The chip removal structure of a car oval punch needle, a mold component, must closely align with the cutting characteristics of its elliptical cross-section and the demands of automotive sheet metal processing. This requires addressing differences in chip production in different areas while also preventing chip accumulation and jamming due to structural inefficiencies, which can negatively impact drilling accuracy and processing efficiency. During automotive sheet metal processing, the contact area and chip production of the cutting edge of a car oval punch needle, a mold component, differ significantly between the long and short axis directions. The long axis direction, due to its wider cutting range, tends to generate more chips, while the short axis direction requires careful consideration of hole position accuracy. If chips are not removed promptly, they can easily accumulate near the cutting edge and even jam the punch needle. Therefore, the chip removal structure requires first defining the primary and secondary chip removal zones, and then designing these channels accordingly.
For the high-chip zone along the long axis of the car oval punch needle, a primary chip flute is designed as the core chip removal channel. The main chip flutes should not be symmetrical. Instead, they should be located along the sides of the punch needle on both sides of the long axis. The flutes can be trapezoidal or curved. These shapes provide ample space for larger chips. The curved inner walls also reduce friction during chip flow, preventing them from becoming stuck in the flutes. Shallower auxiliary chip flutes are required on both sides of the short axis. This minimizes the overall rigidity of the car oval punch needle while allowing for the timely removal of fine chips generated in the short axis area. This prevents these chips from adhering to the cutting edge and forming "chip nodules," which can affect subsequent cutting of automotive sheet metal.
The chip flute design of the car oval punch needle also needs to differ from the conventional spiral flutes of round punch needles. Considering the diverse material types used in automotive sheet metal, such as high-strength steel and aluminum alloy, the chip morphology and fluidity vary significantly. Therefore, the chip flute's helix angle requires flexible adjustment. When machining harder steel, the helix angle can be increased to enhance the axial thrust on the chips and ensure rapid chip removal. When machining more ductile aluminum alloys, the helix angle should be slightly reduced to prevent incomplete chip breakage due to excessive thrust, resulting in long, tangled chips that can become stuck on the car oval punch needle. Furthermore, the starting position of the helix flute must be precisely aligned with the cutting edge to ensure that chips enter the flute as soon as they are generated, minimizing their dwell time in the cutting area.
The detailed interface between the cutting edge and the chip flute is a key optimization point for the chip removal structure of the car oval punch needle. If there is a step or rough surface at the interface, chips are more likely to accumulate there. Therefore, a smooth transition bevel is required between the end of the cutting edge and the entrance of the chip flute. The angle of the transition bevel must match the cutting angle of the cutting edge, allowing chips to slide naturally along the bevel into the chip flute after being separated by the cutting edge. The bevel surface should also be refined to reduce roughness and prevent chips from sticking to the surface. This is especially true when machining aluminum alloy automotive sheet metal, which is prone to chip adhesion. A smooth transition bevel significantly reduces the risk of chip accumulation.
The chip removal structure of a car oval punch needle, a mold accessory, must also be adapted to the varying thicknesses of automotive sheet metal. In automotive production, punch needles may alternate between machining thick and thin sheet metal. If the chip flute depth is fixed, excessive chips can accumulate in the flute when machining thick sheet metal, while excessively deep flutes can cause chips to slosh within the flute when machining thin sheet metal, affecting punching stability. Therefore, the chip flute can be designed with a "gradual depth"—the flute depth gradually increases from the cutting edge to the tail of the punch needle. This allows more chips generated when machining thick sheet metal to be smoothly discharged along the gradual groove toward the tail, while smaller chips generated when machining thin sheet metal can pass through the flute stably and avoid jamming.
While optimizing chip evacuation efficiency, the structural strength of the car oval punch needle, a mold component, must also be considered. Punching holes in automotive sheet metal requires significant punching or cutting pressure. If the chip flutes are too deep or too dense, the punch needle's resistance to breakage will be significantly weakened. Therefore, sufficient width "ribs" are required between the chip flutes. These ribs not only enhance the rigidity of the car oval punch needle, but their surface can also be designed with a slightly curved shape to help guide chips into the flutes, achieving both "chip evacuation efficiency" and "structural strength," preventing processing interruptions caused by punch needle breakage.
Finally, surface treatment of the chip flutes can also enhance chip evacuation. Applying a low-friction coating to the flute walls and transition bevels further reduces friction between chips and the flute walls, facilitating easier chip removal. The coating also enhances the wear resistance of the flute walls, reducing chip wear during long-term processing and preventing deformation that narrows the flute channel and leads to chip accumulation and jamming. In general, the chip removal structure design of the car oval punch needle, a mold accessory, needs to take into account multiple aspects such as the oval characteristics, differences in automotive sheet metal, and processing pressure requirements. Only through multi-dimensional detail optimization can chip accumulation and jamming be effectively avoided, ensuring the smoothness and precision of automotive sheet metal punching processing.
