Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
Plastic products are usually manufactured by direct molding methods, but in some cases, direct molding may be difficult or cutting is required for plastic parts with high precision requirements. This process is usually carried out using equipment that handles metals. Since the properties of plastic are very different from those of metals, and there are many types of plastic, different plastic have different properties, so plastic cutting has its own unique characteristics.
Increasing the cutting speed can shorten the cutting time and improve production efficiency without significantly increasing the cutting force or affecting the surface roughness of the plastic part. However, an increase in cutting speed will lead to an increase in cutting temperature, which in turn will cause thermal expansion, thermal deformation and color change of the plastic parts, all of which will affect the processing quality. In addition, tool wear accelerates and tool life decreases, which increases the time required to replace, sharpen and align tools, ultimately leading to reduced productivity. Therefore, in actual operation, the cutting speed needs to be controlled. The reference data of commonly used plastic processing cutting speeds are shown in the following table:
| Plastic material| Cutting speed (mm/min) | Feed rate (mm/r) | Cutting depth (mm) |
| --- | --- | --- | --- |
| Polyoxymethylene| 120每180 | 0.1每0.25 | 0.12每0.5 |
| Polyamide| 150每180 | 0.05每0.38 | 0.12每0.5 |
| Polycarbonate| 150每300 | 0.12每0.5 | 0.12每0.5 |
| Polyolefin, polytetrafluoroethylene| 90每225 | 0.05每0.25 | 0.12每0.5 |
| Polystyrene| 230每300 | 0.03每0.1 | - |
| Phenolic Laminated Plastic| 150每600 | 0.1每0.25 | -0.25每0.75 |
| Fiberglass Phenolic Laminated Plastic| 45每60 | ＋0.25 | - |
| Plexiglas| 15每80 | 0.1每0.25 | -0.15每0.2 |
Although increasing the feed rate and cutting depth can also shorten the cutting time, the significantly increased cutting force may cause deformation of the plastic part, affect the processing quality, and may even cause damage to the workpiece. Therefore, it is very important to choose the appropriate feed rate and cutting depth. The reference data of commonly used plastic processing feed rate and cutting depth are shown in the following table:
| Plastic material| Cutting speed (mm/min) | Feed rate (mm/r) | Cutting depth (mm) |
| --- | --- | --- | --- |
| Polyoxymethylene| 120每180 | 0.1每0.25 | 0.12每0.5 |
| Polyamide| 150每180 | 0.05每0.38 | 0.12每0.5 |
| Polycarbonate| 150每300 | 0.12每0.5 | 0.12每0.5 |
| Polyolefin, polytetrafluoroethylene| 90每225 | 0.05每0.25 | 0.12每0.5 |
| Polystyrene| 230每300 | 0.03每0.1 | - |
| Phenolic Laminated Plastic| 150每600 | 0.1每0.25 | -0.25每0.75 |
| Fiberglass Phenolic Laminated Plastic| 45每60 | ＋0.25 | - |
| Plexiglas| 15每80 | 0.1每0.25 | -0.15每0.2 |
Compared with metals, plastic have lower heat capacity and poorer thermal conductivity, and their coefficient of thermal expansion is also relatively large. During the cutting process, the heat generated by friction is mainly transferred to the tool. Even if a small amount of heat is transferred to the plastic part, it is difficult to conduct it into the inside of the plastic part, which can easily lead to local overheating and cause the plastic part to discolor, melt or even burn. High temperature can also affect the surface quality and dimensional accuracy of plastic parts. In severe cases, it may cause the workpiece to bounce or even cause a safety accident. Therefore, coolants are often used to reduce the temperature during machining.
The elastic modulus of plastic is much smaller than that of metals, which means that during cutting, if the pressure applied by the tool and fixture is too large, the plastic parts can easily produce large elastic deformation, which will affect the processing accuracy and even make the processing more difficult. Therefore, during cutting processing, the tool parameters should be selected reasonably to ensure that the cutting edge is sharp and the cutting amount is moderate to reduce the cutting force and prevent excessive deformation of the plastic parts.
The tool materials used for plastic cutting mainly include high-speed steel, cemented carbide and diamond. For ordinary plastic, you can choose knives made of the first two materials. In contrast, high-speed steel has better sharpness, and the edge of a finely ground high-speed steel tool is sharper, but its durability is slightly lower than that of a carbide tool. When processing composite materials such as fiberglass, due to their uneven hardness and frequent intermittent cutting, it is recommended to use diamond tools with excellent wear resistance.
In order to ensure the processing quality of plastic parts, improve production efficiency and tool durability, and reduce processing costs, it is very important to choose appropriate tool geometry parameters. The following focuses on the selection principles of turning tool geometric parameters.
The size of the rake angle of the turning tool directly affects the cutting effect. The larger the rake angle, the smaller the cutting deformation, the lower the cutting force, the less cutting heat generated, the lower the cutting temperature, the smaller the blunt radius of the tool edge, and the sharper the cutting edge, which helps to improve the processing quality of plastic parts. However, too large a rake angle may also weaken the tool strength, worsen heat dissipation conditions, and increase cutting temperature, resulting in reduced tool durability and plastic part processing quality. Therefore, it is very important to choose the tool rake angle reasonably. When making a specific selection, factors such as plastic part material, tool material and processing properties should be considered comprehensively.
The size of the back angle also has an important influence on the cutting effect. The larger the back angle, the smaller the friction between the back face of the tool and the plastic part, the smaller the radius of the blunt circle of the tool edge, the sharper the edge, and the easier it is to cut into the workpiece. However, too large a back angle will also weaken the blade strength and reduce the tool's heat dissipation capacity. The main consideration when selecting the back angle is the cutting thickness. When the cutting thickness is large, the cutting force is large. In order to reduce the cutting force and ensure the tool strength, the front angle should be large and the back angle should be small. When the cutting thickness is small, friction and tool wear mainly occur on the back face of the tool, and the cutting force is not large. The tool strength is sufficient, and the back angle should be larger to reduce the friction of the back face of the tool, reduce cutting heat, and make the blade sharp.
During high-speed cutting, the cut plastic chips are in a molten state and solidify quickly when cooled. During the processing, chips are very likely to adhere to the tool, change the tool angle, increase the cutting depth, and affect the processing accuracy of the plastic parts. Therefore, the chips should be removed in time. In addition, plastic parts will generate a large amount of chip dust during the cutting process, and effective ventilation and dust removal measures must be taken to ensure that the dust content in the air meets national standards.
When processing plastic parts, we should choose suitable tool materials, reasonably select tool geometric parameters and cutting parameters according to the properties of plastic, processing conditions and requirements, solve special problems in plastic processing, and achieve the best combination of tool geometric parameters and cutting parameters to achieve the purpose of reducing cutting force, lowering cutting temperature, ensuring processing quality and improving productivity.
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