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Homemade cam grinder

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  • Homemade cam grinder

    This video popped up on YouTube and I thought some of you would find it interesting.

    You would probably be able to play around with master cams being laser cut out of thinner material.

    A few different size master cam follower “wheels” would get you some more life out the the wheel.


  • #2
    Oxford--That is a marvelous video. Rather long winded, but I have enough information now to design/build my own cam grinder. Only problem is that the cam shape has to be milled first and I don't have a cnc mill. I can mill the cam shape on my manual mill, but if I go to the trouble of milling the cam I will mill it to net shape and then knock down any ridges with a strip of emery paper. thank you for the video.--Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #3
      Works just like a rose engine😎

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      • #4
        In the video he says the follower wheel has to be the same exact diameter as the grinding wheel or distortion in the profile results. So, what happens when you need to dress the grinding wheel?

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        • #5
          Originally posted by brian Rupnow View Post
          Oxford--That is a marvelous video. Rather long winded, but I have enough information now to design/build my own cam grinder. Only problem is that the cam shape has to be milled first and I don't have a cnc mill. I can mill the cam shape on my manual mill, but if I go to the trouble of milling the cam I will mill it to net shape and then knock down any ridges with a strip of emery paper. thank you for the video.--Brian
          I'm sure a 3d printed cam from a Resin printer, once adjusted for shrinkage could work very well as a master. Use it to make a proper master, off you go.

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          • #6
            Originally posted by Sparky_NY View Post
            In the video he says the follower wheel has to be the same exact diameter as the grinding wheel or distortion in the profile results. So, what happens when you need to dress the grinding wheel?
            I was thinking the same thing when I watched. He mentioned in the comments it looks like he uses a 150mm wheel and uses it down to 145mm.

            Someone would have to run some numbers and see how bad the distortion gets at what diameters. I think some extra wheels the master cam rides on in different diameters would be easy enough to take more advantage of the grinding wheel.

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            • #7
              Originally posted by RB211 View Post

              I'm sure a 3d printed cam from a Resin printer, once adjusted for shrinkage could work very well as a master. Use it to make a proper master, off you go.
              Another option would be to someone with a CNC table and have master cams cut out of sheet.

              Even a router with cams cut of of wood or plexiglass should work.

              It seems like an easy way to play around with different cam profiles.


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              • #8
                The follower wheel doesn't need to be a wheel at all, just a smooth convex surface who's tangent point is the exact same as the wheels. In fact it would have been cheaper and easier to just make an adjustable finger with a radius on the end that could be set to zero out with the wheel.

                It's a good idea though, and like RB said the master pattern could easily be 3d printed, both by resin and by FDM although the latter would probably need more cleanup and smoothing to produce good results. Of course you could always just layout the cam by hand and hand file it in. It doesn't have to be a thick chunk of steel like shown either, a thin disk of steel 1/2"-3/16" thick would work great and could be easily worked by hand into the profile you need.

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                • #9
                  Originally posted by Dan Dubeau View Post
                  The follower wheel doesn't need to be a wheel at all, just a smooth convex surface who's tangent point is the exact same as the wheels. In fact it would have been cheaper and easier to just make an adjustable finger with a radius on the end that could be set to zero out with the wheel.
                  This is a good point and a much better solution than the fixed wheel.

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                  • #10
                    Originally posted by Sparky_NY View Post
                    In the video he says the follower wheel has to be the same exact diameter as the grinding wheel or distortion in the profile results. .....
                    His moment arm is very short ( Cam follower to pivot point at the base)
                    The longer the moment arm, the less "distortion" will occur.
                    Because he uses a short arm, he reverts to a radial follower instead of a linear follower. So it is a trade off to compensate for the short moment ratio
                    I am not criticizing the construction as he did a beautiful job on the machine , but a 1:1 ratio of Master Cam to Slave Cam means surface finish of the Master must be perfect

                    Rich

                    Green Bay, WI

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                    • #11
                      Not so sure a fixed follower is better. A fixed follower still need the radius to match the grinding wheel, How you gonna make it? Turn a disc on the lathe is probably the easiest way. Furthermore, a fixed follower will require sliding instead of rolling against the master which will create more friction and wear. Tradeoffs...

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                      • #12
                        Originally posted by strokersix View Post
                        Not so sure a fixed follower is better. A fixed follower still need the radius to match the grinding wheel, How you gonna make it? Turn a disc on the lathe is probably the easiest way. Furthermore, a fixed follower will require sliding instead of rolling against the master which will create more friction and wear. Tradeoffs...
                        Yep.

                        The contact of the cam to the follower and wheel is not strictly radial on the line from cam mandrel to wheel arbor, it moves around as the cam turns, and could be way off radial depending on the cam shape. Watch the sparks, or just think about the cam shape.

                        If the follower is a smaller radius, regardless of the length of the arm, the contact point on the follower and on the wheel will be different. That would prevent the shape from being copied exactly...so the shape would be distorted. For small differences, the distortion would be minimal.

                        The only way around that would be a straight line slide, and a flat follower, using the side of the wheel, or a belt instead of a wheel. The wheel side or belt would need to be parallel to the follower
                        2730

                        Keep eye on ball.
                        Hashim Khan

                        Everything not impossible is compulsory

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                        • #13
                          That's cute. And yes, a 3d printed plastic 'master' would work just fine for that. It'd probably want a little finishing, or you might even see the print lines on the formed lobe.

                          It's impressive how tough a properly designed printed part can be. And my printer holds a tolerance of under a tenth of a mm, with repeatability in the hundredths, if I make
                          sure it's clean and tight. I had low expectations when I got it- and am still amazed.

                          t
                          rusting in Seattle

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                          • #14
                            I have a couple of ATI Grande Mark opthalmic lens shaping machines that would do this same task without difficulty.

                            Edge grind to a pattern. The machines have micro adjustment/ compensation as well as coolant provision and two stones used in an automated process sequence.

                            Made for glass or plastic, but wheels are wheels ;-)

                            Pretty nifty machines for small stuff. I've used one of the machines for sizing round work. Adding a straight wheel dressing point would be a required addition. Click image for larger version

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                            • #15
                              I remember we had a cam milling exercise when I was in the apprentice training centre decades ago ( cams were vital for stuff like wickman 6 spindle automatic lathes and stuff, old old school) it was a universal mill, dividing head, table banjo and heaps of gears some took to it like duck to orange sauce, not me I seemed to make heavy going of it, don’t think my math was very good then, he said unashamedly it still. Chills me a bit,
                              mark

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