Postprocessing 3D prints

[Dr. Mike 269]

A member recently messaged me with a question about a brain she printed from this file. I as posting the response here in the hope that it will help others in the community. 

 

QUESTION
"I came across your 3D printable human brain model and was able to successfully print it. Thank you for sharing it! Now I need to post-process it and am wondering if you can explain how you post-processed your print? I have never done the post-processing before and am not sure the best approach to take. I have attached a picture of our printed brain for your reference. Thank you in advance for insight you can offer!"

 

 

RESPONSE:

Based on the picture you attached, it looks like you used a single extruder printer and printed both the supports and model in the same material, presumably PLA. You need to tear off the supports using pliers. This can be a time-consuming job as getting in every nook and cranny can be difficult. If you find the supports are stuck to much to the model, you may have to adjust some of the settings in your slicer software to compensate. There may be a rough surface where the supports touch the model that you can sand off. If you have a dual extrusion printer, you can print the supports using a water soluble material such as PVA, which makes the supports easy to remove by soaking in water. Dual extruders can be finicky and you will likely have to spend a lot of time trying out different settings to get the supports to work just right, including calibrating the XY offset of the second extruder, determining optimal print temperature for the PLA and support to work together, overhang speed, support infill percentage, etc. This process is very time consuming but gratifying once you get your printer dialed in.

 

If you don't want to deal with the headache, embodi3D has a 3D printing service and can print and ship to you. 

Hope this helps.

 

Dr. Mike

 

[arcadia-ncdl 0]

Dr. Mike,

 

How were you able to hollow out the 3D MRI scan? I've watched your hollowing out CT scan tutorial but wonder if it's a similar process for an MRI scan?

[Dr. Mike 269]

You can use a variety of free tools, including Blender or Meshmixer. Meshmixer is probably easiest. Here is the function shown in this picture. 

 

[valchanov 71]

Removing the support is a really hard and painful job, I almost cut one of my fingers the last time I did it (the bleeding was serious though). This is why I prefer to avoid the 3d printing of brain models and I'm making only visualizations. Anyway, here are some tips how to remove the damn thing without hurting yourself:
1. Use a bit lower extrusion temperature or additional cooling fan. For PLA try to print it at 195 degrees instead of 210. This will keep the details nice and steady, the support - easily removable and will eliminate the stringing. It's a bit risky, the model can deattach from the building platform.
2. Use a raft. A real game changer, when we're talking about support removing from complicated organic models.
3. Silk PLA filament. The supports with those filaments are much easier for removal. And it looks really cool.
4. Use different slide thickness at the interface layers. With most of the slicers, you can control the layer thickness in the different parts of your model. You can use lower slide thickness at the interface layers between the support and higher thickness at the rest of the model. This will keep the printing time acceptable and the support - removable.

5. You can try dual extrusion system with PVA as support, if you're ok with the constant oozing and stringing from the second extruder and the terrible performance of most of the PVA filaments. You can also try BVOH with a such system, if you can afford it.

[kopachini 43]

In Slicer PE, now Prusa Slicer, under Support materials, there is a parameter called Contact Z distance, you can increase it to 0.2 (detachable) which makes removing supports more easily

[valchanov 71]

2 minutes ago, kopachini said:

In Slicer PE, now Prusa Slicer, under Support materials, there is a parameter called Contact Z distance, you can increase it to 0.2 (detachable) which makes removing supports more easily

I'm usually avoiding this option, because I had few really bad cases of support deattachment/falling, which hurts a lot in 24+ hours print (I had to hold the support to the model with duck tape, while the printer was still printing). But for the brain model this option will come handy, because of the density of the scaffolds - they are literally everywhere and can compensate few spots of support deattachment. 

[kopachini 43]

This was eye openning for me, now is so much easier for me to remove suppots... but after this post I will probably have same problems as you  (we from Balkans are very superstitious as yo know   at least I am)

[valchanov 71]

[Dan Cardosa 1]

I have a single extruder printer.  Haven't used it yet but I was wondering how to setup a single extruder to make supports for projects.  I am going to use it for bone models prior to surgery for planning purposes.

[valchanov 71]

Every Slicer software have automatic support function. Just click it and it will generate the right amount of support you need.
For bone models the important question is - are your fellow surgeons planning to cut the model or not. It will be a shame, if they break their instruments into your model...
For metal implant premodelling prior the operation, you need smooth bones with high resolution details. In my experience, 0,150mm layer thickness, with 4 perimeters (1,7mm shell thickness with 0,4mm nozzle), 15% gyroid or cuboid infill, a bit colder extrusion temperature (200C for PLA) is perfect. Your fellow surgeons can bend the metalic osteosynthesis implants on the model into their optimal shape, can sterilise them and this whole operation will decrease the surgery time with 1 hour. This is a big difference for the outcome of the operation, the recovery time, the complications ect. ect.
If you want to print fracture fragments, make them in different colors. Then you can make 3D visualization with the corresponding colors. The model will look marvelous and you'll become the surgeon's best buddy. They will love you, they will cheer you and they will give you a lot of money for that.
If you need specific information, please tell us - printer model, slicer software, material on choice. I can give you more specific information, if you do that.

[Dr. Mike 269]

Valchanov, as always terrific post. Thanks for sharing!

 

[Angel Sosa 20]

Excellent 👍

[Dan Cardosa 1]

Wow, that was an excellent response to my question.  I appreciate all the help available here.  It's a great site with a great community!

[Dr. Mike 269]

I've found that printing anatomic parts with a single extruder is difficult, primarily due to limitations on supports with complex, organic geometries. Dual extruder with soluble interfaces is what I use if FDM is required. Stereolithography is also an option although it is messier and arguably requires more postprocessing. Anyone have success with a regular single extruder (excluding specialized setups like MMU)?

 

Mike

[valchanov 71]

I was thinking the same, until I found the Silk PLA. It's a composite - 85% PLA, 15% Polyester and it's dirt cheap. The advantages are:
1. In contrast to the natural PLA, the Silk one doesn't warp or deform during the cooling (or at least the deformation is minimal).
2. It prints really well. You can make the impossible possible with this material.
3. It looks amazing. The layer lines are almost invisible, the silk finishing is appealing, the colors are vivid.
4. The supports falls easily. You just have to pull them and they are done. Tried this on a heart, brain and aorta models. You don't even need increased retraction for this.
5. The stringing is minimal. No more "hairs".
6. It's cheap.
7. Because of those characteristics, this is material of choice for models with accurate morphological measurements. I'm using mostly this material, when I want to have an accurate model.
So, check the local store for this material and try it yourself. You can thank me latter.

P.S. For best results, print it at 200C.
 

Edited September 3, 2019 by valchanov

[Dr. Mike 269]

Wow. Great tip. I'm definitely going to try it. Thanks!

[valchanov 71]

A little update about the Clear PLA filaments for FDM printers. It's also considered Natural PLA, because it doesn't contains additives and colorants, which makes it a bit complicated for printing. It looks a bit transparent, but it doesn't have the optical properties of the glass - for fully transparent prints the STL and DLP are the right choice. The clear PLA is very susceptible to moisture and should be sealed in vacuum back, with silica gel.
For the Clear PLA, higher temperatures are better for best results. The hotend temperature should be 220-230 degrees. Otherwise the adhesion between the layers won't be strong enough and the model will become brittle. I learned all of this the hard way...
The clear PLA is an excellent material for vascular models. A hollow vascular model should be printed with 4 perimeters, 100% concentric infill and support from the build plate only. On the pictures below you can check why I prefer those parameters. Happy printing!
 

[Dr. Mike 269]

Great tip. Thanks for sharing!

[Dr. Mike 269]

Here is a nice article on PLA print finishing. Nothing earth-shattering, but solid ideas. I've never tried the epoxy route. Sounds messy.

https://3dinsider.com/finish-pla-prints/

[kopachini 43]

Some of you could see it on my Instagram account, but for those who didn't, here are some of the tips if you want a really transparent and water tight models:

use Polymaker PolySmooth transparent or Prusament PVB filament. According to Prusa you should set layer height to 0.3mm, but I print with 0.2 mm layer height with very satisfying results. Wall thickness 0.6 (you could make 0.8mm but as thicker it gets, model is less transparent so I didn't go at 0.8mm, maybe once I will try). After the print scrape away some irregularities and after that you can put it in chamber for vapor smoothing with isopropyl alcohol. If you don't own one (as me) just spray the model (inside and outside) with IPA for smoothing results. Don't be aggressive as too much alcohol on the model softens and dissolves PVB so it is better to spray a little bit than after drying, spray it again.

 

Bellow is the example of my aorta model and you can see catheter and guidewire really well.