What should be paid attention to when the precision carving machine of knife die is used in packaging field?

Matters needing attention in the application of knife die precision carving machine in packaging field

The precision carving machine of die is the core equipment for processing packaging die (such as rubber plate die, laser die and etching die), and its processing accuracy directly determines the die-cutting quality, edge flatness and production efficiency of packaging products. When applied in the field of packaging, it needs to be controlled around four core dimensions: material adaptation, precision control, process optimization and safety maintenance. The specific precautions are as follows:

First, before processing: key points of material selection and process planning

The substrate of the knife die is suitable for pipe-controlled packaging. The common substrates of the knife die are birch plywood, density board, aluminum plate and steel plate. Different substrates need to match the differentiated processing parameters:

Rubber board/density board (used for paper box and color box die): the material is soft and prone to burr and edge collapse, so it is necessary to use a double-edged spiral milling cutter to reduce the cutting speed (spindle speed is 12,000–18,000 r/min) to avoid tearing wood fibers when the cutter rotates at high speed; Before machining, it is necessary to confirm the moisture content of the substrate (controlled at 8%–12%). Too high moisture content will easily lead to deformation after machining and affect the accuracy of the die.

Aluminum plate/thin steel plate (used for high-end gift boxes and plastic packaging knife dies): the material hardness is high, so it is necessary to use cemented carbide coated knives or diamond knives to improve the wear resistance of the knives; The aluminum plate is easy to stick to the knife, which needs to be matched with special cooling oil to prevent aluminium scrap from sticking to the knife tip and affecting the machining accuracy.

Machining of tool bar clamping groove: the width of clamping groove should be accurately matched with the thickness of tool bar (tolerance ±0.02mm), so as to prevent the tool bar from loosening due to too wide clamping groove or being too narrow to be embedded; The depth of the slot should be designed according to the height of the cutter die to ensure the uniformity of the cutting edge after the cutter bar is fixed.

Tool Die Drawing and Machining Path Optimization

The imported CAD drawings of cutter die need to be reviewed: delete redundant lines and optimize the transition arc at the corner (to avoid cutting edge collapse caused by acute angle machining); The path of complex patterns (such as hollowed-out patterns of gift boxes) is split, and the outer contour is processed first and then the inner hollowed-out is processed to prevent the base material from being deformed.

Adopt layered cutting technology: for thick substrate or deep groove, set multi-layer cutting depth (0.5–1 mm per layer) to reduce single cutting resistance and avoid substrate warping or tool fracture; When machining hollowed-out parts, connecting bridges (small supporting strips) should be reserved to prevent hollowed-out parts from falling off during machining, damaging the machine tool or affecting the accuracy.

Calibration of equipment and tooling

Before machining, the precision of the engraving machine should be calibrated to zero: the verticality of the spindle and the flatness of the workbench should be detected with a laser probe, and the deviation should be controlled within ±0.01mm; Calibrate the compensation parameters of tool length to avoid machining depth deviation caused by tool wear.

Adaptation of clamping method: vacuum adsorption clamping can be used for rubber plate/density plate to ensure firm clamping and no deformation; The metal substrate needs to be fixed by pressure plate+fixture, and the stress points of the pressure plate are evenly distributed to prevent the uneven stress of the substrate from causing machining errors.

Second, in processing: key points of precision control and process execution.

Dynamic adjustment of core processing parameters

Spindle speed and feed speed matching: when processing rubber sheet, the feed speed is set to 3–5m/min and the speed is 15000r/min, giving consideration to efficiency and surface quality; When processing aluminum plate, the feed speed is reduced to 1–2m/min, and the rotating speed is increased to 20000r/min, thus reducing the risk of sticking the knife.

Cooling and chip removal control: air cooling can be used for rubber sheet processing to avoid the deformation of substrate caused by cooling liquid; The high-pressure cooling system needs to be turned on for metal substrate processing, so as to ensure that the cutting fluid reaches the tip of the knife, take away the cutting heat and metal chips, and prevent aluminium scrap from blocking the slot.

Real-time precision monitoring: Using the on-line detection function of the machine tool, the key dimensions (such as the width of the slot and the outline size of the die) are sampled during the machining process, and the compensation parameters of the tool are adjusted in time when the deviation is found to avoid batch scrapping.

Special requirements for machining complex cutter dies

Die-cutting indentation knife die: the width and depth of indentation line slot should strictly match the indentation line specifications, and the spacing between indentation line and knife bar should be uniform to prevent uneven indentation and line explosion of packaging products; When machining, it is necessary to distinguish between cutter groove and indentation groove to avoid confusion.

Special-shaped hollowing-out knife die: For the special-shaped edges of gift boxes and handbags, slow-moving knife technology should be adopted in processing, and the feed speed should be reduced at corners to ensure smooth edges without serrations and improve the aesthetics of packaged products.

Key measures to avoid machining defects

Prevention of edge collapse: when processing rubber sheet, set the advance and retreat points at the cutting-in and cutting-out positions of the cutter to prevent the cutter from directly hitting the edge of the substrate; Choose a sharp new tool to reduce the edge collapse caused by tool passivation.

Prevention of deformation: when machining large-size knife dies, auxiliary supports should be installed at the bottom of the substrate to reduce the vibration and deformation of the substrate during machining; After machining, place the die in a constant temperature and humidity environment to avoid secondary deformation caused by temperature and humidity changes.

Third, after processing: quality inspection, maintenance and safety control points

Quality inspection standard of cutter die accuracy

Size detection: use digital calipers and projectors to detect the outer contour size and slot spacing of the die, and the tolerance should meet the die-cutting requirements of packaging products (usually within ±0.03mm); Use the plug gauge to detect the fit between the clamping groove and the cutter bar to ensure that the cutter bar is moderately elastic after being embedded.

Appearance inspection: check whether there are burrs, edge collapse and scratches on the surface of the knife die, and whether the edge of the hollowed-out part is smooth; Metal die should be inspected for oxidation and corrosion on the surface, and antirust treatment should be carried out if necessary.

Equipment Maintenance and Tool Management

Regular maintenance of the machine tool: after machining, clean up the sawdust and metal chips on the workbench and guide rail to avoid impurities affecting the accuracy of the machine tool; Regularly add lubricating oil to guide rail and screw rod to prolong the service life of equipment.

Tool maintenance: After using the tool, the residual sawdust and aluminium scrap should be cleaned up in time and stored in categories; Passivated tools need to be sharpened or replaced in time to avoid affecting the subsequent processing quality.

Safety operation specification

During processing, it is forbidden to open the protective cover of the machine tool to prevent debris from splashing and hurting people; When the equipment is running, it is forbidden to touch the tool or substrate by hand.

Wood chips produced by rubber sheet processing should be cleaned in time to avoid fire caused by accumulation; The cooling oil for metal processing needs to be replaced regularly to prevent deterioration from affecting the cooling effect.

Four, the key points of special scene adaptation in packaging field

Food packaging knife mold: environmental protection knives and substrates should be selected to avoid harmful substances during processing; The surface of the die should be cleaned to prevent the residual debris from polluting the food packaging.

High-speed die-cutting die: For the die of automatic die-cutting production line, it is necessary to improve the dimensional consistency of the die, ensure that the die fits the die-cutting plate accurately after being installed in the die-cutting machine, and avoid the problems of shifting and sticking during high-speed die-cutting.