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camshaft machining

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Gadabout:
Hi, I am building the Seal 15cc 4 cylinder engine and want to machine the camshaft on my small cnc mill, The machine has a fourth axis (A) and knee and spindle axis's as well as x and y. I have drawn the two cam profiles( inlet and exhaust) in Solidworks(2001) and have featurecam 5 for cam and mach3 , but I can not get my head around how to get the gcode for the machining of the cam profiles, was thinking of the camshaft axis parallel to the x axis and either using the spindle axis or the knee one for z movement, I think I can hand program the rest of the movements to get the cams in the correct orientation. can anyone help me with what I need to do please as I am not too good at this!!
thanks
Mark

djc:

--- Quote from: Gadabout on August 06, 2019, 05:07:01 PM ---The machine has a fourth axis (A) and knee and spindle axis's
--- End quote ---

When you say knee and spindle axes, do you mean knee and quill or knee and rotary axis?

I assume if you are outside the cam, it is at every point concave (i.e, you can put a straight edge on it and it will touch at one point only).

Can you post a dimensioned drawing of a typical cam profile? Is it made up solely of circular arcs?

Use the centreline of the cam as your datum. Pick an arbitrary point as your zero rotation. Measure the distance from centre of cam to outer edge. Write it down. Rotate one degree. Repeat. You will get a list of 'coordinate pairs' of angle and Z-height above centre.

Set cutter clear of work. Drop down to Z-height, move in X until cutter is clear of work. Move A-axis one increment on your coordinate pair list, move to new Z-height, move in X until clear of work. Repeat. The smaller the A-axis increments, the smoother your cam will be. If you can define it mathematically, so there is a formulaic connection between A and Z, you can use a spreadsheet to do a lot of the coordinate pair calculation for you.

Gadabout:
Djc, thanks for the reply. My mill has cnc on the x,y,z(knee) ,A (rotary table) and B (quill) has vertical as well as horizontal spindles. Mach3 is the controller.
The camshaft in question has eight lobes(4 inlet, 4 exhaust) and I would like to write a gcode program to machine the lobes. I have drawn the lobe profiles in Solidworks 2001 and would like to work out how I write the gcode for the lobe paroles as I can write the rest ok. I will post the cam profiles later when I get to the pc they are on.
Thanks
Mark

chipenter:
Solidcam is made to do just that , export the drawing into cam it will convert to G code .

djc:

--- Quote from: chipenter on August 10, 2019, 01:24:46 AM ---Solidcam is made to do just that, export the drawing into cam it will convert to G code.

--- End quote ---

He says he has FeatureCAM.

For his setup, he needs something will output G-code to do simultaneous motion in A- and Z- . This is not quite so easy.

To the OP, have a look on this site for a post by Andrew Mawson entitled 'maths help'. It might look at first sight as if his issue was completely different to your own, but the concept is identical. For every point on the 360 degrees of the circle, you need an equation that tells you the distance of the part edge from the centre of that circle.

For A-axis machining, you can cheat a bit and fool the controller into thinking the A-axis is a linear axis. Effectively, you unwrap the profile from around the circle and turn it into a straight line. Then you can command simultaneous motion in Z- and your-now-linear A- .

Have a look at a program called CNC wrapper. There is also a little bit on this technique in the documentation for Dolphin Partsmaster.

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