# Complex casting



## matt-jaysey

Hi, im new to this site so i'd like to say hello all! 
I've wanted to make engine models for years now, and finally im gonna give it a go. However, I want to make modern engine models not old school ones. Nothing against then I just like the new stuff. I'm starting out with a Subaru 2.5 liter STI 4 cylinder boxer. I've collected hundreds of pictures and constructed a basic model on the computer. What i wanted to bring to peoples attention is how im planning to get the scaled model off the computer to here in the real world. 

Unfortunately I can't afford a CNC milling machine. I had to come up with a simpler amd less costly method. At work one day a was using our Epilog CO2 laser and it hit me. Searching around at work I found some card that was exactly 0.5mm thick and was heading for the bin. I collected this card, and when i finished my shift, i cut out a simple gasket shape to see how it performed. It came out fantastic.

After a few weeks I sliced my 3d model into 0.5mm thick sections and set about with the card and laser. I produced several sheets with acurrately cut out sections. Im going to have to take and upload some photos this evening if i can on my progress, hope this is of some intrest to some of you.

matt+


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## 90LX_Notch

What's your machining and metal working background? I'm not saying it can't be done; but, that's a lofty goal unless you've done this before. This is a hobby that isn't as easy as it looks. You really have to understand fits and tolerances, especially for an internal combustion engine. Anyhow, best of luck with it and keep us posted. Make sure to post your progress; it will be a neat model.


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## matt-jaysey

Hi notch

Im 26 years old and from England, I have worked for various machining companies, I used to work for a company that make surgical instruments for the British army. No this is my first model engine project but I have about 15 years engine experiance. But im here to learn as much as i can as i only cut my first piece on the lathe 5 years ago and I know thats not long at all. Cheers for the reply

matt+


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## 90LX_Notch

Matt,

Well that's good to hear. If you are serious about this, take this advice: build some simple engines first. You'll be amazed at what you'll learn.

Bob


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## Lakc

Congrats, .5mm cardstock should work fine, thats basically how the first rapid prototype machines worked. Having a good pattern is a great start to parts coming out of the sand correctly.


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## matt-jaysey

When you mean simple whjat exactly do you mean? Surely an engine from a casting is an engine from a casting if its shape is complex or not. I have seen what alot of people have done on this sight. Machining entire crankcases from a billet block. Thats amazing and well above my ability. But I only want to cast a block and then drill and ream some holes. 

Ah one thing i didnt mention before is that this engine isn't going to run. I know that seems abit crazy. I just want to make a model replica. After hopefully completing this one and possibly afew more I want to give a running one a stab. but for now just a scale replica. 

matt+


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## matt-jaysey

I must appologise i sound rude but im just telling you what my ideas are. This is probably gonna end up tits up but i love just jumping in and having a stab at it. 

matt+


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## matt-jaysey

Hi all, 

Ive got some pictures i justy hope they load





This is the crank built up before slicing.





This is the head before splitting. This took me about 6 hours to construct. (Im not the fastest modeler in the world)





This is the head split into 71 0.5mm sections the scale of the head and engine is 1 to 4.

I then cut the card with the epilog laser and ended up with sets of card. Theee were then stuck together to form a solid 3 dimentional object. More pictures coming soon

matt+


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## 90LX_Notch

Matt,

You have to realize that the engines on this site actually run. That's why I was trying to convey that it is not as easy as it looks. A static model is a whole different story. Good luck with it. Keep us posted.


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## Tin Falcon

Matt first of all welcome to the forum. 
Bob was just trying to offer some friendly advice. the consensus here if for most folks to start out with a simple air powered single cylinder wobbler or the like . 

it may be benificial to read these threads :
Getting started in Model engineering :
http://www.homemodelenginemachinist.com/index.php?topic=9413.0

selecting a first engine to build. 
http://www.homemodelenginemachinist.com/index.php?topic=16003.0

Jump in where you feel comfortable. 

My first build attempt was from castings in retrospect a different choice would have been better. 
Tin


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## matt-jaysey

Thanks fellas for all the input. I have done alot of casting in the past and its what im comfortable with but i here what you say. However I've read through alot of peoples post and many people seem to ignore what engine builders have done for years. Many of the engines posted on this site have tiny crankpins. Bears are made from brass without oil feed holes and not much attention is focuses on hardening steel parts. I maybe young but I ahve been doing this type of work since i can remember. Im not a novice and i appreciate that there are many people that have started project with bright ideas and not finished them. Only time will tell of course. One question that I do have is does anyone use core drills to great effect and what dimentions do they undersize to? cheers 

matt+


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## Mosey

Matt, Welcome.
Keep rocking the boat! I love it. Who knows what you can accomplish?
Mosey


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## idahoan

Matt

I'm not completely clear how you plan to use the laser cutouts; will they somehow be used as a casting pattern or just glued up for a full scale mock up?

About your comment on the crank pins, brass bearings and lubrication; keep in mind that a lot of these small models are not a scale models of any particular full size machines; but in many cases they are scale models and they did have bronze or Babbitt bearings and used drip lubrication or grease cups. Primitive I know but that is the way stationary engines were made back in the day.

Please keep posting pictures of your progress.

Best regards,

Dave


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## gbritnell

Matt,
Good luck on your future projects.
gbritnell


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## matt-jaysey

Just thought I'd add some more pictures of how things are going. Yes im stacking the layers of card together to make a 3D 'plug' to mould from





This is some of the sections for the left side cylinder head cut out. The white tape is to keep then in order before gluing.





Here is the cylinder head glued together and sprayed with primer to give you and idea and better look at how the layers build up. It took me 2 hours to glue and isn't perfect, but im going to sand it back slightly and fill in the steps between the layers. The Aluminium casting is going to shrink slightly. Therefore im going to use high build primer to build up the model. I'll use a dial caliper to measure how much i've put on roughly. Im looking for about 2% increase in dimensions. 

The holes havent been cut as they will be drilled and tapped when the casting is complete. The model will be painted and polished before apply the RTC silicone. This will aid in removing it from the silicone casting. 

Below are some more pictures to give you an idea......





You can see the protrusions sticking out where the valve seats are to go. This is for the core prints needed when casting the metal. I'll show them when ive finished them all.





This is the back end. The not so round sections will get the treatment from the filler then cut back into shape. 










The con-rod half finished although this was a dummy run just to give you an idea. the actual rods wont have the holes incorporated into the casting, they will be drilled and reamed. I'm gonna make up a jig for the hole alignment.






Hope you enjoy! Any ideas, questions or criticisms please fell free to comment.

matt+


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## matt-jaysey

Sorry i've kinda missed the point of what im trying to achieve. Im building up scale replicas of each part from models that i've done in 3d on the computer. Ive then built these from card and im going to pour RTV silicone in 2 or more planes, like sand casting. Im then going to pour paraffin wax into the silicone impression to give me a wax model of the head and other components. This will have the cores already incorporated into the silicone before pouring. Im then going to submerge the wax in green sand and turn the sand box upside down and melt the wax away in the oven. Once this is done i'll have a void in the shape of the head. Then in goes the aluminium and bam! i'll have a perfect copy of the head in aluminium.


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## stevehuckss396

Can't wait to see the outcome. Keep the pictures coming!


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## IronHorse

Fantastic idea! I'm going to be following this for sure ;D

IronHorse


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## Jasonb

So if you are using that laminated card as your casting pattern how will you pull it from the sand, you will also need loose pieces, cores, core prints etc and have you allowed for shrinkage. What have you added for a machining allowance on all the machined surfaces, I can't see much if any allowance.

I would have cut it out of something that can be melted away then you can use a lost wax/foam type process.

J


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## matt-jaysey

matt-jaysey  said:
			
		

> Sorry i've kinda missed the point of what im trying to achieve. Im building up scale replicas of each part from models that i've done in 3d on the computer. Ive then built these from card and im going to pour RTC silicone in 2 or more planes, like sand casting. _*Im then going to pour paraffin wax into the silicone impression to give me a wax model of the head and other components*_. This will have the cores already incorporated into the silicone before pouring. Im then going to submerge the wax in green sand and turn the sand box upside down and melt the wax away in the oven. Once this is done i'll have a void in the shape of the head. Then in goes the aluminium and bam! i'll have a perfect copy of the head in aluminium.



1mm was added to the valve cover surface and 1mm (2 sections of card) was added to the head surface. shrinkage is added by layers of U-POL high build primer number 5.

matt+


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## dmac

Watching with interest


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## kvom

Novel approach. The cardboard part in itself is pretty cool.


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## Jasonb

matt-jaysey  said:
			
		

> 1mm was added to the valve cover surface and 1mm (2 sections of card) was added to the head surface. shrinkage is added by layers of U-POL high build primer number 5.
> 
> matt+



Missed that bit about waxbut you need to think again about shrinkage, your primer may be OK on the thickness of the parts but it won't account for overall shrinkage, you need to make evey thing approx 2% larger as the casting will shrink in all directions.

J


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## Nickademusss

This is an interesting way to make castings!
 THe other posts about metal shrinkage are right, my own experiments in casting soft metals like brass and aluminum, show that the metal pulls away from the mold as it cooled, not much bt some, did you make your positive a little smaller so that you final cast will have enough material for machining?

You should also look into the 3D printer, looks like great fun to play with !


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## matt-jaysey

Yes I have made allowances for shrinkage, the casting is 30mm wide, 2% of this is 0.6mm the filler used to even out the texture with the addition of the high build primer adds about 0.8mm each side of the pattern. The model itself was scaled up universally by 102%. This addition also makes allowances for the shrinkage of the wax when it itself cools. The machinable surfaces have 1.5mm excess so they can be planed. Ive done some test runs before doing this version and they range between +0.2mm to -0.1mm out of spec.

matt+


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## John S

Matt,
Colour me impressed, a very novel and unique way to obtain various shapes that may not be related to casting.
From halfway down the first page I was hooked.

John S.


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## Billzilla

Hey Matt, if you're interested I could make most of those parts with my 3D printer.
I've read that the ABS plastic is uses just burns away without any residue when used in sand casting, so it might be a good thing for you. It'll print objects up to about 130 mm cubed.

And my usual car is a 2.5 litre WRX. 


Edit - If you want to see what the printer can do, please send me a copy of something, say a conrod file in .STL format, and I'll print it for you as a sample.


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## Anzaniste

matt-jaysey  said:
			
		

> Im then going to submerge the wax in green sand and turn the sand box upside down and melt the wax away in the oven. Once this is done i'll have a void in the shape of the head. Then in goes the aluminium and bam! i'll have a perfect copy of the head in aluminium.



Here's where I think you will have a problem.

In the days when my company used to make investment castings we used to coat the wax pattern with a ceramic slurry which was then allowed to dry. The dried ceramic covered wax pattern was then baked which had the effect of making the ceramic shell hard and also completely removing all traces of wax by vapourising. The thin delicate shell was then supported in packed sand for the metal to be poured.

With your more direct approach I fear some of the melted wax will soak into the green sand waiting to vaporise violently when the molten metal is poured. I remember as youngster the narrow escape I had when experimenting with casting lead in damp sand moulds. 

It is some years since I was involved so I referred to wikipedia to refresh my memory with reference to terminology. Look up both investment and lost wax casting for a much mor detailed explanation than mine.

Your idea seems to me a super novel way of producing the wax pattern that I shall follow with interest.


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## JorgensenSteam

I am not sure your process for making the cores will work.

I am no casting expert, just a beginner, but it seems like submerging wax in green sand and then heating it will just cause the wax to soak into the green sand and make a big mess.

Many (including myself) use a fine sand mixed with sodium silicate core binder, which can then be solidified with CO2. If you use the correct amount of binder, and a fine sand, you can produce complex cores with very little trouble.


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## matt-jaysey

Thanks for the comments

Its a very good point, but thats what im doing, giving it a go and see what works. Im not sure that the wax will vapourize voilently?! Look at when lost foam is used, this remains in the mould and foam is a polymer. Most of the wax will be melted from the sand then the metal poured. Because of the density of the alumiunium in comparison to the wax the wax should defuse further through the sand and not into the mould, but we'll just have to waiting and see. Im probably going to have to create a custom sand blend for this kind of casting method. 

matt+


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## Tin Falcon

Another non expert but we do have a couple guys here very experienced in lost wax /invesment casting. 
in the reading I have done investment casting is suited to complex shapes. and a smooth finish. 
so that would likely be the way to go.
tin


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## 90LX_Notch

It's been awhile so some of this is fuzzy; as I remember it:

The foundry that I worked in used autoclaves with high pressure steam to melt the wax out. The ceramic shell molds were then fired in kilns to set the ceramic. Plaster molds were baked for days. Both types of molds were preheated before the pours to ensure that any moisture was removed from the molds. Water/moisture is the real "bomb". It flashes to steam and causes violent results (Ceramic and plaster don't make good pressure vessals). Residual wax caused more of a bad casting (voids/inclusions).

-Bob


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## matt-jaysey

Like i said all I can do is give it a go. Obviously being very careful. I have tried this in a simpler fashion before and the casting wasn't very good but that was probably down to the speed and lack of prep. But anyways im gonna have a go and report back with what happens. 

One thing i was thinking of would be to 'spray' the wax with somekind of barrier agent before putting it into the sand. They do this with investment casting, i was thinking something like charcoal or something, not too sure yet. At present the best thing to do is to cast first and work out what needs to be changed in what way. Thanks for the comments though, they are really appreciated.

matt+


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## JorgensenSteam

I think heating green sand will cause it to loose its shape.
It is difficult enough to keep green sand in the proper mold shape without heating it.

Pouring molten metal onto a combustible material such as wax is a sure way to disaster, no doubt about that. (Get lots of life insurance if you decide to use that method.)

Don't forget that the sand has to vent also, and so if you seal the mold with melted wax, then no venting will occur, and you will either blow out the mold, or have tons of holes.

I have seen many play around with custom green sand and various baked core mixes, but often people come around to petrobond and sodium silicate core binder because the petrobond makes for a very fine finish, and does not have most of the gassing problems since it contains no moisture.

The sodium silicate makes a quick and easy core in minutes with no baking, and if used with a fine sand such as 400 grit, it makes a very good finished surface.

Experimentation is good, just don't take chances when pouring molten metal.
It does not like the slightest bit of moisture, or it blows up in your face, so be prepared for that event (full face shield and leather coverings on everything, including the tops of your shoes and your neck).


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## matt-jaysey

After talking with some of you im kinda going off the idea. Can i ask one thing though. I wet my green sand before to make it bondable again when used several times, surely this is adding moisture to the mold when pouring?

matt+


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## matt-jaysey

Just been doing some more research, in loss wax casting, the wax replica in covered in a silica slurry then dipped in sand, this is repeated until a inch thick coating covers the wax. The wax is then heated and it melts away. The silica shell is then cooked for a couple of hours and sometimes water tested to reveal cracks. It is then dried out and molten metal is poured in. The silica shell doesn't vent any gas out apart from afew vent holes and the spru. There's no mention of retained wax, pressure explosions or anything. The silica shell is the only thing stopping the molten metal escaping, but no venting through the actual material. Green sand vents slightly, so this surely wouldn't hinder the casting. The point about heating, i fully understand what you mean but when a cast has been poured, the sand seems to hold pretty firm until you give it a good tap, but thats the same before a regular pour. I not saying any of you are wrong and your words of caution are for my own benefit. Because of this im going to try a very small piece first. Im going to set up a 2 inch deep crucible and rig up and rod operated pouring craddle, just incase it goes pop. I away pour with rigger boots on full apron and face shield, and 2 pair of welding gloves. 

If it goes pop 4 feet away is too close but better than over the top of the damn thing! if the sand doesn't hold then its back to the drawing board or get some silica and start dipping. One other thing. The wax im using melts at around 75 degrees centigrade, which possible might not disrupt the integrity of the sand but i break one apart before pouring my first cast just to have a look. I'll post picture of how this works out. Thank you all for your input.

matt+


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## John S

Matt.
Please keep us informed, I for one are very interested in that i can see a commercial application for this process on parts that cost 5K upwards by conventional means


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## RonGinger

> Just been doing some more research, in loss wax casting, the wax replica in covered in a silica slurry then dipped in sand, this is repeated until a inch thick coating covers the wax. The wax is then heated and it melts away. The silica shell is then cooked for a couple of hours and sometimes water tested to reveal cracks. It is then dried out and molten metal is poured in.



I believe the shell is embedded into a box of sand to support the shell. 

I have done several small investment casting, and have had many made in a commercial foundry. These use the old jewelers process of investing the wax in a plaster like product. The investment cures in an hour or so then goes into an oven where the temperature is raised slowly. After an hour or so, with the temp at about 200 dF the wax melts out. I stand my molds upside down to just let the wax run out into a pan. Then they are placed upright and the temp raised to abut 1200 dF over 5-6 hours. At that point the metal is poured in. You do need to keep a vacuum under the investment to help get the gasses out and the metal in.

This process will result in extremely fine detail look as your wife's jewelery collection to see some of the detail possible.


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## 90LX_Notch

I never suggested pre heating sand molds; that's a whole different animal. The foundry I worked in did lost wax in two different "flavors". One was the ceramic type and the other was plaster of paris with chopped fiber glass. We also did RPM. Rubber Plaster Molding where a silicone rubber pattern is coated in corn oil and placed in a flask. Plaster is then poured around it and once it is sets up the pattern is removed. The corn oil acts as the release agent. These were for centrifugal supercharger impellers.

The ceramic molds never had residual wax because the ceramic and sand molds are fired in a kiln. Any wax is totally burned off. The Plaster Molds rarely had wax residue. Even then it's trace amounts. As stated above, the wax was melted out in an autoclave. Nothing ever exploded from wax residue. 

Water is what you have to worry about. Once it turns to steam the volume increases by some crazy number. Hence the danger of explosion.

It's been a long time since I worked there; so I might not have it all correct. It was a neat place to work but the health hazards were frightening. The sand is Free Silica Sand. Very Bad stuff before it's fired; causes lung cancer. Chopped fiber glass floated through the air etc.


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## JorgensenSteam

Here is a good site for some good casting information, since there are a number of methods covered.

I got into casting recently, and am still early in the learning curve, but as I understand it, the water-based green sand does have water mixed in with it, but it is not a large amount of water, and your venting is much more critical if you use water-based sand.

Pouring molten metal into ingot molds can be dangerous if you don't pre-dry the mold. An ingot mold may look dry, but unless you put it into the flue gases and get it hot, it is not dry, and it may eject the metal into your face. Likewise with any other metal, crucibles, etc. It is not dry until you put it either into the oven or in the flue stream for a while. Crucibles absorb moisture, but you can't see that.

My experience with petrobond (oil-based green sand mix) is that you can get a very fine finish with it, and little if any gassing problems. You do have to mull 30 weight non-detergent oil into it every so often, as it will dry out even though it is oil-based.

I looked at many different methods before choosing petrobond (green sand) casting. 

The whole lost-wax process is too complex for my home shop.
You have to cast the wax, dip the wax into ceramic slurry and then sand multiple times, have a bake-out oven that operates at 1200 degrees to get the wax out, and then you have to break off all the solidified sand/slurry after you are done, and you can't reuse it I don't think.
Your propane usage would probably double with the bake-out.

I really don't have time to spend a day making and baking the molds for the lost wax process. With green sand, I can start the furnace and put in some AL, then while the metal is melting, ram up a mold in 15 minutes, make a core in 15 minutes, be pouring in 45 minutes, and be cooling and trimming the part to size within an hour. Can't do that with any other method that I am aware of.

Accuracy with petrobond and fine sand cores is very good (if you are careful in your setup), and too good to justify lost wax or other methods (for me anyway). Petrobond can be reused repeatedly.

Here is a link with many casting methods examined.
http://www.sfsa.org/tutorials/index.html

Here is a US supplier for casting supplies.
http://budgetcastingsupply.com/

I don't use flux with AL, and you don't need to use flux or degasser if you heat quickly, don't stir, and pour at the right temperature (not too cold).

Pat J


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## matt-jaysey

90LX_Notch  said:
			
		

> It's been a long time since I worked there; so I might not have it all correct.



Thanks for the comments, and im not doubting you in any way, Im just experimenting, this may work (40%) and maybe a total disaster (60%) but if problems arise, which they always seem to do, there maybe a way around them, changing the method/ materials used etc...

Im going to try different temperatures and different sand mixtures im even thinking of using a fire clay based mixture that slightly hardens when heat to melt the wax. I don't know at the moment, just gone do an extra safe test. I'll also video the test for you all to look at. 

Cheers matt+


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## abby

Lost wax casting at home is possible but requires a fairly large investment - excuse the pun - in equipment even if like mine most of it is home made .
I started about 25 years ago and have made thousands of castings for all sorts of applications.
There are many mis-understandings and mis-conceptions amongst these posts but the basic idea for producing a pattern is sound , although having it rapid prototyped would not be too expensive and the finish would be far superior.







A typical mould such as this can contain a hundred or more separate castings which are accurate to a couple of thou and require very little in the way of fettling.
I won't bore you with the subject but if anyone wants more information with regard to lost wax casting you can visit http://www.unionsteammodels.co.uk
Matt if you can make a suitable silicone rubber mould I will send you some wax and see if you get a decent pattern. 
Dan.


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## matt-jaysey

That is an incredible offer, thanks very much. What would you like in terms of monetary compensation? (that was a mouth full!) Do you use a special type of wax or is it just basic paraffin wax? And what do you use to coat the wax with? If these are your own 'trade secrets' then I fully understand. And what is the process you use for removing the wax, i.e. what melting times/equipment do you use? I have a muffler furnace and a small firing kiln if that helps in any way? Thanks again 

matt+


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## matt-jaysey

Had a look at the site, simply brilliant and I advice all to take a peek. The machine wax casting dies are brilliant. Switching green sand for foundry cement is and excellent idea and most probably the one to try first. One question if you don't mind, apart from the main spru is there any other integrated vents? Also the foundry cement (fire clay) has to be broken off? Is this damaging if using aluminium? I.e how much of a beating do the shell need to free the casting? I have a sand blaster already in the workshop (brilliant for cleaning up tired looking cylinder heads) for the remaining fragments. I understand that the fire clay is a one time deal but if i produce 20 heads then the return is worth it. 

many thanks abby 

matt+


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## matt-jaysey

Just thought I'd upload some more pics of some of the cardboard test pieces I did





This is the first one i did, just to see how it panned out. I cut out the wrist pin hole and you can see slight grooves for the piston rings, like I said only a try out.





This is my v8 crank assembly, the clearances were bang on. The rods were 2 piece but I glued them together just to see how well they fit.





You can see how the layers build up.





A rocker cover, although weighty I know (if cast) This was to demonstrate/investigate how well the card + glue could coupe with larger surface areas. The card didnt warp as I thought it might.





And finally a close up.

Hope im not boring anyone, took me bloody hours mind.

matt+


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## ProdEng

It's an interesting looking technique, keep going 

Jan


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## small.planes

Nice. Keep us informed.
 I have done some aluminium casting using Wickes one coat patching plaster, that might be a viable way to lost wax cast. 

Dave


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## 90LX_Notch

Matt,

If all else fails. You could make a cool static model just from the cardboard. Some filler, sanding and paint and it would yield a nice model. It is a very neat technique that you are developing.

Bob


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## matt-jaysey

small.planes  said:
			
		

> Nice. Keep us informed.
> I have done some aluminium casting using Wickes one coat patching plaster, that might be a viable way to lost wax cast.
> 
> Dave



What method did you use and how big was the casting?

Matt+


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## small.planes

It was a couple of wheels for a freestyle traction engine. 
I made the pattern from plastic, about 2" diameter and around 1/2" thick roughly.
I then 'invested' it in a ramakin made of Pyrex ( dont tell swmbo where that dissappeared to)
IIRC, and its about 7 or 8 years ago, I did up to a parting line, then used clingfilm to give a split line.
Melted some vauxhall F10(?) Gearbox casing on the BBQ and poured it in.
The mould had been set for a day or so, and i warmed it up alongside the melt.
The pour was uneventful. Once cooled the part came out clean with very little plaster stuck to it. 
The plaster had changed from a white colour to an ashen grey for about 1 mm depth, and lost its solidity.

I'm not certain of the exact plaster composition, but it was white, and very fine, but didn't set as 'china like' as plaster of paris. I mixed it quite stiff IIRC.

Presented as a how I did it, try carefully at your own risk 

Dave


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## kustomkb

That's pretty cool, what you are coming up with Matt.

Here is a little lost wax casting video;

[ame]http://www.youtube.com/watch?v=wItj5V9a6yY[/ame]


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## Tin Falcon

Cool How thing are made has some interesting stuff. I do find details are often lost or wrong terms used. but when tying to explain an entire process in a few minutes you can only hit the basics they do do a good job of that. 

look up the episode of how golf clubs are made another shell casting video but they also include some design stuff.
Tin


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## Billzilla

*bump* time.
Here's some photos of one of the heads, the file was kindly provided to me by matt-jaysey.  (send me your address, I'll post this to you)
And just out of interest, a compressor wheel. For some reason I just can't get a good photo of the objects I print, in person they look a heck of a lot better than they do in the photos.


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## jasonh

I like making patterns and making castings - more so than whittling parts out of billet material. For complex patterns (that is- ones which push my woodworking capability to the limit) I have contemplated doing what you suggest. ie- Build a CAD model, slice it into thin layers and cut them out of sheet material on a laser cutter. Glue the layers together and your done- almost. Patterns need to be smooth to come out of the sand cleanly and the little steps between the layers would need to be filled in and smoothed or they would tear at the sand. That's quite a bit of hand finishing- and I hate tedious things like that, so I haven't pursued it further. Still - by all means give it a shot. My suggestion would be to start with something small (like a thermostat cover) to validate the concept before you try to bite off a whole engine block.

>But I only want to cast a block and then drill and ream some holes. 

An modern engine block is pretty much the pinnacle of the pattern makers art. It's possible to climb a mountain, but jumping straight to the top is unlikely.

Have fun -jasonh

PS - Having read the other posts it's now clear that your trying some sort of investment casting, rather than sand casting- so you don't have the remove from sand issues. It sounds like plastic 3d printing would be the way to go, but I have no direct experience of such a process.


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## matt-jaysey

Thanks for the massive interest guys. Haven't been on here in ages, major problems at home. Anyways everything's good now and I'm gonna get back onto the project asap. After doing alot of reading, watching of videos and talking to some casting people things have changed slightly and most of you will be pleased to know that you were right and I'm gonna follow your advice. 

I've been directed by 'myfordboy' from Youtube to a sight here in the uk called http://artisanfoundry.co.uk/ this place is great and well priced. I'm going to buy some investment from them and do it the ceramic/sand coating way. Been talking to a guy called sam who works there and he said that wax in a mold will burn and probably mess up your casting but WONT explode. The rapid evapouration of water i.e expansion is what explodes which most of us I gather knew. Anyway, The method of card sticking is going to be modified slightly. I changed were I work and no longer have use of their laser but never mind I'm buying my own shortly. Anyway Happy New Year to all, thanks for reading and I'll post as soon as I have something to tell all. cheers 

matt+


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## matt-jaysey

Right been along time, no excuses. Made some progress and loads of set back, hindsight has 20 - 20 vision.

The problems and some sucesses - and yes I have to bow down to others lol what can I say I'm young and dumb lol

#1 - the card makes life hell. I've now switched to Styrene, cuts perfectly on the laser. 0.5mm is great 1mm ok and anything bigger is shabby. The quicker the cut speed the better, until you hit the wall and it won't go all the way through. I've found that multiple passes are crap so stopped doing that instantly.

#2 - Don't glue the entire pattern at once, can't get into the deep recesses. So will have to build lower section then smooth out with filler and continue. Worked really well the second time.

#3 I found using PVA/wood glue added thickness over 100 layers by 0.8mm which throws everything slightly out. I've switched to humbrol airfix glue, tiny drops with the nozzle type applicator. Melt the styrene together, works a perfectly.

#4 - bought the investment stuff from artisanfoundry, great stuff, been casting toy solders just to get used to how it works. The temperature is a massive concern with investment and i mix it all together in a sacrificial blender i bought from tescos to mix it properly, very important.

#5 - Used one of the piston from the previous cardboard version - which i need to clarify was a proof of concept model not the actual product. Played with the RTV silicone molding stuff - need to build a vacuum pot - got myself a vacuum pump and going to purchase an old pressure cooker pot and some perspex. Anyways poured some melted wax inside and turned out ok apart from the bubbles - again need a hot wax injector, got my eye on one so waiting for funds to build up lol aren't we all.

#6 - As for the piston test run the shrinkage was around 8% until I bought some machining wax from artisan, fantastic can't get a repeatable shrinkage reading over 15mm so all good and it smells like old machinery! which is an added bonus. Been playing will melting zinc, although its really hard to find in large quantities even the alloys. Boat anodes cost a fortune, wheel weight you can't be sure what the alloy is, problem is in the states 17lbs for $15 off amazon, i hate this country. United stated please take me away.

Anyroad, i'll take some pictures and track my progress a little closer from now on.

Matt


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## Lakc

Thanks for the update, and watch out for those zinc fumes. Water heater anodes would probably be cheaper, boats = $$$.


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## matt-jaysey

Lakc said:


> Thanks for the update, and watch out for those zinc fumes. Water heater anodes would probably be cheaper, boats = $$$.



Yeah thats what I thought anything to do with the boat scene they automatically add 200% lol And thank for the warning, I had the extractor and my 3M chemical respirator on at the time, I make a point of looking up what anything does when you heat/weld or melt it. Similar to Lead, i read that melting it can produce lead monoxide which can be fatal if inhaled.

Thanks again


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## Desmo

Matt, any electroplating business should be able to supply you with zinc billets at a reasonable price, specifically those that sell DIY plating kits.


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## bigscale

I wish I had your skills and availability to equipment and the knowledge to operate them. See my attempt at a model engine on bigscale. Rob


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## bigscale

It's all about the lighting!!!!!!! Try turning off the flash and use separate lights. Sometimes day light works best, depending on the time of day. A white object can be difficult to capture;it shows up "hot" and washed out.  Rob


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## matt-jaysey

bigscale said:


> I wish I had your skills and availability to equipment and the knowledge to operate them. See my attempt at a model engine on bigscale. Rob



Thanks for the comment, but i think 'skill' is pushing it abit lol more like 'keep going until something explodes or someone who is skilled bollocks me and shows me how to do it properly' lol


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## Chiptosser

Giving This a bump!     I would like to know if know this is an ongoing project?


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