Knowing your plywood: how to optimise CNC router performance

Plywood can be one of the trickier sheet materials to rout consistently on a CNC.

Unlike MDF or particleboard, plywood is made from layers of natural timber veneer running in alternating grain directions. Add different adhesives, laminates or fire-retardant treatments and two sheets that look reasonably similar can behave very differently under a cutter.

That affects everything from edge finish and chip formation to heat build-up and cutter life. So before choosing the tooling, it helps to know exactly what type of plywood you're cutting.

A few things matter across all plywood types

There are some fundamentals that apply regardless of the plywood you're machining.

1. Plywood generally needs a higher chip load
   Plywood tends to cut best with a larger chip than MDF or particleboard.
   
   That makes matching your feed rate and spindle RPM particularly important. If the chip is too small, more heat stays in the cutter rather than leaving with the chip. The result can be burning, accelerated tool wear and, in extreme cases, cutter failure.
   
   Use our Feed Speed Calculator for recommended starting settings, or talk to us about the cutter and material you're running.
   
   
2. Don't automatically solve it by increasing feed speed
   Compared with other board products, plywood will often benefit from either increasing feed speed or reducing spindle RPM to achieve the required chip load.
   
   In many cases, we prefer reducing the RPM rather than pushing the programmed feed rate higher.
   
   On smaller parts or detailed work, the CNC may spend much of the cut accelerating and decelerating and never actually reach the programmed feed speed. Reducing the RPM can give you a more consistent chip load throughout the job.
   
   
3. Check your cutting direction
   If you've got the right cutter and cutting conditions but the edge on your finished component is still not as good as the offcut, look at whether you're climb or conventional cutting.
   
   Changing the direction the cutter travels around the component can move the cleaner edge onto the side of the cut that matters.
   
   

Standard Plywood – Hardwood, Softwood & Marine ply

Standard plywood can include everything from inexpensive softwood construction ply through to hardwood and marine-grade sheets.

The timber species, quality of the veneers and adhesive system all influence how cleanly a sheet will rout.

One of the common challenges is the natural grain. Rather than producing the very consistent chip you get from manufactured board, plywood can be prone to grain pull-out, fluffing and rough edges.

How to Rout Standard Plywood on a CNC router.

A conventional two-flute compression cutter can work well in some plywoods, but for regular plywood routing we normally look at tooling designed to deal more effectively with the chip and changing grain direction.

There are two main tungsten options we would consider.

1. Chipbreaker Compression Cutters
   Our Chipbreaker Compression Cutters are a proven option for general plywood routing.
   
   Small offset chipbreaker slots along the cutting edge help break up and evacuate the chip. This can reduce problems such as grain pull-out and fluffing while still retaining the compression action needed to protect the top and bottom faces of the sheet.
   
   The result is a cleaner edge and less sanding or other finishing after the part comes off the CNC.
   
   For workshops cutting plywood occasionally, or where a dependable and cost-effective cutter is the priority, the chipbreaker remains a very good choice.
   
   View the Chipbreaker Compression Cutter range.
   
   
2. Blue Mamba 2+4 Compression Cutters
   For workshops routing plywood regularly, our Blue Mamba 2+4 Compression Cutters are the next step up from the standard chipbreaker range.
   
   They are designed to provide longer cutter life and a better edge finish in plywood, making them particularly useful where plywood is a regular part of production.
   
   The 2+4 compression geometry gives a strong shearing action through the material while still compressing the top and bottom faces towards the centre of the sheet.
   
   We would look at Blue Mamba where:

• • plywood is being cut regularly;
  • edge finish is particularly important;
  • reducing cutter changes has value;
  • or you want more performance and life from a tungsten cutter before moving into PCD diamond tooling.
    

They cost more than a standard chipbreaker cutter, but for regular plywood production the increased tool life and improved finish can make them the more economical option overall.

View the Blue Mamba 2+4 Compression Cutter range.

When does PCD diamond make more sense?

For most standard plywood work, a good tungsten cutter will still be the logical choice.

The calculation starts to change when the board becomes particularly abrasive, or when production volumes are high enough that cutter changes and tool life have a significant effect on machine time.

That's where PCD diamond tooling becomes worth considering.

Fire Retardant Plywood

Fire-retardant plywood is treated to slow the spread of flame and is commonly used where additional fire performance is required.

The important difference from a machining point of view is the treatment within the board.

Fire-retardant plywood can contain significant levels of salts and other compounds, making it much more abrasive to cut than standard plywood.

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

Tungsten compression tooling, including Chipbreaker and Blue Mamba cutters, can cut fire-retardant plywood cleanly.

The problem is tool life.

The abrasive material creates considerably more wear on a tungsten cutting edge, particularly on jobs involving a lot of small slots, perforations or detailed machining where the cutter spends a lot of time engaged in the material.

For regular FR plywood work, we recommend moving to PCD diamond tooling.

PCD is substantially more wear-resistant than tungsten and can retain its cutting edge for much longer in abrasive sheet materials.

If you're simply profiling larger shapes, a high-performance PCD compression cutter is normally the better option because it combines long life with productive feed rates.

For smaller slots and detailed patterns where a larger compression tool won't fit, smaller-diameter single-flute PCD cutters may be required.

The important point is that while a premium tungsten cutter can improve performance, FR plywood is one of the applications where the material itself can make diamond tooling the more economical choice.

Plywood with HPL (High Pressure Laminate)

HPL-faced plywood combines a plywood core with a hard decorative laminate bonded to one or both faces.

It creates a strong, durable panel, but that hard laminate introduces another challenge for the cutter.

Even when your feed rate and RPM are correct, the HPL can wear a groove into the cutting edge of a tungsten cutter surprisingly quickly.

How much HPL-faced plywood you're cutting therefore has a big influence on which cutter makes sense.

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. 

Option 1: Chipbreaker Compression Cutter

If you've only got a small amount of HPL plywood to cut, a Chipbreaker Compression Cutter may still be the most economical option.

You'll get the compression action and chip control required for the plywood core without investing in diamond tooling for a one-off or very occasional job.

The trade-off is cutter life. The hard laminate will wear tungsten considerably faster than standard plywood.

View the Chipbreaker Compression Cutter range.

Option 2: Blue Mamba Compression Cutter

If HPL plywood forms a more regular part of your work and you want to improve on the finish and life you're getting from a standard chipbreaker cutter, Blue Mamba provides another tungsten option.

You retain the strong cutting and chip-clearance characteristics of a solid tungsten compression cutter while stepping up in both edge finish and tool life.

However, HPL is still an abrasive material.

Blue Mamba will last longer than a conventional tungsten option, but the laminate will still wear tungsten significantly faster than PCD diamond.

For occasional to moderate HPL plywood work, that may be a good balance.

For ongoing production, we would normally move to diamond.

Option 3: Eco PCD Diamond Cutter

If you've got a reasonable quantity of HPL plywood to cut but it isn't something you're running constantly, an Eco PCD Diamond Cutter can make sense.

The diamond cutting edge provides far greater wear resistance than tungsten, so it will stand up much better to the abrasive laminate.

The trade-off is cutting speed.

Because PCD tools use diamond segments brazed onto the cutter body rather than the continuous spiral flute possible with solid tungsten tooling, chip evacuation is different and these tools generally need to be run more conservatively.

For occasional abrasive work where cutter life matters more than maximum production speed, they can be a very practical option.

Option 4: High-Performance PCD Diamond Compression Cutter

For regular production of HPL-faced plywood, the premium option is our High-Performance PCD Diamond Compression Cutter.

These tools use multiple diamond segments arranged in a close compression pattern to provide much better chip clearance than a conventional straight PCD tool.

That gives you the main benefits you want from diamond — exceptional wear resistance and long cutter life — while still allowing productive feed rates and a clean finished edge.

They cost substantially more than a tungsten cutter, so they're not the answer for every plywood job.

But once you're regularly machining abrasive laminated plywood, the reduction in tool changes and the much longer cutting life can change the economics considerably.

One customer cutting HPL-faced plywood reported getting around 60–70 metres from their tungsten compression cutters before the laminate had worn a groove into the cutting edge.

After changing to the high-performance diamond cutter, they had passed 900 metres of cutting and were still achieving a good finish, with no significant groove visible in the cutting edge.

View the High-Performance PCD Diamond Cutter range.

Which Plywood Cutter Should You Use?

There isn't one cutter that is automatically best for every plywood job.

The right choice depends on the plywood, the amount you're cutting and what you need from the finished part.

As a general guide:

Standard plywood / occasional work
Start with a Chipbreaker Compression Cutter for dependable performance and good value.

Standard plywood / regular production
Step up to a Blue Mamba 2+4 Compression Cutters for longer cutter life and a better edge finish.

Occasional abrasive plywood
A tungsten cutter may still be economical, or an Eco PCD Cutter may make sense where tool life is becoming an issue.

Regular FR or HPL plywood production
Move to a High-Performance PCD Diamond Cutter where the additional tool life and reduced cutter changes justify the investment.

The cutter is only part of the setup. Feed speed, spindle RPM, cutting direction, material hold-down and the condition of your toolholding all influence the final result.

Not Sure Which Option Makes Sense?

Tell us what plywood you're cutting, the thickness, how much you're running and the CNC you're using.

We'll help you match the cutter and starting cutting conditions to the application rather than simply replacing the tool you're already using.

Call Tungsten & Tool on 0800 488 647 or contact our team for advice.