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PreWar Workshop: Casting a cylinder head


PreWar Workshop

As most people in the hobby know, a large portion of the pre-war car enthusiasm is sourcing or repairing parts which have been worn out or destroyed in some other way.In this case, it’s a cast-iron cylinder head which has been repaired over and over again over the years. Last time, David Palmer of Cast Iron Welding Services Ltd did a fabulous repair on it, which lasted a while but at another spot it cracked again. It’s just tired after 90 years of service!

So now it’s time to cast a new one. Since I’m very familiar with additive manufacturing technologies, I decided to explore this possibility instead of traditional patternmaking for this part. This has the large advantage that any detail can be easily altered by choice, the dimension accuracy is much easier to control and the location of the core, which is a rather large one in this casting with little support, can be controlled very well. This gives uniform wall thicknesses overall, which the original casting didn’t have.

First a model needs to be made of this head. This is done by 3d scanning it completely, and then working from there in a CAD program to add every dimension and add wall thicknesses etc. With the 3D scanning process, every detail is caught and it gives a very accurate model.
Simultaneously, in this process the machined version is being made, from which the machining afterwards can be done much easier on a CNC machine, since there is already a machined 3D model for the machine to work with.

After the scan, the mold is being made from this in a CAD program. On the computer, all the vent holes, sprues and risers and the casting position are being added to the model, and a complete mold is being made digitally. The biggest advantage of this is that you need no draft angles at all, which makes mold design and core design much easier.
As a final stage, the completely digital mold is being 3d printed in casting sand, and when this print is done, it’s cleaned up and cast-iron can be cast straight into it.

This will be a 2-part article on this cylinder head. After a few weeks when I have the completed castings, I will give you an update. For now, please enjoy the photos of the scanning process! And if you have any parts that would need casting like this or if you need one of these Alvis FWD heads, please contact me for any questions at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

The photo album can be found here: https://goo.gl/photos/Puc28VNfHE55mSzT8

Article by Jos van Genugten

  

Comments 

 
#12 2017-11-06 12:05
I'm very interested in what you've been able to achieve. Would like to discuss a project with you. Please contact me.
 
 
#11 2017-03-17 14:04
Sid, Pattern making shops today use CNC machines to make patterns from CAD drawings. The old skilled trade of the woodworking patternmaker is mostly gone. And finding a mold maker who is willing to make a one-off engine block and get it right first time, is also nearly impossible. These new processes aren't cheaper, but they are reliable and predictable.
 
 
#10 2017-03-17 13:50
Parts can be directly metal printed today, but the cost is way too high for most things. For instance, a leaf spring clip or u-bolt costs 500 Euro each.
 
 
#9 2017-03-17 13:45
I have used this method to make reproduction castings in the USA for 6 years. The 3D printed sand mold process has been around for over 10 years. I believe it is the way to go for making low volume, complex castings. You have to start with a CAD model that is dimensionally and visually accurate.
 
 
#8 2017-03-16 15:41
The time for 3D printing is already here.
Watch this von Jay Leno Garage.
http://www.nbc.com/jay-lenos-garage/video/direct-metal-laser-printing/3469067
 
 
#7 2017-03-16 15:04
This is very neat, but it represents another skilled trade destroyed, that of pattern-maker. It also diminishes the need for the skills of the mold maker. It seems so many of the old skills and trades are disappearing or being diminished under the onslaught of computer technology. And yes, I AM a dinosaur.
 
 
#6 2017-03-16 12:32
Will be very interested to view the second part of this article ! very interesting indeed !
 
 
#5 2017-03-16 10:10
Thank you all for your comments.
Stuart: It does have internal waterways. In fact, the whole head is hollow. It's measured with a 3d probe in the head, to where you can reach it and then extrapolated and corrected due to internal corrosion and such. This makes it quite some work, it's a complex casting!

Duncan, Exactly, the resin is "glued" together with high precision, making the core stable and solid. Disadvantage is removind the sand after casting, this requires some time and tedious work. But this is no different in conventional casting techniques.

Flip, Actually, metal 3D printers are already around but have lots of limitations in price, accuracy, strength etc. I have no doubts that this will improve very quick or that it might be already available and I just don't know about it yet. This technology goes faster than we can imagine!
 
 
#4 2017-03-15 17:39
Again an excellent article Jos! Thank you for your technical contributions to prewarcar.com.

A question: how long before we can directly 3D print these components in cast iron/steel/aluminium?
 
 
#3 2017-03-15 15:00
Interesting article! I can't wait to see the finished results.
You can set the internal cores in exactly the same way as you would with a conventional pattern. The sand is "stuck" together with a phenolic resin and control over this gives lots of opportunity to improve finish etc.
I find the ethical issues over design changes very interesting. Some are easy to justify for safety or longevity, but what about performance improving ones? Would it matter if we start seeing massive increases in performance from these new but "original" components?
 

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