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View Full Version : Intentional lobe turning on a lathe



ikdor
06-01-2017, 05:50 PM
I saw a video on youtube recently where a lathe was breaking the chip by moving the turning tool synchronised with the spindle. I was wondering whether there are lathes which have such a fast x control that it is possible to turn intentional lobes on the outside of a shaft. Imagine a sine wave on the outside.
Anyone know of such a machine or perhaps one that is using a cam to move the tool and thus create the pattern?

I guess theoretically you could turn the spindle very slow and match the available speed on the x-axis, but that would ruin productivity and this is not a hobby related question.

Igor

CalM
06-01-2017, 05:54 PM
Relieving lathes have done as much for nearly a hundred years,

Cam control is not a new technology.
https://www.youtube.com/watch?v=sYO0Yp4Ag5g

754
06-01-2017, 06:22 PM
Can be done using a cam and tool following cam on an engine lathe.

My Herbert lathe for chip breaking had a CHIPRUPTER... That is not like disengaging feed on an engine lathe.
The Herbert had a momentary interrupt that could happen in a second or under.. Probably leaving very little evidence on the finish.

larry_g
06-01-2017, 11:19 PM
Are you trying to make a barrel cam?

https://www.youtube.com/watch?v=QQqY0etn2kk

https://www.youtube.com/watch?v=izkTWXZji2U

lg
no neat sig line

ikdor
06-02-2017, 12:54 AM
Are you trying to make a barrel cam?


I'd like to make flower shaped discs. I don't have a computer here to make a sketch but imagine a circle with a sine wave superpositioned on the outer circumference.

elf
06-02-2017, 03:09 AM
I'm in the process of finishing a build of one now :cool: They're called ornamental lathes or rose engines and have been around since the early 1700's.
http://img.photobucket.com/albums/v649/etfrench/Rose%20Engine/GT2-5_108t_Model.jpg

Here's a 24 lobe sine wave rosette:
http://img.photobucket.com/albums/v649/etfrench/Rose%20Engine/Sine24.jpg

BCRider
06-02-2017, 04:34 AM
That video of the lathe making heavy cuts by jabbing at the work so the chips came off in pieces worked because it was not moving a large amount of tooling. Even then the mechanism to do the interrupted cuts a number of times per revolution was rather large and powerful. I don't see any way of doing that on a home lathe at any sort of reasonable speed.

Cutting sinusoidal shapes is something we COULD do if we slow the machine down and perhaps make the compound slide work from a cam control. It would require a strong return spring and a custom cam for each shape and a link through proper reduction gearing to make it work. Or, of course, CNC actuators that are timed to control the compound rest in time with the rotary position of the head.

A lot of work for something occasional though.

elf
06-02-2017, 01:13 PM
That video of the lathe making heavy cuts by jabbing at the work so the chips came off in pieces worked because it was not moving a large amount of tooling. Even then the mechanism to do the interrupted cuts a number of times per revolution was rather large and powerful. I don't see any way of doing that on a home lathe at any sort of reasonable speed.

Cutting sinusoidal shapes is something we COULD do if we slow the machine down and perhaps make the compound slide work from a cam control. It would require a strong return spring and a custom cam for each shape and a link through proper reduction gearing to make it work. Or, of course, CNC actuators that are timed to control the compound rest in time with the rotary position of the head.

A lot of work for something occasional though.

No need to re-invent the wheel. There are quite a few rose engine adaptations for plain lathes.

Jaakko Fagerlund
06-04-2017, 09:46 AM
There is loads of videos on this type of cutting with a CNC lathe run with LinuxCNC, for example hexagon hole boring.