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variable section sweep

saspinall

Member
Got a cylindrical part which I need to do a strange cut on to simulate being machined in a certain way. The idea being that a 2" cutter is brought in from the top of the cylindrical part and then the cutter remains in the vertical plane while the cylindrial part would rotate, In reality the cutter would move of course but I dont know what angles it would move at. The thing is that Ive simulated it in Autocad and the cutting sketch would rotate downwards in proportion to the part ie when the part has rotated 90 degrees the sketch would also rotate down 90 degrees. A colleague has suggested a variable section sweep using some pivot to change the angle of the sketch sections, anyone got a walkthrough for this advanced modelling technique ... WilView attachment 993dfire 2
 

jeff4136

New member
If the cut is purely annular, e.g. the tube would be rotated under the cutter with no axial or lateral translation, a revolved rectangular section will represent the cut (and, of course, revolved or extruded cuts at the ends).

If that's not it, holler back.

[It might be of interest to note that for an axial displacment (barrel or cylindrical) cam; a VSS looks sorta like it makes a "good" groove, but it doesn't.]

Addendum:
Can you see all your posted text on your display without scrolling laterally?


Edited by: jeff4136
 

wsylvester

New member
Yes,like Jeff saysyou can revolve a rectangle around using a variable angle....rect outer wall/inner wall.. then you can add an arc at the start to round out one end and arc at the other for it... you will need to create a plane that will be tan to the cyl and thru the edge of the ending line of the rect.


That will give a true rep of the cut and will allow adjusting ofthe angle, but will bomb at 180.. so anything less will fly


Too early in the morning to be thinking of things like this



three cuts and aextra datum...but works
 

wsylvester

New member
If you want to get some cam action in on it , use a helical cut instead of the revolved cut and play around with the pitch and length.


You'dmight create a analysis feature if you were looking for a certain distance of travel.


If I was smart enough I post a picture... what do I have to do ftp a pic to my isp storage and then link it??? Kind of looks like that's what I do??
 

saspinall

Member
Cheers all, dont know if it's exactly what i require but I will try.


Wsylv, just hit the camera icon in the toolbar above the reply box to add a picture


Maybe my pic was a bit big in size thats what has affected the text scrolling.
 

jeff4136

New member
wsylvester said:
If you want to get some cam action in on it , use a helical cut ...
Just for fun and may be of interest (or maybe I'm incorrect and someone will correct me); it doesn't. For "practical" purposes (?) it does. The reasoning: The tangent angle for any given cutter section (I'm thinking of a plain end mill, section normal to cutter axis; e.g. a circle) is dependant on radius of the cut stock (where along the length of the cutter the section is taken). So, a planar section can't precisely represent the swept body of the cutter where there is a combined axial and annular (workpiece relative cutter) component.

Just for fun.
 

wsylvester

New member
Good call Jeff



As the pitch increase , it does squeeze the slot. I dropped it into a assy and added a part to mimic the endmill. With a plane to move it in the slot.


The ends get hooked more as that is larger also. looks like solution would be to create extra datums thru side edges then normal and tangent on the radius so the ends will turn as pitch is changed.


One may be able to adjust slot size with a trig based relation based on the pitch angle, but it might have to beassy. based. So a better way there is. but for the other it work fine.


Time to go mix firewater and firecrackers
 

jeff4136

New member
The best method I've found for such a groove is using surface offsets from a "mid" surface that represents the cutter axis for "side" surfaces. Groove bottom is still a little ambiguous; cylindrical for annular component, planar for axial, "who knows" for combined components.

"... firewater and fireworks ..." Have fun and watch those fingers.
 

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