A low-temperature and low-pressure integrated forming method for a robot embedded component

Abstract

The application relates to a robot pre-embedded component low-temperature and low-pressure integrated forming method, which comprises the following steps: integrated forming, i.e. filling a mold cavity with liquid two-component reaction materials under the driving of vacuum negative pressure, coating a robot pre-embedded component and then rapidly crosslinking and solidifying; the liquid two-component reaction materials are one of a low-temperature curing epoxy resin system, a polyurethane RIM system, a polyurea RIM system and a PDCPD-RIM system; the forming temperature is controlled to be less than or equal to 60 DEG C and the forming pressure is controlled to be less than or equal to 0.1 MPa during integrated forming; the low-temperature curing epoxy resin system is composed of a bisphenol A epoxy resin and a modified polythiol or aliphatic amine curing agent; the polyurethane RIM system is composed of a polyol mixture and a polyisocyanate prepolymer; the polyurea RIM system is composed of an amino-terminated polyether and an isocyanate prepolymer; and the PDCPD-RIM system is composed of dicyclopentadiene monomers and a tungsten-based catalyst. The high-temperature and high-pressure mechanical damage and thermal damage risks of pre-embedded precision components are eliminated, and the range of pre-embedded components is expanded.

Description

Technical Field

[0001] This invention relates to the field of robot manufacturing, specifically to a method for low-temperature, low-pressure integrated molding of robot pre-embedded components. Background Technology

[0002] To achieve a compact structure, high protection level, and high assembly efficiency, the design envisions embedding electronic components, sensors, and metal inserts within a plastic housing, using injection molding for encapsulation and fixation. Traditional injection molding requires high temperatures (180-300°C) and high pressures (30-200 MPa), an environment prone to deformation, displacement, or thermal damage to the embedded precision electronic components and sensors, potentially leading to solder joint detachment and chip cracking. Circuit boards (PCBs) and their surface mount components (SMDs) typically have a temperature resistance not exceeding 125-150°C, and lead-free solder has a melting point of approximately 217-227°C. They will inevitably be damaged under thermal shock from a molten metal at 260-290°C and mechanical impact at 2000 atmospheres. According to the JEDEC J-STD-020 standard, the exposure time of industrial-grade components at the peak reflow soldering temperature of 260°C must be strictly controlled within 30-60 seconds, while the high temperature and high pressure duration of injection molding typically ranges from several minutes to tens of minutes, far exceeding the component's tolerance limits. Summary of the Invention

[0003] This invention proposes a low-temperature, low-pressure integrated molding method for robot pre-embedded components.

[0004] The technical solution of the present invention: A method for low-temperature, low-pressure integrated molding of robot pre-embedded components, the method comprising: integrated molding in which a liquid two-component reactive material is filled into a mold cavity under vacuum negative pressure, covering the robot pre-embedded component, and then rapidly cross-linked and cured; the liquid two-component reactive material is one of a low-temperature curing epoxy resin system, a polyurethane RIM system, a polyurea RIM system, and a PDCPD-RIM system; the molding temperature is controlled to be ≤60°C and the molding pressure to be ≤0.1MPa during integrated molding; the low-temperature curing epoxy resin system is composed of bisphenol A epoxy resin and a modified polythiol or fatty amine curing agent, the polyurethane RIM system is composed of a polyol mixture and a polyisocyanate prepolymer, the polyurea RIM system is composed of an amino-terminated polyether and an isocyanate prepolymer, and the PDCPD-RIM system is composed of a dicyclopentadiene monomer and a tungsten-based catalyst.

[0005] Further refining the above technical solution, the robot embedded part is fixed in the mold cavity by at least one of the following: magnetic positioning mechanism, internal support reinforcing cage mechanism, external wrapping cage mechanism, soluble / fusible temporary support, and suspension balance positioning. This eliminates the traditional design of "using mechanical clamps such as positioning pins, wedge-shaped locking blocks, and hydraulic clamping mechanisms to position the embedded part in the mold cavity," fundamentally eliminating the risk of mechanical clamps and covering materials solidifying and adhering.

[0006] To further refine the above technical solution, the method also includes: 1) classifying the robot pre-embedded components into categories A (direct pre-embedded parts) and B (protective pre-embedded parts); 2) the protective pre-embedded parts adopt at least one protective measure.

[0007] The above technical solution is further refined. The robot pre-embedded component includes a motor, which is a protective pre-embedded part. The protective measures for the motor include: 1) coating the surface of the motor housing with a ceramic-based heat-insulating coating and / or covering it with heat-resistant heat-insulating felt; 2) filling the gap between the motor output shaft and the housing, and the bearing gap with high-temperature resistant grease or installing Teflon sealing rings; 3) in the mold design, setting a thin-walled covering layer in the corresponding area of ​​the motor or making the motor housing directly contact the outside air.

[0008] The above technical solution is further refined. When integral molding, the applicable period should be greater than the sum of the injection time and the venting time, and a safety margin of no less than 1 minute should be reserved. This can avoid incomplete filling caused by premature curing.

[0009] To further refine the above technical solution, reinforcing fillers are added to the liquid two-component reactive material; the reinforcing fillers include: ground glass fiber, chopped glass fiber, fabric reinforcement, and calcium carbonate filler.

[0010] Further refining the above technical solution, the robot pre-embedded component also includes a harmonic reducer flexure wheel, which is a protective pre-embedded part; the protective measures for the harmonic reducer flexure wheel include: inserting a detachable rigid support mandrel into the inner hole of the flexure wheel before mold closing.

[0011] The above technical solution is further refined by reserving interfaces for robot-installed components and non-embedded components in the mold during the one-piece molding process.

[0012] Further refining the above technical solution, the robot retrofit component includes a circuit board; the robot pre-embedded component includes a wire harness; conductive contacts and a metal shielding layer are pre-embedded during integral molding; one end of the conductive contact is connected to the wire harness terminal and the other end is exposed in the circuit board mounting interface; the metal shielding layer covers the circuit board mounting interface and is connected to the circuit board grounding contact.

[0013] Further refining the above technical solution, the robot includes relatively rotating components; the relatively rotating components employ at least one protective measure; the protective measures for the relatively rotating components include: 1) within the mold, a gap is reserved between the relatively moving components, and a peelable isolation film is placed; after molding, the isolation film is removed to obtain a clean rotation gap; 2) within the mold, a metal spacer is pre-placed, the inner hole of the metal spacer is clearance-fitted with the outer diameter of the rotating shaft, and the outer wall of the metal spacer contacts the mold or is embedded in liquid two-component reactive material; after molding, the metal spacer is fixed to form a precise bearing seat or bushing, and the rotating shaft rotates freely within the metal spacer; 3) within the mold, the relatively moving components are completely separated, each being encased in liquid two-component reactive material, with a cavity reserved between them; after molding, an independent rotary joint module is subsequently installed in the cavity.

[0014] The advantages of this invention are its reasonable design and ingenious concept. It uses a liquid two-component reactive material and is supplemented by a molding temperature ≤60°C and molding pressure ≤0.1MPa, which eliminates the risk of mechanical and thermal damage to the pre-embedded precision components due to high temperature and high pressure. It expands the range of components that can be pre-embedded (such as ordinary enameled wire motors, PVC wires, etc., which cannot be pre-embedded in traditional one-piece molding), and can even include motors. It can achieve a gel time ≤10 minutes and a demolding time ≤30 minutes, meeting the requirements of mass production efficiency. Attached Figure Description

[0015] Figure 1 It is a process flow diagram (low-temperature and low-pressure integrated molding of robot pre-embedded components). Detailed Implementation

[0016] As shown in the figure: A method for low-temperature, low-pressure integrated molding of robot pre-embedded components, the method comprising the following steps: Step 1: Component Selection and Classification: Divide the robot components into categories A, B, and C. Category A - Directly Embedded Components: Components whose function is not affected after being covered with grout and which do not require maintenance or replacement during their service life; including: aluminum alloy skeleton (frame type / honeycomb type), metal structural parts / supports, metal inserts, wire harnesses, pre-embedded conductive contacts, bearing seats, and empty sensor housings (internal sensitive elements have been removed).

[0017] Category B – Protective Embedded Components: Components whose function is not affected after being covered by grouting material, but which require special protection measures or reserved maintenance interfaces; including: motors (ensuring unobstructed heat dissipation paths, and winding temperature resistance ≥60°C), harmonic reducer steel wheels, and torque sensor metal elastomers (strain gauge areas need to be isolated and protected).

[0018] Category C—Non-pre-embedded / post-installed components: Components whose functionality is affected by potting compound coating, or which require frequent maintenance and replacement; including: Circuit boards with mounted components: potting compound blocks heat dissipation and is not repairable, altering RF performance due to changes in dielectric constant; Batteries / supercapacitors / electrolytic capacitors: risk of electrolyte leakage and short circuits, thermal runaway hazards, requiring replacement and maintenance; Optical sensors (cameras, LiDAR, ToF): optical window contamination, reduced light transmittance; Acoustic devices (microphones, speakers): diaphragms / cavities are filled, resulting in loss of acoustic performance; Wireless communication modules (WiFi / Bluetooth / 4G): antenna coating leads to RF performance degradation; FPC cables: become brittle and break after interlayer penetration and curing.

[0019] Step 2: Mold preparation: Design and manufacture the mold according to the robot's shape, and pre-set wire harness channels, pre-embed conductive contacts and reserve C-type component installation interfaces in the mold.

[0020] Step 3: Pre-treatment and positioning of embedded parts: Surface pretreatment of the heat-resistant part of the embedded part: sandblasting roughening (Ra 3.2-12.5μm), coating with silane coupling agent or polyurethane / epoxy special primer to enhance the chemical bond with the coating material.

[0021] Knurling (diamond knurling or spiral groove) or annular groove (1-3mm wide, 0.5-2mm deep) is applied to metal parts such as aluminum alloy frames to form a mechanical interlocking structure.

[0022] The embedded parts shall be fixed in the mold cavity by at least one of the following: magnetic positioning mechanism, internal support reinforcing mesh cage mechanism, external wrapping mesh cage mechanism, soluble / fusible temporary support positioning or suspension balance positioning. Mechanical clamps that extend into the mold cavity are strictly prohibited. 1) Magnetic Positioning: For metal embedded parts (such as aluminum alloy frames and steel wheels), an electromagnet or permanent magnet positioning seat is set at the bottom of the mold. The embedded part is attracted and fixed to the bottom surface of the cavity by magnetic attraction. The magnetic force can penetrate the covering material layer and act on the metal embedded part, eliminating the need for the embedded part to be exposed. After casting, the mold can be demolded by demagnetizing or mechanically separating the magnetic seat. The surface of the magnetic seat can be covered with a PTFE release film to prevent adhesion to the embedded part. 2) Internal Support Reinforced Cage (Disposable): For hollow structure embedded parts (such as frame-type aluminum alloy skeletons and hollow sensor housings), a disposable aluminum alloy mesh support cage (wire diameter 0.5-1mm, mesh size 5-10mm, surface roughened by sandblasting to Ra6.3-12.5μm and coated with silane coupling agent) is used to internally support and fix the part. After injection, the aluminum mesh cage forms a mechanical and chemical bond with the covering material through the mesh, permanently embedding itself inside the hollow structure as an internal reinforcing skeleton. It does not need to be removed, fundamentally avoiding the problems of traditional internal support clamps sticking to the finished product and being difficult to demold. The quality of the aluminum mesh cage is controlled within 5% of the total weight of the embedded part and does not directly contact Class C sensitive elements. 3) Outer Wire Mesh Cage (Disposable): For solid or irregularly shaped embedded parts (such as metal inserts, bearing housings, and motor housings), a disposable aluminum alloy wire mesh support cage (wire diameter 0.5-1mm, mesh size 5-10mm, surface roughened by sandblasting to Ra 6.3-12.5μm and coated with silane coupling agent) is used to completely wrap the embedded part and fix it in the mold cavity. The wire mesh cage contacts the mold to achieve positioning. After casting, the wire mesh cage and the covering material together form a permanent integrated structure, and the wire mesh cage becomes a reinforcing skeleton connecting the embedded part and the housing. The weight of the outer wire mesh cage is controlled within 3% of the total weight of the embedded part. 4) Soluble / fusible temporary support positioning: Use water-soluble PVA support or low melting point alloy (melting point ≤60°C) to make temporary support structure, and suspend the embedded part in the correct position in the mold cavity; after casting, dissolve the PVA support with water or melt the low melting point alloy at ≤60°C, and the support material flows out from the reserved outlet, and the embedded part is left in the correct position. 5) Suspension and Balance Positioning: For small and lightweight embedded parts, density matching or buoyancy balance design (such as embedding counterweights or hollow cavities inside the embedded parts) can be used to make the average density of the embedded parts in the liquid material close to that of the injection material, so that they can be naturally suspended in the center of the mold cavity.

[0023] For Class B embedded parts, the heat-sensitive parts should be removed and stored separately.

[0024] For motors as Class B embedded parts, their housing surfaces are coated with a ceramic-based heat-insulating coating (such as zirconium oxide, 50-150μm thick) and / or covered with heat-resistant insulating felt (such as quartz fiber or glass fiber cloth, 1-2mm thick). The gaps between the output shaft and the housing, and the bearing gaps are filled with high-temperature resistant grease (such as perfluoropolyether grease) or PTFE sealing rings are installed.

[0025] For the flexure of the harmonic reducer as a Class B embedded part (wall thickness 0.3-0.5mm), before mold closing, the detachable rigid support mandrel is inserted into the inner hole of the flexure. The mandrel material is mold steel Cr12MoV, the surface is plated with hard chrome, the hardness is HRC60, and the clearance between the outer diameter of the mandrel and the inner diameter of the flexure is 0.02-0.05mm.

[0026] Step 4: Mold closing and vacuuming: Close the upper and lower molds to form a sealed mold cavity using the sealing ring; start the vacuum system to pump the absolute pressure of the mold cavity to 0.01-0.04 MPa (corresponding to a gauge pressure of approximately -0.06 to -0.09 MPa, based on standard atmospheric pressure of 0.1013 MPa) and maintain it stable; maintain the mold temperature at 30-60°C using a circulating water bath or electric heating.

[0027] Step 5: Two-component mixing and vacuum-assisted infusion: Components A and B are injected into a static mixer at a precise ratio (volume ratio 1:1-1.2:1) using a metering pump and mixed thoroughly. The viscosity of the mixed material is controlled at 300-800 mPa·s (25°C), and the working time is ≥3 minutes; The pouring speed should be controlled within the range of 0.5-5L / min. When the mold cavity volume is ≤1L, the pouring speed should be 1-2L / min. When the mold cavity volume is 1-5L, the pouring speed should be 2-4L / min to ensure that the material flow is in a laminar state (Reynolds number Re≤2300) and to avoid turbulence from entraining air bubbles. The mixture enters the mold cavity through the pouring port, flows evenly under the vacuum negative pressure suction and covers the embedded parts; After the infusion is completed, maintain the vacuum for 1-3 minutes to allow the micro-bubbles to expand in a low-pressure environment and be discharged through the exhaust channel.

[0028] Before mold closing, spray silicone oil-based release agent or apply PTFE dry release coating evenly on the surface of the mold cavity, or apply release film to the contact surface between the embedded part and the mold to ensure smooth demolding after curing without damaging the surface finish of the shell.

[0029] Step Six: Rapid Curing: The material undergoes a rapid cross-linking reaction within the mold, with a gel time of 2-10 minutes and a demolding time of 10-30 minutes. The curing reaction is exothermic, and the mold temperature control system limits the peak temperature to ≤60°C.

[0030] Step 7 Cooling and Demolding: After curing, the pressure inside the mold cavity returns to normal pressure, and the semi-finished product is removed from the mold. Since this invention uses a one-time mesh cage positioning (internal support or external wrapping), there is no need to remove any mechanical clamps, making the demolding process simple and efficient. For the flex wheel of the harmonic reducer, after curing and before mold opening, the support mandrel is smoothly ejected from the flex wheel through the ejection mechanism of the mold, with the ejection stroke slightly greater than the height of the flex wheel. Since the inner hole of the flex wheel maintains its original machining accuracy under the protection of the support mandrel, the wave generator and rigid wheel can be smoothly installed according to the standard process after demolding.

[0031] Step 8: Post-installation of Class C components: Insert the circuit board along the reserved mounting interface so that the gold fingers and the pre-embedded conductive contacts form an elastic electrical connection; The optical sensor is installed in the reserved window, and the acoustic device is installed in the reserved sound cavity; Install the battery into the reserved battery compartment.

[0032] Step 9: Sealing and Encapsulation: Seal the circuit board mounting port, sensor window, sound cavity, and battery compartment (ultrasonic welding, O-ring pressing, or potting compound sealing).

[0033] Step 10 Post-processing: Remove the gate and burrs, perform necessary machining, and connect the external interface.

[0034] For circuit boards as retrofit components; (a) Pre-embedded conductive contacts Metal conductive contacts (such as gold-plated beryllium copper, gold-plated phosphor bronze, or gold-plated stainless steel) are pre-set in the mold. One end of the contact is exposed in the circuit board mounting groove, and the other end is embedded in the coating material matrix after casting and connected to the terminal of the pre-embedded wire harness. The contact adopts an elastic structure design (cantilever beam spring, crown spring, or claw spring structure) to ensure reliable contact with the gold fingers or pads of the circuit board, with a contact resistance ≤10mΩ.

[0035] Contact protection design: A removable protective cover (made of mold steel or ceramic material, 1-2mm thick) is installed above the contact. The protective cover covers the contact during casting and is removed after demolding to restore the contact's elasticity. The protective cover is connected to the mold via a locating pin.

[0036] (ii) Circuit board mounting slots / rails A circuit board mounting slot is designed inside the mold. The slot width is 0.1-0.3mm larger than the circuit board thickness, and the slot depth matches the circuit board length. Guide rails (boss or groove structure) are set on both sides of the slot to ensure the positioning accuracy (±0.2mm) when the circuit board is inserted. A limiting step is set at the bottom of the mounting slot to prevent excessive insertion and damage to the contacts.

[0037] The mounting groove is formed by a detachable insert within the mold during casting. The insert is rigidly fixed to the mold sidewall by a conical self-locking mechanism or bolts to prevent displacement during casting. After demolding, removing the insert creates an open mounting groove.

[0038] (III) Circuit Board Selection Since the circuit board does not need to withstand the casting environment, a conventional FR-4 substrate (temperature resistance 130-150℃) or a common PI substrate can be used. Components can be of industrial or commercial grade, which greatly reduces material costs. The circuit board edge is designed with gold fingers or large-area pads as contact interfaces, corresponding to the pre-embedded contacts.

[0039] (iv) Sealed encapsulation structure After the circuit board is inserted, it is sealed using the following method: Sealing cover: The cover is made of the same material as or compatible with the outer shell and is welded to the mounting groove by ultrasonic welding to form a permanent seal; O-ring seal: A silicone rubber or fluororubber O-ring is installed in the mounting groove, and the cover plate is tightened with screws to seal, which facilitates later maintenance; Encapsulation: Epoxy resin or silicone rubber encapsulation is injected into the mounting groove. After curing, it forms a sealed protective layer and enhances the vibration resistance of the circuit board.

[0040] (v) Electromagnetic shielding design A metal shielding layer (such as copper foil or conductive paint coating) is pre-embedded in the inner wall of the circuit board mounting slot and connected to the grounding contact of the circuit board to form a Faraday cage structure, thereby achieving electromagnetic shielding function.

[0041] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for low-temperature, low-pressure integrated molding of robot pre-embedded components, characterized in that, The method includes: integral molding, in which liquid two-component reactive material is filled into the mold cavity under vacuum negative pressure, wrapped with robot pre-embedded components, and then rapidly cross-linked and cured; the liquid two-component reactive material is one of low-temperature curing epoxy resin system, polyurethane RIM system, polyurea RIM system, and PDCPD-RIM system; during integral molding, the molding temperature is controlled to be ≤60°C and the molding pressure is controlled to be ≤0.1MPa; The low-temperature curing epoxy resin system is composed of bisphenol A epoxy resin and modified polythiol or fatty amine curing agent; the polyurethane RIM system is composed of polyol mixture and polyisocyanate prepolymer; the polyurea RIM system is composed of amino-terminated polyether and isocyanate prepolymer; and the PDCPD-RIM system is composed of dicyclopentadiene monomer and tungsten-based catalyst.

2. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, The robot pre-embedded part is fixed in the mold cavity by at least one of the following: magnetic positioning mechanism, internal support reinforcing cage mechanism, external wrapping cage mechanism, soluble / fusible temporary support, and suspension balance positioning.

3. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, The method further includes: 1) classifying the robot pre-embedded components, with Class A being direct pre-embedded components and Class B being protective pre-embedded components; 2) the protective pre-embedded components adopting at least one protective measure.

4. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 3, characterized in that, The robot's pre-embedded components include a motor, which is a protective pre-embedded component; Protective measures for motors include: 1) coating the motor housing with a ceramic-based heat-insulating coating and / or covering it with heat-resistant insulating felt; 2) filling the gap between the motor output shaft and the housing, and the bearing gap with high-temperature resistant grease or installing Teflon seals; 3) in the mold design, setting a thin-walled covering layer in the corresponding area of ​​the motor or making the motor housing directly contact the outside air.

5. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, When molding in one piece, the control period should be longer than the sum of the injection time and the venting time, and a safety margin of no less than 1 minute should be reserved.

6. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, Add reinforcing fillers to the liquid two-component reactive material; The reinforcing filler includes: ground glass fiber, chopped glass fiber, fabric reinforcement, and calcium carbonate filler.

7. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 3, characterized in that, The robot pre-embedded component also includes a harmonic reducer flex wheel, which is a protective pre-embedded component; Protective measures for the flexure of a harmonic reducer include inserting a removable rigid support mandrel into the inner hole of the flexure before mold closing.

8. The method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, When molding a single piece, the mold is used to reserve installation interfaces for robot-installed components and non-embedded components.

9. A method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 8, characterized in that, The robot's aftermarket components include a circuit board; the robot's pre-embedded components include a wiring harness. Conductive contacts and a metal shielding layer are pre-embedded during the one-piece molding process; one end of the conductive contact is connected to the wire harness terminal and the other end is exposed in the circuit board mounting interface; the metal shielding layer covers the circuit board mounting interface and is connected to the circuit board grounding contact.

10. A method for low-temperature, low-pressure integrated molding of robot pre-embedded components according to claim 1, characterized in that, The robot includes relatively rotating components; the relatively rotating components are equipped with at least one protective measure; Protective measures for relatively rotating components include: 1) In the mold, a gap is reserved between the relatively moving components, and a peelable isolation film is placed; after molding, the isolation film is removed to obtain a clean rotation gap; 2) In the mold, a metal spacer is pre-placed, with the inner hole of the metal spacer fitting the outer diameter of the rotating shaft with clearance, and the outer wall of the metal spacer contacting the mold or embedding liquid two-component reactive material; after molding, the metal spacer is fixed to form a precise bearing seat or bushing, and the rotating shaft rotates freely within the metal spacer; 3) In the mold, the relatively moving components are completely separated and each is covered in liquid two-component reactive material, with a cavity reserved between them; after molding, an independent rotating joint module is installed in the cavity.

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