Turn or mill this part? (or machine as two pieces and join somehow)
Turn or mill this part? (or machine as two pieces and join somehow)
(OP)
I'm looking to make a small aluminum cup style hydraulic cylinder. (single acting)
I can't seem to figure out the best way of going about making the "body" of the cylinder. I've attached a picture of the basic shape (cross section). There are some dimensions on there in mm, but they are just rough figures. I do not know yet what they will be, but I do know the depth of the cup will be approximately 50mm.
Since there will be seals on the piston that run along the inner faces, the finish and tolerances will have to be pretty good (have to get it hard anodized after). I'm wondering if it is practical to have this shape turned? I was told that it will be pretty tough to do at that depth... Then I considered milling, but it seems that the inner sleeve might be too tall. Having a relatively small diameter end mill reach that far would probably lead to deflection and poor surface finish / tolerance.
I've also considered making it two pieces and having the inner sleeve welded to the outer sleeve from the backside. However, this only welds them at the back and I'm concerned about the integrity of the whole piece and warpage from the heat.
Would love to hear everyone's thoughts.
Thank you!
I can't seem to figure out the best way of going about making the "body" of the cylinder. I've attached a picture of the basic shape (cross section). There are some dimensions on there in mm, but they are just rough figures. I do not know yet what they will be, but I do know the depth of the cup will be approximately 50mm.
Since there will be seals on the piston that run along the inner faces, the finish and tolerances will have to be pretty good (have to get it hard anodized after). I'm wondering if it is practical to have this shape turned? I was told that it will be pretty tough to do at that depth... Then I considered milling, but it seems that the inner sleeve might be too tall. Having a relatively small diameter end mill reach that far would probably lead to deflection and poor surface finish / tolerance.
I've also considered making it two pieces and having the inner sleeve welded to the outer sleeve from the backside. However, this only welds them at the back and I'm concerned about the integrity of the whole piece and warpage from the heat.
Would love to hear everyone's thoughts.
Thank you!





RE: Turn or mill this part? (or machine as two pieces and join somehow)
Getting the chips out without them forming 'birds nests' will be a bitch. It will be easier with a free machining alloy like 2024-T4 or similar, _IF_ you can get enough spindle speed to break up the chips into small flakes and make them fly out. I'm thinking at least 3000 rpm for the 70mm and 90mm diameter cuts, more if you can get it. Trying to cut slower will just jam up the chips and break tools. Machinists who 'baby' their tools so they last forever will not be able to make the part successfully. It's a 'balls to the wall' part.
You will need modest radii at the 'corners' of the recess, or you will spend a lot of money replacing the cutters.
Mike Halloran
Pembroke Pines, FL, USA
RE: Turn or mill this part? (or machine as two pieces and join somehow)
Impact extrusion can make similarly shaped parts, although I think the depth:diameter ratio would make it difficult to make in one piece.
A two-piece design made from wrought parts (tubes, forgings, extrusions) could be welded by multiple techniques, although friction stir welding appears to be the best choice based on tolerances and distortion.
Either of these options would be expensive unless the required numbers of pieces are high.
RE: Turn or mill this part? (or machine as two pieces and join somehow)
Good luck.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Turn or mill this part? (or machine as two pieces and join somehow)
Gives me some ideas in the meantime.
At my work we actually have a similar piece being made from AISI 4340 in Asia. I might be able to have this made there (easier in Al.? ) since they have the tooling.
Thanks again!
RE: Turn or mill this part? (or machine as two pieces and join somehow)
In all probability, the machine they use for steel can't get anywhere near the RPM required to make friable chips in aluminum. They will fill the cavity with long birdcaged chips and break the cutting tool.
Mike Halloran
Pembroke Pines, FL, USA
RE: Turn or mill this part? (or machine as two pieces and join somehow)
Regards
Greg
RE: Turn or mill this part? (or machine as two pieces and join somehow)
RE: Turn or mill this part? (or machine as two pieces and join somehow)
I did have a similar two piece design drawn up that would require welding. I'm not opposed to it, but I was hoping there was an elegant (and cost effective solution) that could produce the part in one piece.
RE: Turn or mill this part? (or machine as two pieces and join somehow)
Honestly, depending on how many you are making and your timeframe, welding may well be a good and cost-effective solution. It shouldn't require any special tooling on the part of the machinists unless you wish to skim the barrel after welding.
Is there any particular reason you've chosen to go with aluminum for this cylinder? What kind of pressure are you expecting?
RE: Turn or mill this part? (or machine as two pieces and join somehow)
RE: Turn or mill this part? (or machine as two pieces and join somehow)