Plastic suction mold and molding method thereof

Abstract

The plastic suction mold comprises a mold base body composed of the following raw materials of, by weight, 88%-92% of aluminum, 8%-12% of silicon, 0.5%-1% of copper, 0.3%-0.6% of magnesium and smaller than or equal to 0.2% and a ceramic layer generated on the surface of the mold base body through micro-arc oxidation, the thickness of the ceramic layer ranges from 50 micrometers to 100 micrometers, and the hardness of the ceramic layer is larger than or equal to HV1500. The uniform and compact Al2O3 ceramic layer is formed on the surface of the mold base body through micro-arc oxidation treatment, the hardness of the Al2O3 ceramic layer is obviously higher than that of a traditional plating layer, the thermal expansion coefficient matching performance of the ceramic layer and the aluminum alloy base body is better, the ceramic layer is not prone to stripping in repeated thermal circulation of the plastic uptake technology, and the service life of the mold is prolonged.

Description

Technical Field

[0001] The invention relates to the field of plastic suction mould manufacturing, in particular to a plastic suction mould and a mould making method thereof. Background Art

[0002] Blister molding is a plastics processing technology widely used in industries such as packaging, medical treatment, and electronics. The performance of its core component, the blister mold, directly impacts the product's molding precision, surface quality, and production efficiency. Traditional blister molds are mostly made of aluminum alloy or steel. Aluminum alloy molds, due to their light weight, excellent thermal conductivity, and ease of processing, play a key role in small and medium-volume production. As industry requirements for product precision and mold life increase, the development of aluminum alloy blister molds that combine high wear resistance, high thermal stability, and low cost has become a technological trend.

[0003] In the existing technology, some high-wear-resistant aluminum alloy blister molds use high-manganese steel coatings to enhance surface properties. However, the thermal expansion coefficients of high-manganese steel and the aluminum alloy substrate are significantly different. Under the repeated heating / cooling cycles of the blister process, the coating is easily peeled off due to the accumulation of thermal stress, resulting in a shortened mold life. This defect limits the reliability of such molds under long-term high-temperature working conditions. Summary of the Invention

[0004] The object of the present invention is to provide a plastic suction mold and a molding method thereof to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A blister mold includes a mold base composed of the following raw materials in percentage by weight:

[0007] 88% to 92% aluminum, 8% to 12% silicon, 0.5% to 1% copper, 0.3% to 0.6% magnesium, ≤0.2% and a ceramic layer generated on the surface of the mold base by micro-arc oxidation, wherein the ceramic layer has a thickness of 50μm to 100μm and a hardness of ≥HV1500.

[0008] The main component of the ceramic layer is Al2O3, and the ceramic layer is metallurgically bonded to the mold substrate.

[0009] The mold base is formed by 3D printing and is provided with a pore structure inside.

[0010] A method for making a blister mold comprises the following steps:

[0011] Step S1, 3D printing the mold base, using selective laser melting technology, using aluminum-silicon alloy powder as raw material, 3D printing under nitrogen protection, laser power of 300W to 400W, layer thickness of 30μm, and directly forming the mold base;

[0012] Step S2, micro-arc oxidation to form a ceramic layer, immersing the mold substrate in an electrolyte, wherein the electrolyte is a mixed solution of sodium silicate and phosphate, applying a pulse voltage of 400W to 600V, and treating for 30min to 60min to in-situ form an Al2O3 ceramic layer on the surface of the mold substrate, wherein the ceramic layer formed by the micro-arc oxidation has a thickness of 50μm to 100μm and a hardness of ≥HV1500;

[0013] Step S3, reaction sintering strengthening, heating to 800° C. to 850° C. in a nitrogen atmosphere, keeping the temperature for 1 to 2 hours, so that silicon and aluminum react to form an Al-Si eutectic phase;

[0014] Step S4, low temperature polishing, using dry ice blasting to remove surface burrs and make the surface roughness of the mold base Ra less than 0.2 μm. After the dry ice polishing, no cleaning is required and the mold can be directly used for blister production.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention forms a uniform and dense Al2O3 ceramic layer on the surface of the mold substrate through micro-arc oxidation treatment. Its hardness is significantly higher than that of traditional coatings, and the thermal expansion coefficient of the ceramic layer is better matched with that of the aluminum alloy substrate. It is not easy to peel off during repeated thermal cycles of the blister process, and the mold life is improved;

[0017] 2. The present invention adopts gas atomization alloy powder and 3D printing integrated molding technology, which improves material utilization, and by optimizing the micro-arc oxidation voltage and sintering temperature, shortens the total heat treatment time, reduces energy consumption, and improves production efficiency;

[0018] 3. The present invention adopts dry ice polishing technology to effectively avoid surface damage caused by mechanical polishing. Combined with the Al-Si eutectic network formed by reaction sintering, the mold surface has both low friction coefficient and high dimensional stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process of 3D printing mold base of the present invention;

[0020] Figure 2 This is a schematic diagram of the process of forming a ceramic layer through micro-arc oxidation according to the present invention;

[0021] Figure 3 Schematic diagram of the process of reaction sintering strengthening of the present invention;

[0022] Figure 4 Schematic diagram of the low-temperature polishing process of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Example 1

[0025] The present invention provides a technical solution: a blister mold, comprising the following raw materials:

[0026] 90% aluminum, 9% silicon, 0.7% copper, 0.4% magnesium and 0.15% iron are mixed and then alloy powder is prepared by gas atomization method, and the powder particle size is controlled at 15 to 53 μm.

[0027] like Figure 1 As shown, in step S1, the 3D printing mold base is specifically as follows:

[0028] Step S101, use EOS M290 metal 3D printer for printing, and set printing parameters, wherein the laser power is 350W (preferred range 300W-400W, corresponding to power density 80-120J / mm3, when the power is <300W, the density decreases by >5%), the scanning speed is 1200mm / s, the layer thickness is 30μm, the protective gas is high-purity nitrogen (purity ≥99.99%), the oxygen content of the printing chamber is <0.1%, the scanning strategy adopts chessboard partition scanning, the partition size is 5mm×5mm, the support structure adopts dot matrix support, the support diameter is 0.3mm, and the spacing is 2mm.

[0029] Step S102: After printing is completed, a uniformly distributed pore structure is formed inside the mold substrate, with an average pore diameter of 50 μm and a porosity of 15%.

[0030] like Figure 2 As shown, in step S2, the micro-arc oxidation treatment is specifically as follows:

[0031] Step S201, pre-processing, the specific steps are as follows:

[0032] Step S2011, degreasing, immersing the workpiece in acetone ultrasonic cleaning for 10 minutes, and soaking in 60°C alkaline cleaning agent (pH = 13) for 5 minutes. The alkaline cleaning agent is prepared in accordance with the GB / T 25146-2010 standard. Alkali-resistant gloves (material: butyl rubber, thickness ≥ 0.5mm) must be worn during operation.

[0033] Step S201 , activation, using 10% nitric acid solution to soak for 30 seconds, and then rinsing with deionized water until neutral (conductivity < 5 μS / cm).

[0034] Step S202: preparing electrolyte. The specific steps are as follows:

[0035] Step S2021, prepare the following raw materials: 10 g / L sodium silicate, 5 g / L sodium dihydrogen phosphate, potassium hydroxide to adjust the pH to 9.5, 0.5 g / L sodium fluoride, and finally adjust the volume to 1 L with deionized water.

[0036] Step S2022, dissolving sodium silicate: then take about 800 mL of deionized water, heat it to 40-50° C. (to accelerate dissolution), slowly add 10 g of sodium silicate, and stir until completely dissolved.

[0037] Step S2023, adding sodium dihydrogen phosphate: while stirring, add 5 g of sodium dihydrogen phosphate and continue stirring for 10 minutes until it is completely dissolved.

[0038] Step S2024, adjust the pH value: use a pH meter to monitor the solution pH in real time, and add 10% potassium hydroxide solution (or add solid potassium hydroxide after dissolving it) dropwise until the pH stabilizes at 9.5±0.1 (if the pH exceeds 9.5, add a small amount of dilute phosphoric acid to adjust it).

[0039] Step S2025, adding sodium fluoride: add 0.5 g of sodium fluoride and stir for 20 minutes to ensure complete dissolution.

[0040] Step S2026, volume adjustment and filtration: transfer the solution to a 1 L volumetric flask, adjust the volume to the mark with deionized water, and filter using a 0.45 μm filter membrane to remove insoluble impurities.

[0041] Step S203, electrolytic treatment, the voltage is 500V (pulse frequency 1000Hz, duty cycle 30%), the treatment time is 45min, the electrolyte temperature is 25±2℃, wherein, the voltage is 300V (pre-oxidation) 5 minutes before the reaction, and the voltage rises to 500V (spark discharge stage) 5 minutes after the reaction. After treatment, a uniform Al2O3 ceramic layer is formed on the surface of the mold substrate with a thickness of 80μm, a hardness of HV1550 (load 200g), and a porosity of <2%.

[0042] Step S204, post-cleaning, the specific steps are as follows:

[0043] Step S2041: primary cleaning, ultrasonication in deionized water at 60°C for 5 minutes.

[0044] Step S2042: deep cleaning, using a high-pressure water gun (0.3 MPa) to flush complex structural parts.

[0045] Step S2043: drying, hot air circulation drying at 80°C for 30 minutes.

[0046] like Figure 3As shown, in step S3, the reaction sintering strengthening is specifically as follows:

[0047] Step S301, pre-treatment furnace loading, the specific steps are as follows:

[0048] Step S3011: Clean the mold substrate. The mold substrate after micro-arc oxidation is ultrasonically cleaned with anhydrous ethanol for 15 minutes, and high-pressure nitrogen (0.3 MPa) is used to purge residual particles on the surface.

[0049] Step S3012: Install the furnace and fix it. Use an alumina crucible to hold the mold. Lay graphite paper (thickness 0.5 mm) between the mold and the crucible to prevent adhesion. Ensure that the distance between the molds is ≥20 mm to ensure a uniform thermal field.

[0050] Step S302, programmed temperature rising stage, the specific steps are as follows:

[0051] Step S3021: Initial temperature increase from room temperature to 300°C at a rate of 5°C / min. During this stage, nitrogen protection (flow rate 5L / min) is turned on.

[0052] Step S3022: intermediate heat preservation, 300°C for 30 minutes (to eliminate stress in the micro-arc oxidation layer)

[0053] Step S3023, the key heating stage, continues to increase the temperature to 820°C at 5°C / min, and monitors the oxygen content in the furnace in real time (controlled at <50ppm).

[0054] Step S303, isothermal reaction sintering, the specific steps are as follows:

[0055] Step S3031: Temperature control. When the temperature reaches 820°C, start PID precise temperature control (fluctuation range ±2°C).

[0056] Step S3032: Atmosphere management: maintain nitrogen flow at 5 L / min and monitor moisture content (≤ -40°C) using a dew point meter.

[0057] Step S3033, reaction process, 0min to 30min: silicon element begins to diffuse along the grain boundary (diffusion front is observed by SEM), 30min to 90min: a stable Al-Si eutectic network is formed (XRD shows that the peak intensity of β-Al5FeSi phase increases).

[0058] Step S304: Controllable cooling. The specific steps are as follows:

[0059] Step S3041, stage cooling, first slowly cooling to 600℃ at 3℃ / min (to prevent thermal stress cracks), then cooling to below 300℃ with the furnace

[0060] Step S3042: Atmosphere switching: switch to argon protection (flow rate 3L / min) at 300°C to avoid nitriding reaction at low temperature.

[0061] Step S3043, oven removal standard, the oven temperature drops below 80°C, the oven is opened, the parts are taken out, and immediately placed in a dryer (humidity < 10% RH).

[0062] like Figure 4 As shown, in step S4, the cryogenic polishing is specifically as follows:

[0063] Step S401: pre-treatment and cleaning. The specific steps are as follows:

[0064] Step S4011: Remove surface residues by blowing the mold surface with compressed air (pressure 0.3 MPa), ultrasonically clean the mold with anhydrous ethanol (frequency 40 kHz, time 5 min), and then dry it with hot air at 80°C for 10 min.

[0065] Step S4012: Surface condition detection: initial roughness (Ra=0.8-1.2 μm) is confirmed by laser confocal microscopy, and surface energy is detected by contact angle meter (≤30° is qualified).

[0066] Step S402: Prepare the dry ice blasting system. The specific steps are as follows:

[0067] Step S4021: Equipment debugging, using the CryoSnow series dry ice blasting machine, and setting the following parameters:

[0068] Dry ice storage tank temperature: -78.5℃ (liquid CO2 phase maintained).

[0069] Transmission pipeline insulation: double-layer vacuum insulation structure.

[0070] Step S4022, process parameter setting, dry ice particle diameter: 50 μm (obtained by screening and classification), spray pressure: 0.6 MPa (calibrated by pressure sensor), spray distance: 100 mm (robotic arm positioning accuracy ±0.5 mm), spray angle: 90° (vertical incidence).

[0071] Step S403: graded polishing process, the specific steps are as follows:

[0072] Step S4031, rough polishing stage (0-1min), using fan-shaped spray mode (covering width 20mm), focusing on removing the surface protrusions of the micro-arc oxide layer (SEM observation shows that the protrusion height is 2-5μm)

[0073] Step S4032, fine polishing stage (1 to 3 minutes), switch to focused injection mode (beam spot diameter 3 mm), and adjust the parameters, including reducing the injection pressure to 0.4 MPa and the robot arm movement speed to 10 mm / s.

[0074] Step S4033, porosity verification, the polished surface is inspected by metallographic microscope (400×), and it is confirmed that the porosity retention rate of the ceramic layer is greater than 98% (compared with less than 2% before polishing). When the surface roughness Ra is reduced from 1.2μm to 0.08μm, the standard deviation of the pore size distribution is less than 5μm.

[0075] Example 2

[0076] After the blister mold is prepared, performance tests are required, including mechanical performance tests and thermal stability tests. The mechanical performance tests further include hardness tests and wear resistance tests.

[0077] Hardness test, the test steps are as follows:

[0078] Test step A1, sample preparation, cut a 10mm×10mm sample from the blister mold prepared in Example 1, use epoxy resin to embed it, and then polish the test surface with 400#, 800#, and 1200# sandpaper in sequence, and finally mirror polish it with 0.5μm diamond polishing paste.

[0079] Test step A2: Set the test conditions, use an HV-1000 microhardness tester, set the load to 200 gf (1.96 N), set the hold time to 15 s, and distribute the test points on the surface of the ceramic layer in a 5×5 matrix with 25 points. The ambient temperature is 23±1°C.

[0080] Test step A3, data processing, remove the highest and lowest 3 values ​​and take the average value, and calculate the standard deviation (SD < 50HV is valid).

[0081] Wear resistance test, the test steps are as follows:

[0082] Test step B1, sample processing, the mold of Example 1 is processed into The disc specimen was polished to Ra < 0.1 μm, ultrasonically cleaned and then dried (60 ° C, 2 h).

[0083] Test step B2: Set the test conditions using a Taber 5155 abrasion tester with a CS-10 rubber wheel (Shore A hardness of 90) and a load of 1 kg (9.8 N). The speed is 60 rpm, the number of revolutions is 1000, and the ambient humidity is 50 ± 5% RH.

[0084] Test step B3, comparative test, the control group is SKD61 mold steel (heat treated to HRC52), and three groups are tested in parallel under the same test conditions.

[0085] Thermal stability test, the test steps are as follows:

[0086] Test step C1, test preparation: prepare a 25 mm × 25 mm × 5 mm square specimen, polish all six sides to Ra < 0.2 μm, mark a 10 mm × 10 mm measurement grid on the specimen surface with a laser, calibrate the temperature control system using a standard thermocouple (type K), and verify the temperature uniformity of the high-temperature chamber (±2°C).

[0087] Test step C2, loop step:

[0088] Step C201, low temperature stage, cool down to -40°C at 10°C / min, keep warm for 30 minutes, and measure the grid size with a laser rangefinder (accuracy 0.1μm)

[0089] Step C202, high temperature stage, heating to 200°C at 10°C / min, keeping warm for 30 minutes, and performing secondary dimensional measurement.

[0090] Step C203, cycle control, automatically records the dimensional change of each cycle, and performs SEM surface observation every 20 cycles.

[0091] Test step C3, actual working condition simulation, the blister mold of Example 1 is installed on the corresponding blister machine, and 5000 PET products (thickness 0.5 mm, heating temperature 180°C) are continuously produced. The dimensional change rate of the blister mold is less than 0.05% (detected by a three-coordinate measuring machine with an accuracy of 0.1 μm), and no Al2O3 layer peeling occurs (confirmed by SEM observation with a magnification of 1000×).

[0092] Example 3

[0093] In order to further verify the influence of process parameters on the performance of the ceramic layer and clarify the scientific basis for the parameter selection in Example 1, this example systematically optimizes the two core variables of micro-arc oxidation voltage and sintering temperature. By comparing the thickness, hardness and wear resistance of the ceramic layer under different parameter combinations, the correlation between process parameters and performance is revealed, thereby providing theoretical support for actual production.

[0094] This embodiment not only supplements the technical logic chain of the first and second embodiments, but also avoids the empiricism and blindness of parameter selection, thereby ensuring the repeatability of the process and the stability of product performance.

[0095] In this embodiment, the process parameter optimization comparison includes micro-arc oxidation voltage comparison and sintering temperature comparison.

[0096] When comparing the micro-arc oxidation voltage, other parameters are fixed and the processing voltage is changed, as shown in the following table:

[0097] Voltage (V) Processing time (min) Ceramic layer thickness (μm) Hardness (HV) 400 60 50 1200 500 45 80 1550 600 30 100 1800

[0098] According to the above table, the optimal scheme for micro-arc oxidation voltage is: 500V, 45min (taking into account both efficiency and performance).

[0099] When comparing sintering temperatures, the holding time is fixed at 1.5h and the temperature is changed, as shown in the following table:

[0100] Temperature (℃) Al-Si phase content (%) Flexural strength (MPa) 800 8 450 820 12 520 850 15 480

[0101] According to the above table, the preferred sintering temperature is 820°C (peak strength).

[0102] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0103] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A blister mold, characterized in that: The mold base is composed of the following raw materials by weight: 88% to 92% aluminum, 8% to 12% silicon, 0.5% to 1% copper, 0.3% to 0.6% magnesium, ≤0.2% and a ceramic layer generated on the surface of the mold base by micro-arc oxidation, wherein the ceramic layer has a thickness of 50μm to 100μm and a hardness of ≥HV1500.

2. The blister mold according to claim 1, characterized in that: The main component of the ceramic layer is Al2O3, and the ceramic layer is metallurgically bonded to the mold substrate.

3. The blister mold according to claim 1 or 2, characterized in that: The mold base is formed by 3D printing and is provided with a pore structure inside.

4. A method for making a blister mold, characterized in that: The following steps are involved: Step S1, 3D printing the mold base, using selective laser melting technology, using aluminum-silicon alloy powder as raw material, 3D printing under nitrogen protection, laser power of 300W to 400W, layer thickness of 30μm, and directly forming the mold base; Step S2, micro-arc oxidation to form a ceramic layer, immersing the mold substrate in an electrolyte, applying a pulse voltage of 400V to 600V, and treating for 30min to 60min to in-situ form an Al2O3 ceramic layer on the surface of the mold substrate; Step S3, reaction sintering strengthening, heating to 800° C. to 850° C. in a nitrogen atmosphere, keeping the temperature for 1 to 2 hours, so that silicon and aluminum react to form an Al-Si eutectic phase; Step S4: low-temperature polishing, using dry ice blasting to remove surface burrs and make the surface roughness of the mold base Ra less than 0.2 μm.

5. The molding method according to claim 4, wherein: The electrolyte is a mixed solution of sodium silicate and phosphate.

6. The molding method according to claim 4, wherein: The ceramic layer generated by the micro-arc oxidation has a thickness of 50 μm to 100 μm and a hardness of ≥ HV1500.

7. The molding method according to claim 4, wherein: The dry ice polishing process does not require cleaning and can be directly used in blister production.

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