Author Topic: 3D resin Printing question / idea ?  (Read 321 times)

Offline picclock

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3D resin Printing question / idea ?
« on: July 25, 2017, 11:05:19 AM »
Seeking someone who is more knowledgeable than I for an answer. There are some very fast 3D resin printers out there with very high specifications. All of these shine a uv light pattern via a projector to cure the resin. AFAIK these all shine the light under the resin and grow the object upwards out of the resin bath. This needs a barrier or semi permeable plate to ensure the resin does not adhere to the light source interface.

So why do they not shine the uv on the surface of the resin and sink the item carrier as the model is produced ? This way no separation plate would be needed, and as long as a viewing filter was installed it should be simpler and very much faster, also allowing for easier construction of high thickness solid forms. Only clever bit would be detecting when the resin had flowed over the item and was at the correct depth for the next hardening exposure. If the volume in the liquid resin was kept constant a surface wave would be all that was needed to overcome any surface tension/ meniscus effect, assuming the set and liquid resin had the same displacement for volume. Even if the set/liquid resin ratio volume varied, it would be trivial to calculate the offset and maintain the correct level.

Just very curious about this.

Best Regards

picclock   
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline PK

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Re: 3D resin Printing question / idea ?
« Reply #1 on: July 25, 2017, 03:07:00 PM »
There are printers that do it that way, although I'm not aware of any DLP (projector) variants. They're usually a scanning laser. The downside is that you need to have a large(r) bath of expensive resin and a mechanism to keep the resin level perfectly consistent (think about thermal expansion for a minute).  As such it works well for high volume applications...

Offline picclock

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Re: 3D resin Printing question / idea ?
« Reply #2 on: July 27, 2017, 09:08:50 AM »
Hi PK

Thanks for your interest.

As a quick thought accurate level should be quite doable using a reflected or converging light technique as in the dambusters bouncing bomb. A couple of IR lasers and a system to detect minimum spot size should easily put it in the ball park. Level could be changed by inserting or retracting a dummy displacer. As long as the resin will remain uncured and still have a long shelf life I'm not sure the value of it would be that significant after the initial outlay. The resin shelf life may be the major snag to using this type of arrangement. It may be possible to minimise resin volume by using a container just larger than the model or by floating a  layer of resin over a denser inert liquid such as glycerine ?? at a guess this ought to work well.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)