Aluminium manual die casting technique....

[axis_control]

Hi,
here are some pics of aluminium casted in a PDC machine.

my querry is, can aluminium upto 60 grams be die casted using manual pressure ? remember the fine finish achived using centrifugal casting technique for jewellery making. I guess manual aluminium die casting should be as good.

may be a manual machine where once the laddle filled with molten metal is loaded into the shot, then a human plunges the shot piston using a lever system & the molten metal is transfered into the die to be casted. just like the industrial pdc machines , but on a very small level.

I am asking this because i want to cast aluminium pieaces of a scale model chopper bike & the parts have very fine details + the number of bikes is limited to 100 pieaces. getting them cast in a pdc machine would be an expensive affair & no one would agree to set up a die for 100 pieaces on their pdc machines.

Has anyone tried this before?.

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[handlewanker]

Hi, die casting is usually for a hundred thousands parts, hence the expense of having a die made.
For a 100 parts I'd use lost wax casting.

This is in the region of DIY capability with a small electric or propane furnace for the melt, whereas the diecasting set-up is not user friendly due to the technique of getting the molten metal into the die etc.

There was a design in the Model Engineer magazine some years back where a guy made a small press like device for making small diesel engine pistons in aluminium alloy.

The device had a vertical plunger that was removed to pour the metal in and then the plunger was quickly reinserted and a lever used to force the metal to fill every detail in the cavity.

As the cavity was for pistons, the design was fairly simple, with machining to finish them off later.

If a complex shape was being considered, then it would need someone with an EDM set-up to spark out the design, or a pantograph machine.

If time is no problem then there is a small EDM design, that is also in the Model Engineer, and is capable of being made and used to do quite serious work by the average DIY'er with some electronic knowledge.
Ian.

[axis_control]

There was a design in the Model Engineer magazine some years back where a guy made a small press like device for making small diesel engine pistons in aluminium alloy.

The device had a vertical plunger that was removed to pour the metal in and then the plunger was quickly reinserted and a lever used to force the metal to fill every detail in the cavity.

As the cavity was for pistons, the design was fairly simple, with machining to finish them off later.

If a complex shape was being considered, then it would need someone with an EDM set-up to spark out the design, or a pantograph machine.

If time is no problem then there is a small EDM design, that is also in the Model Engineer, and is capable of being made and used to do quite serious work by the average DIY'er with some electronic knowledge.
Ian.

Thank you for the reply...

The machine built by the guy must be a non ferrous metal forging machine. Even today almost all piston`s are made using the same process.

My parts are complex but can be done in a two part die (male-female). their thickness is from 1mm to 10 mm. If i get the die done & use the manual mold fill technique as discribed by me earlier, do u think i will achive a good finish on the aluminium?. I don,t think its necessary to use couple of 100 tons of pressure to achive that.

wow!..i have always wanted to build my own spark erossion machine..:rainfro: please please tell me where can i find that design for the EDM.

[dang]

Hi,

Currently, I do Aluminum Gravity Die Castings in my backyard. Basically, I make a steel die on my mini mill. This die is built out of several different pieces of steel. After it's cut, I then polish the die to a mirror like shine and weld those pieces together.

When the die is finished, I melt the aluminum and simply pour it into the die. Gravity does the rest. The die is clamped together with simple screw clamps. I also use sand cores. The actual solidification of the Alum takes about a minute inside of the die. The surface detail is really good.

This is for larger parts.

Knowing what I know now, I'd do a few things differently.

1st I'd use Graphite for the actual mold structure. It's easy to cut. Waaay easier than steel is. I've seen people use a freakin Dremel to cut the stuff. It's permanent. It'll take the heat.

2nd, I'd cast using Zinc or Zamak instead of Aluminum. Especially for smaller parts which are mass produced. It has a lower melting point than Alum does, it requires about 2/3 of the energy expenditure to melt, and can deliver many of the same features. At least for non critical parts or those that don't require low weight and high strength. Oh, and if the mold is to be clamped shut, you'll find that the smaller die casting machines (200 ton and under), ONLY use Zinc. Aluminum is hotter and requires more force to keep the clamps shut tight. I believe that this high clamping pressure is so the machine can handle very large parts or molds. Also, repeatability and reliability is a big concern.

With that said, I'd skip the EDM machine all together. I'd build the molds on a small CNC mill that's enclosed to limit my exposure to nasty Graphite dust. That'd probably be best for a smaller operation.

I've also run across that homemade die casting machine article. It wasn't that impressive. Frankly, it looked a little dangerous to me. The molten material wasn't enclosed, that material was also manually fed, from a height, which is a dangerous lift all by itself. I wouldn't use it.

[axis_control]

Hi,

Currently, I do Aluminum Gravity Die Castings in my backyard. Basically, I make a steel die on my mini mill. This die is built out of several different pieces of steel. After it's cut, I then polish the die to a mirror like shine and weld those pieces together.

When the die is finished, I melt the aluminum and simply pour it into the die. Gravity does the rest. The die is clamped together with simple screw clamps. I also use sand cores. The actual solidification of the Alum takes about a minute inside of the die. The surface detail is really good.

This is for larger parts.

Knowing what I know now, I'd do a few things differently.

1st I'd use Graphite for the actual mold structure. It's easy to cut. Waaay easier than steel is. I've seen people use a freakin Dremel to cut the stuff. It's permanent. It'll take the heat.

2nd, I'd cast using Zinc or Zamak instead of Aluminum. Especially for smaller parts which are mass produced. It has a lower melting point than Alum does, it requires about 2/3 of the energy expenditure to melt, and can deliver many of the same features. At least for non critical parts or those that don't require low weight and high strength. Oh, and if the mold is to be clamped shut, you'll find that the smaller die casting machines (200 ton and under), ONLY use Zinc. Aluminum is hotter and requires more force to keep the clamps shut tight. I believe that this high clamping pressure is so the machine can handle very large parts or molds. Also, repeatability and reliability is a big concern.

Sorry to reply late...was a bit busy

I loved reading your reply as its informative & also has arrowsed a few questions in my mind.

i really want to see some pics of the aluminium part surface that u casted in ur built die:rainfro: i have seen lot of pdc casted & centrifugal casted pieaces (lost wax) of aluminium , but never seen or handeled an aluminium pieace that was gravity casted that to in a metal die.

do u use this die for continious production or couple of pieaces ?.. also do u have a water cooling system in ur die?

About grafite ..I din know it can be used for molds & that to for casting of metal. I do know that it is used to make electrode for spark erossion die making process. now i will find out more info on the grafite mould technique, looks intresting & logical. I will also keep in mind about using zinc, but again my product is a scale model (show pieace) & demands excellent crome plating. I remember reading a table saying zinc has better plating properties than aluminium.

I will design a CAD model concept for the manual die casting machine & post the pic here soon (it might take couple of days) i would want to have sugestion on it.

Thanks for your reply !...cheers

[handlewanker]

Hi axis, you're right about the zinc taking chrome plating better than ally.

I used to work in the door furniture (locks,handles etc.) industry, and all of the components were made of zinc or brass.

The zinc stuff had the flash from the mold split removed, and the surface was then polished using various graded grit abrasive belts, and a final soft mop with a white waxy polishing compound to get the bright polish required for chrome plating.

If you're contemplating having the parts plated straight from the mold, it won't work.

The die casting, although giving a very smooth finish, still requires abrasive taping and bright polishing to get the finish for chrome plating, otherwise it has a dull fine pebbly finish.

A polished and chrome plated item has a MIRROR finish that will reflect clearly like a mirror.

We tried a vibro finishing process, where the parts are shaken up with abrasive pebbles, in a vibro finishing machine, especially formulated and shaped to get into the crevices, but they never came up to the finish of hand polishing.

You can cast anything by any method but the surface finish reflects the method used, and the pressure die cast method still isn't good enough to get highly finished items without further polishing, ask anyone in the tap ware industry.
Ian.

[handlewanker]

BTW, graphite is worse than cast iron for mess and if you have to use the stuff, use a good respirator and a vacuum cleaner.

If you want to have the EDM plans for a small home built EDM then give me your email adress and I'll send the direct.
Ian.

[dang]

I'd have to agree about finishing being the most important step toward getting a good shine. Although it can take up alotta time, polishing before any sort of plating is extremely important.

On my steel molds, I used Diamond Polishing Paste that goes all the way up to .5 Microns. I still see inclusions in my castings from stray bits of the sand core as well as translation (mold to casting) scratches that I couldn't see even after I polished the mold interior.

For my part, I'm gonna be attempting to build a vibratory deburring machine in the near future. Like this one, http://www.cnczone.com/forums/showthread.php?t=14464
Hopefully it'll knock most of my casting's scratches and burrs.

For parts as defined and intricate as those being discussed here, I think some Diamond Paste like I used on the molds would work fine. It's available on Ebay.

And regarding that graphite mess, I'm totally gonna use a vacuum, maybe two, and an enclosure. The dust is really dangerous and shouldn't be underestimated.

[handlewanker]

Hi, no matter how good the mold is, the parts still require polishing to a mirror finish using Tripoli polishing compound on the mop if you want to have a mirror chrome finish.

If you cut down on the preperation wysiwyg for chrome finishing.

BTW, the best vibratory finishing cannot approach hand polishing unfortunately, and only gives you a dull sheen like the shine on alluminium foil, shiny but not mirror finish.
Ian.

[axis_control]

If you're contemplating having the parts plated straight from the mold, it won't work.

The die casting, although giving a very smooth finish, still requires abrasive taping and bright polishing to get the finish for chrome plating, otherwise it has a dull fine pebbly finish.

A polished and chrome plated item has a MIRROR finish that will reflect clearly like a mirror.

You can cast anything by any method but the surface finish reflects the method used, and the pressure die cast method still isn't good enough to get highly finished items without further polishing, ask anyone in the tap ware industry.
Ian.

Hi Ian ,
Thank you for your reply!.

I agree that the parts won’t get a mirror finish if I directly plate them after casting without any processing. I am thinking of using a die grinder & felt bobs.

What r ur views of building a small manual pressure die casting machine? The parts to be cast r not more than a volume of 25cc (may be I will try zinc) it might come upto 60 grms max. Here once when the metal is fed into the shot by a ladle , a person using a lever arrangement pushes the piston to force the metal into the die. The whole system works just like the industrial pdc machines, only that here the machine size is very small & hydraulics is replaced by human mussle. The machine would also be horizontal like the industrial pdc machines.

The tap ware industry is definitely the place where I can get exact knowledge about excellent finishes. Your replies reflect the same.

[axis_control]

BTW, graphite is worse than cast iron for mess and if you have to use the stuff, use a good respirator and a vacuum cleaner.

If you want to have the EDM plans for a small home built EDM then give me your email adress and I'll send the direct.
Ian.

I have never worked with graphite & have got more advice`s regarding the safety issue. I surely got to be careful if i am using it.

regarding the EDM plans , i have pm u my email id.
Thanks a lot!

[axis_control]

For parts as defined and intricate as those being discussed here, I think some Diamond Paste like I used on the molds would work fine. It's available on Ebay.

if i have those casted in aluminium or zinc ...would only Diamond Paste polishing work?.. should i need to buff them before DP polishing ?

Here i have attached the pics of the part to be casted.Its an harley scale engine. The CAD modelling is not yet complete.
The engine would be casted in two parts split from the centre right upto the gear box. The fins on the engine block r 1mm in thickness & the groves r upto 2mm in depth. The engine is 60 mm high.
I visualize an excellent mirror finish on the finished product. now i wonder how much time will it take to polish a single pieace using a die grinder.

[dang]

The idea for a manual casting machine is a good one. But that's not why you called. Those parts are a bit more intricate than I believe manual gravity casting can manufacture. Maybe even with a shot sleeve and a low pressure injection system. You may want to send those files to a mold and die maker to see how much a proper mold would cost to build. You may also want to send them to a Die Casting Shop to get quotes there as well.

After all, design and manufacture almost always depends on cost vs reward.

All that said, I'd still build the low pressure injection system. You never know, it might work for this project. It'll certainly work for another. Make sure though, that the shot sleeve is detachable. They're the most often replaced parts on the large professional die casting machines.

[axis_control]

Those parts are a bit more intricate than I believe manual gravity casting can manufacture. Maybe even with a shot sleeve and a low pressure injection system.

After all, design and manufacture almost always depends on cost vs reward.

All that said, I'd still build the low pressure injection system. You never know, it might work for this project. It'll certainly work for another.

Make sure though, that the shot sleeve is detachable. They're the most often replaced parts on the large professional die casting machines.

I have seen centrifugal jewellery casting & the end result are pretty good even when casted in plaster of paris & the pressure hardly being 10 times the weight of the metal. I think when i am using a metal die & rapid cooling with atleast 50 kg of force , i should be able to achive this. (my judgement is only from what i have seen & not done technical calculations yet)

I had been to the PDC shop & they told me that uploading a die for a few hundred pieaces is not at all economic for them as well as for the customer as it takes more than an hour or two to just set the die on the machine. They need a daily requirement of atleast 1000 pieaces a day. so this is not for me as my requirement is not that high. Hence i am going for an alternative.

yes i would design in a way where the shot sleeve is easily detachable.
You have a good knowledge about PDC machines....how come?

[dang]

Research. That's why. I had to, and still do tons of it.

Well, I found a couple of links that might interest you.

http://www.muller.net/mullermachine/docs/case_num.html

And my personal favorite.

http://villagecast.com/MoldMach.html

That low pressure die casting machine looks more and more possible every day! I have a setup similar to the one shown in the photo. In that photo though, they left out the assorted hammers and pry-bars, chewing gum and bailing wire which is vital to any gravity die casting operation. That's corporate business for ya. Always churchin' up their appearances, making everything look so darn easy.

[handlewanker]

Hi Axis, I think If I were contemplating making intricate parts like these I'd use the centrifugal casting process.

A DIY pressure die casting set-up is, even at a very basic level is too complicated whereas the centrifugal method is quite common for relatively low volume work.

I have some information somewhere that shows the molds made from silicon rubber for casting zinc based alloys.

The molds are made from a master pattern and assembled on a rotaing plate fed from the centre and rotated at speed to give the mold filling capacity.

As far as I can remember the finish is very good as far as detail is concerned.
Ian.

[axis_control]

That low pressure die casting machine looks more and more possible every day! I have a setup similar to the one shown in the photo. In that photo though, they left out the assorted hammers and pry-bars, chewing gum and bailing wire which is vital to any gravity die casting operation. That's corporate business for ya. Always churchin' up their appearances, making everything look so darn easy.

Thanks for those links dang...
wow!....u r already building ur own LPDC machine?:rainfro:

[axis_control]

A DIY pressure die casting set-up is, even at a very basic level is too complicated whereas the centrifugal method is quite common for relatively low volume work.

I have some information somewhere that shows the molds made from silicon rubber for casting zinc based alloys.

The molds are made from a master pattern and assembled on a rotaing plate fed from the centre and rotated at speed to give the mold filling capacity.

As far as I can remember the finish is very good as far as detail is concerned.
Ian.

Yes u r right, that the the pdc setup is complicated at a very basic level too. Its just that i am willing to get a good surface finish from the castings & hence i opted for low pdc machine.I know compared to centrifugal casting i will have to invest less time in polishing the low pdc casted parts.

I had herd that there r some kinda black colour hard rubbers available (not sure if silicones) that can be used as mould for casting metals with low melting point, but never got any info above this.There is a company called DOW Corning which sells silicone products here. Can u please forward me the link to the information regarding the rubber moulds for metal casting....this could be the key against the lpdc machine

Thank you!..cheers!
regards,
Pradeep

[axis_control]

I just found this link Ian

http://www.michtoy.com/MTSCnewSite/s.../castingx.html

there is a part where the owner explains that they r selling special metals that can be casted at 160 degree F

here i copied the whole part

Low Temperature Casting Metal Alloys
CAST YOUR OWN METAL PARTS WITH THESE LOW TEMPERATURE ALLOYS
Now you can cast metal parts with fine detail with our complete selection of casting metals and materials. No foundry is needed - just melt the metal in a ladle held over a flame and pour into a silicone rubber mold. Save money by casting your own ship fittings, miniature figures, toy wheels, dollhouse hardware, model railroad detail items and much, much more...and have fun doing it!
#80962 Type 160. Tin/lead/cadmium/bismuth alloy. Melts at approximately 160° F. Can be melted with a candle flame. Extremely low temperature allows this metal to be poured into molds of clay, wood, even cardboard. Can also be poured into model RR locomotives to increase traction weight. Keep away from children. One 11.4 oz bar (approximately 3/4” x 1 1/2” x 1 7/8”)......................$14.95
#80960 Type 280. Tin/bismuth alloy; lead and cadmium free. Melts at approximately 280° F. Can be melted with small butane torch. One 11.4 oz bar (approximately 3/4” x 1 1/2” x 1 7/8”)......................$14.95
#80963 Type CT. Almost pure lead. Melts at approximately 500° F. Can be melted with propane torch (plumbing type torch sold at hardware stores). Keep away from children. One 22 oz bar (approximately 1 1/2” x 1 5/8” x 2”)...........................$8.95
#82319 Type R. Lead-free crown pewter (92% tin). Melts at approximately 575° F. Can be melted with propane torch (plumbing type torch sold at hardware stores). One 21 oz bar (approximately 1 1/2” x 1 5/8” x 2”)...........................................$1 9.95

i will be doing some research on this today...this could save me a lot of expenses:rainfro: & make the whole thing lot easier..

[dang]

That low temp alloy might work for you. It looks a bit on the expensive side though. Anyway, I'm not building the LPDC Machine yet. I emailed the owner of the site and got a price. Frankly, that price was more than a little bit higher than I'd imagined. Still a good idea though.

Axis, I'd definetly look into that Centrifugal Casting that Handlewanker mentioned. For parts that are as small and as detailed as yours need to be, it might just be the thing. If you look at the 1st link I provided, you'll see 3 different casting techniques documented on miniature engines built by Kawasaki. Engines with 1mm thick heatsinks. Some techniques don't do so well at the micro level.