Just a note, for others that follow….

The bench top type of CO2 laser machines imported from China will not cut metals without some major modifications. It is basically a reaction between the combination of the laser beam heat, the assist gas and the carbon content of the material which allows metals to be cut (with stainless steel being the preference).
A group of us, here in the UK, investigated metal cutting but as quite large volumes of Oxygen were required as the assist gas it was concluded to be an extremely dangerous venture for a home shop environment and it was suspended.

Tweakie.

Ah... so I guess it explains the video then.

Dan

A picture of a very good friend, laser etched using GCode produced with the free software DotG.

Tweakie.

Appologies to John (Picengraver) I forgot to mention, in the previous post, that the original drawing was converted to a dithered image using his fine software PicDither – then the GCode was created with DotG.

Tweakie.

Thanks Tweakie - much appreciated.  I'm glad PicDither is useful.

BTW, as we discussed, PicDither is now posted on eBay.

My Best Regards, Friend,
John Champlain
www.picengrave.com

Something I have perhaps only briefly mentioned in earlier posts is the advantage, even the necessity, of Air assist.

When laser cutting wood, for example, carbon is produced and if this occupies the bottom of the kerf it will reduce penetration considerably. Air assist, if correctly orientated, will remove these carbon particles from the kerf as they are produced and cutting efficiency is much improved as a result. Although wood is perhaps the best example, many other materials will exhibit similar properties and the end product will almost certainly benefit from the use of air assist.

If the air is applied co-axial to the laser beam, for example – the air is fed into the side of the lens assembly and then exits through the same (small diameter) nozzle as the beam, this has the added advantage of preventing vapours or particles from the work piece being deposited onto the surface of the focus lens thus extending the life of the lens and reducing the necessity of frequent cleaning of this component. The disadvantage is that a clean, dry and oil-less air supply is required. The Koi pond aerator type pumps are pretty well suited to this task, they are available in various sizes and air flow rates and are not expensive to buy. These are relatively quiet in operation and are probably the most commonly used type for small laser machines. Shop air could also be used, providing the necessary traps / filters (similar to those used for vehicle spray work) are included in the line together with suitable pressure regulation but with a compressor there is always the potential risk of oil contamination of the lens if the filters are not changed regularly.

For cutting thin materials (veneers, gaskets and the like) a relatively low air pressure / flow rate is all that is necessary – too high a pressure can result in the cut parts or waste material being blown around on the cutting bed and causing problems. For this type of work I use a small Koi pond pump and also have an air-bleed valve in the line so that I can reduce pressure / flow rate if necessary. For the thicker materials I use an old twin cylinder Gast Roc-R pump and between these two different pumps manage to cover most eventualities.

Tweakie.

I have been asked by Picengraver to test a beta version of his latest software ‘PicLaser’ and as I have no commercial interest in this product think it would be OK to post a few details here.

PicLaser takes a bitmap image and enables it to be converted to a dithered halftone (using one of a number of different, industry standard algorithms) then generates the necessary GCode to reproduce the image. It uses a unique method to create a laser ‘on time’ dwell which makes it just as suitable for high as well as low power lasers. I have not yet tried it using an impact magnet (my next task) but I have every confidence.

This was my first test piece with the laser, it is faux aluminium faced engraving laminate, with the image just slightly larger than life size and took around 20 minutes to complete. I have deliberately scaled the image up a bit and kept the focus tight so the individual dots are clearly visible but for portrait work it is generally considered best to de-focus slightly, producing a somewhat larger dot size which blends in a smoother manner.

Tweakie.

By way of an update - I have now tested PicLaser generated GCode with an impact magnet (using exactly the same code I would use with the laser) and the results have been posted in this thread -  http://www.machsupport.com/forum/index.php/topic,20490.msg154622.html#msg154622

Tweakie.

Eventually my laser has started to show some erratic behaviour by failing to trigger properly at low current settings and it is now evident that it is time to replace the tube.
The original has done some sterling service over the last few years (imported from the USA in March 2007) but they don’t last forever and must always be regarded as expendable components.

Also as always, nothing is ever simple and I have not been able to easily obtain a ‘size for size’ replacement so some modifications are going to be required to accommodate a longer length of tube.

The standard 30/40 Watt Chinese laser tube is approx. 700mm overall length and offering one up to the existing enclosure shows that I will need to construct bit of an extension to enclose the high voltage end.

Something I learnt a few years back – no CNC project is ever finished it always remains an ongoing adventure.  

Tweakie.

What would cause this? Do you think the CO2 is breaking down or the mirrors are clouding up? I would think the power supply would quit before the tube.

I just looked, it's been 3 years, almost to the day, since you started this thread.