thermal isolator. Otherwise you might want to put a hexagonal hole for sliding and use hex bar as the thermal isolator (or mill it into a hex). That would prevent it from twisting if any forces torque it. Consider pre-loading it with PTFE screws so it doesn't wobble at all. Also, I'm not sure about the water channels and stuff but you might want to move the nozzles closer together towards the center.

Stuff like this needs tight tolerances, and remember than aluminum is a really bad wear material. Anodize and lubricate it with PTFE lube if you can.

Normally I'd offer to CNC it for you for free but I don't know if I'll have time in the near future. Good luck with this and keep us updated!

[Chrissi]

What if the parts had a 45* chamfer at the mating point so that centering accuracy would be consistent?

[mikefazz]

Thanks for the input some things to try...

Generic Default:
- I definitely agree tight tolerances and a better wear surface are a must.
- I think one reason I had to add so much slop was the press fit was a bit tight and wasn't completely centered I used an H drill bit instead of 6.8 or 6.9mm.
- With my design I can't really move the hot ends closer to the center and still use the top quick release mechanism but I am trying to keep the hot end mechanism within the 40mm inner platform diameter to keep it compatible with most RoStocks
- As to the hot end turning (was wondering if anyone would mention this) I am not convinced that a little rotation is a problem so long as the hot ends don't hit and everything stays centered.
- So my next steps will be to add a bronze bushing or two (can I use a bronze bushing inside another one for this application?) and get proper drill bits for proper interference fits

Chrissi:
- Good idea should be easy to add, the hole in the water block has a slight taper from the drill bit (118 degree?) but a 45 would really help. The seating surface is really thin so this may not make a big difference