Using Interpolation on C-Axis to create a cam profile?

[PVN06]

I have an Emco 325-II CNC lathe (using 5C collets) which has a Sauter head with 12 stations, 6 of which are driven.
I have written numerous programs in raw G-Code (Siemens not Fanuc) over the last few years, allowing creation of milled fastenings - and also have subroutines that came from previous owner that allowed milling of Hex and squares for numerous fasteners.

However, I have wanted to machine motorcycle cams using this machine for some time - and know it can be done using Interpolation programming . . . but I am not knowledable enough myself to know how to approach this. I know the cam profile by degree (i.e. cam lift opening and closing points and lift per degree), but would love to find some kind of canned program that I can adopt to create some trial cam profiles to the dimensions I have.
Anyone out there have any ideas or possible programs? Expecting I will use 6mm 4 flute endmill in WTO parrallel VDI16 live tool, expecting base cam profile to be approx 25mm diameter.

Any help much appreciated, many thx
Paul Norman
www.RacingNorton.co.uk

 

[CarbideBob]

This is some sort of poking the world joke,... yes?.... I hope.

 

[pcasanova]

840c or 840d?

 

[PVN06]

According to the Emco manual period to my machine it is - Emco WinNC Sinumerik 810D/840D, approx 2006-2007. I say this because back when I first bought the machine about 8 years ago I was trying to work out if Emco used generic Siemens, or if they had their own slightly different version.
I know that G112/G113 are supposed to activate Polar Coodination Mode . . . but nothing in that early manual I have to cover anything like a cam program for C-axis programming. My hexagon subroutine just uses variables with cosine and tangents programming - probably beyond my processing power to do similar for a cam routing.
Not sure what you mean CarbideBob . . . only an occasional visitor here - not joking, serious question.
thx
Paul

 

[newcomer]

You understand that at best this would be a roughing operation prior to heat treatment and precision grinding post HT? While you certainly can long hand the program, you would be best served by a cam package. The more pressing matter is do you have curve parameters of the cam lobes? You don't just guesstimate it you know... Since you have the C axis you can interpolate it manually with the handle and a sphere tipped indicator on an existing camshaft that's in pristine condition. The cam shape greatly affects the duration of compression and exhaust but I assume you already know that. Lastly your cam profile has to be a series of tangential arcs instead of splines.

 

[PVN06]

Understand all of above, already produce cams by another method, have profiles etc. Also, have final cam profiler device (currently not working) for post hardening. However, as said . . . am after a similar G-code subroutine if someone has one one available (which I will amend to my profile) . . .as said, for CNC, not manually. And to the last point, I could do this by writing program to do it by 1 degree increments (I believe that is called notching) .. . but that would not give a tangential arc. thx.

 

[Triaged]

Understand all of above, already produce cams by another method, have profiles etc. Also, have final cam profiler device (currently not working) for post hardening. However, as said . . . am after a similar G-code subroutine if someone has one one available (which I will amend to my profile) . . .as said, for CNC, not manually. And to the last point, I could do this by writing program to do it by 1 degree increments (I believe that is called notching) .. . but that would not give a tangential arc. thx.

For just rough I guess it would work. If you don't have CAM how about some ExcelCAM? Only 360'ish lines of code/excel.

The other replies are obviously concerned that you would finish a cam with this technique. Cams need to have smooth profiles that you would only get with the proper grinder.

First derivative of position is velocity. Second is acceleration. The third derivative of position is often called jerk. I have heard that cam designers look at the 4th 5th and 6th derivatives and that they are called Snap, Crackle, and Pop!

 

[newcomer]

https://www.maruf.ca/files/caadoc/CAAScdPriUseCases/CAAPriCamShaft.htm

Perhaps this link might help. Macro programming allows for curve equations. Let us know how it goes. This is something I might be interested to learn when a job needing it comes up.