The latest kitchen design trends are demanding that solid wood and MDF doors appear in the same space with multi-colored cabinet layouts. This reality has challenged door makers to produce MDF doors that resemble solid wood profiles. Production limitations have traditionally made it impossible to make MDF doors on a CNC router that match solid wood doors made on traditional moulders and tennoners.
Advancements in MDF door tooling design and related software packages have made it possible to machine MDF doors on a CNC router that could pass as solid wood. A cohesive combination of smart tool design, flexible software, and proper material can produce an MDF product that is almost an exact match to solid wood once the door has been finished and installed.
The application is possible, but does require some critical tools and design strategy to achieve a door with tight corners and good surface finish that can be primed with minimal sanding. There are a couple of problems that must be overcome before achieving success.
IMAGE 1 shows the current possibilities of MDF profiled doors on a CNC router. Notice the detailed moldings and small radius on the corners of the inside profile that can be achieved.
Problem #1: Moulding details and tight inside corners
In the past, a simple profile made from a single pass with a profile tool would create a rounded corner affect that made it obvious to the customer that the door was made from MDF and machined from above with a CNC router bit. Detailed moldings and tight corners were impossible, if not very inefficient to produce.
Solution #1:
The key to this issue is as much software related as it is tooling, and any solution must include effective communication between tool designers and software programmers. The obvious solution to create a smaller radius in the corners is to use a smaller diameter tool. However, this can lead to dramatically increased cycle time, which can be prohibitive from a production standpoint. Primitive software made it necessary to have all tools do a complete pass around the door profile, but modern systems allow the smaller diameter tools to isolate all four corners after the larger profile tools have done their work. The key is to start with a large profile tool to remove the majority of material and then break up the profile into small sections, and design the smallest diameter tool possible to clean the corners.
It is important to understand the limitations of the smaller diameter tools, and adjust feed rates and RPM accordingly to avoid tool breakage. The smaller diameter tools will often be designed with single flutes, so a drop in feed rate will also ensure better cut quality. Many small carving tools are better suited to solid carbide or carbide insert, rather than diamond due to design constraints.
Any tool inventory must include larger diameter tools for maximum material removal at higher feed rates, and matching tools with the smallest possible diameter to perform critical detailed carving applications in the corner of inside door profiles.
Problem #2: Surface finish
MDF is generally very consistent and easy to finish on the outside of the panel, but profiling on the inside of the panel can create a surface that is very difficult to finish due to machining lines and ‘fibre tearout.’ MDF is obviously a porous material that tends to show loose fibres when machined in the core of the board. The density of the MDF panel can have a dramatic impact on the resulting cut quality, but regardless of the quality of MDF, it is impossible to achieve a surface finish in the core that is equivalent to the outside layer.
Flat surfacing on the inside door panels is notoriously difficult as tools tend to leave machining lines on the overlapping tool path. Depending on the fibre size in the core, tools can also pull fibres, which creates a pitted effect that must be filled by primmer. If fibres are not sheared off, they tend to raise up during priming, resulting in additional sanding or priming requirements.
Solution #2:
There are some machine parameter adjustments that can be made to improve surface finish. Smaller chip loads will obviously provide less feathering of fibres, but excessively small chip loads will cause heat generation and reduced tool life, so feed rate reduction is not always ideal. The solution lies in the tool design and cutting edge geometry.
IMAGE 2 shows an example of a diamond-surfacing tool designed to provide premium surface finish on MDF door panels. Notice the ‘integrated’ tool holder and tool body, which ensures optimal performance and allows the tool to remove material at higher feed rates without sacrificing cut quality
The cutting edge geometry helps limit ‘overlap lines’ between tools passes, which reduces the amount of sanding required before priming. Up shear geometry helps extract large chip loads at higher feed rates to reduce cycle time. The diamond cutting edge is critical to providing prolonged tool life in difficult surfacing applications that produce excessive heat generation and cutting edge wear. To achieve optimal results, it is best to run multiple tool passes and leave 3-4 mm for the final finishing pass.
Cabinet doors will always be the focal point of any kitchen and generally require the most attention to detail. Proper tooling design and application can help ensure the customer’s expectations are met, but also ensure that production cycle times and finishing costs are controlled. Consult your tool designers to discover many creative ways to make your MDF doors look as good as wood.
Scott Burton is the Sales and Marketing Manager for Royce//Ayr Cutting Tools.
He can be reached at sburton@royceayr.com
