Phenolic countertops

Phenolic resin countertops have traditionally been used for various commercial applications in healthcare labs, water treatment plants, photography labs and other highly sensitive work environments.
In recent years, various manufacturers have introduced product lines for residential use in kitchens, bathrooms and closets. These countertops are engineered to stand up to everyday use and provide a contemporary style to match modern cabinetry designs. Most designs are thinner than traditional countertops, and generally range from ¾ to ½ inch thick.
With proper care, phenolic resin countertops can last for decades, due to density and wear resistance properties. However, this type of wear resistant material can be very difficult to machine on CNC routers or other traditional woodworking equipment.

Phenolic resin properties
Phenolic resin countertops are manufactured by layering natural kraft papers that have been saturated with phenolic resin (a synthetic polymer obtained by the reaction of phenol or substituted phenol with formaldehyde) and cured under high heat to form a composite panel. Phenolic resin counter tops are lightweight, hard, durable and highly chemical resistant. They are oil and moisture resistant and do not support the growth of most bacteria and fungus. Phenolic countertops have extremely high impact resistance and durability ratings to withstand everyday wear and tear in kitchen environments. Phenolic compositions can also deal with high heat situations, which are very common around cooking areas of the kitchen. They can withstand temperatures up to 350 degrees Fahrenheit. Epoxy resin can withstand temperatures over 350 degrees Fahrenheit, and in some cases temperatures up to 600 degrees Fahrenheit.  

Cutting challenges
Phenolic resin materials machine like hard plastics, but have much higher density depending on grade of material. Therefore, there is increased force applied to cutting tools and machine spindle. It can be challenging to maintain a balance between cut quality and tool longevity, as phenolic is more abrasive than traditional plastics and generates far more heat when machining. Heat generation inevitably causes premature cutting-edge failure, leading to cut quality deterioration



Polycrystalline 
diamond vs. carbide tool geometry:
Image 1 shows an example of a polycrystalline diamond (PCD) router bit design to machine phenolic resin countertop material. Although price point for PCD tools can be 5 to 10 times higher than carbide, PCD has proven to outlast carbide by 50 to 150 times on phenolic materials depending on 
density and machining strategy. There are some epoxy resin phenolic grades which are simply too hard for machining with carbide tooling, so PCD is the only option in some scenarios. The only limiting factor of PCD tooling is the 
flat face geometry, which does not provide the same chip extraction rates as helical carbide geometry. Image 1 shows a PCD tool with flat face geometry, which is not as efficient at chip extraction.
Image 2 shows a carbide router tool with helical geometry and fluted face, which extracts chips more efficiently and allows the machine to run at slightly higher feed rates.

Machining strategy
In general, phenolic materials are far less forgiving than traditional plastic grades. Poly plastics and other softer grades tend to melt and reweld back onto the cutting tool. Phenolic materials react very differently and send heat generation back onto the cutting tool, which results in excessive heat generation.
Excess heat will cause premature cutting-edge wear, or in some cases, complete braze failure. This can cause the diamond tip to be released from the tool body and create a dangerous situation for operator and any other employees close to the machining area. Proper machine parameters are critical when machining resin reinforced plastic material. Machine spindles speeds must be reduced to prevent heat generation. RPM is generally dropped to 12,000 or 14,000 depending on tool diameter. Feed rate will vary based on material thickness and composition, but 150 to 450 inches per minute is an acceptable range in most cases. It is always recommended to run multiple passes at higher feed rates, to limit heat and improve material extraction. Many manufacturers seek cutting tools, which provide hogging and finishing capabilities in one tool. It is possible to use a single tool for both applications; however, there can be overlap lines left by the hogging tool, which are not acceptable depending on end product.  Image 1 shows a tool, which can be used for hogging and finishing, but if small overlap lines are problematic, a straight edge-finishing tool must be used in a second pass operation.

Profiling
As designers have transitioned to more contemporary designs, the need for profiling has diminished and most phenolic countertops are produced with a square edge tool to produce a flat edge on countertop.
Although large deep complex profiles are no longer popular in contemporary designs, there is often a requirement to add radius or bevel to the top and bottom of countertop edge.  
Image 3 shows an example of a double radius tool for phenolic countertops. Notice the small cut length on the bottom of tool, which allows countertops to be fixtured closer to the bed of CNC. The tool diameter must also remain as small as possible to limit inside corner radius on the countertop components. Often a straight tool can be used as a first pass to create a square countertop edge and then small bevels, or radius can be added in second pass to break the sharp edges for practical safety reasons. These secondary operations can be done manually off the machine, which does increase labor costs substantially. Small solid carbide radius tools can be used on the CNC router to achieve greater accuracy and efficiency.

Conclusion
As countertop material options continue to evolve, machinery and cutting tool solutions will remain critical factors to optimize production processes.  CNC router technology has automated custom cabinet construction methods in recent years, but countertop fabrication has traditionally 
involved more manual processes. However, as manufacturers 
continue to develop material 
types more compatible to standard CNC equipment, countertop production can be more easily automated. CNC router tooling solutions and machining strategies play a vital role in automation of countertop manufacturing.