On Topic - Can a modern CNC Lathe Do This ?

Greetings fellas,
Now and then, I have a pattern cut into brake rotors for an off road application. It is currently done on a mill, and it takes quite a bit
of time, not to mention that the tooling does not last very long as it sometimes must reach quite deep to get around the "hat" height of some rotors. My question is whether there is a modern CNC lathe that could put this pattern in via an indexed spindle and a coordinated tool movement, that progresses deeper with each pass. I imagine a few turns of the spindle and this path could be cut.
Here is a photo of what my sample part looks like:
http://www.data-cut.com/images/rotorpattern.JPG
I just imagine that there would be a lathe that could do this much faster and cheaper than a mill would do it. The profile or shape of the groove is typical to a 30 degree, flat bottom engraving bit, .030 deep and about .060 wide.
If there is a Lathe that can do this, is there a specific brand I could start asking shops if they have one ?
Thanks,
Grummy
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On Oct 10, 4:02 pm, snipped-for-privacy@sbcglobal.net wrote:

I doubt you can gen an even shape for the profile wall moving the tool like that on a lathe.
DanP
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wrote:

I doubt you can gen an even shape for the profile wall moving the tool like that on a lathe. ==============Ahm no spert, but it looks like you'd need a big goddamm lathe, too.
Cake for a cnc mill. Just need to know what the curves are.
If these curves can't be approximated by circ arcs/blends, then you would need to digitize, for a shitload of points -- which is no problem for shops set up for this. If a local shop is not set up, proly some cadcam/drawing people can digitize it, then bring it over to the shop.
Is that exact pattern critical? I've seen many different types of patterns in rotors, was always curious what the rhyme/reason behind a particular pattern was.
Once you have the curve/points figgered out, it looks to me like that pattern could be done in well under a minute, proly in one pass, mebbe a real fast finish pass if nec. I don't think the finish inside the groove is that critical, other than aesthetically.
Even a cnc router could do this, iffin you could slow it down a bit, but then mebbe with carbide, you wouldn't even need to.
--
PV'd


DanP



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NOT critical... and producing the pattern/toolpath is simple in cad/ cam. If you look at it, you will see that the pattern is nothing more than two separate triangular patterns overlaid each other evenly.
The technical goal is to "let the gasses escape" from the pads under heavy braking, but the simple goal is more along the lines of give a kid some money, and he'll waste it on something he "thinks" he needs. I dont need patterns in MY brake rotors.... trust me. Nonetheless, I have the desire to do this, in order to make their money, my money. Is that not what it is all about ?

Correct
I did the first ones on my cnc router, and yes, it machines fairly easy. The challenge comes in on the other side of the rotor, as some have a "hat" or center section that is raised by near 5" on some rotors, making necessary to run a pretty narrow diameter tool, pretty far out of the collet, then you have to .
I am surprised that so far, no one has indicated that a modern lathe can do this... I thought that if you ran the spindle way down to something under 30 rpm or so, the cross slide axis could move in and out fast enough to make the pattern. Three passes and a cleanup and it would be done. I know a guy could build a cam follower machine by using a traditional rotor lathe, but I have different sizes.
I dont think this is much different than turning anything triangular, like a Wankel Rotary piston.......
Grummy
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This is actually a very common problem when turning automotive pistons, and the solution to which is a closely gaurded secret.

2 tools mounted on a rod, ( gets you both grooves at once and negates the need for a 180 index) ...an adjustable throw crankshaft driven by the chuck and geared at 1:3 ratio to provide epicyclic motion.
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On Fri, 10 Oct 2008 08:02:28 -0700 (PDT), snipped-for-privacy@sbcglobal.net wrote:

Well.........the simple answer is YES, you could do this on a lathe. However, you won't be able to 'turn' it. You'd need a C-axis lathe with a revolving face milling tool. Which would then be nothing more than a horizontal mill:-)
Programming the spindle rotation and X moves would be rather involved, and most likely take longer and cost a bit more to produce.
Matt
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On Fri, 10 Oct 2008 08:02:28 -0700 (PDT), snipped-for-privacy@sbcglobal.net wrote:

My .02 Live tooling on a lathe will be the same as on a mill, long tool stick-out to get near the "hat". Use a VMC with a rotary table tilted at say 30 degrees so the tool can get in close to the corner of the "hat". Groove would need to be cut with a ball mill most likely.
You're thinking face grooving tool on a lathe? that I don't know about.
Thank You, Randy
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Thats where I was thinking.... Simple insert tooling.... and the tooling axis simply moves in and out in fine harmony the rotary axis. It is just a 3 axis operation, albeit a non rotating tool.
Thanks for that thought on a ballnose via an angled rotary table. I never thought about that one. If I could get close enough that way with shorter tooling, it clearly could speed things up.
Still, on the mill, each particular rotor would need a setup jig. I was noticing that all the rotors have an already trued post casting machined surface right in the center hole (inside the bolt pattern) that could be grabbed with the right "inverse" or expanding collet system, even if that was something that had to be made.
Thanks, Grummy
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wrote:

Do all rotors have that center hat on one side? I seem to recall seeing rotors as just thick disks (well, a thick "sandwiched" plate) , that bolted on to the hat/hub.
Was I mistaken?
Also, how close do the pads actually get to the center hub? I seem to recall a good bit of an inch! So maybe you have more room than you think.
--
PV'd



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snipped-for-privacy@sbcglobal.net wrote:

A face grooving tool on a lathe would work on paper, but not in real life. Because the cut changes so much in diameter during a single rev, you'd need huge side clearance angles on both sides of the tool. That would make it weak as a toothpick, with little chance of success.
Setting the rotor at an angle to shorten tools, as someone else suggested, then rotating the rotor while milling, is probably the best bet.
KG
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Perhaps two tools should be used to help that situation, one for each side of the groove ?
I'll keep hunting for the best solution. The Sink EDM method sounds interesting but I will need to find out the cost and longevity of each die, as well as how long it would take to sink each side of a rotor.
All of the tips are helpful and I thank you all.
Grummy
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snipped-for-privacy@sbcglobal.net wrote in

First you'd need to design a tool that could cut and had clearance on all sides.
--

Dan

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If you cut those patterns in production, EDM is lot faster, once you have the electrodes made. JS

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Your speaking of SINK EDM, right ? So we cut some carbon patterns and sink the pattern into the rotor..... h'mmm.
This would be fast ? Wire i am familiar with, sink... I understand the concept.
Now I need to do some research. thanks !
Grummy
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wrote:

Yea, sinker EDM! Those patterns are not very deep. If you don't care about the finish, can be rough, EDM would do it fast 1/2-1 hour I think. Copper electrodes have less wear too. JS
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