Patterns for castings

[John S]

I'll bet Jo is eating her heart out after refusing my hand in marriage the workshop after seeing these pics. 

One of the reasons for buying the laser cutter was from a post I saw on Madmodder where some guy [ only posted once and never returned or answered PM's or email ] mocked a cylinder head up for a Subaru out of 1/5mm card.

Can't show some of the work as it's propitiatory and the customer doesn't like work splashed round  t'internet so did this instead.



Five layers cut out of 3.2mm thick MDF to replicate a timing cover or similar.

The holes are needed to accept wooden dowels to line up whist the glue is drying under clamping pressure.



Assembled with M5 screws holding it together for the photo shoot, as an idea of size the small inner diameter is 20mm and the larger inner diameter is 40mm, bosses are 10mm.



Angled shot of the same showing a bit of scrubbing with a strip of emery. If this was a genuine pattern each layer would be slightly larger than it's predecessor to give a draft angle.
It's a doddle to do this and also allow for shrinkage as it's all a question of scale in simple 2D CAD.

Simple job and not using draft angle it took 20 minutes from off the top of the head drawing to bolting the cut parts for the photo shoot.

How about it Jo ? If it's borderline I can throw 7 lathes, 11 mills, 6 welders, 2 plasma cutters and the laser into the hat ? 

[Chris J]

Jo is obviously picky but I might be tempted

Let's have some details of your cutter John.

[Jo]

How about it Jo ? If it's borderline I can throw 7 lathes, 11 mills, 6 welders, 2 plasma cutters and the laser into the hat ? 

Clearly a man after my own heart.. 

Would you like to talk castings?

Jo

[Jasonb]

Jo the same method can be used for traction ploughing engine parts but don't get tempted to go to 6" like Andy's

Just glue them together ad a bit of body filler, blend then paint and you are good to go.

JS I don't know what MDF you are using but if you try the MR (moisture resistant) type which is usually tinted green tou will find it far more stable on thickness and it also has a denser "grain" so the edges don't fluff up so much when you start painting the pattern

[Jo]

but don't get tempted to go to 6" like Andy's

I have no desires for a 6" , it is just too big to handle.

Jo

[John S]

Jason,

I do have a limit on what I can cut, it's only a small machine. Sticking to 3mm means I can get decent detail where the pattern changes.
As these are not big patterns, largest so far is 12" x 12" x 4" I get the local body shop to soak them in clear coat sealer for a couple of hours then they go into the low bake oven.
This cures the fluffiness and as they are all one or three off at the most I don't paint.

I do have one to do that exceeds the work envelope of the machine so each layer will be done in two pieces but the join will vary on each layer and coincide with a dowel hole to get the most glue bond around the join.

It follows slightly along the lines of 3D printing but is far, far quicker. Software is getting better all the while and there is a free  program out there [ not tried it ] called Slicer or Slice8 ? that takes a STL file from such as Alibre and spits out the diffent layers at whatever thickness you require.

So far all my work can be done in 2D CAD as it's not that hard.

[Jasonb]

John, would the lazer work with a dense foam as well then it may be possible to do more intricate parts that would be hard to pull from a split pattern with lost foam ? Something like this flywheel which I built up with waterjet cut steel would have been hard to get out of a two piece mould but rammed up in sand and let the metal melt the foam out would have been ideal

As you say its just like 3D printing with thick layers.