How does our Laser cutter work?
Our Laser cutting machine
works with a
new precision Italian manufactured laser tube based on CO2 (carbon
dioxide)
gas. It is rated at 120 Watts of infra red (invisible heat) power. The
infra red light is emitted as a concentrated and coherent beam at a
wavelength of 10.6 µm. When it exits
the tube it is a thin <2mm diameter beam and is
directed to the
(x
axis) moving gantry by special gold mirrors.
On the moving gantry, further mirrors direct the beam down onto a cooled ZnSe focussing lens. Filtered, dried air is supplied to this lens, and excess air is blown out a small nozzle towards the focal point of the cutting. This also helps keep smoke, and residues from vapourising up, and onto the expensive focus lens.
The focus lens converges our 2mm laser beam into a 0.2mm narrow pin-point. It is this 0.2mm beam that does the cutting, with the focal point adjusted so it is in the center of the material being cut. As with any focussed light, there is this focal point, before which the 2mm beam converges into 0.2mm focus, and after the focal point the laser beam diverges out of focus. This is where any laser cut material gets its slightly angular cut even when all the mirrors are adjusted perfectly square, and the cutting beam is perpendicular to the material. Also the some cheap budget laser cutters, begin with a 3-4mm beam, which is then focussed into a 0.4mm+ focal point. This causes a more angular focus, which causes a more angular cut. Some of these lasers also burn the top edge of the cut because the beam is not sharp, but fades in power from the center of the beam. Our laser does not suffer from these poor quality issues.
A laser cutting head can also be raster scanned (zig-zagging), over an engravable material, and the laser beam power is turned on and off at high speed producing rows of precision burnt dots A laser in this mode can engrave very high density images, and graphics into materials. Our main laser is not set up to do this, as we use it purely for cutting. However we have a smaller 50 Watt laser dedicated to engraving.
On the moving gantry, further mirrors direct the beam down onto a cooled ZnSe focussing lens. Filtered, dried air is supplied to this lens, and excess air is blown out a small nozzle towards the focal point of the cutting. This also helps keep smoke, and residues from vapourising up, and onto the expensive focus lens.
The focus lens converges our 2mm laser beam into a 0.2mm narrow pin-point. It is this 0.2mm beam that does the cutting, with the focal point adjusted so it is in the center of the material being cut. As with any focussed light, there is this focal point, before which the 2mm beam converges into 0.2mm focus, and after the focal point the laser beam diverges out of focus. This is where any laser cut material gets its slightly angular cut even when all the mirrors are adjusted perfectly square, and the cutting beam is perpendicular to the material. Also the some cheap budget laser cutters, begin with a 3-4mm beam, which is then focussed into a 0.4mm+ focal point. This causes a more angular focus, which causes a more angular cut. Some of these lasers also burn the top edge of the cut because the beam is not sharp, but fades in power from the center of the beam. Our laser does not suffer from these poor quality issues.
A laser cutting head can also be raster scanned (zig-zagging), over an engravable material, and the laser beam power is turned on and off at high speed producing rows of precision burnt dots A laser in this mode can engrave very high density images, and graphics into materials. Our main laser is not set up to do this, as we use it purely for cutting. However we have a smaller 50 Watt laser dedicated to engraving.
The position of the laser cutting head (the focus lens assembly) on the gantry, the speed, direction, and laser power are all controlled by a special control unit. This control unit receives your vector file
after it has been specially processed for laser cutting. We do all this in house for you, as it can vary from laser to laser. This processing is necessary for accurate and orderly cutting. All the lines must be "offset", or moved outside the actual cutting lines by 0.1mm. The laser beam will then follow this new line around the outside by 0.1mm This is half the width of the laser beam. Remember, the laser beam removes 0.2mm of material along the line, so if you don't do this, your cutout will be 0.2mm smaller (0.1mm all around). We also offset all inside cutouts the opposite way - being 0.1mm inside the cutting line. We also change the cutting order, so that inside cutouts are cut first, then the outside profile is cut (this stops the lasercut part falling free, before the inside cuts are complete). We also make the laser cut from one side of a sheet to the other, this shortens total job cutting time.
This pre-processing is fairly straight forward and almost automatic, provided your vector files, drawings are drawn correctly.
We do this processing as standard, and it only takes a few minutes, if your vector drawing is tidy.
You may supply us your cutting file with offsetting already done, or if 0.2mm is not important, we can simply cut your job as is. Please let us know your preference if this is the case.
File formats and vectors (The following is similar to our CNC router cutting information page).
For all laser cutting we can use any flat 2D "vector" file format. A vector is a CAD drawing format based on points called vectors. These vector points are joined and displayed on your monitor as straight lines and arcs, of various thicknesses and colours. Vector graphics are fully scalable without loosing resolution / detail. Vector shapes can also be colour filled to represent the materials used. However, for running a cutting machine, all we require is lines defining the edge of the cut. This line must be the finest possible (0.1 or better), and be continuous from start to finish. ie, not all broken up into seperate lines, dashes or seperated curves. If they are, we will let you know, and you can fix it at the design stage, rather than us fix it later.
When exporting a file, ready to send to us, please make sure you un-click all the extra include options in your export details box. Items like "include thumbnails", and "embed" fonts must be unticked. We just need the basic vector file. Anything extra can corrupt a vector file, and make it unreadable for our software.
There is a large range of easy to use software that creates vector graphics. The format is shown by the filename extension, and most are "export" options in most software. The best error free common export format we have come across is EPS, if you can, please use it. EPS files should be no more than 500kb in file size. Usually alot smaller. If your eps file is larger, it has been saved non-standard and is probably full of extra picture and graphic information which we do not need. This extra data in the file can cause problems for our machines ability to read, or use the file for a CAM process.
Other formats we can use are CorelDraw - CDR (version14 or earlier), Adobe Illustrator - AI (version CS or earlier), CasMate - SCV, Adobe PDF - vectored pdf only, DXF in it's most basic form, PLT files, which are hpgl - with hpgl PLT files, make sure you check that your curves are curves and not made from lots of shorter flat lines!
Also, make sure there is a mention of at least one measurement in the file, or a bounding box is drawn of a known size. We MUST know this measurement as a double check that your drawing software hasn't resized your drawing for your printer, or plotter, and then we get the wrong size version.
We can usually extract vector lines from dxf exported files from software like Solidworks, however Solidworks exports an odd dxf format which isn't compatable with alot of cnc machining software. The lines and arcs are all seperated, and doubled up, this can cause problems when offsetting, and in generating a consistent "closed" toolpath for the laser to follow. I hope someone can advise a fix, or fix Solidworks.
Adobe Illustrator is another drawing package available, although it produces incredibly oversize vector format files. We are able to convert AI files (version CS or earlier) for use with our machines. Corel Draw is another popular drawing package which can print directly to most laser cutting machines (with the correct driver).
Sketchup (free version) can produce vector drawings, and a free plugin is required to export a vector file.
We can "nest" (closely arrange) your cutout parts to suit the material and minimise wastage. This can mean we move the parts around on the material, and sometimes "rotating" cutout shapes to fit closer together. We can do this if the material is expensive, or you only have a limited size to use. Note, we cannot rotate cutout parts in the material if the material has a "grain" or linish to it. (most wood grain cutouts look tidier if the grain is running horizontally, and any rotation will ruin the horizontal grain).
You may "nest" your parts before sending us your file, using your CAD software if you like, all we need, and specify is that you allow a small border of uncut material around your cutout designs. This is called a "safe area", by some laser cutters. We only need a small border of 10mm all around. Or just make sure the material you use is 20mm larger than your cutout area. This is simply so we dont have to spend too much time aligning your materials on the laser bed. We can cut right to the edge of a sheet of material, but it will require some double checking of the placement of material.
As mentioned, our laser size is 1200mm by 1200mm. The machine can take oversize sheets (4 ft, which is 1220mm), but will not cut on the extra 20mm width. All small parts cutting is preferably done in the front 600mm by 1200mm wide, this is simply because is easier to pick out the small parts without reaching way over to the back of the machine!
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Quality and finishing.
We have an exceptionally high quality of cut due to our use of precision machines, and quality Italian laser tube. If we are cutting a new and unknown material type, or density, or quality, we prefer to do a test cut on a small area, or seperate sample first to determine specific cutting parameters. There are alot of factors which can lower cutting quality, and we try to always achieve the best possible. Pease note, that we are a cutting service, not a finishing service. If the edge of your material requires a polished, perfect finish, it may require further treatment after cutting (flame polishing / sanding etc). This is not covered by our cutting service. The laser will "flame" polish acrylic plastic as it cuts leaving a shiny edge, or a clear edge on clear acrylic. This clear shiny edge is still not optically perfect, and for a perfectly flat clear edge, it will still require some finishing after lasercutting.-
Please use the following as a guide only, for laser cutting materials.
We can also cnc router cut most of these materials.
Our laser will NOT cut metals, this includes steel, aluminium and tin foil. We do NOT lasercut cut any metal, try Metco Engineering in Wingate, Lower Hutt.
Also, we don't lasercut PVC (polyvinyl chloride), which includes vinyl tiles. PVC creates toxic fumes, and these fumes are also very corrosive to metal machinery parts. We CNC routercut most PVC materials.
We do cut all the following:
MDF (composite wood) - flat clean cut, black, or brown burnt edge, smells after cutting, but disipates after a few days. Edge is semi sealed for painting, less primer required. Some people prefer lasercut MDf if left as is, or painted a dark colour. From our customers feedback, I have heard that if painting the black/brown lasercut edge white, or a light colour, it requires a good primer, or lots of coats, and can be frustrating and time consuming if painting many small items. These customers prefer CNC routercutting MDF.
NOTE: MDF is a porous composite material, and is unstable in wet or damp conditions. MDF is NOT suitable for outdoor projects, as even when sealed, water will find its way into the material and dissolve the bonding. MDF will soak up liquids and swell beyond repair.
Plywood - thin <10mm and specialty laminates cut fine with usual black edge.
Plywood - thicker >10mm will cut, but knots and glue upset cutting, so we generally use CNC router.
Leather - clean cut but brown, black burnt edge, can be sanded, and cleaned ok.
Paper, and cardboard, cuts, but with brown edge.
Fiberglass - G10 etc, (non copper, clad) thin <1mm lasercuts fine - black edge.
Fabrics - most synthetic (polyester, etc) fabrics will lasercut cleanly, sealing the edge as it cuts.
Foam - thin neoprene, (gaskets) lasercuts fine, but requires sacrificial backing board to keep flat.
HMWPE <6mm (polyethylene) nylon, teflon, all cut but with varying degress of melt, and rewelding.
HMWPE >6mm (polyethylene) nylon, teflon is CNC cut on our router with very good finish.
Styrene, clean clear cut, with some melt along edge.
Polycarbonate - up to 2mm cuts clean and usually clear, yellow/brown edge.
Polycarbonate - 3mm, will cut, but burns edges blacker. Can be sanded to clean and clear edge.
Polypropylene, clean clear cut, some waxy residues on edge, perfect for stencils, as non stick.
Acrylic - most popular lasercut product - cuts clean and clear, up to 20mm thick, and 25mm thick by special request. Available in many colours.
Rubber - thin foam rubber only - clean cut, black dust to remove..
Rubber - thin nitrile (white) - clean cut, and clear, no burning.. but lots of dust to wash off.
Rubber - thicker and fiber reinforced can be easily CNC routercut.
We also engrave patterns, logos, names and designs into many materials with our laser engravers.
