Contents:
Plywood is one of the most common materials processed on a CNC milling machine. It comes in various thicknesses, sizes, qualities, and production methods. In this article, we will focus on FSF plywood, known for its increased moisture resistance.
Machine dimensions
When selecting plywood, it is essential to consider both the dimensions of the machine and the size of the workpieces. The parts should be placed on the milling machine in a way that allows for a small power reserve during cutting. This ensures smooth and efficient processing without unnecessary strain on the machine.
Spindle power
The milling process depends on the spindle power and can be performed in two ways:
- High-speed method – this involves a fast feed rate with a low spindle rotation speed. It is mainly used for finishing and does not require high power or cutting force.
- Power method – this requires increased torque and sufficient power to cut through the material effectively.
Both low-power and high-power spindles can be used for plywood milling. However, the speed and depth of the cut will depend on the available power.
How to fix the workpiece on a milling machine?
There are different ways to secure a workpiece, including clamps, self-tapping screws, and vacuum tables. Let’s examine the two most common methods.
Vacuum table
A vacuum table holds the workpiece in place using a vacuum pump. It typically includes a backing cord that allows for cutting off sections that do not fit within the machine’s working area. To secure wood, MDF, or chipboard, a pump with at least 5 kW capacity is required. However, this results in higher energy consumption. Despite this, a vacuum table remains the best option for milling large workpieces from various materials.
T-Slot table
If the machine does not have a vacuum table, T-slot clamps or self-tapping screws can be used instead. When working with these clamps, it is crucial to prepare the model carefully and ensure that no moving machine parts come into contact with the fasteners during processing.
Choosing the right cutter
For plywood milling on CNC machines, three types of cutters are commonly used:
- Up-cut mills
- Down-cut mills
- Compression mills
While a new and sharp cutter will perform well regardless of the type, prolonged use of up-cut mills can lead to creases and defects on the top edges of the material. Similarly, down-cut mills may cause imperfections on the bottom edge. Compression mills, however, eliminate these issues and are the recommended choice for cutting plywood.
Avoiding workpiece displacement
When preparing a model, keep in mind that slight lateral pressure is applied to the part during machining. If a small workpiece is not securely held by the vacuum table, it may shift or even fly off, potentially damaging the tool or the part itself. To prevent this, consider adding small “jumper” connections to keep the piece attached to the surrounding material during milling. These can be removed easily after the process is complete.
Optimizing cutting parameters
To achieve high-quality results, it is essential to choose the correct cutting mode. The feed rate should be adjusted according to the cutter’s diameter to prevent bending and excessive vibrations. The recommended movement speed ranges from 10 to 15 mm/s.
Key indicators for proper cutting
- Sound: the milling process should produce a smooth and consistent sound without sudden increases in noise.
- Edge quality: burn marks indicate excessive speed or insufficient air supply. A fuzzy edge suggests a dull tool or inadequate spindle speed. Roughness may indicate cutter bending, requiring an adjustment in feed air supply and movement speed.
- Chip removal: efficient dust and chip removal is crucial. A clean workspace helps extend the lifespan of both the milling machine and the tools.
Conclusion
Milling plywood on a CNC machine requires careful consideration of spindle power, workpiece fixation, cutter selection, and cutting parameters.
By using compression mills, adjusting feed rates, and ensuring proper workpiece holding, you can achieve clean and precise cuts. Additionally, maintaining a dust-free environment will enhance both machine performance and tool longevity. Following these guidelines will help optimize the milling process and produce high-quality results.
