So Watt Journal

The 5 Biggest CNC Mistakes.... And How To Avoid Them

The 5 Biggest CNC Mistakes.... And How To Avoid Them

CNC routing is a relatively new technology, and creating the artwork for your project to send out to Sydney CNC router companies and manufacturers like us can be tricky.

We see a lot of CNC projects come through that are either not appropriate for a CNC router style of making or the artwork requires a lot of tweaking which extends the lead time and cost of the project.

Here are a few tips you might find useful if you are looking to start a CNC project with us.

1. Tolerances and Tool Diameter

Tolerances are a crucial factor in any CNC job in order for your parts to fit together when it comes time to assemble. When cutting a slot for another piece of material to fit within, it is important to leave a small tolerance which accounts for variations in material thickness, added thickness from finishes etc. This will ensure your CNC routed panels fit together perfectly.

 

Meet The Negotiator!

Your best friend for a tight fit, or your worst enemy if you forget your tolerances all together.

 

2. Dog Bones

Known in CNC manufacturing as dog bones, these cuts take into account the fact that the router bit is circular, and therefore cannot cut square corners. For projects where a square corner is needed to fit another piece of material, a dog bone is necessary to create space in that corner. For reference we usually cut with a 10mm bit, meaning the diameter of your dog bones must be at least 10.5mm in order to achieve a comfortable fit. Don’t forget your tolerances!

3. File Formats

Our CNC has its own software that reads certain files and then nests them to fit as many parts as possible onto a sheet. This software then speaks to our CNC machine, a Biesse Rover K, which cuts the parts from the sheet of material held on the machine bed by powerful vacuums.

In order to create a more efficient and quicker experience, and therefore to minimise the cost of the job, we always recommend sending across files that our CNC software can read. Our preferred file format is .DXF which has been exported from 3D CAD software. And remember we only need the 2D view on a single plane!

Unfortunately, Adobe Illustrator .DXF files of any curved lines import as millions of tiny points so we must re-draw anything like this in our CAD software, SolidWorks.

 

This is an example of the 2D layout for our Billi Stool, available on our shop. Each part includes tolerances and dog bones, and the lines are clearly defined.

 

4. Part Size

It is also important to keep in mind the size of your parts for CNC manufacture.

Our CNC machine has a bed size of 2.5 metres x 1.2 metres, so parts any larger than that cannot be cut in one go.

The CNC uses a vacuum to hold the sheet material down as it cuts, so if your part is too small for there to be enough surface area for the vacuum you may lose your part or it can move on the bed and catch on the tool bit. If you are in need of much smaller parts, have you considered Laser Cutting?

 

5. Material Thickness

As we use natural birch plywood and other timber sheet materials, there is always the possibility that the sheet may be slightly thicker or thinner than its specified thickness, or even vary across the same sheet. Always keep this in mind when designing and drawing cut files, particularly when using slotting elements. Thats where the tolerances really come in to play!

 

For more information on CNC routing, please refer to our CNC guide on the downloads section of our website.

 

If you would like to work with us on your next project, please get in touch

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