DIY Laser levelling using webcam and laser level

[John McNamara]

Hi Joe
Hi All

Also see previous post LeoLFS

If you are wondering what we have been doing while holed up due to Covid the following design has occupied us for quite a while. I am also halfway through moving house.

The attached images show the CAD drawings for a machine that uses a microscope and two suspended wires to generate a reference plane. The wires are tensioned by a heavy weight suspended in a container of oil. Gravity will assure that the wires are parallel and coplanar. Music wire is easily obtainable down to about 0.003inches. The thickness is consistent and accurate to sub microns.

A microscope on each side of the carriage is used to position a cutting head that is used to machine a plane surface on the workpiece. It is planned that this is done using software.

The spindle carries a small cutter 2 to 3 mm in diameter. It will have two modes: one a small peck cut, then a re-reference of the wires by the software and a small positioning move of about half the cutter diameter then a cut. This will be the slowest mode however due to the averaging effect of so many small measurements (not unlike hand scraping), it is expected that this will create a very high quality result.

The second mode will create a reset of the carriage on a line by line basis. This will be considerably faster.

The plane of the wire and the cutting plane are aligned. As shown, the moving crossmember carries a platform that is aligned to the wires. The main frame of the machine is 2 x 100mm square tubes. Yes, there are no precision rails: the crossmember rides on ball bearings firmly against the frame tubes. It is certain that the tubes will have a small amount of curvature as delivered by the factory that made them. It certain therefore that there will be a small “tramming” error as the carriage moves up and down the tubes. This has been considered carefully. With the small cutter diameter planned the tilt error will be very small. Remember that the cutter height is aligned to the wires. Commercial tube suppliers in Australia quote a straightness error of about 0.5mm per meter, so with a very large radius - 250m - the error will be very small indeed.

The machine has been designed to use laser cut 5mm steel, assembled by the tab and slot and bolt method. No welding will be used to avoid distortion. This method has proven itself in many past projects. The x across motion is guided by 500mm linear rails - these need to be shimmed straight. Drive is via a 16mm ballscrew. The total travel across is 220mm, however in most cases the machined surface will be between 25 and 50mm. As shown a 100x100mm workpiece is mounted Blue and Red. Using a different clamp tubes up to 200mm square can be accommodated.

The spindle motion in and out is mounted on 300mm linear rails. Travel is 120mm to allow for easy cutter changing. In use the total travel will be a few mm as the spindle moves in and out of a cut. It is driven by a 16mm ballscrew.

The carriage moves up and down the column using a 50:1 Asian worm drive gearbox (Not shown) and counterbalanced 20mm T2.5 synchronised timing belts.

All drives are step motors.
It was not intended to create a general purpose CNC machine. This allows a much-simplified drive system. Only the precision needed to create small overlapping cuts to create a flat surface was considered.

As you can see there are two people contributing to this machine design The CAD by myself and control system design by LeoLFS We have been mates for a decade or two. The machine is made possible by the excellent software developed by Joe,” Devmonkey”

For a single builder some of the parts can be reused in the final machine they build. Or better still a few enthusiasts can team together and share its use.
We are well on the way to assembling a prototype with many parts in hand.

Once the design is finalised I will place the plans on Grabcad.

Regards
John