I recently completed building a MEM Corliss steam engine and decided it needs a display case.
So an acrylic display case had to be made. I found this very informative youtube video on the subject:
[youtube1]https://youtu.be/ufwUaZaM0ig[/youtube1]
Methylene chloride melts acrylic. It is hazardous, so take all necessary health precautions! It has a very low viscosity and when applied to an acrylic joint with a syringe needle, capillary action spreads the solvent, resulting in the two pieces of acrylic being welded together. After 24 hours, the joint is as strong as the parent material.
I bought some methylene chloride from a perspex fabricator and practised joining some scrap pieces of acrylic using a syringe needle. The two faces to be joined must be perfectly smooth and flat, as the methylene chloride has no gap filling properties. Milling the edges on a milling machine produced the best results.
I also found that the joint must not touch any other surface (such as a vertical backing plate). Capillary action will pull the solvent between the backing surface and the acrylic, damaging the acrylic in the process. It works best to hold the pieces together with masking tape when applying the solvent.
I bought 3mm acrylic sheets for the four sides and the top of the case. These were ordered slightly oversize, to allow the edges to be accurately milled on the milling machine.
The protective covering was removed and all the milled edges deburred. The case was then assembled with masking tape and all joints were checked for a good fit.
A test fit on the model base was also done.
The corners were first tacked as described in the video. Then all the edges were glued by running the syringe along the inside corner of each edge, taking care to apply only the required amount of solvent (i.e. very little!). After a few minutes, the case can be handled and the tape removed. 24 hours later the joints are fully cured.
The neatness of the resulting joints is quite surprising, and I am very pleased with the final result.