cam dimensioning

[tha89sx]

i have a cycloidal, inner cam ring, that needs to be dimensioned for machining.

what dimensions do i need?
can i place a table of dimensions for every other degree?

its a six lobe cam.

 

[ctopher]

You need whatever dimensions are needed to machine the part. I can't say without seeing the part or the parts it mates to.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

 

[tha89sx]

okay, the dimensions that im thinking will be needed are something like a list of radial distance and their respective angles?

is that what a machinist will need?

 

[SincoTC]

Most machinist will have their favourite way of machining things and the dimensions required will vary to suit their method. I would ask them what they want first, maybe show them an eDrawing Model of the part and get their opinion and requirements. You could also take a look at the CNC and Engineering forums on this site.

To be honest, for components that need so many dimensions to properly define them, I suggest you find a machinist with CAM software that can directly import your SolidWorks model part file (there are quite a few). In this way, the full machining capabilities and strategies of the machine's CNC controller will be exploited to the full and you won't need any messy and possibly confusing drawings, just one with a few critical check dimensions. If these are right, then it's almost certain that the complex profile will be correct; the joy of CNC! We use FeatureCam and have never had any problems, provided the tooling is good and the method of holding the part is well thought out.

If anything needs changing, modify your model and they re-import it and it regenerates the CNC code (The code is long and almost impossible to edit, but you will get what you model)

The next option down, is to send the profile as a simple DXF file that can be imported into lower end CAD systems. Again send check dimensions and be VERY wary about the possibilities of scaling errors. See my reply to draftsman101 (Newbie Question) in this forum on 19th July. This route is not really suitable for complex components and I would go for the imported solid model every time.

Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
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[rrohret]

I have done similar cams. Check out the Clyde Moon book at

http://www.camcoindex.com/svcman/moonbook.pdf

Some specific cam manufacturers would only need the type of transition -(modified sine in your case), the rise, and the angle, cam follower diameter, to machine the cam. A vendor like this is preferred. They will generally sweep the cutter around the path that the cam follower would follow. A CNC machining center may also do this. In this case, CAM ability is very helpful. Your model should be very accurate. I have also given the points in an x,y list in Excel for disk cams. The more points the better. I have had cams made in all three methods.

 

[EngJW]

If it's a cam for an engine all you need is a table of follower lift per degree of cam rotation, and then specify whether it is a flat follower or a roller as the cam shape is different for both, even for the same lift table. The cnc software will translate the lift table into grinding wheel movement.

Also, if you are using a lift table for the cam specification, you can just approximate the shape of the lobe in your model, like is often done for a gear tooth.