This looks like a simple. 3D printed coat hanger. But if we take a close look at it, it’’s something you probably haven’t seen so far. This is a PLA part overmolded with Foaming TPU in a single print on the E3D Toolchanger similar to the overmolding on power tools nowadays. This is not only multi-color but really multi-material 3D printing, which opens up quite a lot of new opportunities but also faced me with a couple of challenges. Let’’s find out more. Guten Tag everybody! I’m Stefan. And welcome to CNC Kitchen. These coat hanger hooks were one of my first practical 3D prints. I did years back when I got my first. 3D printer and they served us very well. As you might know, we’’re currently renovating, which also meant re-painting the staircase railing. The old hooks were fine, though. They scratched the paint and also regularly fell off while removing a jacket. For this reason, I thought that it was finally time to create a version 2 of it. I wanted to retain the general shape of the hook because that worked well, though I wanted to add a soft padding that touched the railing. This way I could make it fit snuggly, so that it’’s safer in position, and it also doesn’t scratch the paint. I could have just taped some felt on the inside of the old design. But, hey, why do I have all of these fancy? 3D printers (That’s. At least what my wife tends to ask). As you also might know, –. I’ve had an E3D Toolchanger for around a year now. That machine is special because it features four individual Toolheads This doesn’t only let me combine different colors of filament, but I can also put different types of material in each toolhead. Why is that important Systems like the Prusa MMU or the Mosaic Pallete that use the same nozzle for all materials are great if you use the same polymer, mostly PLA just in different colors or use at least kind of compatible materials like PLA and the water-soluble PVA. When they start struggling is when you try to print materials that don’’t work that well together like PLA and Nylon or in my case, PLA and TPU due to different extrusion temperatures or just non-adhering polymers. Even if you can run your materials through a single nozzle, you would need significant amounts of purging, so pushing out the old filament to not run into layer adhesion problems. And this is where a multi-nozzle or even a multi-tool setup like the E3D Toolchanger comes into play. Every nozzle gets loaded with its own material and then just the small amount of molten material that sat in the hot nozzle during idle is purged before it’’s ready to print. People tend to ask why I still use a purge tower with the toolchanger and this is the reason, though it’’s way smaller than with a MMU or a Palette, You can even install different extruders on the machine. So, tool one two and tree are general-purpose. Hemera extruders and the fourth is an Omniadrop extruder that is specially designed to printing every flexible material You can imagine. Let’’s now quickly. Look at the design that I made in Fusion 360. First. I designed a simple hook shape. Noteworthy is maybe that I ted to use the surface tools for these thin parts, which I then thickened to a solid body. In my opinion, the cleanest way to create parts that you’d like to have with a consistent wall thickness. Then I made the internal padding by also just thickening part of the surface, but in the other direction, If you’d use two materials that adhere well to each other you’d already be good to go. PLA and TPU. Even though they stick okay to each other have a significant weakness at their interface and might potentially de-laminate. To prevent that I designed pockets with undercuts into the hook in which the TPU can later properly grab into. This is basically similar to what they do in injection molding when, for example, over-molding your Nylon cordless drill housing with TPU. The Nylon part also features several holes in which the overmolding can later flow to improve bonding. To do this, I simply extruded rectangles and then used the draft tool to generate the undercut. At first, I only did this to the TPU padding and in one of the last steps used a Boolean operation to subtract the material from the PLA Hook. Finally, I just decreased the hook’’s width in the front for better usability and exported both hook and padding as separate STL’s. Let’’s next jump into PrusaSlicer, which I used to setup the print and which caused me quite some headaches until I got nice results. The process is in general. Pretty simple, You load. Both stls at once, which will then automatically merges the parts into a group. I assigned regular PLA to the hook part and Foaming TPU to the padding. Collorfabb’s VarioShore TPU is a really cool material that let’s you adjust its density, depending on the print temperature. So in order to make it as soft and squishy as possible, I printed it at 215°C and reduced the material flow to only 55% because the material expands almost to double its volume. The big problem with this material, though, is that it horribly oozes out of the nozzle during travel moves. If we don’’t do anything against that, the parts will look horrible in the end because the nice matte PLA surface will be covered with strings and pimples. Unfortunately, PrusaSlicer doesn’’t offer an ooze shield, which is basically a second layer around the part where oozed out material will be wiped off and therefore should reduce those artifacts to a minimum. The second option is “Avoid crossing perimeters”. This means that travel moves don’’t go in straight lines from start to end anymore, but the slicer tries to re-route the paths in a way that perimeters should not be crossed. This is a complex process and unfortunately, it’’s also not working perfectly in PrusaSlicer. Sometimes it worked great; other times. It just didn’’t re-route the moves. This feature has been re-worked in the latest Prusaslicer release to work way more reliably –. Unfortunately, not with my problem. The developers only fixed travel-moves within the parts and basically don’t even consider outside moves anymore. A pity and I hope that they will further improve the algorithm because CURA, for example, Does a way better job in that regard Anyways. I ended up rearranging the parts in a way that travel moves Didn’t cross any perimeters and got to printing. And here we go. After some minor cleanup, we end up with these beautiful multi-material coat hangers Overengineered Maybe Cool, looking and feeling Definitely And in the end. I think this was a fun project and shows what the E3D Toolchanger is really useful for. Yes, it can multi-color print really nicely. But it starts shining at more challenging tasks like multi-material printing. But what do you think about this project? And what is in your opinion? A toolchanger really useful for Post a comment down below? Thanks for watching everyone. If you found this small project and technology demonstration, interesting than leave a like, share it with the community and make sure that you’re subscribed for more. If you want to support my work head over to Patreon, become a Youtube member or check out my merch. Stay healthy, auf wiedersehen. And I hope to see you in the next one.