Fan *~@"ing-tatic!!!
I know a lot of advancements are happening in 3D printing and it seems to me like you are on the cutting edge!!!
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Well the mold is reporting 1.5kg of plastic and 59 hours (actually less than I thought)⌠Here are the components so far (I spread the molds halves - I am printing these separately since a failure would be bad and kill both halves):
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What kind of build volume do you have on that printer? (And what printer are you using? )
I have 2 printers going on this project. My E3D BigBox dual hybrid at home and my Taz6 in the lab. The Taz is 280 mm x 280 mm x 250 mm (11 in x 11 in x 9.8 in). The BigBox is 300mm x 200mm x ~280mm (12" x 8" x ~12").
All of the molds are printed in MeltInk3D Silver PLA/PHA (yes, the color matters, the silver produces the highest quality prints)
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Taz made the short list when I was buying, but i ultimately decided I donât need to print that large. Youâre getting some really nice prints out of those. 
Iâm not sure Iâd purchase the Taz again, if you want smaller Iâd go with the real Prusa i3mk2, and larger the Gmax 1.5 or something. My BigBox when itâs not being temperamental produces amazing prints, but itâs more of a hackable platform than a off-the-shelf product. The taz is a bit of a pain since they sort of expect you to send it back or something whenever something goes wrong (like a serious clog, you arenât âallowedâ to unscrew the nozzle) which of course happens all the time with 3D printers⌠My motherboard blew due to power spikes, but itâs just a Rambo 1.3 board, so thatâs not their fault.
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YeahâŚthat ainât gonna happen (Sending it in for maintenance).
I eventually decided on the MakerGear M2, and upgraded to a dual, and itâs a sweet setup. (A dual with different filaments in each of the nozzles would work really well for your support removal issues, if you get to doing the small stuff again, but the print time just about quadruples with a dual, so that might be kind of tough on those 60 hour jobs.) Weâve had guys run jobs that take 10-12 days thoughâŚyou just have to pause the print and feed a new filament end in when you get close to the end of the spool.
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Yes, my BigBox is a dual as well. It started out (V1-KS) as a dual-direct extruders, and then I transitioned it to the V1.1 Hybrid (main extruder direct, support extruder bowden) which greatly lowered the mass of the x-carriage when the Titan extruder came out. I am deciding whether to go to the dual direct carriage that someone invented from the community vs. waiting for the V2 BigBox which is dual independent heads. The challenge for dual printing with PVA support material is that it really doesnât like to bake, so on top of the purge tower (and the BigBox does ram-purging which cuts down on the waste) you have to cool the head with each tool change and then heat it back up⌠I like the Prusa system for multi-material printing which uses an internal purge/fill with one nozzle:
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Youâre printing PVA in order to ultimately dissolve it right? Since youâve got a dual setup, you might want to try PVA for your main print, with PETG in the other nozzle for support. I discovered that the PETG and PLA /PVA just donât stick to each other - support snaps off clean without damaging anything, and you can reduce your vertical separation to zero, getting really good support and clean bottoms on the main print.
For something as thin as your artery print, you would want to use a high infill for strength, but other than that it should (theoretically, because Iâve never tried to print something quite that tall and skinny) work pretty well.
(I hated printing with PVAâŚhad a lot of sticking trouble with it, so I eventually switched to PLA and PETG, but I didnât have to dissolve it out, so youâre stuck with it, I guess.)
AnywayâŚitâs an idea that might work if you run into any more tight support situations in the things you need to print. Iâm sure these wonât be your last.
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Wow!
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So I am actually using Scaffold from E3D, which is a slightly modified PVA, so sticks quite well. For the larger arteries itâs pretty easy to print with supports as is, the small one turned out to be so fragile as to be unworkable (it cracked just holding it), but interestingly the radial artery turns out to be 2.5-3.5mm in I.D. so that made it pretty easy, instead for that specific model we are simply bending 2.85mm filament using a heat-gun to the shape using a PLA one as a guide.
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PVA can cause violent allergic reaction in the eyes, Be careful.
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Hopefully that wonât be a problem (barring some horrible sink related accident)
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So very excited that one of my projects FINALLY involves laser cutting. And typical of my stuff, Iâm not starting small! This beast of a laser cutter is 55x48" and my first cut area is 41x35". I was making the last video in the series I have been working on, and needed to laser and CNC some stuff on film. Well kill 2 birds with one stone, and I am on my way over to NuVu studios near MIT to work with the faculty on the filming.
This design I will cut is the base plate for a 3D printed project, which is designed to suspend either a pig colon or stomach/small bowel for practice colonoscopy or endoscopy that we canât do on my silicone molded version (because they involve actual electrocautery on tissue layers). However since the colon or stomach you get at the butcher (waste) is âdeadâ it doesnât have blood in it, which is the substance that conducts electricity primarily in your body when we do electric procedures. So had to solve some electrical grounding problems on the organs. These parts are huge (a colon is about 60cm in length for instance). The parts are all printed in amphora and lock together via magnets embedded in the parts, and then lock onto the case (what will be laser printed) via pins that come up from the case floor. There were a million little engineering problems to solve here, including keeping this from becoming a giant petri dish (everything is copper or silver), dealing with the fact that electricity is running through a moist/acidic environment with multiple types of metals (battery) which will cause electrolysis (sacrificial zincs) and the fact that these very complex spline based objects are way, way bigger than any printer, so had to creatively section them, and embed magnets to lock them back into one piece.
I used MakerCase for the case base design, then edited it in adobe illustrator (how painful after using a parametric CAD to do high-precision CAD work).
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By far one of the most-interesting use cases Iâve seen!
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I will add this was my first use of 2KG printing spools (custom ordered from ColorFabb) of nGen. This finish is before I add a gloss coat of clear coat epoxy for bacterial control!
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You can say that again!
So some major updates this week, as my âreal jobâ of software development had a slight lull, so did a huge amount of molding this week. This post will be an update on the artery molding project.
So first off if you recall we have blood vessels 3D reconstructed from CT scans (angiograms) which I print in PVA (E3D Scaffold) to form the lumen (inside) of the arteries and veins. Our intention was to be able to ultrasound and use fluoroscopy on these blood vessels inside various body parts to perform procedures in training situations. So this week we decided to make it happen; we failed by learned a lot, and have a new offshoot that works even better:
Mold outer box in PLA (just a test block) and the distal iliac and femoral arteries in PVA
We coated the vessels in platinum cured mold making silicon from Reynolds. Took multiple dripped on coats over multiple days. Itâs blue at baseline, so we couldnât color itâŚ
Then we hot-glued the coated artery in the mold box so it was sealed against the edges. And then poured in our standard 50-weight silicone with skin color dye.
We picked the ends off the PVA so that the water could attack the PVA core (very optimistic of us). So over 36 hours we hit it with our high-pressure hot water hose, which certainly blew a lot of PVA gunk out, but it never really got totally clear.
Then my colleague Jeff from interventional radiology tried ultra sounding it with, which never quite worked, as the 50 silicone just is too dense, so we are trying other silicone for the body tissue. But he was able to successfully insert a needle under guidance into the lumen but it was a battle.
We were able to snake a bronchoscope up there (itâs like a $20000 bore scope) and there is our needle (and lots of little bits of PVA on the walls)
Luckily Jeff said, hey letâs try it under fluoroscopy (x-ray camera) and see if we can use it to practice a totally different procedure which is a blind inserted billiary drain. Itâs clearly the wrong shape (itâs a large artery, but could we see and inject dye in a realistic manner).
So with a surgery resident in tow who wanted to play with the fluoroscopy (and itâs perfect since heâs a noob at fluoroscopy guided procedures since that is not his specialty), we ran upstairs and threw it on the table.
You can see the needle coming in on the left into the branch of the artery (which is showing up clearly as it is full of air right now) and injecting dye (black). You can also tell that the artery is clogged with PVA since it is a narrow little section. But we did do a pretend billiary drain insertion which worked out great. So while we research silicones (itâs quite complicated as they also have to be chemically compatible with our other components) we are making the easy part (haha) which is a practice billiary drain kit. And that was just one of the projects mostly done today!
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Believe it or not, we did a second molding project at the same time as the above (pretty sure I am going to die of some exotic cancer due to all the silicone that got splashed on my skin despite gloves, etc)⌠So if you recall way back, we were also working on a molded colon. Well that got a lot of attention this week. First off I tromped off the OR with my colleague Tom (one of our colorectal surgeons) to look at the much more closely than in prior cases at a colon.
since the case was not a cancer case, I could actually examine and cut into the specimen after removal (still canât âloseâ any part, but can at least examine it). And after measuring the thickness, color and consistency of each layer (super important to the structure), off to CAD/printing and the sim center for some molding.
First step was to see if we could make the colon suturable, and in the colon only the submucosa can hold a stitch. So it is important as a training aid, that any other layer tear, and that the submucosa be absolutely correct. So in case you are wondering what simulates tough connective tissue? It is power mesh. That is the fabric used in the crotch of womenâs bathing suits. Totally amazing stuff, which is almost untearable, incredibly fine weave mesh, super thin, flexible beyond belief and has other interesting mechanical properties. And it bonds great to 50 weight silicone.
So first we made a big colon (like horse sized) to see how it would work (same mold as before):
So we laid out the power mesh first, and pour out some silicone
This actually turned out to be too much, but this was a quick test
It needs to be stippled in to make best contact
Skim coat on the mold core
Powermesh rolled over the mold core
Now your colon has a connective tissue stripe called the Tinea Coli which is way, way less stretchy, so we rolled the power mesh around an endotracheal tube stylet and then flattened that out. Worked amazingly well
Into the mold for another 40 minutes
Sutures hold perfectly, and you can do full and half-thickness sutures, but super shallow tear out (as they should). Everyone commented how realistic the suturing experience was (other than this being huge)
So now to produce a small segment of proper size colon, we used a real anatomic model of the colon to scale, with the core printed in PVA again.
Mold core and power mesh
Waiting for final coat
Final coat
Soon to make a better outer mold (meshmixer keeps crashing on this model), and onto the full size colon. But in the mean time. this is super quick to make and the residents can practice anastomosis (attaching the ends together). This also holds staples, so they can use an endo-stapler, but those are insanely expensive compared to expired suture material. We hope to get these down to around $1 per practice.
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