For medium sized factories that are always looking for higher productivity with consistent quality a CNC machining center is the solution for their requirements. Small units purchase an entry level 3-axis machine whereas medium level units try to augment their production by adding an aggregate or by going in for a 5-axis machining center or a nesting machine with a flat bed.
CNC processing has normally been done at slower feed speeds and using basic entry level tools which has affected the productivity and not being able to use the capacity of the machine at its optimum levels.
The objective of this article would be to take a look at some of the common processing requirements where productivity is not being achieved during machining and the optimum tooling solutions that can help overcome these production bottlenecks.
Sizing of boards on CNC Routers
When processing prelaminated boards or boards with HPL, the general practice has been to use turn blade knife tools for a roughing and finishing cut or use a Spiral roughing cutter in combination with a finishing tool in the Turn blade knife design.
This has been preferred since it is only required to maintain sufficient inventory of the turn blade knives.
The result is a loss of productivity since the machine can be run only at low feed speeds of 5 to 6 m/min and has to be frequently stopped for changing the knives.
In most cases the Turn blade knife Router cutter is used for both roughing and finishing operations which results in high wear out on the knives.
When sizing boards with 0.8 mm or 1 mm HPL wear out is very much higher on the Tungsten Carbide knife edges resulting also in breakage of the knives and sometimes breakage of the tool itself.
All these factors result in productivity losses and maintenance of a large inventory of turn blade knives.
The solution is to use Diamaster Router cutters. The advantages when using Diamaster Routers cutters are −
- Separate roughing and finishing cut is not required. The Diamaster Router cutters have a spiral cutting edge arrangement with alternate shear angle. This gives a chip free finish on the top and bottom laminate and a good edge finish suitable for edge banding is achieved.
- When using a turn blade knife, the machine has to be stopped twice once to change the cutting edge and the second time to change the knife itself. Life of Diamaster Router cutters are about 15 times more than that of the Carbide Router cutters and so machine stoppage time is considerably reduced.
- The Diamaster Routers are available in Z 2+2 version for medium level production and in Z 3+3 with DFC for high speed production.
Grooving on CNC Routers
Reasons for breakage are −
- The small dia Turn blade design Router cutters are single knife tools without a plunging edge.
- Collet condition needs to be checked regularly and timely replacement needs to be done. If this is not done the clamping efficiency of the collet is lost and this causes the breakage of the tool near the shank.
Solutions to avoid breakage/
- Use tools with plunging edge.
- Use tools designed for mechanical feed for CNC routers.
- For best results on CNC routers use Diamaster Pro grooving router cutters with negative shear angle. This tool is designed for high productivity with excellent finish.
- Worn out collet results in improper tool clamping and the collet must be replaced after 500 hours of operations.
- Use of the Shrink fit chuck (Thermogrip) instead of Collet chuck helps in eliminating the problem of breakage of tools caused by using collets that are not in a good condition. It also helps to achieve increased tool life and better finish.
- Use ramp plunging method when making blind grooves.
What is Nesting?
Nesting is waste-optimized machining concept to divide / size and / or profile boards on CNC machining centres. It is possible to perform only sizing cuts as well as sizing and profiling (outside profile and ornamental groove profiling) in one step and with one tool.
The work piece has to be clamped on its complete area by an adapted vacuum system. The work piece is clamped via vacuum suction through a thin MDF board (spoil-board / sacrifice board). The depth of cut (Z-axis) should be adjusted only ≈ 0.3-0.5 mm deeper than the work piece thickness. This prevents excessive wear of the spoil-board
Typical work piece, materials and application for nesting:
- As a replacement or a supplement to a conventional panel saw.
- Furniture fronts out of wood derived materials which will be coated or varnished afterwards.
- Interior parts for mobile homes or yachts.
- Machining small figured parts out of solid wood, wood derived materials, plastics and non-ferrous metals.
Tips & Tricks:
For optimum result, the following should be considered:
- The MDF spoil-board / sacrifice-board should be as thin as possible to ensure maximum efficiency of the vacuum clamping.
- The edges of the MDF-board should be sealed (with paint or thin edging material) to increase the efficiency of the vacuum suction.
- From time-to-time the MDF-spoil board must be resurfaced by using a turn blade planing cutter to ensure consistent vacuum hold down forces.
Ideal tool for profiling cuts:
- Cutter heads with replaceable tungsten carbide insert knives
- Diamond tipped profiling tools (jumbo DP tablets)
Ideal tool characteristics:
- High feed rates (# of flutes)
- High quality cut (helix)
- High degree of stiffness
- Little up-lift (helix)
- Long lifetime