What is offset routing?

Best practices: Offset routing

What is offset routing?

Offset routing is a method of determining the cut path your CNC machine creates and uses. In this method, CAD software is used to create the shape parts to be cut. This is sent to the CNC machine, which creates the cut path. The diameter of the tool being used to cut the path is added to the CNC machine, which uses this information when creating the cut path.

We have found that offset routing is used less frequently than centreline routing by many cut-to-size manufacturers. In this article, we will be discussing why we consider it the best practice when cutting board, and why.

cut-to-size manufacturing using offset routing

What is the difference between offset routing and centreline routing?

As described above, the process of cutting using offset routing begins with the shapes being created in CAD software. They are then sent to the CNC machine which creates the cut paths taking the cutter size into consideration.

In contrast, with centreline routing, the process of creating the shapes and exact tool path is all done by the CAD software and then sent to the CNC machine. The predefined tool diameter Is incorporated into the cut path by the CAD software. This may, at first glance, seem a simpler and quicker method of getting the job done. But carry on reading to see scenarios in which this is not the case.

Using different cutters

Imagine this, it’s the weekend and you want to get ahead and cut some board for cabinets. Your 9.5mm compression cutter is blunt. You go to your supply cabinet, but there are no more 9.5mm compression cutters. You do have a 12.7mm compression cutter and want to use it.

If you are using offset routing, this is not a difficult situation. All you will need to do is is adjust the tool dimensions at the CNC machine and a new cut path will be created. This should take no more than 2 minutes. If, on the other hand, you were using centreline routing, all the shapes would need to be reprogrammed in the CAD software. After being reprogrammed, they would also need to be exported to the CNC machine.

Sharpening cutters

Another instance where offset routing trumps centreline routing is when cutters are sharpened. The common 9.5mm compression cutter can be resharpened approximately 1-2 times. When a cutter is resharpened, it loses approximately 0.5mm in diameter. With offset routing, it is a quick process to adjust the cut paths to account for this difference. When the tool is changed we can tell the machine the different cutter size and continue cutting with the same generated code.

The cost of the 9.5mm cutter is approximately $70 and to be resharpened is approximately $30. While resharpened cutters won’t be able to cut as many boards as a new one will (200 boards cut by a new cutter compared to 120 boards by a resharpened cutter), there is going to be a cost saving. And let’s face it, nowadays we’re all trying to save money wherever possible.

Another reason why we are in favour of resharpening cutters is for environmental reasons. We are living in an age where recycling and reusing is becoming increasingly commonplace. We believe that everyone needs to do their bit for the environment wherever they can. So it makes complete sense to sharpen the cutters and, at the same time, save a bit of money.

Better cornering

In our opinion, cutting corners with offset routing is superior to cutting corners with centreline routing. With offset routing, the cutter never completely stops but slows and “rolls” around the corner. With centreline routing, the cutter reaches the corner, stops, and then begins cutting again in a different direction. 

This slowing down and “rolling” around corners is better in the long run for the CNC machine than the straight stop and start of centreline routing.

Offset routing vs centreline routing

To sum up

What we like most about offset routing is it’s flexibility. The shapes to be cut are first created in the CAD software and then sent to the CNC machine. If there are any changes to the tool diameter it only needs to takes place at the machine. This means that the person who changes the cutter can change the cut path quickly and easily without sophisticated CAD software knowledge or accessing other computers. It also eliminates potential “broken telephone” effect where, for instance, someone has changed the new cutter with a resharpened cutter and not informed the person running the CAD software.

We believe that centreline routing is used more predominantly because, in the past, most CAD software could only produce tool paths using it. Nowadays, the software has become more sophisticated, giving us options. 

Many people are resistant to moving away from tried and tested methods. But in order to keep progressing, new methodologies need to be explored. We encourage you to enquire about your CNC machines offset routing capabilities and give it a try.