Shaped and profiled MDF panels and components are widely used in the furniture, fitments and building industry. Routers and particularly CNC routers, are used most effectively to satisfy this demand.
Most companies use brazed double straight fluted, fixed blade cutters, but disposable TC tips, solid helical TC and polycrystalline diamond (PCD) cutters are becoming more popular.
Router cutters generally incorporate cutting angles in the range 15° and 25° and clearance angles in the range 15° to 18°.
Disposable blade cutters
When the edge of a disposable cutter is worn, the cutter can be reversed or replaced whilst its body is still held in the spindle of the machine. Not only does this reduce the down time necessary to replace a whole tool, but it also obviates the need to adjust the cutter diameter and cutter length offsets in the controller of a CNC machine. The likely substantial savings can be assessed when the relative costs of disposable blades are compared with the costs for a complete replacement cutter.
Two and three flute spiral or helical cutters, available in solid high speed steel, carbide tipped and solid carbide, run quieter and more efficiently than straight flute cutters. They are unfortunately, considerably more expensive than the equivalent straight flute cutters which are commonly used and considered to be satisfactory for most applications.
PCD cutters are not as resilient as TCT cutters when exposed to abrasive inclusions but they are particularly effective when machining MDF which normally has a low grit content resulting from the use of screened and washed wood chips. Although PCD cutters are more expensive than carbide cutters, their better performance and longer life results in reduced tooling costs overall, subject to careful handling.
When routers are operated at high spindle speed and low feed speed to ensure well cut edges free from cutter marks, tool wear is known to be excessive. Experience has, however, shown that satisfactory cut edge quality, consistent with minimum tool wear is possible if the cutting conditions are chosen so that the amount of material removed by each cut, known as the chipload, is in the range 0.15 to 0.25 mm.
Tool wear increases rapidly with reducing chipload.
The relationship between cutting conditions and chipload is defined as follows:
RPM x No. of flutes x chipload (mm).
Feed speed (m/min) =
Typical cutting conditions based on a chipload of 0.2 mm are given in the Table. The use of a standard straight flute cutter has been assumed with the depth of cut ideally not exceeding the cutting diameter. The cutting diameter should ideally not exceed twice the shank diameter of the tool.