Quotationof Investment Casting 1

[Tsiolkovsky]

Hi all,

Any chance anyone has received quotations or deals with investment casting products?

I can only receive limited quotes in my area and want to benchmark against widely accepted costs worldwide for interest.

On a high level, the part I wish to cast is a single stage model jet engine axial turbine rotor.

It is a very small component, roughly being a 10cm diameter rotor. The shape is complex due to the airfoils cross-sections but its still one part.

Balancing will not be required as I plan to do this myself. Material will be a non-exotic steel. Only 1 requires a cast (prototype).

My questions are thus:
1) Can you give high level indication of unit part cost no matter which country/currenct you're in?
2) How does the manufacturer make the cast for casting the lost wax model (not the final product but the model). I understand it is usually an aluminium die. But how do they make this if the wax model assumes the shape of a complex airfoil?
3) Does your manufacturer let you keep the die for the wax mould for future use?

 

[ajack1]

If you are only after one part you can 3D print in wax which will be much cheaper than getting a mould made for one part.
Prices will vary hugely depending on where you have the part made, not many companies will be that interested in a one off, they make there money on volume production.

 

[Tsiolkovsky]

Hi Ajack,

Thank you for your swift response.

I did indeed consider a 3D wax print. However, I noticed that some 3D prints normally come with "print Lines" but upon a quick google search I see there are some high quality ones out there, thanks will consider. In this case I would obviously cut the costs big time.

Your explanation on the manufacturers requiring volumes is also a valid one and explains the high cost for once off parts.

Nevertheless would you have any indication of cost given that I provide the manufacturer with a 3D wax lost-cast? (I understand the variability in cost is huge)

 

[ajack1]

I don't know where in the world you are but we have used these guys and been very impressed with them, they can give a far more accurate cost than my "guess" would ever be.

 

[ornerynorsk]

Yes, printed patterns do, indeed, have print lines. A model can be finished or touched-up after printing, if necessary. Another alternative is to have the wax pattern machined and smoothed if surface finishes demand it.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[tbuelna]

There are investment foundries that will rapid prototype a one-off casting. But if you are not offering them any follow-on work with the order, they will charge you some hefty non-recurring fees. The same is true with the 3D metal laser sinter outfits. Their machines are expensive to buy and operate, and they don't make a profit by running one part at a time.

If your turbine wheel prototype requires accurate surface geometry and a smooth finish, you might find that having it machined on a 5-axis CNC mill will be cost competitive overall with the other approaches you are considering. With CNC machining, the cost of your part will mostly be time spent on the machine. It also helps if you are using a material that is not too difficult to machine. There are lots of small machine shops with 5-axis CNC mills capable of machining your 10cm turbine wheel. If you can find one that needs work, you can probably negotiate a low price and quick turn-around, especially if you are paying cash.

Good luck.
Terry

 

[MintJulep]

Why does it have to be one piece?

 

[MikeHalloran]

>>>Material will be a non-exotic steel.<<<

I hope you mean at least a common stainless steel.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Why does it have to be one piece?

Since it's an axial turbine wheel, it's probably a good idea to make it from a single piece of material. Even though it's for a model aircraft engine, a 10cm steel turbine wheel spinning at high speed will release huge amounts of energy if it fails, and the fragments can create quite a bit of damage. Take a look at the turbine housing on any automotive turbocharger. You'll see that the walls of cast iron turbine housing are quite thick, and the reason for this is to contain a fragmentation failure of the turbine wheel.

 

[MintJulep]

Since it's an axial turbine wheel, it's probably a good idea to make it from a single piece of material

GE, Rolls-Royce etc. disagree.

 

[tbuelna]

GE, Rolls-Royce etc. disagree

Actually, they don't technically disagree. R-R and GE make their HP turbines from individual blades attached to a hub. The HP turbine blades are made from castings which allows them to incorporate complex air-cooling passages. But if there was a practical way for them to make the blades and hub in a single piece they would do it.

 

[ajack1]

This getting slightly off topic now but the BBC have a series how to build .. one of the shows was a Rolls Royce jet engine, well worth watching if you have a spare hour.