Aug.2023 21
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Grinding machines, milling machines, and CNC (Computer Numerical Control) machines, why are they all used? What are their differences?
Details

In simple terms, CNC is used for Cow, milling machines are for chicken, and grinding machines are used for depilation ...This is the general idea.

The differences are significant and involve various considerations, including requirements for surface finish of products, surface finish requirements for mold parts, mold cost, manufacturing cost, delivery time, and more.

Let's start with milling machines. Milling machines are generally used in molds for roughing and initial shaping. They are the first step after cutting with a saw in the mold-making process. They are used to mill the rough blanks, shape the outer contours, create holes, thread tapping, and leave room for subsequent processes. The part is then sent for heat treatment. In cases where high precision is required, the part may be reprocessed using a grinding machine before heat treatment. Right angles, holes, slots, steps, etc., are all left with allowances. After heat treatment, the part is processed again using a grinding machine, which is the precision machining stage. All dimensions that can be controlled need to be precise, and the surface finish should meet the requirements of the drawings.

If some parts have irregular shapes or complex forms that are difficult or expensive to machine with other tools, CNC machines are used. This outlines the general process or basic differences. Of course, there are cases where CNC is not suitable. For instance, if a part requires a 0.2mm groove with specific depth and chamfer requirements, a grinding machine or wire EDM might be used. In essence, there is no absolute distinction. The choice of machine is based on maximizing benefits. The suitable machine is chosen for the task at hand.

The specific differences depend on the complexity of the mold. For example, molds for plastic frame of a television cathode-ray tube deflection coil and molds for DVD or computer optical drive trays would require the use of grinding machines, milling machines, and CNC. The former has a trumpet-like shape on the product, while the latter requires specific patterns, necessitating CNC processing.

Wire cutting comes in three types: high-speed wire cutting, medium-speed wire cutting, and slow wire cutting. I won't go into the details of the processing principle. Wire cutting is commonly used to create slots or holes in inserts, such as a rectangular hole in the center of a plate for fitting another plate. While milling machines can also achieve this, they might not be able to achieve sharp corners around the perimeter.

The mold-making process involves numerous considerations that cannot all be listed here. The most important aspect is adhering to the design drawings. Even if you strictly follow the design drawings and manufacture the mold parts, there might still be issues during assembly due to design considerations like accumulated tolerances, etc.

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