Re: [CAD_CAM_EDM_DRO] Re: Tubing Notcher

We only used a single axis to tilt the torch in plane radial to the tube
centerline, remember the pipe notch and the bevel is a surface of
revolution. The pipe or tube is rotated under the torch and the bevel is
generated as a spline along the torch axis.

I am leaving B'ham in the morning for a meeting in Seattle but will be
back on Friday, I will try to do a rough hand sketch over the weekend.
The generation of the notch and bevel actually turns out to be much
simpler than it seems.

gary

douglasr987 wrote:

>Gary,
>
>Torch is aligned radially to the pipe. Rotation and linear movement
>of the pipe relative to the torch define the position on the pipe
>which is being cut.
>
>The cutting angle will need to change in two dimensions to obtain
>the appropriate angle for the cut relative to the pipe. ie., the
>torch angle must change both relative to the length of the pipe and
>in the transverse direction. Consequently, surely 2 rotational axis
>are required to control the torch?
>
>At the point of the cut furthest from the end of the pipe, the torch
>will be angled along the length of the pipe whereas at other cutting
>positions, the torch must be angled across the length of the pipe.
>In the general position of cut, the torch would be angled in both
>planes.
>
>The same would apply to implement a standard plasma cutting machine
>for flat plate with a bevel cutting feature. For a rectangular
>plate, whilst cutting in the x direction the torch would have to
>rotate in the plane of the y-axis and when cutting a side of the
>plate in the y direction the torch would have to rotate in the plane
>of the x-axis. Again, two rotational motions would be required to
>control the torch angle.
>
>Is there some flaw in my logic and/ or a special trick that you used
>in your machine to control the torch angle with just one rotational
>movement?
>
>I shall look into pipe threaders. Such a machine would seem to
>provide a good solution for holding the workpiece.
>
>It is interesting that pipe threaders seem to generally work on the
>principle of rotating the pipe rather than the cutter albeit that
>the pipe is relatively heavy.
>
>Douglas
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, gary <garyclick1@c...> wrote:
>
>
>>The tube ends are beveled in addition to being notched to create
>>
>>
>a
>
>
>>welding preparation for welding from the outside. Since the
>>
>>
>outside is
>
>
>>cut away for the bevel the intersecting surface remaining is the
>>
>>
>sharp
>
>
>>edge of the inside of the tube. To generate the welding bevel the
>>
>>
>second
>
>
>>rotary axis tilts the torch +/-75 degrees, if the center of the
>>
>>
>pivot to
>
>
>>tilt the torch is not aligned to the tube ID, tilting the torch
>>
>>
>will
>
>
>>increase or decrease the length of the tube making the notch
>>
>>
>inaccurate.
>
>
>>As far as the rotation of the torch is concerned in more than one
>>
>>
>plane,
>
>
>>remember we were notching the end of the tube and the tube was
>>
>>
>being
>
>
>>rotated. The torch centerline was aligned with a radial element of
>>
>>
>the
>
>
>>tube centerline. The notch or "fishmouth" was generated by
>>
>>
>rotating the
>
>
>>tube around its axis and moving the torch along a linear axis
>>
>>
>parallel
>
>
>>to the tube centerline. The tube was mounted in a large hollow
>>
>>
>chuck
>
>
>>stolen from a very large Landis pipe threading machine.
>>
>>gary
>>
>>
>
>
>
>
>
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