How to use cad compress

Quick Guide

For a quick introduction into CAD Compress and how it can reduce your entity count, and increase your cut quality watch this YouTube clip:

In Depth Guide

CAD Compress is a great tool to reduce the number of entities on a drawing, and increase accuracy of your cutting. For graphic design parts it can save a lot of time and effort, as they can come out with an extremely large number of entities, even for relatively simple shapes.

Here is a sample file you can have a look at (it is METRIC, so be sure to bring it into FastCAM as such)

If you load this into FastCAM you should see the following:

It looks pretty good at the moment, but if you cut this, you would find the quality would be lacking. 

Look at the entity count (1) in the below image, you can see for what appears to be a very simple drawing, has quite a large number of entities (5179 Entities!). Turn on Control Points, (2) in the image below, to see where all the entities are located.

This mass of entities can cause the cutting to slow as it attempts to cut all these very small entities. You can see they are mostly formed in the Arcs of the Drawing. 

To fix this we will do a CAD Compress to reduce the number of entities. Click Erase > CAD Compress

The next few options are:

CAD Clean? (Yes/no)

CAD Clean can be used to fix broken entities, and lines drawn on-top of one another. For your first pass Compression, it is recommended you do NOT run CAD Clean. You can run it independently later, using Erase > CAD Clean.

In our example we say No

Maximum Line Length to Round (millimeters for Metric units, or Inch for Imperial units)

This number tells the Compression how long a line can be at a maximum for entity compression. A good rule of thumb is ~2-5% of a shape’s largest dimension. You can increase this for more compression.

In our example, we will use 5 mm.

Maximum Shape Divergence (millimeters for Metric units, or Inch for Imperial units)

This number says how far an arc fitted onto the entities can diverge for the compression. 

The larger you make this value, the more it will compress, so fewer entities but your arcs can flatten out.

The smaller the value, the less compression will be applied, so you will have more entities, but your drawing will be closer to the original.

So you need to find a balance between accuracy to your original drawing, and entity reduction.

In the example, we will use the default of 0.00698 mm

Compress Arcs? (Yes/no)

This option will say if you want to compress the arcs that are present in the drawing. Recommended to say Yes to this.

In our example, say Yes

Check against original

It will then ask you to check against the original drawing, you can use this to verify the shape of your drawing has not changed significantly from the original. If you cannot see any major differences, then your drawing has maintained its shape, whilst having its entities reduced.

It will then ask if you are satisfied with the result, you can click Yes / No / Retry

Click yes, to apply the compression. 


You can see the difference the Compression made on our example here reducing the Entity count from 5179 to 112. A 4624% decrease!


The FastCAM Team

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