I had been warned that they hadn’t come out great with the caster complaining that the waxes didn’t burn out cleanly and that the surface was very pitted. He also said he didn’t like this resin/wax and wouldn’t do any more.
I was gutted. Felt like giving up for awhile. So disappointed that I wouldn’t have any complete kits to sell this weekend at the 7mm NGA Convention.
…….If it didn’t actually work
Time for a bit of digging.
A chat with Formlabs online support pointed me to a spec for using this material. A chat with the caster revealed another clue and a further chat with Formlabs covered the situation in one.
The spec and chats with Formlabs brought home the fact that a wax filled photo polymer needs handling differently to ensure a clean burn out without residue. This is a very precise temperature and time schedule.
This is shown in the graph to the left.
There’s a whole load of other stuff on material handling and casting mould materials for best results and some pictures of the work fine detail the process can produce if done right.
So it works then
Right, so the next stage in the investigation was to have a chat with the caster which was quite revealing. Don’t get me wrong he is an excellent caster and has always done great work for me by the traditional method and I will still use him for this sort of work.
Hmm, back to the drawing board then.
Now one of the problems with these castings is I have designed them to take advantage of the printed wax process and they won’t reproduce in the normal silicon mould to make waxes method. Seems like there are two options for the way forward.
- Redesign the 3D models for the castings so they will work by the mould from masters method. This would mean the likes of the cab valve (Christmas tree) would come in several parts and need some assembly.
- Find a progressive caster that works with Formlabs resins and produces results like those above and below
There are only two in the UK and one of them only does precious metals (gold cab fittings anyone?).
The UK casters are casting companies that just cast your stuff which lacks a certain amount of control and a chat with one suggests limited experience with these photo polymers.
The most promising lead at the moment seems to be with a Polish company who use the Form2 printer in house to produce waxes that they then cast in house. Early days yet but looking promising. I will be following this up next week. It may be that for speed this kit gets the redesign to flat parts that will cast by the old methods whilst we get the printed waxes sorted for the next kit.
Now what to sell on Saturday now I won’t have the kits ready? Well, I am going to take orders and there will be a special offer for orders placed at the show. That will include two package deals of the kit including the chassis (I only have two B4’s)
Hope to see a few familiar faces on Saturday.