Question about machining aluminum

[mustbenu]

what kind of machine would i need to produce pieces like in the picture?
i want to manufactor parts for rc-cars. ive gotten quotes for these peices to be made professionally, lets say 1 company wanted around 40$ a piece, another company wanted 20$ a piece... im not willing to let these people rip me off. If anyone could direct me to a machine that would be able to produce this, it would be greatly appreciated

[nervis1]

You will need a cnc mill. I don't think those quotes are out of line at all.

All but the flat one there will require multiple setups, that middle one there a fixture has to be made to hold it while those holes are drilled. Figure a couple hours programming and verification time plus setup and stock cost. Plus tooling cost. Plus polishing or chrome, whatever finish those parts have on them.

20 bucks a piece is cheap.

That is unless you tell them you want 50,000 of them then I'm sure the price will drop.

If you want a machine to do parts with that quality finish, and in quantity start looking at used VMCs, ie: Fadal, Haas, Okuma, etc etc. they start at about 15k for an old machine on up to the millions. Figure a few thousand in tooling, a few thou for the software, coolant, phase convertor (unless you already have three phase power).

You may also look into a used converted Bridgeport or clone, in working condition maybe 3-4-10 k depending. Ebay will give you some ideas of what is out there.

[RotarySMP]

That first, flat one could be done on a little router based CNC. For the others Nervis1 one right. Even if you have the machine to do them yourself, the programming time, set up, deburring, polishing etc will lead to your time being about 0.03c/hour for these $40 parts.

Do you like machining as a hobby, or do you like RC cars as a hobby?

[gjahnke]

MUCH better idea than a machine that will cut them in aluminum (which is going to be high $)

Machine that will cut foam, then build yourself a little home foundry. Can be done for less than $25. Cut the pieces in foam, then cast them.

[mustbenu]

what do you mean cut them in foam then cast them?

[gjahnke]

We do lost foam casting for the aircraft industry. It is also how toyota motors are done. The basic process is simple:

1: Cut your shapes out of foam, add runners and sprues
2: Cover the foam with a refractory shell
3: Bury the part in loose sand and vibrate to pack the sand
4: Pour the part
5: break off shell and cut off sprues

There are several advantages to this over simply machining the part out of a chunk of aluminum. First, for the home hobbyist, you only need a CNC machine capable of cutting foam. These are realtively easy to build, as opposed to machines desingend to cut aluminum, which are much, much mroe expensive. For the professional shop, thre is a decrease in tool costs, since an end mill used only on foam will last nearly forever, and they are much, much cheaper than standard endmills (we commonly use bits for a dremel, just make sure you measure the actual bit you are going to use and input it in your tool library). Machining time is also much lower.

In either case, your materials are going to be cheaper, since aluminum ingot is much cheaper than billet. Lost foam is a little more labor intensive, but for the home hobbyist, it is probably a more logical process from a cost standpoint

[mustbenu]

thank you for your response but i have no idea what any of this means, i am a extremly handy person but i know 0 when it comes to this stuff.
Can you supply me with some pictures so i can get a better idea of what your talking about.
1: Cut your shapes out of foam, ??add runners and sprues??
2: Cover the foam with a ??refractory shell??
3: Bury the part in loose sand and vibrate to pack the sand
4: Pour the part?? LIQUID ALUMINUM??
5: break off shell and cut off sprues

[miljnor]

http://www.backyardmetalcasting.com/index.html

try this one out

[CNCgr]

You'll find lots of info on casting here.

Bear in mind though that a cast part will still require machining and the surface quality and mechanical properties won't be as good as a machined from stock part.

Nikolas

Edit: Miljnor beat me to it by 2 minutes...

[miljnor]

its all those years of typing!

[gjahnke]

Originally Posted by mustbenu thank you for your response but i have no idea what any of this means, i am a extremly handy person but i know 0 when it comes to this stuff. Can you supply me with some pictures so i can get a better idea of what your talking about. 1: Cut your shapes out of foam, ??add runners and sprues?? 2: Cover the foam with a ??refractory shell?? 3: Bury the part in loose sand and vibrate to pack the sand 4: Pour the part?? LIQUID ALUMINUM?? 5: break off shell and cut off sprues

Sorry.

In a greensand mold, sprues are the tunnel that you pour the metal into. They are connected to the part by a runner. In lost foam, the sprue is just an extra piece of foam stuck on there that sticks up out of the sand. You pour your metal down that to fill your part, then you cut it off later.

Refractory shell....the foam is coated with something that can take the heat form the molten aluminum without breaking or burning. We use a ceramic product whose name escapes me at the moment, but I could find it if you need it. Most guys at home use drywall mud thinned in water.

Yes, liquid aluminum. you melt it in a furnace. Any idiot can do it (there iwll be those who tell you it is difficult or impossible, it is nothing), and do it cheaply. Check out the page the other guys linked. There is some pretty good info there for somebody new to the craft.

Bear in mind though that a cast part will still require machining and the surface quality and mechanical properties won't be as good as a machined from stock part.

The finished part MAY require machining, and if suface quality is a consideration, that can be taken into account and corrected for. Lost foam is comparabe to lost wax as far as surface quality possibilities. If you know that surface finish is a consideration, you can treat your foam and end up with something that you really only have to run through the polisher for a mirror finish.

You are correct about mechanical properties, though. Any casting is going to have different mechanical properties from a machined part. For what is being done here (the parts at the top), it should not make a difference. Our shop has cast mounts for jet engines, and they do fine. The important thing is to rememebr when you are designing your part to consider the properties fo cast aluminum as opposed to billet, and make sure you adjust for that in your design if need be.

[mishikwest]

20$ a piece... im not willing to let these people rip me off.

You've got to look beyond the 1$ worth of material, and I'd say that's a fair price.

Small mill $30,000+
software $10,000
tooling $10,000
support equiptment $10,000
(air, measuring equtp., etc)

You've got a $ 60k investment right there. Plus all the usual business expenses, utilities, overhead, employees, insurance, bus. license and paperwork, accounting, office supplies/staff, taxes, etc. etc. etc.

Ok, you've got that for a business expense.

PLUS
Programming 1-3 hrs.
jigging and fixtures 4-5 hrs.
trial and test parts 1-2 hrs.
at 65-75$ an hour....

You can amotize those costs over as many parts as you'd like. If you want one part, thats about 650$ right there....All for about a 5-10 minute cycle time...

For the DIY'ers, what's YOUR time worth?

Oh, if your looking into casting, your're gonna have to still machine those A-arms. Unless of you go 30K$ for die casting tooling. Oh, and polish.

Sorry for the rant, but I'm a shop owner and hope to inform folks why parts cost what they do.