Authorbmarl

Some images of the current cooler design

Slot Cooler 03 Slot Cooler 02 Slot Cooler 01

On the RepRap forum the question came up how the Merlinb hotend is cooled when printing Polycarbonate @ 260°C
The design i currently use is rather simple, it focuses on cooling the lower part of the PEEK and guides the airflow as far around to the backside of the hotend as possible. Ultimately i would like to be able to press all air through a small gap at the lower end of the PEEK, but that is a tight fit given that the heater block needs to be insulated.

A few Hotends

Hotends

Here are a few hotends i have lying around,. While i obviously use the Merlin most, i also employ the Hexagon sometimes.

I haven’t come around to actually using the E3D yet, though i did some extruder designs for it. The Prusa hotend will very likely remain unused till the end of time 🙂

Merlin in Deckung

Merlin unter der Rettungsdecke

Merlin unter der Rettungsdecke

Merlins neuester Lieblingsplatz, unter der Rettungsdecke die ich verwende um den Drucker Prototypen abzudecken

Esun ePC and the Duo Cube

ePC Benchy01 ePC Benchy02

For testing purposes i bought a spool of the new Esun ePC polycarbonate from RepRapWorld. While not cheap it isn’t actually very expensive with €20 for 1/2 Kg. Given that the Merlin Hotend uses a PTFE inliner i was a bit sceptic if it would withstand the 255°C, but no problems turned up at all.

As can be seen in the images bridging does not seem to be optimal, there are even some holes in the top surfaces, something that did not happen with a simpler testprint before. Maybe a bit slower print speed (this one was done with 130 mm/s default in S3D) or maybe lower temperature will help. The stability is good, i destroyed an earlier print using a pair of pliers and i had to use quite a bit of force. Also noteable, the layer adherence was excellent, the part did not brake along layers at all.

Given the very good heat resitance (even better than ABS) i think i will find a lot of uses for machine parts, especially extruder parts since according to Esun the ePC material is not inflamable.

One thing to note, the ePC did not stick to glass when i used 3DLac, i had to print it with an ABS raft, easy enough with the DuoCube 🙂

Testing the Duo Cube – 50% Benchy

Duo Cube printing a 50% scale Benchy @ 0.02mm layer height

Duo Cube printing a 50% scale Benchy @ 0.02mm layer height and 0.2mm nozzle

Trying to print a 50% scale Benchy with a layer height of 0.02mm. A first test to print a M4 screw did work, the screw was functional and stable, showed that there might be a problem with bridges and steep overhangs at this scale. Als Top Layer don’t close easily.

This time i try it with a maxium speed of 40mm/s instead of 20.

 

Edit: As it turned out, overhangs and bridging don’t work at all. I have to invest a lot more time in determining a working setup for this,

Alter Kram

160208-02 160208-01 160208-06 160208-05 160208-04 160208-03

Duo Cube is alive

thing92556halfsize

Thing 92556 printed @ 50%

 

 

The Duo Cube works just fine, dual printing now as well

DuoCube dual color testprint

Z Axis setup for the Duo Cube

At the top the M8 threaded rod is mounted using an axial ball bearing, so it just hangs down from it.
At the lower end it goes through a radial bearing that is mounted from the bottom. The pulley is mounted in a way that the whole screw is tightened slightly, that way it never bends but will always be straight.
I use an axial bearing at the top since the load is the weight of the X assembly plus the tension on the screw, while at the bottom i only use a radial bearing since it mostly has to cope with the pull of the belt and in axial direction only with the tension force.

Z-Axis-01 Z-Axis-05 Z-Axis-04 Z-Axis-03 Z-Axis-02

Using Sinterbronce bearings

This popped up a couple of times on the reprap forum.

Often people ask what bearings to use and i am surprised how often the recommendation is LM8UU for linear bearings.

While LM8UU are cheap (at least the low quality ones) and easy to source, they come with some drawbacks. Ballbearings like LM8UU are designed to withstand rather high loads, much higher loads than are usually encountered when building 3D printer. They are also comparably loud and bulky.

For me sinterbronce bearings are a much preferable alternative for most cases.

They are cheap, even the quality stuff, they are silent, small and very easy to use.

Here are a few images on how i use them for linear motion.

 

x carriage

DSCN1033_small DSCN1032_small DSCN1029_small DSCN1028_small DSCN1024_small DSCN1022_small

 

 

 

 

 

 

 

 

 

 

 

 

 

As you can see i only use the rather thick walled variation, they don’t deform easily, which makes it much easier to use them.

The images show the use for the X carriage of my Duo Cube printer as well as the use for Z. Depending on load and available space i either use zip ties or counter plates to mount the bearings.

The rendering shows the shape of the mount. It only holds the bearing in the middle and stops it from leaving the mount. Other than that it can rotate rather easily, which makes it super easy to align the bearings.

I have been using this type of mount in various prototypes over the last year and never had any problems, on the contrary, the precision fit is first class, even the small X carriage has no noticable give at all, but runs smooth and easy.

 

LM8UU to Sleave bearing adaptor

DSCN1020

 

 

 

If you want to replace a LM8UU linear ball bearing with it’s more silent, cheaper and less weighty sleave counter part 8x12x12 you canuse this adaptor.

I basically only use sleave bearing for all linear bearings nowadays and for quite a few radial bearing uses as well. The smaller formfactor alone is a huge argument for me.

LM8UU Adaptor

 

On Thingiverse

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