Tag: Laser Cutter

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Laser Cutting: Preparing the File

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File format required is Adobe Illustrator (any version)

You can import many common file formats into Illustrator for preparation; e.g. AutoCAD DWG, DXF, Adobe PDF

Illustrator objects are made up of FILLS – the inside of the shape – and STROKES – the outline. Correct preparation of the Illustrator is all about the stroke colour and thickness:

lasercutting-strokefill

Fills are only relevant to laser cutting if you want to engrave solid areas, for straightforward line cutting and etching none of your objects should have fills; if necessary set the Fill property as “none”

lasercutting--fill

The Stroke sets the colour and thickness of the graphic and this is what directs the laser cutter to etch or cut – the stroke thickness needs to be 0.1pts

lasercutting-strokethickness

Colour of the stroke is important too – and it has to be a particular type of colour: RGB. It is best if you set you Illustrator document to RGB color space with:

File -> Document Colour Mode -> RGB

Then open up the colour window

Windows -> Colour

The look varies between different versions of Illustrator but the function is the same.

lasercutting-colourguide

Make sure the swatch is set to RGB by clicking and selecting from the little down arrow in the top right hand corner (circled).

Now when you select a graphic in the drawing its colour value is shown – and can be changed – from this window

The colours you are most likely to be using here are Red – for cutting, and Blue – for etching. Black works too but that is for a much slower raster etch where it will draw one dot at a time.

Select your graphic and set it at RGB Blue or Red by setting the RGB values in the Colour Window at

Red
R: 255 / G: 0 / B:0

Blue
R: 0 / G:0 / B:255

lasercutting-checkcolour

This star is now proper RGB red, at 0.1 stroke thickness. If this was sent to the laser cutter it would cut out a shape of a star in the materi- al. Had it been drawn in RGB blue it would etch a drawn shape of the star into the material.

You can do a select multiple objects – or even all of them – and set their colour correctly all in one go. Keep an eye on the Fill property while you do this and make sure it really is None and not just white.

The example above is a very simple one; but problems are likely to arise with more complex shapes and drawings that come in from oth- er sources. Typical issues are:

Multiple Lines

This is when there are two or more lines on top of each other. It often occurs when drawings are brought in from a big AutoCAD file. What it would mean is the laser going over those lines again and again cre- ating inconsistent width lines (and taking longer to complete).

If it is just two lines on top of each other you could probably get away with printing it anyway, if there are more then you really should de- lete the duplicates. Unfortunately this can be a tedious job; a couple of things that might help you are

  • The AutoCAD 2013 has a tool called “Overkill” that will detect and delete duplicate objects in a selection set. Just type “overkill” then follow the prompts.
  • In Illustrator you could window select an instance of multiple lines, then shift select, to deselect the top one, then hit delete to delete all but that one.

Nested Groups

An Illustrator file that appears to be non-filled lines may still have fills and wrong line-weights hidden inside groups. This is quite common in stock illustrations grabbed off the internet. You may have to ex- plode groups to investigate this.

Errors like this will show up when you bring your file into the laser control software –

If you have lines to be cut in red, or etched in blue and they preview in the laser software as black then they won’t laser in the proper way.
The onus is on you to go back and investigate!

 

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Advanced Laser Cutting

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Here are some interesting examples of laser cutting where software techniques are used to slice a 3d computer file into 2d shapes to be cut for re-assembly as a physical model.

 

The free Autodesk software 123DMake will import a 3d file (.STL) and then generate 2d cut-able parts that are used to construct the model. It can do this in a variety of styles:

Stacked Slices

The model is simply divided into slices that are assembled on top of each other to form the shape.  Typically the model is sliced horizontally but the software does give the option to change the slice angle so the shapes run front to back for example.  This is the easiest type of model to assemble and gives the most accurate form, it’s likely to create the most amount of cutting though

stackedslice-3ds

This was a quick 3d studio model (render on right) – a lofted circle shelled with much twist / bend / taper modifiers applied to it.  The laser cut model looks (and feels) a lot better than the stark flat computer render.

stacked-zaha

A version of Zaha Hadid’s Heydar Aliyev Centre in Azerbaijan.  The 3d model was downloaded from 3D Warehouse and fixed in 3D Studio (3d Warehouse models often need repairing before they are ready for cutting).

stacked-skulls

A skull model that was actually captured using iPad 3d scanner software (another free piece of Autodesk software called 123Capture).  This takes many photos of the shape and creates a 3d file from that information.  The file can then be brought into 123DMake and made into cut layers.

In this model each layer has been padded with a piece of card – that card should actually have been thicker as the skull still looks a little squashed.  On the right is a photo of the same model (proper dimensions) printed on the z450 3D printer.

stacked-head

This model was printed on 1.5mm grey card and gives a quite smooth version of a head.  The model has been smoothed on the right hand side by sanding and Dremeling it down – however the dirty, rough non sanded version is has a nice textured quality that is lost on the clean and smooth version.

Slotted Slices

In addition to the relatively straightforward stacked slices the 123DMake software can also generate model cuts in a more figurative way:

slotted-slices

In this image the model on the left is the original followed by three possible variations of “interlocked slices”, “curve” and “radial slices”.  The parameters for each can be tweaked to alter the number of slices and spacing – this could be useful for mimicking floors / storeys in a building model.

Here is a real version of a radial sliced model, using 1mm grey card.

slotted-head

This radial slice version of the “Walkie Talkie” building in Fenchurch Street London had a shell modifier in 3D Studio applied to so it is just a thin hollow shell. The slice operation then creates a skeletal form rather than solid planes.  The result is quite striking and only uses a small amount of material.

lasercut-walkietalkie

These types of models do use less material but they are more difficult to assemble – like a 3d jigsaw.  With complex shapes with gaps in the middle slices have to be put together in a particular order – the software in fact has a feature where it will show the order to put them in.

The slot models are less detailed than the stacks and are not suitable for all situations for example if more detail is needed.  They can make for very interesting conceptual models though.

Folded Panels

The software also has the option to create a paper model version that can be folded and glued together.  It is an appealing idea for quick, cheap paper models but the reality is that it’s only the simplest of shapes that produce a usable result.  Here is what the software makes of head shape and simple house shape

folded-slices

The head would be quite difficult to fold together correctly and probably would not give a great result.

Materials

These models could conceivably be cut on any laser-cut material, e.g plywood, acrylic, cardboard, etc. – the software does allow for the required layer thickness to be altered to match.  For the slot models it is a lot easier to work with a material with some flexibility like card rather than a rigid material as the parts do need to slide together and interlock.  For a more advanced project a mixture of materials could be used, for example wood for the horizontal slabs and clear acrylic for the uprights.

The interlocking models ought to fit together with no glue needed whereas the stacked models do need to be glued – this can take some time and patience.   Complex multi layered models would also mean a lot of cutting so although a cost saving could be made on using cheap materials like cardboard, the actual cutting time can be long, especially when multiple sheets area required to be cut.