As many may know, I will be casting my own white metal parts as part of my Highlander Models production process. I've just had a brand new mould delivered for class 26 and 27 bogie furniture and the development casts that came with them were ok. Two of the parts that are available from the mould are composite suspension parts which ..... whilst they cast fine, due to their rather fragile dimensions, are a little susceptible to breaking. They wont necessarily break as a matter of course but they do have the potential to break if not handled carefully. Now .... I thought ...... bother, I can see this being a potential issue further down the line but .... not necessarily as there are various types of white metal with differing composite make ups. There are a few elements that go into making up the finished " white metal " the over arching name I am taking as being a generic description. Change the mix ( or compound make up ) and the properties will change with it. Add a bit more of one type of ingredient and it will make the finished product more malible or brittle or harder or softer ........ you get my meaning. So ...... as well as the learning curve I have with the production of " kits " per se ........ I need to consider what compounds are best for what application. One man's food ...... is another mans poison as they say. Am I glad that I studied properties of materials as part of my university degree. At the time , I could not quite work out why I was having to study the properties of metals, concrete and God knows what else in order to become a commercial quantity surveyor ......... thank God I did. More on the experimenting with different grades of white metal ingots as it happens. Cheers Toto
You could place some 0.5mm wire in the mould where the break might occure as reinforcement. All white metals will perform the same with that thickness.
Not necessarily Steve. Their characteristics change and Dan make all the difference even at the given thickness. Maybe not a huge difference but non the less..... you cant change the laws of physics.
First experimentation with white metal casting was covered in the Highlander workshop thread but will continue in here. I will demonstrate my fight with physics as I chop and change spin speeds etc in my quest to get the best results put of my casting moulds. My next and subsequent results can be followed in this thread. Cheers Toto
I've been playing with the next sets of white metal bogie casts for the class 26 / 27 kit. I've stopped for the moment as I've done 4 experimental spins and the moulds are beginning to heat up a little. So ..... time to cool off. I started from a spin speed of 2 and worked up to 8 in 2 speed increments. Varied results but generally the higher spin speed produces the best results. I will get useable casts from these moulds. A couple of smaller parts consistently do not turn out. No metal in the " cast target area at all ". I looked at the gate that let's the metal enter the part cast and I don't think it has been formed sufficiently. Ie it does not enter the cast bed. So I will take a scalpel and take a little slither of the ,ould away to clear the entrance. We are talking a minute fraction of the mould here. This will allow a clear path through. I have some pictures that I will post up later. I'll also show the result after clearing the gate as discussed above. I'm pretty happy with the results so far and will be happier still once I've cleared the gate and have a 100 % yield from the mould. Looking good. There is still a little flash comes through on the castings with does not seem to depend on spin speed as it happens sporadically at various speeds. My guess it is down to getting a constant regime in place for tightening the moulds between the plates. I am working on this. It is not crucial but it reduces the amount of clean up that is required prior to despatching within the overall kit. There will always be a minimal degree of this and the purchaser may wish to take that further. It's very, minimal and wont detract from the intended form of the finished part. Back soon. Cheers Toto
and some photos ..... the first pour of the day ...... cold mould and set at spin speed 2. very little actually cast. getting a little better and a slightly faster spin speed ..... getting there now but a little flash that will require cleaning up. mixed results ..... some parts missed. Hmmmm ..... and again ...... getting better ..... the two pieces where I will be enlarging the gates slightly .... some of the parts. a little bit of a tidy up required ..... and again .... an individual shot of the leaf suspension composite part ...... more later .... cheers toto
Those secondary suspension units with the swing link arms seem to have come out all right which is great news seeing as we had quite a complex master to work with. All looking good Toto
its early days and it may take a significant number of spins to achieve enough full sets of parts but that should reduce as time and experience passes. I'll concentrate on getting enough done for the demo builds for now then turn my attention to enough volume for the first production runs of say 5 per class. toto
Hit the shed again today in order to get some more practice in with the spincaster. Still very mixed results. I suspect it will take some time to perfect it. I seem to be getting a bit flash on some of the parts and it looks like it's on the dividing mould line. This suggests that either the moulds are still not tight enough together or the spin speed needs to come down. Possibly a reduction in spin time as well. If it's too fast and the mould has filled then the extra pressure maybe trying to force the material out through the join as it has no where else to go. If the spin duration is too long, that would also exacerbate the issue. Some experimentation is required. That's for next weekend ..... now ..... back to the grind tomorrow. Cheers Toto
a few more photo's covering todays efforts. Still loads of experimenting going on with spin speeds etc. Started off with slower spin speeds and worked up slowly improving as the speed increased. and some parts ..... and again ....... and leaf spring suspension ....... and again ...... and another couple of general shots ........ another ...... the moulds were getting a little hot so I have left them for the moment and will return for another session with them later. as I said, still very much in the experimentation stages yet and some parts could end up going down the lost wax route if I cant get them to a good enough standard. Time will tell. cheers toto
So far an approximate spin time of 30 seconds at a speed of mark 7 on the spincaster seems to work best. Molten metal temp of 325degrees is a constant. I will continue to tweak both spin speed and spin duration a bit further. Not as much flash lately as I have tightened the moulds together with the assistance of a set of grips. ( not over tightened though ). much more experimentation to go though. toto
Sounds like things are heading in the right direction... just as after though would a spin time of say 20 seconds with moulds up to temp reduce flashover? Or would that shortened spin time leave voids in some of the mould cavities?
I'd need to try it yorkie although I'd think it may leave cavities towards the outer edge of the mould. Only one way to find out. No harm trying it.
G`day Toto, Are you confident that the two faces of the mould are dead flat.???? If not...it won`t matter how well they are tightened down, there will be seepage. Think engine block and head..........I know there is a gasket involved in a car engine, but the machining is precise anyway. Gormo
In regards to the slow spin speed, is the molten white metal cooling off too quickly as it passes through the narrower gates ? This maybe why at a faster spin speed you are getting better results... Cheers, Gary.
Are you putting any reservoirs on the sprues Tom ?? I add them so they are the last to cool, helps the casting.
