[Tymco]

I want to Re-cut some part so i can rebuild some cam for a dune buggie. The part has three ramps on it tied together by a ring base. i will attach the part with to the three jaw chuck on the rotory table. but i do not how to turn the rotory table and the cnc mill at the same speed and i do not know the angle on the ramp at this time. I have a Supermax with a Centroid controller.
Thanks

[NC Cams]

Until/unless you can define the cam shape (lift versus angle of rotation), you'll NOT ever be able to copy/modify it decently.

THen you get into the issue of "bottom cutting" versus "edge cutting" cutters, cutter offsets and all sorts of other technicalities to properly and accurately cut a cam.

It can be done by cutting hundreds of "flats" but, you'll need to "map" the cam (existing versus desired) to do that.

Finally, if you read the cam with a "flat" as opposed to a "radius" bottom cutter, you'll get entirely different motion profiles from the same physical cam shape. THere are ways to get around that but it is not a technique I can teach/explain via a message board.

[Pressfit]

This sounds like a real technical challenge with all the various lobe centers, lifts and degrees of duration involved. Then the matter of getting a real good surface finish for durability and wear resistance.

[NC Cams]

If the intent is to redo the engine cam, I'm 99.9999% certain that it can NOT be done with a mill and rotary table.

First and foremost, the material (hardenable gray or chilled iron) used to make cams is barely cuttable with cutting tools due to hardness - it pretty much HAS to be ground.

Second but not to any less degree, the surface finishes needed for the cam lobes NOT to wear or NOT to tear up the followers can NOT be generated with a cutting tool - again, the surfaces pretty much HAVE to be ground.

Finally, the profiles at the cam are not simple. Even the most mundane are complex blends of curvalinear shapes (basically 4th or 5th order polynomials strung together into ramps and main events).

Profiles smooth enough to not jerk the hell out of the valvetrain can't be made using "stepped" functions which is pretty much all that can be made with mills and 4th axis.

Using some VERY sophisticated CNC programs and profile design programs, one can use a good quality, very high encoder count servo operated VMC or tool path grinder (forget steppers) to cut the tooling that can/will be used to finish grind the lobes. However, these same programs are NOT capable of finish shaping/grinding the cam lobes - we've already tried and so have any number of others in the industry. ANYTHING BUT a smooth continuous profile will fail and/or tear up the valvetrain.

Guys claim to have done so (cut cams) with go-kart cams. In light of the lightness and relative stiffness and durability requirements of such applications, perhaps they can get by. However, the stresses associated with automotive engines place much more responsibility on the cam grinder/finisher in order for these parts to live. In light of our experiences both with and in grinding/making SMOOTH, continuous, jerk free cams,

I'd encourage you to seek the aid of a competent cam grinder - the few bucks you save by DIY'ing a cam isn't worth the grief or expense that you'll encounter learning how to make cams that both make power and/or survive.

Automotive cam grinding/refinishing is hardly a self taught, DIY enterprise to dabble in/with unless you have LOTS of money and a huge time budget to fix/replace broken/damaged parts.....

[Tymco]

Attache are two pictures of what i need to re-cut. If i could lay them flat it is three triangles. the only thing that i have to do is to keep the rolling surface on the same angle when it is cutting. I want to say thanks to all the responded to this post.

[RICHARD ZASTROW]

Tymco, They look like secondary clutch cams for CVT (like snowmobile etc.). I think NC Cams thinks you are referring to engine cams (that lift & drop valves) If it's a "button" type cam follower it's probably not as critical but I was told for best results on a roller follower to use an end mill the same dia. as the roller. I don't why, just heard that. FYI, Aaenn sells them and probably can make custom units as well.

Good Luck

[Tymco]

I use about 10 to 15 of the driven clutch that this part comes out of and the hole idea is to cut coast and put the money back into the company. We rent Dune Buggies on the avarage 45 buggies a day. Thanks again for all that have answered this post.

[NC Cams]

Guys with 5 axis EDM or lazers can cut them faster than you can ever imagine using tubing and their CNC operated tool path - if you can draw the cam ramp, they can wrap and burn them.

If you don't know how to coordinate the axis rotation versus the spindle motion, you're as bad off trying to machine these as machining an automotive cam.

BTW, DZASTR, it takes more than a roller shaped cutter to truly and properly duplicate the actual and intended lift curve with an automotive and/or clutch cam. You need some rather sophisticated cutter paths to properly get the OD edges of the cutter to trace the exact path that you're trying to generate -

REASON: the true tangency point of the cutter is constantly moving and you have to account for the move (both axially and radially) as you rotate the axis and/or oscillate the cutter axis up/down/in/out. Been there, done that in creating our cam master cutting program - suffice it to say, it ain't easy to do.