CategoryMerlin Hotend

Cooling with compressed air

Just a short post on the current state of compressed air cooling.

I am currently testing the Merlin extruder, i decided to name it in the same way as the hotend since the two belong together, which uses compressed air from an aquarium membrane pump (bubble pump). A medium size pump is sufficient for one hotend and one part cooler.

I made the mistake of ordering a larger pump than needed, which makes the printer unnecessarily loud due to to much air hissing out of the small gaps. On the up side, i might be able to push the Merlin hotend beyond 260°C with this. 🙂

 

Compressed air part cooler

Merlin Extruder with compressed air hotend and part cooling

Merlin Extruder with compressed air hotend and part cooling

Merlin extruder with compressed air cooling

 

 

Dual material file heft

This is something i wanted to do for a while. A handle, in this case a file heft, that is a mix of soft but tough material on the outside and hard plastic on the inside.

Like the bottle cap it’s ABS with TPU, but this time the ABS is the bulk of the piece. There are 2 perimeter shells of TPU around a 50% ABS hexagonal infill.

The heft weighs just 24 g, but is very stable with a smooth and grip friendly surface.

You can see the ABS infill structure through the transparent TPU perimeter

Assembled file

Dual material bottle caps

After some terrible experience with TPE i tried TPU. What a difference!

TPU prints super easy and gives you high quality surfaces and it is super tough.

Today my wife needed a new cap for an expensive cleaner, so i took 10 minutes to model one in C4D and printed it in TPU. The first print worked immediately, but i wanted to try something new. I set the TPU up together with ABS and printed the cap with ABS for the infill and TPU for the perimeter.

The result is very much  worth the extra effort. The TPU gives a nice finishe and due to it’s elasticity it seals the bottle very nicely. The ABS gives the extra bit of stiffness so the cap does not deform so easily.

Next up is a file heft made up in the same way.

Printed bottlecaps as replacement

 

 

 

 

 

 

 

 

 

 

SainSmart TPU on Amazon

New GreenTec Filament from Extrudr

GreenTec 02 GreenTec 01 Greentec 03

 

 

 

 

On the left printed @0.15mm Layer height with an 0.5mm nozzle on my DuoCore @210°C. On the right printed @0.2mm Layer height with an unknown nozzle @200°C on a friends i3. What is interesting are the differences in slicing, the left was sliced using S3D, the right one with Slic3r.

I was very positively surprised by the new GreenTec filament from Extrudr, that i ordered on a whim alongside a couple of kilos of my usual ABS.

Not only does it produce a nice matte finish, it prints without any hint of warp, the stability is excellent and it is a dream to postprocess with any kind of tool.

The only two drawbacks i found so far are that it sticks so strongly to the printplate (aluminum with 3Dlac @60°C) that damage to the part or printplate are a very real threat and the current price of €56 / Kg

I hope the price goes down over time, but even at the premium it might be worth it, especially considered that i don’t have to feel so bad about producing garbage prints since GreenTec decomposes neatly, different to PLA.

biodegradable plastics

Thermal Runaway – Silicone cover to the rescue

Silicone Cover after Thermal Runaway

Silicone Cover after Thermal Runaway

As it turned out, it was a lot earlier than expected that the silicone sleaves from this posting

Silicone Sleave for Merlin made the trouble worthwhile. Some peculiar behavior of Marlin lead to a thermal runaway for a couple of seconds at full power. The silicone, that is rated for 450°C deteriorated, but the extruder remains unharmed and even the hotend survived thanks to the new cooling.

For those interested, what happened was that while homing Z Marlin stopped working completely. Everything was frozen including menu and the PID for the hotend, which got stuck with the heater switched on. I haven’t found the reason for the behavior yet, but i’ll do the homing before the heating in the foreseeable future.

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 🙂

Silicone Sleave for Merlin

After i did the cover that you can mold around the Merlin heater block, i wanted to make a sleave that can be put over the heater.

The mold comes in three parts, just drill up the holes to 3mm and assemble the parts with M3 screws to hold them tight. It is strongly recommended to use PTFE spray or other any other separating agent. The resulting sleave has a thickness of 1mm and can be easily ripped.

I recommend printing the mold in high quality to get a smooth surface, the silicone will show every small fault of the print.

MerlinSleave03 MerlinSleave05 MerlinSleave04Heatblock Sleave 03

Silicone cover for Merlin Hotend

Thomas Kramm from Hackerspace FFM created some nice Silicone sleaves for the Merlin hotend. Since he uses different heating elements than I, he uses shorter ones that I currently don’t have, I created an own version of this cover.

It protects against blisters 😉 and will reduce the amount of heat lost during print. With the cover the already printed parts will not be exposed to the heat as much as without and you can be a lot less discriminate with material cooling.

You can find the STL for the mold attached

I used silicone meant for tin molds, it holds up till 450°C and i think it will last quite a while at the <300°C it is used in this case.

I used Troll Factory Type 3 silicone

 

 

MerlinCover01 MerlinCover02 MerlinCover03 MerlinCover04 Heatblock Cover

Material Test: FPE Shore 40D Naturel

mat_FPE01First test print with FPE Naturel – Shore 40D
The brown border at the bottom is residue from printing Lay wood before. It turned out that this residue made the FPE stick nicely to the plate, later tests with pure FPE did not work as nicely.

Filament Diameter: 1.71 mm
Nozzle Diameter (Set): 0.2 mm
Nozzle Diameter (Used): 0.2 mm
Nozzle Temperature: 215
Bed Temperature: 100
Bed Surface: Aluminium with Water/Woodglue (3:1)
Layerheight: 0.2 mm
Infill: 100%
Perimeter Speed: 5 mm/s
Infill speed: 7,5 mm/s
Retract: 3 mm

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