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K40-III laser z-space increase

Problem

A K40-III laser, aka "Blue Horror", was obtained from China. Quickly it proved useful for cutting shapes into plastic panels.

The laser bed is good for placing flat objects on. On the stock bed there is a hole with a clamp, for placing objects to engrave. However, the space between the top of the laser bed and the bottom of the steel chassis is only about 75 mm.

Solution

After some rumination it was decided to cut away a part of the chassis, to facilitate insertion of larger objects to the clamped hole.

An angle griner was chosen as the tool.

It was decided to not strip the mechanics from the chassis before the modification, due to the time consumption and risk of screwing up something.

Dust protection

There was a risk of contamination of the mechanics and optics by the grinding dust.

For the mechanics, the dust was to be contained by filling the space between the bed and the chassis with crumpled newspapers. The paper was damped with water to prevent its ignition by the grinding heat and sparks.

For the optics the contamination risk was further mitigated by covering the lens holes and mirrors with masking tape.


Optics protection

Optics protection

Cutting

The laser was turned on its back side. The outline of the desired hole was drawn on the bottom, taken from the clamping hole in the stock laser bed with further inch of space on each side.

The angle grinder was taken to cut along the lines. The lighting in the shop was poor from that side, so following the line was not entirely easy. In retrospect, using an additional light or lining the edge with the masking tape would be advisable.

The wet newspaper filling was moved after each cut to match the position of the next cut.

There is a reinforcement beam welded to the bottom of the chassis. It was in the way and was decided to cut away. There is some loss of the chassis mechanical rigidity, which was decided to be worth living with; an additional strengthening beam can be added later if needed.


Bottom of the laser

Bottom of the laser

draft of the hole size

First cut

Cutting process

Cutting process

Cutting process

Cutting process

Cutout hole

Cutout hole

Cutout hole

Look inside

Look inside

Look inside

Look inside

Look inside

Look from top

Look from top

Results

The crumpled newspaper filling was successful as dust collector. The mass of the material served to keep the particles from flying around, and the wetness served as additional way to get the particles to stick. There was considerable amount of cutting/grinding smoke, but such ultrafine particles were hoped to not cause issues.

There was no visible dust present on the sticky tape used for protection of the optics.


No dust on dust test collector

The laser was positioned on two large block-spaced plastic flowerpots, located on the sides of the chassis. There is now a copious amount of space available in the z-direction. It is also possible to watch the bottom side of the workpiece, to assess the cut depth and not waste laser power or extraneous passes.

Cutting a side of a box


Clamped box, from top

Clamped box, from bottom

Clamped box, from bottom

Clamped box, top after cutting

Further mods

The nightmarish software that comes with the laser requires a hardware key. The key was placed in the back port of the control laptop, but there was a risk of damaging it. A small cheap USB hub was glued to the side of the laser cutter with a doublesided tape to eliminate this risk.


USB hub

USB hub

The original Chinese-made switches on the panel are made from some sort of phenolic resin, which tends to crack. One switch already failed, the plastic shattered to pieces; the part was replaced in an uneventful repair. The other switch is about to fail, the third one shows no signs of deterioration yet.


A switch about to fail

Possible improvements

The laser bed is removable, mounted on the four tall posts. It is possible to replace it with a z-adjustable bed, with a honeycomb top.

It is also possible to add a rotary positioner for engraving of cylinders, or a multiaxis positioning system for advanced laser-ablation manufacturing.

It would be also possible to replace the aluminium-sheet bed with a steel one, to allow attaching parts with magnets.

Caveat

The hole in the bottom allows passing of the laser beam. There is a minor but existing risk of specular reflection with a potentially dangerous power level. Some sort of a curtain may be advisable to cover the front bottom access.


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