Re: Rope turnings in wood.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "oreos40" <oreos40@...> wrote:

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> I am new to this group. Some here may have seen me post this question in other groups.
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> I want to do "rope" turnings in wood on a metal lathe. I plan to use shaper blades on a spindle to do the cutting.

I am having a struggle visualizing your idea. I assume you want to cut the shape of the blade as the profile (say a half round of the size you want the flute?) and move that down the stock in a spiral fashion?

The foundation of what I want to do is to couple an encoder and a stepper. the encoder will be on the spindle and the stepper will be on the longitudinal(carriage) to drive them in sync. I need a user adjustable ratio to vary the pitch of the twist. yes its a lot like threading but the ELS wont work. it requires a minimum rpm and relies on a count once per rev of the spindle. it becomes less accurate the more coarse the twist of the "rope"(thread) becomes. The second problem I have is one of power. all of the DIY drivers i have been able to find are for less than 7-8. I have a motor rated at 9 amps 2.5 v per phase 900oz/in I figure I will need at least 600oz/ins

To turn the Spindle axis or to shove the cutter down the length? You can get motors that have ratings of 960 oz-in with 7A of current. It may be cheaper than drives that will handle the higher current. You are aware that stepper ratings are "holding torque" where there is no work being performed? The torque drops off at RPM but at slow step rates it can be pretty close to holding torque.

unless I want to get wild on the reduction side of the drive and then I will have trouble fitting it under the cover on the headstock. I would really rather not go outboard with a drive.I have been to the commercial sites and know I can buy a driver for the motor but that's not why I am here. I have been told to run the motor with reduced power. I need the power that's why I have the motor!

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> Anyone got a handle on the electronic side of this? coupling actually two steppers with a handwheel input and being able to input a ratio between the two outputs for the drivers.

Its no so much the electronics but the motion software/programming. You can hook two motors up to two drives and move two axis without encoder feedback. The math is done in the software. If you can draw it you can cut it. The control software will figure out how to make the axis follow the toolpath (coordinated moves)

If you look at this differntly and view it as a three axis CNC motion problem then you can start to utilize conventional software and programming instead of trying to build an electronic gearbox

So if you had an X, Y and Z with a router bit with the rigth profile you could cut spirals or even tapered spirals You could FIX the X and rotate the spindle using (rotary cutting)..

Take a look at some of the things that have been cut using independent axis control via MACH and CAM software like VCarvePro.

http://www.vectric.com/WebSite/Vectric/vcp/whats_new/vcp_v5/whats_new_toolpath.htm


There is nothing keeping you from doing it the way you want to in hardware but you probably won't find anything off-the-shelf and there will be some programming involved. It can get pretty lonely when you drift out of the mainstream (:-)

I have seen some of the manual gear driven rope/spiral turning machines. Just replacing the gears with electronics may not be the best way to go especially if you want to build one.

TOM caudle
www.CandCNC.com

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