3D printed casts

[MarkRausa]

Hi guys

Can anyone help me? I’m a health professional looking to get in to 3D printing for casts and splints. More specifically for the immobilisation of broken bones, sprains etc.

There are a few designs out there at the moment such as the Osteoid cast and Cortex exoskeleton cast.

I was just wondering if anyone knows of what sort of 3D scanner would be needed to scan a body part such as a forearm, wrist, ankle etc, what sort of 3d printer would be sufficient to print the items in Nylon and probably most importantly, would anyone know of any software for designing and rendering the casts once the body part is scanned?

Any information would be gratefully received.

Many Thanks

Mark

[HobbyWorld3D]

I think most FDM printers would be able to print in Nylon. A heated print bed is also recommended though not required.

[MarkRausa]

Thanks for you reply. Do you recommend any specific model of FDM printer? Budget would be around £2-3k.

I think finding the correct software is going to be the biggest challenge.

[HobbyWorld3D]

My personal experience is with a much larger printer. However, 3DHubs did a study a while back asking hubs to give feedback on their printers and created a summary of their findings. They also publish printer trends that help to see what printers are gaining and loosing traction in the market. See the following links:

Best 3D Printer Guide 2023 | Hubs

3D printing trend report | Hubs

3DHubs also created a detailed database of printers with reviews and various metrics. When I enter your price range, the LulzBot TAZ 6 comes out on top. I have also heard good things about LulzBot from fellow makers. See that database here:

Best 3D Printer Guide 2023 | Hubs

[HobbyWorld3D]

I cannot say what CAD software is best for working with scanned models but as far as slicing software goes, I use Simplify3D and have had a mostly good experience with the level of control over the printer and the quality of prints it has resulted in.

[cobnut]

Hi @MarkRausa to be honest, you’re asking a lot for a total budget of £3k, so I’d be inclined (for now) to split the problem down into what you need to do and what can be done by others (services). You’re the health professional, so you need to be involved in the modelling of the casts/splints, but you really don’t need to be involved in the actual printing at this stage. 3D printing, especially in specific materials, is a relatively complex task and, at least in the early stages, I believe you should concentrate on producing your digital model, then let a 3D printing professional worry about how it’s actually going to be made.

So, you’ll need a 3D scanner and some software. The scanning part is surprisingly difficult. There are lots of 3D scanners out there, although we can (I think) ignore those that are turntable based/fixed (unless you’re going to chop off the arm/leg to scan it). Handheld scanners start right down at £100 or so and go all the way up to crazy prices (Artec Eva - a snip at €13,700). At this stage, I’d start at the cheap end, perhaps with the Cubify Sense - £400 or even the Kinect version, although that does require more fiddling. I’d start here because even once you’ve got a scan, you’re going to need to do a lot of work in making the actual model. You’ll need to learn how to clean the scan and then how to turn that scan into a voronoid cast such as those you’ve mentioned. The good thing is you don’t need ultra-detail, an arm (or leg or ankle) is really a pretty simple shape (in 3D printing/scanning terms compared to a face or a whole body).

Software wise there are quite a few free apps out there that’ll work well for you. Autodesk Meshmixer is a great tool for simple modelling like this (and their home page actually shows prosthetics and casts, which must be a good sign) and it does voronoid stuff really quite easily. Something like Sculptris might work well.

If you’re insistent on getting a printer, then FDM is going to be a tough ask. Although not ultra detailed, these models are complex and full of holes, two things that FDM really doesn’t like. I can be about 95% certain that all the images associated with the two types you mentioned (Osteoid and Cortex) are not FDM printed parts - they’re way too smooth, so they’re either SLA, DJI or SLS and any way you cut it, £3k ain’t gonna get you that technology at the sort of sizes you might need, so again, I’d say focus on getting yourself a good digital model you’re happy with, upload it here to 3DHubs and get someone (I can’t possibly suggest who) to advise on printing it. Money spent on getting the prints done professionally will save you money in the long run as you’ll have time and money to develop the design end, making sure the products are fit for purpose, rather than having £3k worth of printer sitting there wasted because you never were actually able to produce a digital model.

[MarkRausa]

Wow. Thanks for your detailed reply and advice. I’ll definitely take it all on board and start working towards what you have recommended. Plenty to think about!

[MindFuLL]

The casts would print great on a large, quality, FDM machine but printing nylon isn’t for beginners. If printed correctly, nylon has really good layer to layer adhesion. Taulman makes an FDA approved nylon called 680 that I frequently use for these kinds of projects. It’s strong, safe for food contact, and most importantly it can be sterilized. It’s also translucent enough to visually inspect the internal structure when back lit.
Even with all the holes, these casts are simple enough to print fast with low res if you don’t mind doing some finishing or you can print very high resolution and minimize or eliminate finishing altogether (unless there are supports to remove).

As for 3d scanning, most equipment under $10K are toys and gimmicks. Better hardware (cameras, lasers/projectors, jigs) will save time in the collection of raw data but for the most part, software is the most critical component of a 3d scanning setup as it will be managing all the raw data and turning it into something useful. If you have no background in 3d design, making use of the equipment and its output will come with a significant learning curve. I use a customized David3d stereo structured light (two high res monochromatic cameras & DLP projector) set-up (now owned by HP) that I’m very happy with but I’m very hands on and like lots of flexibility. I put less than $10k into the current set-up and I can scan, on location, anything from an automobile to a fly in full color with very impressive resolution and dimensional accuracy. There are faster (might be important for fidgety children who need a cast) all inclusive (everything proprietary) options but prices go north real fast for such a set-up.

-Jesse

[cobnut]

@MindFuLL in your opinion then, is this project even feasible with the stated budget? I think we can assume that the scanning will have to take place at @MarkRausa’s place of work (rather than in a print bureau) so are we saying that unless Mark can find someone with the right equipment that’s portable and relatively easy to set up, it’s impossible to get the scans needed?

I wonder if Mark can find some local firms with scanners that would be willing to demonstrate them in action? At the very least this might give a more definitive answer to whether it’s even possible within budget.

[MarkRausa]

Thanks for your message. I have a lot to think about. I do think I may have underestimated the work needed to get this up and running but I do believe it is a project worth pursuing and has genuine clinical merit.

I will take your advise and contact some local companies and see if they can offer anything.

[MindFuLL]

Sorry, I started typing that post before there were other replies so I didn’t see the budget or your post (which had good advice as well). I think the budget is probably enough for an FDM machine that can get the job done but I think we both agree that it doesn’t necessarily make it a good idea.

For sure this budget will not cover scanning equipment/software that is necessary to do this professionally. The scans might not require high resolution/detail but they will definitely need to have very tight dimensional accuracy and efficiency.
The budget is not realistic. I think we both agree that each step (scanning, cast design, printing) not only required expensive equipment/software, but investing in such equipment/software without any experience in these areas in not wise. I definitely agree that it would be best to see these processes and equipment in action and then decide which you want to take on or hire out. Like suggested, maybe start with a scan from a local shop and try designing the cast, since there is only software involved and it will give you a better comprehension of the other two steps.

[Lea3DPrint]

I recall seeing a program where a circular set of sensors were fed around the arm and they sensed the dimensions of the arm. This was fed into a model to come up with a 3d design. It was for prosthetics I believe.

[owencombe]

i need one of these casts for a broken hand.

Please contact me if you can make one.

Thanks, Owen

[HobbyWorld3D]

@MindFuLL Perhaps you could help Owen out since you have the scanning and design equipment.

@Owen Unfortunately, I would not be able to print anything for you without a CAD design provided.

[DucoEngDesign]

Hi Mark,

Just read your original post, albeit 7 months late ! I’ve recently proven out a 3D scan to 3D print process for a hand/wrist night time resting splint, for a client who has EDS hyper-mobility type. I’m a chartered engineer by trade and have teamed up with a charter physiotherapist. Equipment I use is within your budget but it’s the software, the ‘middle bit’ is where the costs increase. You’ll need something reasonably powerful to handle the 3D scan data and subsequent design of the splint/cast.

I’m printing using a BCN3D Singma printer with ABS and Nylon, medical approved.

Contact me if you’d like more info, thanks.

[3DEnginner]

Dear @DucoEngDesign ,

Happy to see you are doing so with so kind of budget. My obejctive is almost similar than yours but I am not sure about several things yet:

• the sensor for 3D scanning, I have heard about the Structure Sensor, do you think it is enough for precision and velocity of processing?

• the CAD software to render and modify the models could be any other tipical as Solidworks or so?

• how about the velocity and data volume? do you manage well?

Thank you very much in advance. Regards

[DucoEngDesign]

Hello @3DEnginner, yes, I have found the Structure Sensor to be adequate for scanning a forearm or leg, for example. However, I struggle to get the required resolution for fingers or toes.

You can post process your scan data using Skanect Pro software and using the graphics card processing power of a reasonable PC (a graphics card greater than 4Gb RAM).

Any CAD software will be ok as the scan data can be exported in a variety of generic mesh files, suitable for import.

You’ll need a reasonable PC to run the CAD software as files sizes can become large, greater than 100Mb.

Please contact me if you have any questions.