05 - Resin Vat

Post date: Oct 6, 2015 3:14:58 AM

The two most challenging and time consuming aspects of this project were the vat and the build plate. The vat holds the resin, needs to have an optically clear bottom, be rigid enough to give even layers and yet be "slippery" enough so the cured layer will stick to the build plate and come loose from the bottom of the vat. Easier said than done. The initial (fastest, cheapest) approach was to just try plain window glass. This met all the criteria except the last one. The layers would often stick to the bottom of the vat better than to the build plate. This makes for very short pieces.

Here is an example of the first vat and prints produced. The gears are supposed to be much thicker than they turned out to be (once the print was complete they were found laying in the bottom of the vat).

This was actually very encouraging results since we were getting something recognizable rather than useless blobs of goo.

We had read up on designs that used Borosilicate glass or used a coating called Sylgard on the glass. The Sylgard is expensive, needed to be re-applied after some number of prints in what seemed like a rather involved process.

Ultimately it was decided to try the "flex-vat" design using clear FEP (sort of like a clear Teflon). The construction of the flex-vat was loosely based on a drum-head design. The idea was to sandwich the FEP between two plates cut like picture frames then using a separate piece for the walls, push it down onto the FEP with hardware allowing for variable tension.

Below is a depiction of the above description using Tinkercad.

Below is the first iteration of the flex-vat. Notice the aluminum frame and the rubber between the frame pieces. Also note though not entirely visible, the addition of a pour spout in the corner (lower-left) for more ease in emptying the vat.

The vat above has approx a 10" x 10" inside print area. For calibrating exposure times and quick small piece prototyping this was a bit bulky so a smaller (4" x 4" inner print area) all plastic version was made.

This proved to be a much more manageable size for the next phase which was finding the right build plate material and calibrating the exposure times.