Re: [CAD_CAM_EDM_DRO] Re: Polar Coordinates CNC?

Yes but moving from x(0)y(0) to x(1)y(1) requires the same sort of calc.
However you cut it though, the inherent differences in accuracy at
differing radii in polar machine, is the death knell for practicality.


At 08:23 PM 11/4/02 -0600, you wrote:

>Fred, I have to agree with the other Ray H. A Polar
>machine/software making a move from X(1) to X(2) must
>calculate every position along the path, whereas a
>Recti-linear machine merely has to say' "Am I at X(2)
>yet?... no, well, then add another pulse at the X-axis."
>Now, it's true, that in a Rect. machine/software,
>interpolating a circular move, the program must calculate
>every point on the path, but so must a Polar
>machine/software. Polar machines must, of necessity be more
>complex. I trained o a FANUC 120-iL Robot Welder at the
>Lincoln Electric School in Cleveland, OH, a couple of years
>ago, and that was one complex machine. Six axes, and four
>different reference frames (points of view). Fortunately,
>the programming was done via a Pendant, so it was
>relatively easy... But the machine was complex. It was
>really fearsome, to watch that robot welding, just thinking
>about all the calculations it had to be making every few
>microseconds.
>
>RayHex
>
>----------
>> From: Fred Smith <imserv@...>
>> To: CAD_CAM_EDM_DRO@yahoogroups.com
>> Subject: [CAD_CAM_EDM_DRO] Re: Polar Coordinates CNC?
>> Date: Sunday, November 03, 2002 8:06 PM
>>
>> --- In CAD_CAM_EDM_DRO@y..., Ray Henry <rehenry@u...>
>wrote:
>
>> > along that vector so in effect it is a polar move. I
>can't for the
>> > life of me see how specifying three angles and a
>distance would be more
>> > efficient or would somehow alter the fundamental
>thinking about
>> >milling or turning.
>> >
>>
>> It's the machine that is simpler.
>>
>> Think of a turntable (like a lazy susan) with the part
>mounted in
>> place on the turntable. The rotation is C axis
>>
>> Now place a single horizontal linear axis parallel to the
>face of the
>> turntable (X) above the work piece, and mount a Vertical
>Z axis onto
>> the X. (R is not a valid CNC linear axis so I will refer
>to it as X.)
>>
>> The machine is simplified to a single linear X and a
>bearing for C.
>> Instead of at least 4 precision linear guide components
>for a linear
>> gantry style machine, you reduce it to 2 (shortest
>possible) plus the
>> bearing (Actually only 1 if you use a dove tail
>arrangement like a
>> Bishop-Wisecarver rail). The Z axis is the same
>mechanism in this
>> case.
>
>
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