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2D Design Tips for the Laser cutter

Prototype your designs

It's unlikely you'll create a perfect product straight away. It usually takes a prototype or two to get your design just right.

This means that you're best to start small. You might want to work out what elements are most important, then try those out first before making your whole project – particularly if you're using interlocking parts.

After a couple of tries, you'll be familiar with the design process and how to design for certain kinds of materials and projects.

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Print out your designs on paper!

Don't overlook the advantages of good old-fashioned paper! Print out your design – you could consider this a free and instant first prototype. It's the ideal way to spot sizing errors, see whether you've made holes big enough, and get a feel for what your final result will look like.

To make this even more useful, adjust the width/weight of your stroke lines to match the thickness of the laser cut before you print. This will help you identify any areas that are too finely detailed to provide a good result.

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Optimize your designs & lower the cost

The laser cuts different materials at different speeds. As a rule it takes longer to cut thicker materials than thinner ones. The laser is also faster at cutting straight lines than it is at cutting curves.

One excellent way of reducing your making cost is to share cutting lines. If you have two or more objects in your design with parallel lines, you can lay them side by side and remove one of the now-overlapping lines. This means you're effectively cutting out two pieces at once. (See the Starter Kit for the software package you're using to find out how to remove the unneeded double-lines.)

When using raster fill engraving, you're best to keep all of your raster fill engraved areas as close together as possible. This is because the head of the laser will have to pass over the gaps between the areas to be engraved many times before the job is done. This can unnecessarily increase your making time and cost.

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Get a smooth & even edge on your material sheets

The outside of the orange border in our templates represents the size of the material. This can vary though as the machines that cut the material to fit in the laser cutter are not as accurate as the laser. This also means the sheet is unlikely to have the same high quality finished edge left by the laser.

So if you want to be sure where the edge of the material is and ensure a smooth even edge, we recommend putting an outside cutting line around the edge of the white area. That means the material will be an exact size and have a consistent laser cut edge.

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Avoid overly detailed cutting

The laser burns away around 0.2mm each time it makes a cut. This means any areas in your design where cutting lines come closer together than 0.5mm could be burned away entirely, and any gaps narrower than 1mm are likely to be somewhat fragile.

Read more >>

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Improve your engraving results

There are so many options for your engraving settings, it can be hard to know which will work best for your design. Absolutely nothing beats prototyping a few different options, but we've got a few resources which can help.

First, be sure to check out the engraving photos on each of the material pages in the catalog.

Second, you'll find some great information here and here.

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Make sure your 3D projects fit together well

Find out how to design pieces that fit together perfectly.

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2D design tips for the CNC router

Use construction lines

Use construction lines to mark out your shapes before you add cutting lines. Draw the parts as you want them then change the solid lines to dashed lines. Now generate your cutting lines by drawing new lines or by copying, pasting or enlarging existing shapes. Change the line weight to 0.25"/6.35mm to check you're cutting to the edge you want.

Black dashed lines - the dimensions you want
Blue lines - cutting lines
Thick gray lines - set at 0.25" and used to check sizes.

This approach works well on simple geometric shapes - more complex shapes may be harder to acheive.

Remember to remove your construction lines before uploading your file. You may want to save the uploaded file as a new version so you always have your original file with the construction lines in it.

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Triple check your measurements

Make sure you allow for the width of the router bit in your designs. (You can read more about this in the 'How to design for CNC routing' section of our starter kits.)

Every cut and pocketing line will remove 0.25". This means cut objects will be 0.125" smaller on each side than you have drawn in your design. Cut-out holes will 0.125" larger on each side.

One approach is to change your line weights to the thickness of the router bit. You could also create reference shapes that are the size you want your final cut-out pieces to be. Use an orange fill set to RGB 246,146,30 as this will be ignored by our upload system. You can then use this orange line to check that each of your cutting lines is 0.125" away from the edges of your shapes.

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Creating durable designs

CNC routers use a spinning cutting tool that moves through the material to cut out your design. Having a tool that contacts the material while cutting adds complexity to the process and increases the chances something could go wrong. An advantage of laser cutting is that there is no physical contact between the tool and the material. That means you can cut more intricate designs because pieces will not break off due to the force of the tool. With CNC, your design needs to be able to withstand the force of the spinning tool as it moves along your outline.

Too much detail can cause problems. Features that are too intricate or small may not be able to support themselves during the cutting process. Design for a minimum feature size of 0.25"/6.35mm. The lines you draw to describe these features need to be at least 0.5" apart.

The spinning router bit can set the material on fire if it gets stuck in one spot for too long! This is most likely to happen if a piece breaks off and jams in the machine.

One way to test that your designs are durable enough is to change all your line weights to 6.35mm (0.25") and check the measurements between the lines edges. There should be 0.25" between the edges. Remember to change them back to 0.01mm before saving your final file - or you will have trouble uploading it to your Personal Factory.

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Prototype your designs

Even after making sure all your measurements are correct, it's unlikely you'll create a perfect product straight away. It usually takes a prototype or two to get your design just right.

For this reason, you're best to start small. You might want to work out what elements are most important, then try these out first before making your whole project - particularly if you're using interlocking parts.

After a couple of tries, you'll understand the making process and how to design for certain kinds of materials and projects.

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How to get a better edge finish

The CNC router does not produce a 'finished' edge like the laser. Edges are likely to have burrs and waterlines visible so you'll need to sand the edges after cutting.

Burrs are the stringy fibers of wood that remain after cutting.

Waterlines occur because it takes multiple passes of the router bit to cut through the material. The direction alternates each pass from clockwise to counter clockwise and back again. There is likely to be a waterline on the edge of your material produced by the different depths the router cuts at. This can be sanded off after cutting.

The router produces a different edge finish depending on which side of the bit the work is on. For example, if you're routing a single line, one side of the pocket will be cleaner than the other. This is because the bit is either spinning into the work or out from it.

The edge where the router bit is breaking out is generally rougher than where it has cut in.

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Open vs closed vectors

In order to get the cleanest cut, paths should be a closed loop. An offset of 0.01"/0.25mm is enough for the router to loop arround and ensure the work is cut with the same edge of the router that produces the cleanest result.

A simple offset of 0.01"/0.2mm will produce 2 clean edges.

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Pocketing tips

The nice thing about CNC is you can determine the path of the router so you have a lot of control over how the machine cuts out your design. There are a couple of things to think about when creating a pocket or hole.

The router will cut open vectors before closed vectors. When creating a pocket or hole it's best to remove the material from the middle first and then finish off with a pass around the outside to tidy up the edges. You can direct the CNC to cut this way by creating open vectors to remove internal material with a closed vector as the outline of the pocket. This also ensures greatest accuracy as the parts are held firmly in place before the outline cut is made.

A continuous line (red, green, magenta) is better than a series of disconnected shorter lines. Every time the machine starts a new path/line it has to move to the start of the line, plunge into the material and then move along the line. Repeating this process over and over is not ideal. The edge of your pocket will not be as clean as it will be if you use a continuous line.

Also you can't guarantee which order the router will cut a lot of short disconnected lines. It is possible that it will leave a middle line until last leaving a thin, unstable piece of material that has the potential to break off and damage your job.

One more thing. If you just create the lines shown here there will be little points of material left around the edges. If you want a smooth edge you should make sure you have a line that cuts the perimeter. So if you want a square pocket at a depth of 75% of the material, like this:

Then the path you need to draw would look like this:

Note how the lines are set inside the dashed line (or construction line) which represents the end shape.

The lines are the path the router bit follows. Remembering that the bit is 0.25" in diameter, the lines need to be set in from the outside edge. The router will remove the material in two phases. First it will remove the middle material because the path is an open vector. Then it will remove the material around the perimeter.

It is good practice to make sure the lines you add for removing the material in the middle do not extend so far as to cut the outside perimeter of your pocket. You can see from the solid grey outline on the left of the image above that the router bit does not hit the perimeter. The outline (shown at the right of the image above) should be the only line that will cut the perimeter as this will provide the best edge finish

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Overlapping pockets

It is a good idea to overlap your pocketed areas to make sure you get a clean edge. This is because the tool is round and any slight movement in the machine or material could leave a point on the edge of the board. The overlap should be at least 0.0625". For example, if you want to create a pocket with multiple depths, you will get a cleaner edge by overlapping the pocketed areas.

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Cutting tabs and holes

Tab and hole joints are easy on the laser because you can cut holes with square corners. On the router every cut will have a .125" radius on the corner and therefore you need to overcut part of the shape to remove this radius. In CNC, a 'dog bone' is used when you have a design that needs to fit together and has parts with square corners.

The profiles of a tab and hole joint look like this

Tabs

If you were to just cut around this profile you'd get this result:

There would be a radius left in the corners of the tab and it would not fit all the way into the hole.

The lines you need to cut for the tab are shown below. Note that the line is continuous. The extended cuts will remove a bit more material that is ideal so make sure your tabs are wide enough to support themselves.

And here you can the result, with the grey area representing the material removed and the dashed line showing the profile with square corners .

Holes

You need to take a similar approach to holes or pockets so the tab can fit in. Say you want to fit a tab into a rectangular pocket like this:

Then you need to draw the lines like this:

CNC will make cuts like this:

and then:

So the final shape of the pocket will look like this - with the dashed line showing the rectangle you need without the radius in the corners

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Cutting slots

Slots between 0.5" and 1" in size can be tricky to cut. As the router outlines the slot, small islands of waste can be left in the middle which are not beefy enough to support themselves. These usually break off leaving a rough edge and cause the machine to jam damaging it and your work. If you have a narrow/small strip of waste, it's best to add extra lines so the area is left clear.

For example, if you have lines for a slot or hole that are 0.5"-0.75" apart, you should add extra cut lines to remove the 0.25"-0.5" of waste material in the middle. Like this:

Note the overlap of the cut lines at the top of the right hand image. This will make sure the end of the slot has no points left over.

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Text tips

Keep it simple. You need to convert your text to outlines. Anything less than 2" high is likely to lack definition. A continuous closed path for the router will give you the cleanest result and a simple offset of 0.01"/0.2mm will produce two clean edges. Use a connected hatch line to remove material from the middle if needed.

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Send us your CNC router design tips

If you've got any advice on the best way to use Ponoko for CNC routing, email it through to us at service-at-ponoko-dot-com and we'll add it here - with a credit of course!