Trial and Error in Dhaka February 2012
Finally i have the time to tell you about the prototyping process in Dhaka.
As i menioned in my previous post, the arrival of the molds had a delay of 4 weeks. When we planned my stay in Bangladesh the goal was to have a small scale series of prototypes produced. Unfortunately we didnt get there..
Some details about the production:
The first day i arrived at the workshop the model makers started before to produce a second mold for the lid. This wasn’t planned but they thought this would be important to get better results and to produce faster with 2 molds. It was a good initiative, but since I just had 5 days left to work in Bangladesh, I had to stop the process to focus on the more important steps. The production of one complete set, like we did it in Germany.
On the pictures you can see results from the “trial and error” prototyping phase. We tried different ways and different chemical combinations.
Unfortunately the polyester resin was too liquid. While drying the resin coalesced to “puddles” at the lowest point of the mold. Also the prototype components became very heavy, since too much resin was used. The wall thickness varied a lot.
The Jute mats peeled off the mold surface. One reason could be the too liquid resin. Another possible reason is that the jute mat quality was too thick and not not flexible enough.
After demolding many big air bubbles appeared on the surface of the components. The reason is the gas production during the drying of polyester resin.
Why less air bubbles appeared during the production in Germany is not clear yet. The main difference are the chemicals we used. In Germany epoxy resin and in Bangladesh polyester resin was used. Also In Bangladesh Gelcoat was used as a first layer in the mold. This provides high-quality surface which will be very dense, shiny and water repellant.
Step by step the quality of the samples improved, but unfortunately we couldn’t solve all problems. Thiner jute quality made better results and my advise to push the jute mats while drying constantly on the mold surface helped to stop the jute to peel off. But the resin was still too liquid. The chemicals for thickening were missing and it seemed they were difficult to buy.