Hi all. I am about to commission my first injection moulds, made in China. I trust the company I am contracting to do what they do best, but thought I might ask here for some independent advice, just in case. Many thanks for any help you might be able to offer. The question below is described in general terms, but if you are interested in learning more about the specifics I have included links to detailed information at the bottom of this post.

Two different plastic, injection-moulded parts (one ABS, on PP) have been designed to interlock with a tight fit. Once push-fitted together, the tight-fitting features should provide a resistance to separation. No snap-latch-like features have been used so as to minimise mould complexity (and for aesthetics), so the resistance to separation is provided entirely by frictional forces from the tightly interlocking parts.

I have been told that a somewhat trial-and-error approach might be required, with numerous mould modifications being required before the fit is perfected. Fair enough. However, on the assumption that this will be a process that takes many weeks (even months) it would be very beneficial for us to get a handful of early parts out of the mould that we could use for fundraising/field-trial purposes whilst the mould is being perfected. It would be acceptable for such trial parts to imperfect, but they would have to be "imperfectly-loose", rather than "imperfectly-tight". Is imposing such a restriction on the trial-and-error process likely to cause more problems than it solves? Or is this is a normal request made of mould builders that is easily satisfied?

For further specific details about our parts you can find some illustrations, renderings and prototype photos on our website, and a prototype demonstration video (used for our recent crowd-funding campaign) on youtube. In case it isn't clear already, the interlocking parts described above refer to the white "blocks".

Many thanks for any advice offered.