Hi Devmonky
Hi all

I agree that you could use the output from the sensor to directly plot position.
Using a simple webcam with a 2mm sensor to centre a .008" piano wire or laser, the effective measurement range would be maybe 1mm. The active area of the sensor needs to be found in some way, unless the wire or beam is positioned within the active area all the time.

As you can see below, I have been thinking of making a device that flattens surfaces by "Pecking" using a small cutter stepped over a work piece. The overlapping pecks will create a flat surface that in the end will look like an engine turned surface. Another way of thinking about it is as if the surface was scraped. As with scraping practice the last step is to lightly stone the surface to remove burrs and correct any high spots.

When the positioning device shown earlier was being designed the range of motion was considered - what sort of materials would be measured and for my purposes flattened? I was thinking rolled 50-100mm square steel sections, weldments etc. I reasoned that maybe a 5mm range of motion would be desirable to flatten these objects. Large bends in thin walled tube would obviously not work if severely bent, and would be cut right through without the addition of some sort of built up face made from Steel, Aluminium or Epoxy, standard practice in industry.

My design intent was to design a simple machine to flatten objects that could be built from very low-cost materials. There are numerous posts on the Web regarding the creation of flat surfaces on DIY built CNC Routers Mills and other machines, various methods are used, some quite costly. Many are not entirely successful.

As I described earlier the test jig uses a lever flexure and screw driven by a stepper motor. I used the same mechanism to position a grinding jig to within a repeatable mechanical accuracy of .0001" 2.5 microns. I know it works. It has a range of motion of 5mm.

The mechanism is able to apply a significant force the 10:1 primary lever and flexure provides enough force to easily position the Z carriage. (Flexures are free of backlash although geometric errors have to be considered).

My plan is to also drive the mechanism with a crude Y motion that guides the sensor head and cutter along the work piece. I imagined using a piece of steel, say a piece of I beam or other available steel section with simple ball bearing rollers guiding a carriage along it, the piece being flattened would be placed upon it. The accuracy of the flattening is determined by the wire and sensor not the beam or mechanism. The only preparation of the support beam needed would be to hand grind and stone the surfaces that the ball bearings run on for smooth running.

Two possible arrangements are:

For a horizontally disposed flat surface generator.
The x axis requires very little travel, maybe 75mm will cover just about any bearing surface I can imagine. I am still thinking on this. Moving the work piece laterally on two small slides would be simple enough for shorter lengths. Longer lengths would be a different matter - they would require mid span support or they will deflect slightly due to cutting forces and gravity. The X axis motion will require high precision, however over a very short distance. The two or more slides will all have to be coplanar.

For a vertically disposed flat surface generator. (This has always been my preferred option.)

This solves a number of the design issues of the horizontal arrangement. The y axis can be the same as previously described (except it now has to be described as the Z axis!)

In this case two alignment wires can be used, one each side of the Z axis support beam, simply suspended with a counterweight (the weights can be placed in a container of thick oil to dampen them).

Using this arrangement there is no catenary sag at all, the wires will be perfectly coplanar at all times.

The Cutting head can be mounted on a small precision X axis slide.
To align the x axis slide to the work piece will require two cameras and two stepper driven positioners as described earlier. The software will need to go through a few iterations to get the two cameras in perfect alignment.

The work piece can be simply clamped to the Y axis base beam.

Cost?
2 web cams
2 wire alignment steppers.
2 timing pulleys and a belt

1 X Axis drive stepper.
1 X axis 100mm slide, bought or built.
1 X Axis screw drive - only low resolution is required.

1 Y axis drive stepper
1 Y axis timing belt drive, this will be a long belt
8 or 10 Y axis low cost ball bearings.

1 Z axis Cutter head drive stepper.
2 Z Axis 20mm slides bought or built.
1 Z Axis screw drive (Must have no backlash)

A computer and interface.

A piece of scrap steel beam or tube as long as needed, assorted scrap steel.
Time

It will depend on what you have in stock?

Regards
John