Hi
I bought a CNC lathe(Heid Magdeburg with Siemens 802 controller). it is a CNC lathe with box way.
i don't know why i can't take a good surface finish with this machine, I am skilled in machining and i have two CNC machine (Hyundai , Spinner) also and they are very good with the same cutting condition but in Heid Magdeburg i can't get a good surface finish , it is very interesting that i machining a simple contour finishing on Aluminum with 0.2 millimeter depth on cut, 200 u/min spindle rotation, 350 millimeter work piece diameter, i check feed rate with 0.02, 0.04 and 0.08 mm per rotation but i don't see any change specially on 0.04 and 0.08 i think it is a problem on machine parameter because i check it with other machine and it is very good i don't have any vibration on tool during the machining but i can't have a surface finish.
I check the spindle bearing with indicator tool and it doesn't have any problem, no noise in high spindle rotation.
I can see effect of tool on the surface(like treading with small pitch) it seemed a parameter is not set in machine.
what do you think ? what is your guess? what is the problem?
Please help me to have
First thought: 0.2 for a depth of cut, especially on Aluminium, is very shallow. If it is 0.2 total, then it is only 0.1 per side... and that, in my experience, is too shallow a cut; the tool is pushing the material away rather than cutting it, which leaves a 'torn' finish. If you can, try taking a cut at no less than 0.25 depth of cut (0.5 on the diameter) and see if it improves.
Second thought: What type of Aluminium? If you are getting a shiny surface finish on another machine, it is most likely heat treated to something other than T0 condition - check the hardness or material condition to ensure you are not trying to cut a soft/gummy part.
Third thought: Generally speaking, there is not a parameter that will improve surface finish, so I am curious why you think it would be a parameter - are there other issues with the machine that point to a parameter problem?
Last thought: (well, actually my *first* thought, but I'd hate to not mention it... are you certain the tool has a good cutting tip? I've chased surface finish issues in the past only to discover a chip in the coating on the tip of an insert.
Turret not locked down solidly? Turret not dialed in on center? VDI holder not locked? Tool holder worn, shim or seat worn out? Bad lock screw?
I'm betting you are having a mechanical problem, you just have to find it!
Bad surface finish in CNC lathe
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