Polymer materials are frequently used in the machinery manufacturing industry to meet the demands for flame retardant, insulation, and wear resistance that is imposed by the industry.
In the processing of guide rails, lining boards, wire troughs, and other parts made of plastics such as nylon and phenolic, it is common to use these and other materials such as nylon, phenolic, and other types of plastics.
Molding methods such as injection molding, press molding, extrusion molding, and other similar techniques are not practical for products with complex shapes and small quantities. In most cases, mechanical machining methods are used to cut through them.
Given the characteristics of these materials, combined with issues that may arise during the machining process, we should pay particular attention to and exercise control over the following aspects:
1. The Effect of Heat
In part due to the fact that plastic is more thermally sensitive than metal, most materials become tacky when subjected to high temperatures during machining with cutting tools. During milling, turning, and drilling, the tacky plastic resin solidifies and becomes more rigid.
A. While pouring coolant into the tool at a high flow rate, use the compressed air tube to blow away any plastic debris or tools that have accumulated in the cutting area. The heat generated by the cutting area is reduced, and the plastic debris is prevented from sticking to the cutting tools as a result.
B. In order to maintain nosesharpness, it is necessary to increase the rake angle and back angle of the cutting tool, as well as to reduce frictional heat and to prevent plastic deformation and heat generation.
C. Increase the feedingspeed of the tool on the workpiece surface to an appropriate level; choose 200-300 m/min and 0.05-0.2 mm/rev for the feed amount.
It is possible to increase productivity and tooling by using cutter heads that are made of cobalt-based chromium-tungsten cemented carbide as well as carbide cemented carbide.
2. The result of deformation caused by force
The workpiece warps and twists as a result of the thermal expansion caused by the heat generated during the cutting of the parts. Tool and fixture failure is frequently caused by the rebound force of workpiece deformation acting on them. Tool failure occurs more frequently than fixture failure. The following measures are implemented in order to avoid these occurrences:
A. When machining the flat surface of thin plate parts that are prone to warping, planing or a small diameter milling cutter should be used to stack reciprocating milling operations. Multiple workpieces of the machining method should be used when milling the shape. For example, place multiple workpieces in the middle, fix them with thin metal plates up and down, and then mill them all at the same time. After the machining is completed, remove the workpieces from the machine once they have cooled completely. This will ensure that the plastic material has hardened, the workpiece size has been stabilized, and that warpage and deformation will no longer occur.
B. For thicker parts, the intermittent cutting method is used to process the outer contour by up and down planing and up and down slotting, in order to prevent the cutting tool from breaking and the fixture from cracking due to the rebound force of the workpiece when machining the shape when machining the shape. Turning, boring, molding, and slotting can all be used to replace milling and drilling depending on the part’s shape. For situations where milling and drilling are unavoidable, the diameter of the milling cutter should be kept to a minimum while still ensuring strength.
3. Controlling the roughness of the machining surface
The smooth surfaces of formed plastic products, such as nylon plates and rods, bakelite blocks, and other raw materials, are already present, and these smooth surfaces will be destroyed during mechanical machining.
So when designing the machining process route, make an effort to keep the original material surface as the important shape surface of the workpiece, while machining the workpiece on the invisible and unimportant surface.
Following the machining, some manual post-processing is required to ensure accuracy. Excess materials should be removed with a knife, sandpaper, or a file.