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Home Casting in Mazak

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John Wood111/08/2009 13:51:25
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116 forum posts
I came across an article in ME No. 3650 for February 1981 entitled 'Simple Castings' which details the use of Mazak alloy (monkey metal?) commonly used in the production of motor parts such as carbs, fuel pumps, motorcycle housings, old car door handles etc. This stuff can be found in junk piles and will readily melt on a domestic gas ring or workshop torch. Because of its relatively low melting point it seems one can use simple moulds and patterns made from wood, tin lids etc.
 
I havn't yet tried casting with it but have just acquired a couple of old fuel pumps to strip down and use so will have a go soon.
 
Has anyone any experience of using this stuff?
 
Cheers,  John
Tony Case30/08/2009 12:42:03
1 forum posts
I did some of this many years ago, the main thing I found was not too mix the material up. Motorcycle carburetor bodies are not the same stuff as car door handles and most motorcycle parts are not Mazak at all. I got the impression that quite different alloys were used for the various components, no doubt for some very good reason that wasn't apparent to me ! If you do mix hem up you will probably end up with something like very hard porridge. Don't mix them up, don't overheat them and try to find an appropriate flux, the stuff I used came in an "unmarked brown wrapper" from a guy in the trade. TC
Michael Gray30/08/2009 18:12:48
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One very important point - do NOT mix magnesium alloys in with any other!
The magnesium can and will start burning and you will NOT be able to extinguish it.
Test each piece with some dilute hydrochloric acid, if it fizzes then run, do not walk, to the nearest large hole in the ground and throw it in.
 
Remember too, that when adding more bits to your melt, that every last drop of moisture must be gone.  Steam occupies 1200 times the volume of water it came from.  Believe me you do not want to be around a shrapnel blast of molten metal.  Don't ask me how I know!
 
Before moving into an apartment I used to do a lot of casting with ZA12 - a lovely zinc-aluminum alloy with properties very useful to model engineers (as well as many others) - and had no difficulties at all, so long as I followed some simple rules.
 
regards, Mike

Edited By Michael Gray on 30/08/2009 18:14:18

mgj30/08/2009 19:29:46
1017 forum posts
14 photos
Water/damp. Also applies to whatever you are using as a mould.  Must be bone dry.
Michael Gray30/08/2009 22:30:08
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Meyrick, sorry to disagree with you and not trying to be a smart-a**e, but I did all my casting using "green sand" which is around 8% moisture, just to hold the sand together.  If your mould is properly vented then you'll only have some steam coming out when you break the mould open.
regards,
Mike
Wessexman30/08/2009 23:04:32
28 forum posts
5 photos
Some differences of opinion here - firstly it is extremey good practice to remove all moisture / oil / paint etc from any scrap charging material. This is due not only to the fact of avoidung a potential eruption but also to minimise gas defects within the resultant casting caused by hydrogen gas. Secondly Greensand is not bonded with water but uses water to activate the bentonite clay used in commercial foundries - natural clays such as illites and kaolinites may be used but are not optimal. also in our commercial foundry Greensand moulding line we would never use 8% moisture - good bonding is achieved at around 4-5% moisture. The water is not in a free state but incorporated into the clay mass. Venting is essential to exhaust not just the resultant steam but any and all the volatiles in the moulding sand and especially core sand.
 
Best regards
 
Keith 
mgj30/08/2009 23:32:38
1017 forum posts
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Not an expert at all in casting - merely an observer on the Defence QA side. Armour castings, engine blocks, and one or two other funny things in funny materials.Some of the larger single crystal stuff and some of the exotics being cast under argon.
 
I should apologise if I used the term "dry" loosely - I am familiar with mould construction. I was really referring to "liquid" or "spare" water. which can also lead to hydrogen embrittlement in those materials prone to it.
 
Could I reword that to say that ones process control in making a mould needs to be up to speed with respect to both design and material content, or the pouring process can be frustrating at best, and very interesting at worst?
 
As an aside, but it does show what a bit of water can do. We had an embrittlement problem in ferrous armour welds. No one could track down the problem source. In the end it truned out that they were using the rod drying oven to heat their pies, which gave off steam which got into the rod coating, and since welding is a casting process....... Water control is quite important in castings, even as vapour in small quantities, which is why the MOD specs controlled the amount of water to be used in moulds very closely indeed. 
 
 

Edited By meyrick griffith-jones on 30/08/2009 23:40:43

Edited By meyrick griffith-jones on 30/08/2009 23:47:40

John Wood105/09/2009 15:32:22
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116 forum posts
Seems like a bit of a minefield then! it's difficult to identify the different alloys when all you have are old castings which look very much the same. I realise now perhaps why such a seemingly simple process has not really caught on in the amateur field, which is fair enough.
 
I will have a bit of a go though, bearing all the above advice in mind, but I will make sure and use only a single casting at a time for my material.
 
Many thanks to one and all
 
Regards  John
Lykle Schepers25/09/2009 08:15:07
7 forum posts
3 photos
Hello all
 
Hmm, sounds like the difficulty is in determining what material you are holding.

So what are the ways I can find out what material it is? For Magnesium, use the acid test, but the rest?
 
At the moment I am using broken up alloy wheels as I know that this model is not made from magnesium, but I also have some stuff that just might be Mazak or such stuff.
I think that it would be very difficult to use melting temperatures as the determining factor so is there a fail safe way?

Lykle
Alex du Pre14/02/2010 10:12:30
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24 forum posts
31 photos
Hello everyone! Some useful tips in this thread.  I have been wanting to experiment with aluminium alloy castings for a long time and was wondering if anyone had any experience or views of making the moulds out of plaster of paris or similar, for small castings, particularly with regard to whether it is compatible with alloy casting.  It strikes me that this would be less hastle than sand castings, potentially give a better-defined casting and give moulds that could be reused several, if not many, times.
 
I believe a similar approach is used in investment casting (?) and I can't see why it wouldn't work provided the mould was thoroughly dried out and had the relevant draught angles, vents, etc.
 
Any thoughts would be most welcome.
 
Best regards,
 
Alex.

Edited By Alex DU PRE on 14/02/2010 10:13:13

Les Jones 114/02/2010 10:41:30
2292 forum posts
159 photos
Hi Alex,
             There is a forum on the Yahoo forums that deals with metal casting.
Using plaster for moulds has been discussed but I can not remember what the advice was from experienced members of the group.
Hope this helps.
Les.
Ian Abbott14/02/2010 17:52:32
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279 forum posts
21 photos
Saw an article on casting with silicone moulds recently, can't remember where though, may haver been ME, but I'm not anxious to to dig in the big cold pile in the utility room for it. Anyone remember seeing it?
 
Ian 
Stub Mandrel14/02/2010 18:10:15
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4318 forum posts
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I played around with some bits of a mazak pulley wheel of a washing machine.
 
It was weird stuff, it melted but stayed inside a 'bag' of oxidised material that haf formed on the outside of the part. I couln't make anything useful as the surface tension was so great it didn't flow into corners.
 
I think zinc fume can be an issue with mazac as well, so plenty of fresh air.
 
Neil

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