Knowing your plywood: how to optimise CNC router performance

Plywood is a popular building material used in a wide range of construction and woodworking projects. It is a versatile material made up of thin layers of natural wood veneer glued together in alternate grain directions to form a strong and durable sheet. 

Different types of plywood are suited to different jobs, so it’s important to make sure you’ve chosen the best one for your particular needs. In this blog post, we'll explore the different types of plywood and the best ways of routing them on a CNC router. 

Here's a video showing the process on how it's made:

Firstly, heres some tips on how to rout all types of plywood on a CNC router

Although some plywoods are tricky to cut cleanly, there are some things you can do to help get the best finish you can in ply.

1. Firstly, realise the plywood does cut quite differently from other board products like MDF or particle board. Plywood cuts best with what is called a high cutting pressure. In simple terms, the chip size coming off your cutter is bigger. To get this, its crucial to match your feed rate and RPMs. You can use our online feed speed calculator or give us a call to get the start off speeds. 

2. When compared with cutting other board products, you'll need to increase your chip size by either increasing your feed speed or decreasing your RPM. We usually recommend decreasing your RPM rather than trying to increase your feed rate as often by the time your CNC machine is accelerating and then slowing down for the corners or detail it often isn't getting up to the increased feed speeds. Incorrect speeds will lead to heat build-up, burning, cutter wear and sometimes cutter breakage.

3. Climb or Conventional cut? If you're using the correct tool and speeds, the next thing to check is the quality of edge finish on your offcut piece. If your offcut has a nicer edge finish than your part, change the programme to cut around your piece in the other direction. This will move the finer finish onto the part you’re needing.

Standard Plywood – Hardwood, Softwood & Marine ply

Softwood plywood is made from softwood trees, such as pine or fir. It is the most commonly used type of plywood and is widely available at most hardware stores. Softwood plywood is relatively cheap and is often used in construction projects where cost is a major factor. It is also available for use in furniture-making and can be painted or stained to match any decor. 

Hardwood plywood is made from hardwood trees, such as oak, birch, or maple. It is a more expensive type of plywood, but it is also stronger and more durable than softwood plywood. Hardwood plywood is often used in high-end furniture-making and cabinetry, as well as in construction projects where strength and durability are important.

Marine plywood is a special type of plywood that is designed for use in water-based applications. It is made with a waterproof adhesive that makes it resistant to water damage and rot. Marine plywood is used in boat building as well as in outdoor construction projects and fitments where exposure to water is a concern.

How to Rout Standard Plywood on a CNC router.

Although a standard 2 flute compression cutter will work well in some plywoods, for standard plywood we would recommend a chip breaker compression cutter. These are compression cutters with small offset slots in the edge that help break up and extract the chip to help prevent issues like grain pullout and fluffing which are common with ply. They still have the compression action which leaves a great finish top and bottom and the chipbreakers help avoid a lot of after cut finishing work like sanding and fills holes with putty.

View the range of these tools here – Chipbreaker Cutters. 

Here you can see the difference using the correct cutters makes to the finish: 

Fire Retardant Plywood

Fire retardant plywood is designed to slow the spread of flames in the event of a fire.

It is made with a special type of adhesive that helps to prevent the plywood from catching fire and spreading flames. Fire retardant wood products are typically created through the use of organic and inorganic salts, which are infused into the wood through water-based solutions under pressure. The end result is a product that has up to 1.13KGs of salts per cubic foot of wood product

Fire retardant plywood is often used in construction projects where fire safety is a concern, such as in public buildings or high-rise structures.

With the addition of special adhesives enabling waterproofing and fire resistance its versatility is extended even further. When you add coatings and textures to the visible surfaces, Plywood becomes almost the optimal material for construction.

How to Rout FR (Fire Retardant) plywood on a CNC router.

As you can imagine, the salts in FR plywood are incredibly abrasive and cause immense heat when cutting. This heat build up very quickly breaks down the molecular structure of any tungsten carbide cutting edge which bluntens tools extremely quickly. 

Although the tungsten chipbreaker compression cutters do cut it well, for longer lasting tools, we recommend diamond tooling for cutting FR plywood.

The abrasiveness of the material along with the fact that it is often used for wall and ceiling panelling for architectural or acoustic benefits which requires a lot of smaller slots to be cut which often creates even more heat build up means that harder PCD diamond tipped tooling is able to keep its sharp edge for longer.

If it’s just large shapes being cut out, the best option is one of the high performance diamond tools. These cut clean, cut fast and last for a long time. If however, you are needing to do the small slots and designs in the boards which are often necessary for panelling, the best option is to use the single flute diamond cutters. These are slower cutting but are available in sizes down to 8mm diameter.

Plywood with HPL (High Pressure Laminate)

HPL plywood is made by bonding high pressure laminates, which are layers of decorative paper infused with melamine resin, to both sides of a plywood core.

This results in a strong and durable panel that is resistant to wear, moisture, and stains.

HPL plywood is available in a wide range of colours, patterns, and textures, making it ideal for applications where aesthetics as well as longevity are important. 

How to Rout plywood with HPL on a CNC router.

This really depends on how much cutting you have to do but there are few cutting tool options. 

1. Tungsten Chipbreaker Compression Cutter

As you probably know using the correct, matched feed speeds is critical when cutting standard plywood. Plywood cuts best with a higher cutting pressure which simply means the chips coming off the cutter are bigger. That, along with using a chipbreaker compression cutter is generally a good solution for cutting plywood. 

However, even with matched speeds, the HPL on Plywood bluntens any tungsten cutter quite quickly, the hard laminate cutting a groove into the edge of the tungsten tool. That being said, if you’ve only got 1 – 2 sheets to cut, using a chipbreaker compression cutter may well be the best, most cost-effective option for you. These tools are here – Chipbreaker Cutters 

2. Eco PCD Diamond Cutter

If you’ve got quite a few sheets to do but it’s not really a job that you’re planning on doing in the future, you may be better to use an Eco Diamond cutter. The diamond segments are 20 times harder than tungsten so will last well in the HPL Ply compared with the tungsten cutters.  

Because solid tungsten cutters are ground out of a tungsten rod, they’re able to have very good spiral flutes that shear off the material and extract the chip well. This is obviously different from diamond tools where diamond segments or tips and brazed onto the body of the tool in a replica compression action. This lack of chip extraction and lack of genuine spiral action means that although these tools last well, they tend to be comparatively slow cutting so in a high production environment or for ongoing jobs the slower speeds tool may not be ideal. These tools are here - ECO Diamond Cutters 

3. High Performance PCD Diamond Cutter 

The premium option which gives you a clean edge, long-lasting cutter and fast feed rates, combines the technology of the tungsten compression cutters with the PCD diamond tooling. 

The High Performance diamond cutter for ply has multiple diamond segments tightly arranged in a very close spiral pattern very similar to the compression cutters. This helps them have the clearances and extraction similar to a tungsten cutter. The diamond tips give the long-lasting cutter and the spiral tip pattern gives the fast feed rates. These are ideal for ongoing jobs and/or high production. 

Here is a recent comment about these cutters - “I’m honestly blown away by these cutters – they’re great! We were cutting HPL on plywood and we getting about 60-70 metres of cutting from our tungsten compression cutters before they were totally worn and the laminate had created a groove in the side of the cutter. These diamond cutters are still going strong after 900 metres of cutting – still leaving a great finish and no sign of any groove in the cutting edge from the laminates! Plus the speeds are just as good as the tungsten cutters.” 

View these tools here – High Performance Diamond Cutters 

DO YOU HAVE MORE QUESTIONS?

Every day our team strives to boost your confidence, productivity and results through our accurate service and tailored support. Feel free to contact us at 0800 488 647 or sales@tungstenandtool.co.nz for more information on working with plywood.