3D Printing questions response
Cody Longenbaugh
Description
Collection
Title:
3D Printing questions response
Creator:
Cody Longenbaugh
Date:
7/30/2014
Text:
A big thanks to Steve Byers for all this info!
Response:
Hi Cody,
One of my colleagues forwarded me your original list serve post and I
thought I would share with you a little of the information that WillowWood
has learned in the field. You should also read the following O
< <URL Redacted>
34-FAF916A81D6F> &P blog/article or 2nd O
< <URL Redacted>> &P article if you haven't
already.
There are a couple keys to getting a shape that can withstand the fatigue a
patient places on the brace or socket. The first is the strength of the
plastic, the second is the inner layer bonding strength, and the third is
the reduction of rough surfaces with stress risers.
Many of the ABS plastics used in FDM or SLA are strong but brittle. When
they fail, there is a 'brittle failure' which is jagged and immediate. It
is much more desirable to have a ductile failure, which is basically when
the shape stretches and bends out of shape but doesn't separate or have the
jagged edges of a brittle failure.
The three most common methods for 3D printing are SLA, SLS, and FDM. The
FDM machines are the ones with a coil of plastic which is melted by a hot
tip and applied layer after layer to build the shape. FDM is the type of
machine that Tracy Slemker uses over at PDI in Dayton OH for making
prosthetic sockets. He uses a co-polymer material, but I'm not sure the
exact material. He has fit over 50 patients with these sockets. He made a
customized machine to make the sockets. The trick is getting the plastic to
the correct temperature so that it create a true weld between layers and not
just sticks to each layer.
WillowWood looked at the various technologies and we have an EOS SLS machine
that uses a nylon 12 plastic PA2200. SLS uses powdered plastic and fuses
the layers together. We successfully had 8 patients on these sockets for 6
months and published a research paper on it
< <URL Redacted>> . The
material is strong and generally fails in a ductile mode. Our biggest
challenge is it is very tricky to heat modify the SLS nylon for socket
modifications. This is after the issue that the machine is very expensive
and it can take 48 hours to print and cool a large AK socket.
An interesting note on metal 3D printing. The surface finish is often
rough. We made a titanium component with a 3D printer and put it in
ISO10328 fatigue testing for prothetics components. The part cracked after
a few thousand cycles while a machined part lasts millions of cycles. We
tested a second part that after 3D printing, we machined the outer surface
of the part so the surface was smooth. The smoothed part lasted the
millions of cycles. The rough surfaces of 3D parts creates stress risers
that must be removed for the parts to withstand the stress fatigue of
repeated use.
Another contact that you can look up is Brian Layman in Louisiana. Brian and
his father have been making prosthetic sockets for a couple years now.
<Email Address Redacted> <mailto:<Email Address Redacted>> . Here is an
article on Layman's.
< http://3dprintingindustry.com/2014/03/21/3d-printing-prosthetic-business/ >
Hope this wasn't too much information. :-)
< https://sites.google.com/a/owwco.com/willow-wood-pub/sig/ww_email_sig.gif >
Steve Byers Research Engineer
740-869-3377 ext. 187
www.willowwoodco.com < http://www.willowwoodco.com >
-----------------------------------------------
Cody Longenbaugh C. Ped.
Baker O&P
810 Lipscomb
Fort Worth, TX 76104
(817)332-7313
Response:
Hi Cody,
One of my colleagues forwarded me your original list serve post and I
thought I would share with you a little of the information that WillowWood
has learned in the field. You should also read the following O
< <URL Redacted>
34-FAF916A81D6F> &P blog/article or 2nd O
< <URL Redacted>> &P article if you haven't
already.
There are a couple keys to getting a shape that can withstand the fatigue a
patient places on the brace or socket. The first is the strength of the
plastic, the second is the inner layer bonding strength, and the third is
the reduction of rough surfaces with stress risers.
Many of the ABS plastics used in FDM or SLA are strong but brittle. When
they fail, there is a 'brittle failure' which is jagged and immediate. It
is much more desirable to have a ductile failure, which is basically when
the shape stretches and bends out of shape but doesn't separate or have the
jagged edges of a brittle failure.
The three most common methods for 3D printing are SLA, SLS, and FDM. The
FDM machines are the ones with a coil of plastic which is melted by a hot
tip and applied layer after layer to build the shape. FDM is the type of
machine that Tracy Slemker uses over at PDI in Dayton OH for making
prosthetic sockets. He uses a co-polymer material, but I'm not sure the
exact material. He has fit over 50 patients with these sockets. He made a
customized machine to make the sockets. The trick is getting the plastic to
the correct temperature so that it create a true weld between layers and not
just sticks to each layer.
WillowWood looked at the various technologies and we have an EOS SLS machine
that uses a nylon 12 plastic PA2200. SLS uses powdered plastic and fuses
the layers together. We successfully had 8 patients on these sockets for 6
months and published a research paper on it
< <URL Redacted>> . The
material is strong and generally fails in a ductile mode. Our biggest
challenge is it is very tricky to heat modify the SLS nylon for socket
modifications. This is after the issue that the machine is very expensive
and it can take 48 hours to print and cool a large AK socket.
An interesting note on metal 3D printing. The surface finish is often
rough. We made a titanium component with a 3D printer and put it in
ISO10328 fatigue testing for prothetics components. The part cracked after
a few thousand cycles while a machined part lasts millions of cycles. We
tested a second part that after 3D printing, we machined the outer surface
of the part so the surface was smooth. The smoothed part lasted the
millions of cycles. The rough surfaces of 3D parts creates stress risers
that must be removed for the parts to withstand the stress fatigue of
repeated use.
Another contact that you can look up is Brian Layman in Louisiana. Brian and
his father have been making prosthetic sockets for a couple years now.
<Email Address Redacted> <mailto:<Email Address Redacted>> . Here is an
article on Layman's.
< http://3dprintingindustry.com/2014/03/21/3d-printing-prosthetic-business/ >
Hope this wasn't too much information. :-)
< https://sites.google.com/a/owwco.com/willow-wood-pub/sig/ww_email_sig.gif >
Steve Byers Research Engineer
740-869-3377 ext. 187
www.willowwoodco.com < http://www.willowwoodco.com >
-----------------------------------------------
Cody Longenbaugh C. Ped.
Baker O&P
810 Lipscomb
Fort Worth, TX 76104
(817)332-7313
Citation
Cody Longenbaugh, “3D Printing questions response,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 1, 2024, https://library.drfop.org/items/show/236503.
