# Casting vs. Machining



## Finbar (Dec 29, 2004)

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## idleprocess (Dec 29, 2004)

Casting requires tooling whereas short-run machined lights just require setups.

Sand casting seems to be best-suited to large and/or irregularly-shaped parts made in quantity. Post-casting processes are needed to finish surfaces and to obtain precision thru-holes, threads, critical geometry, etc.

Perhaps there are some other casting methods out there that I'm not familiar with, but everything I've heard about casting leads me to believe that it's best suited for really large-scale production and requires large investments in tooling.

Given that industry turns out millions of tons of precision round/tube stock per year, the relative ease of lathe setups, and the popularity of the cylindrical flashlight, lathes are a natural. Lathes seem more accesable to the home metalworker than a foundry.


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## gadget_lover (Dec 29, 2004)

There are actually a lot of web pages about home foundry setup. They are fairly cheap, but.....

I can convince my wife that it's OK to have a lathe in the garage. When I mentioned a small furnace for melting aluminum she had a fit. And my wife is VERY understanding.

There's something about pouring melted metal that seems less safe than turning it.

Daniel


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## XtremePyro (Dec 29, 2004)

Ive melted a fair bit of aluminum in a small cobled togeather charcoal fired foundry. Not really all that more dangerous than 
anything else, that is if you take the proper precautions.
But for making flashlight bodies, there would be too many drawbacks to make it a viable alternative to turning one on a lathe. First unless you have a really high tech foundry, your going to be pouring almost pure aluminum without any of the minor alloys that help strengthen it. Cast aluminum dosnt machine the best in the world either. However lots of sanding and polishing result in a mirror slick finish better than be optained on say 6061. Which is why I cast a few chuncks the ther day to try my hand at machining some 2" reflectors.
Casting defects is another drawback. The more intricate the part, the more defects would be a problem. Then if you did get a decent result finishing would be a problem. Cast aluminum dosnt anodize the best. It can be done if a desmut/deox is used, but your still not going to get as good a result as you would from using cold rolled bar stock.
But dont let that discourage you. If you dont have a lathe and you want to mess around melting some aluminum, its allot of fun. Just remember with something that hot allot can hapen in very little time.

Tim


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## Finbar (Dec 29, 2004)

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## KC2IXE (Dec 29, 2004)

RE Ruger and Castings:
A lot of folks don't realize it, but casting was Bill Ruger's trick to providing an affordable rifle

It is to the point where Ruger actually makes more money making castings than firearms

About 15 years ago, I used to work for an electronics company that made power supplies. The "frame" of these power supplies were CNC milled out of a BIG block of aluminum - and more than 60% became chips

We went to Ruger - yep - they could cast the frame well enough that about 80% of the features didn't need to be machined to hold tolerance, and we could post machine the rest. Nice stuff - all lost wax - had a damaged lost wax patern on my desk for a long time

BTW they also do almost all the Ti castings you see. Can't talk about some of the stuff that they were casting (they asked me not to), but I can say that there were major parts of various missles that were Ti Castings done by them

Seriously? You want GOOD castings - call up Ruger


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## Finbar (Dec 29, 2004)

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## jayflash (Dec 29, 2004)

As a child I poured hundreds of lead soldiers without safety goggles or gloves and only received one little scald. I got the kit when I was only seven years old - waaay before OSHA, lawsuits, and lead poisoning was feared. Maybe it's the Pb in me that causes the voices, visions, vibrations, and vices. /ubbthreads/images/graemlins/evilgrin07.gif

Happy smelting.


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## KC2IXE (Dec 29, 2004)

[ QUOTE ]
*Finbar said:*
...snip...
My only problem now would be how many units that would be required to make a production run.
...snip...

[/ QUOTE ]

Might be a lot lower than you think - I know that our product runs were in the rough order of 100-150 per year. They were NOT making master molds for us - they used a machinable wax, and made the masters that way!!! It's just a lot cheaper to machine wax (where they can remelt the chips) than a 6061 block 19"x9"x8" and throw 60%+ percent of it away


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## tvodrd (Dec 29, 2004)

There is lead stuck to the ceiling in my garage from recycling bullets recovered from my "range" out in the desert. Get one with a little moisture trapped in it and it blows lead all over the place. /ubbthreads/images/graemlins/icon15.gif Damn good thing I'm 4-eyed! (Wear glasses.)

Unless flashlight parts get a lot larger, castings won't find their way into your typical flashlight. The lost wax process could be used for "artistic" lights, and there are custom jewelry outfits that are happy to take your wax pattern and return it to you in gold or silver. (Search amateur jewelry making.) The process is capable, when combined with centrifugal processes, in the right metals, of producing usable threads if the "shrink" is figured right.

Other casting processes like sand casting, permanent mold casting and liquid injection molding are available, but all have drawbacks exceeding their benifits for a typical flashlight. Even for Mag, which prides themselves in holding costs stabile and has the capital, I don't think casts anything.

Oh yeah, zinc alloy die-casting. Used for things like carburators and auto door handles. (If you predate EFI) Would you want a "pot-metal" flashlight? /ubbthreads/images/graemlins/grin.gif

(Just adding some _noise_ to this thread, based on a bunch of years in manufacturing engineering mostly with molded plastic stuff.)

Larry


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## HarryN (Dec 30, 2004)

Casting is certainly feasible. A few points - you will need to carefully look at the alloy selection. Most castable Al alloys are not nearly as strong, tough, or hard as even 6000 series Al. They also tend to have Mg and Cu in the alloy, which makes anodizing certainly more complex.


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## idleprocess (Dec 30, 2004)

Gotta love cheap molded zamak (zinc-magnesium) fittings - about half as much as aluminum and are less than half as strong!

I had no idea that there was "machinable" wax out there - I keep thinking about all wax being as stable - mechanically, thermally, and dimensionally - as, well, a candle...


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## KC2IXE (Dec 30, 2004)

[ QUOTE ]
*idleprocess said:*
...snip...
I had no idea that there was "machinable" wax out there - I keep thinking about all wax being as stable - mechanically, thermally, and dimensionally - as, well, a candle... 

[/ QUOTE ]

Oh yeah - machinable wax feels a LOT like slightly slick plastic - very cool stuff. A lot of CNC shops keep a block or 2 around - it's perfect for proofing your programs - if you crash a tool - the part gives instead of breaking a tool, or worse


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## CNC Dan (Dec 30, 2004)

The cost for makiing a mold for die casting will run into the $10,000 range.

Best bet is a jewelry caster. Many things can be made with good detail with lost wax. But I wouldn't give up on machining just yet. If you have a good 'print you should bring it to a few machine shops for quoting.


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## KC2IXE (Dec 30, 2004)

Dan,
NO one was talking die casting - like I said, we did lost wax, in a machine shop - Ruger would machine lost wax casting wax in a CNC, invest it just like a jeweler would, burn it out, and lost wax cast the frame - they do lost wax castings that are longer than 6 ft long!


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## CNC Dan (Dec 31, 2004)

[ QUOTE ]
*KC2IXE said:*
Dan,
NO one was talking die casting - like I said, we did lost wax, in a machine shop - Ruger would machine lost wax casting wax in a CNC, invest it just like a jeweler would, burn it out, and lost wax cast the frame - they do lost wax castings that are longer than 6 ft long! 

[/ QUOTE ]

But he said that the shape couldn't be machined. So how would you machine the wax pattern? And if you could machine the wax pattern, then you could machine the part to start with.


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## McGizmo (Dec 31, 2004)

Some small and intricate metal parts ae best made from powdered or sintered (sp) metal. Technology is making some great advancments in how various parts can be formed but this is beyond the scope of this thread I suspect as the tooling and equipment go well beyond the home shop.


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## KC2IXE (Dec 31, 2004)

Well, they can do things like machine multiple parts, and actually attach the wax to itself - effectively glue the parts together, With lost wax, you can combine machining and fabrication, and then make the mold and go

It's wild stuff


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## kenny (Dec 31, 2004)

There are a lot of ways to do this, but the first anything is where the money is the biggest. There are several ways to do rapid prototyping, which is kind of what you are talking about. They even have 3D printers where you can make a 'burnable' part that you can use as a lost wax-type process just as you would when using a wax. Any special one-off, or low-production items ARE going to be relitively expensive, Even if you do your own 3-D modeling work, the electronic data has to go to either a programible lathe (and if I'm not wrong, somthing that may be capable of a little milling as well), sterolythography, or other rapid prototyping equipment. Realistically, none of this will be cheap -- forget the casting process, which is it's own can-o-worms.

Casting. We take a 33% reduction in strength do to casting because of porousity and imperfections in the castings that occur as part of the process. Strength isn't a big issue with flashlights, but unfortunately, the same porousity often is seen on the surface as well -- there is often cleanup that needs to be done after casting, and that also adds to the cost. This may be a more significant problem with higher stregth aluminums like A356 or A357, maybe less structural (robust) alloys cast will flow better.

There are other casting considerations as well including shrinkage that might make some threaded parts difficult to opperate smoothly, without a secondary operation, again, adding to the cost. There are also minimum thicknesses required to get the molten metal to flow properly during casting.

Your best bet may be to use one of these combination lathe/milling machines -- You can turn the part, and also do some milling orthoganally to the part. I might be able to offer some help, I could even hit up some manufacturing types at work, but I'd have to know a few more specifics.


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## CNC Dan (Jan 1, 2005)

[ QUOTE ]
*kenny said:*
Your best bet may be to use one of these combination lathe/milling machines -- You can turn the part, and also do some milling orthoganally to the part. I might be able to offer some help, I could even hit up some manufacturing types at work, but I'd have to know a few more specifics. 

[/ QUOTE ]

I agree. I program for a 6 axis lathe at work(Citizen L25), and you would be suprised at the stuff that can be made in one operation.

Dan


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## PEU (Jan 1, 2005)

is this the one Dan? 








machine envy to the MAX /ubbthreads/images/graemlins/smile.gif


Pablo


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## kenny (Jan 1, 2005)

I just wet myself! CNC Dan -- you do any stuff on the side? Can ANYONE afford you?! /ubbthreads/images/graemlins/grin.gif


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## gadget_lover (Jan 1, 2005)

I had to ask, but I learned about some of the axis;
right left
in out
spinning

So far, all of us can do that.

Then we have offset tailstock for tapers. I guess that makes 4....

What are the other axis in a 6 axis lathe?

Thanks

Daniel


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## tvodrd (Jan 1, 2005)

Allow me to plead stupid and ask how many spindles it has? I'm guessing 2.

Larry


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## PEU (Jan 1, 2005)

X, Y, Z , Present, Past & Future is my best guess /ubbthreads/images/graemlins/crackup.gif

I'm sure a machine this advanced is capable of time travelling /ubbthreads/images/graemlins/crackup.gif


Pablo


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## HarryN (Jan 1, 2005)

The additional axis refer to the normal X, Y, Z, translations of these, plus machining heads that can come into the piece from other directions (such as from the side or offset from the main axis.

For some reason, the number = 9 axis sits in my head as the max I have heard of.


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## CNC Dan (Jan 2, 2005)

Yes PEU, that is the one. Actualy we have two. And an M20 as well.

From Star we have an SB16.


Others have asked about the six axies.

X and Z are just like a manual lathe.
In addition it has a Y axis. This is mostly used with the live tooling.
That's the four shiney shafts you see in the pic. With these you can make bolt heads, slots, cross holes, and taped cross holes.

Then there is a second spindle that moves on X2 and Z2. This spindle is used to pick off the part when it is being cut off on the main side.
Then when the part is in the second spindle, the back side can be worked on.

The sixth axis is the 'C' axis. The main spindle as well as spinning at up to 8,000 RPM can also function as an indexer or a rotary table.
This is used to make flats, or bolt heads. The part can be rotated with great precision, to any position. Down to 000.001 degrees.

In the pic, you can see the guide bushing. That shiney hole under the tool block. When in use the bar of stock would come through that hole, held by a collet like thing. Behind that bushing is the main spindle.
The bushing does not move, it just supports the stock like a steady rest. The main spindle moves on Z to move the stock through the bushing into the tools. The tools move on X and Y only, not on Z.

To control all this the "brain" is running two programs at once.
One for X Z Y and C. And one for X2 and Z2. Sometimes the main side program takes control of Z2 to preform end work with the three tools that are mounted on the second spindle's carrage.

On one of the L25's I have a high pressure cooant system. It is a 7hp hydrolic pump that operates at up to 2000psi and about 5gpm. The pump is controled by the 'brain'. The system has 8 lines that can be individualy turned on and off.

Well, that's about it.

Dan

PS this is the type of machine that I made the CNC-123 on.


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## Rothrandir (Jan 2, 2005)

dan, that's insane!

i run and setup 2-axis lathes (mazak) at a local machine shop, and while they can do some pretty insane stuff, it's nothing like that!!!

i don't suppose you're hiring...? /ubbthreads/images/graemlins/poke2.gif


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## CNC Dan (Jan 3, 2005)

[ QUOTE ]
*Rothrandir said:*
dan, that's insane!

i run and setup 2-axis lathes (mazak) at a local machine shop, and while they can do some pretty insane stuff, it's nothing like that!!!
i don't suppose you're hiring...? /ubbthreads/images/graemlins/poke2.gif 

[/ QUOTE ]

I don't think we need anyone for lathes right now, mabey in the milling dept. The guy that we hired last is real good with the 2 axis lathes, but when I show him some of the complex stuff I can do it just blows his mind.


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