The limits of brass casting?

[Hauk]

I am in the process of designing some masters for fittings that are to be used on that 0-scale mineral wagon.
Here are a screen-dump of the masters at their present state:



Is it at all possible to cast such fairly long and slim parts in brass? The cross section of the parts are 1,4 mm X 0,4 mm. (0,055"X0,016"). The longest one is around 30 mm (1,2") long.
I would guess that the arrangement of filling funnels and escape channels for trapped air is fairly important. Tips on designing those are also much appreciated!

But maybe the printability of the parts in wax is a bigger problem than casting the parts?

[lab-dad]

Why not just cut them out or photoetch?
I would think the one with the larger ends could be folded up to make the shape.
The top end could be wrapped over a tube to also add thickness.
The holes could then be filled with NBW's

-Mj

[Hauk]

Why not just cut them out or photoetch?
I would think the one with the larger ends could be folded up to make the shape.
The top end could be wrapped over a tube to also add thickness.
The holes could then be filled with NBW's

-Mj

Been, there, considered that!
I decided against it because I plan to build around 20 cars. That means 2640 NBWs that needs holes to be drilled. Etched parts needs a lot of cleaning up (especially the edges). And as the prototype is forged iron, a brass casting will be a better representation than etched.

But I might have to reconsider as the printing of a wax pattern is the big obstacle. Maybe wax is the wrong material, there are a lot of more durable (compared to wax) plastics that burn out well. I know some modellers with B9 printers that might be willing to take on a job such as this.

Would be interesting to do a test etch. Maybe I should put the casting project on the back burner and finish the etching artwork for the underframe on the wagon. Not much extra work to add a few ekstra parts to the fret.

[finescalerr]

One problem you might encounter with metal casting is the over scale thickness of the straps. Another is a potentially rough surface. Although urethane castings would be delicate they also might be cleaner and closer to scale thickness. Just thinking out loud .... -- Russ

[narrowgauger]

Hauk

absolutely no problem in casting these in brass using conventional lost wax techniques.

make your masters around 5% oversize for the long width to length configuration of the part.  I would urge you not to drill any critical holes in the masters, spot mark them only and post drill after casting.

I would place all parts on a sprue looping around all the parts with an attachment point top & bottom to each part.  master injection point to the main runner at a single point only.

talk to our German friends to determine a caster in Germany since they are by far the best in the world for precision parts in brass or nickel silver.  if you want best possible quality specify nickel silver instead of brass.  In fact you may find that 925 silver may give you the best quality / price equation.

good luck.  send me a personal email if you need more info

stay cool
BernardS

[Hauk]

Hauk

absolutely no problem in casting these in brass using conventional lost wax techniques.

make your masters around 5% oversize for the long width to length configuration of the part.  I would urge you not to drill any critical holes in the masters, spot mark them only and post drill after casting.

I would place all parts on a sprue looping around all the parts with an attachment point top & bottom to each part.  master injection point to the main runner at a single point only.

talk to our German friends to determine a caster in Germany since they are by far the best in the world for precision parts in brass or nickel silver.  if you want best possible quality specify nickel silver instead of brass.  In fact you may find that 925 silver may give you the best quality / price equation.

good luck.  send me a personal email if you need more info

stay cool
BernardS

Thanks for the info, Bernard!
I have found a couple of german companies that looks promising.

I have arranged the parts within a frame to be more solid.
Comments?

[narrowgauger]

Hauk,

far too many connections to the parts.  The internal runners will soak up the heat and likely to cause problems with casting.

you need to form a single "frame surrounding the parts with a top 7 bottom connection to each part.  That will be particularly important on the part that has the hinge detail at the base.  At that point I would do a small "Y" connection to both sides.

the further problem you will have with some many runners is that it will become very difficult to de-sprue the parts, even with a jewellers saw, which in turn will risk damage etc.

hope this assists
stay cool
BernardS

[Hauk]

Hauk,

far too many connections to the parts.  The internal runners will soak up the heat and likely to cause problems with casting.

you need to form a single "frame surrounding the parts with a top 7 bottom connection to each part.  That will be particularly important on the part that has the hinge detail at the base.  At that point I would do a small "Y" connection to both sides.

the further problem you will have with some many runners is that it will become very difficult to de-sprue the parts, even with a jewellers saw, which in turn will risk damage etc.

hope this assists
stay cool
BernardS

This is very helpful, Bernard. I had a little hangover this morning from last nights designing. It is an awful lot of connections to file off!
But do you mind making a little sketch of how the bottom "Y" connection should look like? I am having a little trouble visualising that one.

[Franck Tavernier]

Be careful with the lost wax casting, you are limited in thickness, with thickness beginning from 0.25mm...

Franck