Description:FIELD OF INVENTION
[0001] The present disclosure relates to the manufacturing of surgical instruments, and more specifically pertains to a Metal Injection Molding (MIM)-based method for producing articulated surgical instruments without requiring secondary machining operations.
BACKGROUND
[0002] The background section is presented solely to facilitate understanding of the invention disclosed herein. It is not admission in this section that is intended to imply or acknowledge any of the described information constitutes prior art or bears relevance to the subject matter of the present claims, nor should any cited or mentioned publications be construed as prior art
[0003] Articulated surgical instruments must exhibit high dimensional accuracy, mechanical strength, and corrosion resistance to ensure consistent clinical performance under sterile and high-stress conditions. The functional efficiency of instruments directly depends on the precision of their jaws, hinge alignment, and locking mechanism. Therefore, manufacturing processes must adhere to stringent tolerances and surface finish requirements to meet surgical-grade standards. Consistency in quality and biocompatibility is paramount to ensure safe and effective usage in diverse clinical environments.
[0004] Conventional manufacturing methods for articulated surgical instruments, such as machining, investment casting, and die casting, typically involve multiple stages and secondary operations to achieve the necessary dimensional accuracy and surface finish. These traditional approaches are often labor-intensive, time-consuming, and may result in inconsistent quality or higher production costs.
[0005] Metal Injection Molding (MIM) has gained considerable attention as a transformative manufacturing technique for producing high-precision medical components. It enables the fabrication of complex and miniaturized geometries that are often difficult to achieve through conventional methods. MIM combines the design flexibility of plastic injection molding with the material strength of metal, resulting in parts with superior mechanical properties. Additionally, the process offers excellent surface finish and dimensional consistency, while significantly reducing material waste through near-net-shape production. These advantages make MIM highly suitable for the medical device industry, where performance and precision are critical.
[0006] Metal Injection Molding (MIM) is used for manufacturing small, high-precision components, its adoption in producing articulated surgical instruments such as artery forceps remains significantly limited. This underutilization stems from the inherent technical difficulties in forming complex geometries with moving and interlocking parts, which are essential to the functional performance of such instruments. Components like ratchets and jaws demand high accuracy and tight tolerances, which are difficult to achieve directly through conventional MIM processes.
[0007] One of the primary challenges in applying MIM to articulated surgical instruments is the control of distortion during the sintering phase. The elongated and slender geometries typical of surgical instruments are particularly prone to warping and deformation, which can misalign mating features and compromise mechanical articulation. The risk of dimensional deviation increases with structural complexity, affecting the precision fit and operational integrity of key elements such as the locking ratchet and hinged jaws.
[0008] Current MIM-based manufacturing techniques have not demonstrated the capability to consistently produce articulated surgical instruments with the necessary mechanical strength and dimensional precision without resorting to secondary operations like machining or manual fitting. These additional steps reduce the efficiency, scalability, and economic viability of MIM for articulated surgical tools. Therefore, there is a pressing need for an improved MIM methodology that addresses these deficiencies and enables the direct, high-fidelity production of complex, functional surgical instruments. Also, the traditional debinding methods, such as purely thermal or solvent-based debinding, often suffer from drawbacks such as part distortion, uneven binder removal, or excessive processing times. Thermal debinding can induce stresses due to rapid heating, while solvent debinding may leave residual binder or require additional steps. There is a need for a controlled debinding process that efficiently removes binders without compromising part geometry.
[0009] Patent CN110919007A describes a MIM process for producing high-precision parts using 17-4PH stainless steel, suitable for general industrial applications. The method uses fine powder (≤22μm) mixed with a binder, followed by injection molding and thermal debinding in nitrogen or inert atmospheres. Sintering is performed in a vacuum to enhance structural properties. Post-processing includes heat treatment, nitriding, and optional vacuum demagnetization for magnetic control. The process delivers components with high density, hardness, and mechanical reliability. It focuses purely on structural performance without ergonomic or device-specific features. No surgical instruments or forceps are covered.
[0010] Patent US 8,745,840 B2 describes electrosurgical forceps that incorporate elongated jaws equipped with conductive sealing plates applied via vapor deposition onto polymer-based insulators. The manufacturing method involves injection molding for producing the insulating components, which are then assembled with both electrical and mechanical connections to form the complete instrument. This hybrid design combines metal and polymer elements, but does not utilize Metal Injection Molding (MIM). Additionally, it requires secondary machining, limiting its suitability for streamlined, high-precision production.
[0011] While prior art disclosures focus on achieving high density, mechanical strength, and corrosion resistance through optimized thermal cycles, they often overlook the critical role of mold flow and distortion control in Metal Injection Molding (MIM). For complex surgical instruments with intricate geometries and tight tolerances, precise mold flow management is essential to avoid defects and ensure dimensional accuracy. Distortion during molding or sintering can compromise alignment and mechanical performance, especially in articulated components where interdependent movement is vital. The proposed method uniquely integrates to support defect-free fabrication, thus enabling superior functionality and reliability compared to earlier MIM-based techniques.
[0012] With this consideration, the current disclosure addresses and resolves the issues linked to traditional synthesis methods by providing a novel and optimized method for manufacturing articulated surgical instruments using single-step Metal Injection Molding (MIM) technology. It eliminates the need for secondary machining such as grinding, drilling, tapping, polishing etc. None of the cited prior art achieves this level of integration for articulated surgical instruments. This results in enhanced manufacturing efficiency, reduced production costs, and improved reliability. Overall, the invention marks a significant advancement in both technical and commercial aspects.
[0013] The present disclosure pertains to a scalable and precision-driven method for manufacturing articulated surgical instruments with high dimensional accuracy and mechanical reliability. This invention addresses limitations associated with traditional fabrication techniques by integrating optimized gate placement, and process parameter calibration to reduce part distortion and maintain critical geometry. A predetermined shrinkage coefficient is established to ensure dimensional consistency across complex features. Additionally, the method incorporates controlled thermal cycles and surface treatments to enhance corrosion resistance, surface finish, and functional performance. Significantly, the process enables streamlined, cost-effective production suitable for high-precision surgical applications.
OBJECTS OF THE INVENTION
[0014] It is an object to develop an improved method for manufacturing articulated surgical instruments by using Metal Injection Molding (MIM) to overcome challenges of defects and distortion due to complex steps involved in the processing.
[0015] It is an object of the invention to enable highly scalable production of articulated surgical instruments. The method ensures consistent and repeatable manufacturing outcomes across large volumes.
[0016] It is an object of the present disclosure to provide reliable MIM-based process that enables the direct fabrication of articulated surgical instruments with high dimensional accuracy and mechanical strength, without requiring secondary operations such as post-machining.
[0017] It is an object of the present disclosure to optimize mold design and processing parameters through gate placement to reduce internal stress and shrinkage during sintering to achieve single-shot manufacturing of articulated surgical instruments.
[0018] It is an object of the present disclosure to enable the production of ready-to-use, articulated surgical instruments with excellent functional integrity, reduced weight for extended procedures of the surgeries, and structural stability with minimized production time and cost.
SUMMARY
[0019] The present disclosure enables single-cycle production of articulated surgical instruments with built-in articulation, locking, and ergonomic elements, eliminating post-molding assembly while using 17-4PH stainless steel, known for its yield strength and corrosion resistance. It provides a scalable method for one-step manufacturing of articulated surgical instruments with high dimensional precision and structural integrity. The process integrates mold optimization, improved gate design, and calibrated processing parameters to minimize distortion. A fixed shrinkage coefficient ensures consistent geometry across complex features, while thermal and surface treatments enhance durability and performance. The process eliminates secondary machining, enabling efficient and cost-effective production for surgical-grade instruments.
[0020] In an embodiment, the present disclosure introduces an optimized mold design and process configuration for producing articulated artery forceps in a single injection cycle. By leveraging strategic gate placement, internal stress and sintering-induced shrinkage are effectively minimized. This approach eliminates the need for post-processing or manual assembly. The result is a high-precision, monolithic surgical instrument tailored for efficient, scalable manufacturing. In particular embodiments for the artery forceps, the mold compensates for sintering shrinkage and maintains critical tolerances: ±0.02 mm hinge socket, 0.5 mm ratchet pitch, and 1.2 mm jaw wall thickness.
[0021] In an attempt of the present disclosure, the feedstock metal powder volume fraction provides optimal moldability and green part integrity. The injection is conducted in two stages: Stage I at 30% speed, Stage II at 26% speed, both at 130 bar pressure, ensuring uniform cavity packing and minimal stress. The barrel temperatures range from 175 °C to 155 °C, with the nozzle maintained at 175 °C to ensure consistent melt flow.
[0022] In an aspect of the present disclosure, for artery forceps, the mold integrates micro-serrations on jaws, a spring-pawl ratchet with overtravel protection, and ergonomic loops via collapsible cores. The three-point hot-runner gating system ensures balanced filling across sections of varying thickness (1.2 mm jaws vs. 3.0 mm hinge), while the venting system includes 0.02 mm-deep slots. Ejector pins with air-popper assists prevent warpage and facilitate clean demolding.
[0023] In an aspect of the present disclosure, catalytic debinding uses 98% nitric acid in an N₂-purged environment at 120 °C for 10 hours, monitored by real-time weight loss. In an attempt of the present disclosure, for artery forceps, the sintering profile ramps from 500 °C to 1300 °C in an argon atmosphere, promoting densification, neck growth, and refined microstructure. The post-sintered forceps exhibit ~7.60 g/cc density, 35–40 HRC hardness, and 96–99% relative density, suitable for surgical use.
[0024] In an aspect of the present disclosure, structural ribs (~0.8 mm thick) around hinge sockets enhance rigidity and ensure long-term articulation stability. The mold supports over 300,000 injection cycles, preserving surface finish and dimensional accuracy across large-scale production. In an attempt of the present disclosure, the controlled cooling from 1300 °C to 50 °C reduces residual stress and oxidation, improving durability, wear resistance, and ductility.
[0025] In an attempt of the present disclosure, the assembly begins with two identical halves of the artery forceps, each incorporating a handle ring and tip section, aligned for ergonomic and functional precision. Alignment ensures that pivot holes or riveting points match accurately, followed by secure joint formation enabling smooth articulation.
[0026] In an attempt of the present disclosure on artery forceps, the assembled units undergo mechanical testing to validate gripping force, tip closure accuracy, and overall alignment performance. In an attempt of final inspections, dimensional conformity, high-quality surface finish, and mechanical stability are confirmed before sterilization or packaging. In an aspect, the completed forceps weigh ≤30 grams lighter than conventional models available in the market and require no secondary machining post-assembly. This approach facilitates consistent, distortion-controlled production of surgical instruments, supporting scalable industrial manufacturing.
[0027] It is worth noting from the present disclosure has been described with respect to a defined set of functional modules; any other module or set of modules can be added/deleted/modified/combined and any such changes in architecture/construction of the proposed system are completely within the scope of the present disclosure. Furthermore, each described module may be subdivided into multiple functional sub-modules, all of which remain encompassed within the scope of the present invention.
[0028] The inventive subject matter presents objectives, features, functional attributes, aspects and performance advantages. These will be further clarified in the detailed description of preferred embodiments that follow. Associated drawing, figures illustrate functional geometries and component interactions in visual detail. The tables provide structured data and comparative insights to support the technical specifications and functional features of the present invention. Consistent numbering is used to identify corresponding parts across multiple views. Design rationale, material choices, and operational behavior are also highlighted for completeness. Together, these descriptions offer a comprehensive understanding of the invention's scope and utility.

BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiment of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0030] FIG. 1 is a flow chart of the process involved in the manufacturing of articulated surgical instruments using Metal Injection Molding in accordance with an embodiment of the present disclosure.
[0031] Fig.2 represents the steps involved in the mold preparation
[0032] FIG. 3 is the graph illustrating the sintering cycle
[0033] FIG. 4 Top view of articulated artery forceps formed via Metal Injection Molding (MIM) process, including the handle, hinge region, and jaw sections after the sintering.

DETAILED DESCRIPTION
[0034] The process (100) integrates the complete geometry of the forceps including jaws, hinge, and locking ratchet, directly into the mold, eliminating the need for any secondary operations such as machining or alignment. This approach overcomes typical challenges in manufacturing such as distortion, misalignment, and complexity of post-processing found in conventional methods like die casting or investment casting.
[0035] The aspects of the present disclosure relate to the method of manufacturing articulated artery forceps that supports complex geometries, including jaws and locking mechanisms, with high dimensional accuracy through Metal Injection Molding Technology.

METHODOLOGY
[0036] The flowchart in Figure 1 depicts the manufacturing process begins with feedstock preparation, wherein powdered metal and binder are homogeneously mixed. The blend is injection molded to form green parts that replicate the desired geometry. Debinding removes the binder system through a controlled process, followed by sintering to achieve densification and mechanical strength. Final assembly integrates the sintered components into a complete product, ready for functional application.
I) Feedstock Preparation (101)
[0037] In accordance with embodiments of the present invention, the disclosed manufacturing method for surgical instruments employs Metal Injection Molding (MIM) of biocompatible metal powders to achieve superior mechanical properties and dimensional precision. The preferred embodiment utilizes 17-4PH stainless steel powder (ASTM F3184) due to its demonstrated combination of high yield strength (≥1100 MPa post-sintering), exceptional corrosion resistance (per ASTM G48 testing), and controlled shrinkage behavior during thermal processing to facilitate the production of surgical components with tailored performance characteristics. Alternative material embodiments include medical-grade 316L stainless steel, 420 stainless steel, and titanium alloys for weight-critical applications. The MIM process parameters, including powder loading percentage (58-65 vol%), debinding protocols, and sintering profiles are specifically optimized for the alloy system to ensure consistent mechanical properties and defect-free microstructure in the final surgical instruments. Table 1, as shown below provides the composition and properties of the material that is selected for the artery forceps is a precipitation-hardened stainless-steel alloy designated as SS 17-4PH.

Table 1: The composition and properties of 17-4PH stainless steel material
Material Designation Alloy
Composition
(wt.%) Condition Hardness Density
(gm/cc)

SS
17-4PH C % - <0.07
Sintered
HRC
26-34
≥7.60
Cr % - 15-17.50
Ni% - 03-05
Nb% - 0.15-0.45
Si% - <1.0 Heat Treated HRC
38-46 ≥7.60
Mn% - <1.0

[0038] The chemical composition of the alloy comprises less than 0.07 wt.% carbon (C), 15–17.5 wt.% chromium (Cr), 3–5 wt.% nickel (Ni), 0.15–0.45 wt.% niobium (Nb), and less than 1.0 wt.% each of silicon (Si) and manganese (Mn). The material was evaluated in both sintered and heat-treated conditions. In the sintered state, the alloy exhibits a hardness ranging from HRC 26 to 34 with a density of at least 7.60 g/cm³. Upon heat treatment, the hardness increases to the range of HRC 38 to 46, while maintaining the density at ≥7.60 g/cm³. The selected material composition and processing conditions are optimized to deliver high mechanical strength, dimensional stability, and biocompatibility, suitable for surgical instrumentation.
II) Mold Design and Optimization (102)
[0039] The custom Mold is precision-engineered for monolithic production of artery forceps, integrating functional articulation, locking mechanisms, and ergonomic features in a single injection cycle while eliminating secondary machining like precision machining, milling, drilling, grinding and surface finishing. Designed to accommodate the instrument's final geometry, the mold incorporates shrinkage compensation for sintering, ensuring dimensional accuracy in critical areas such as the ±0.02mm tolerance hinge socket, 2.33mm pitch ratchet teeth, and 4.2mm-thick jaw walls. To maintain precise alignment of critical components, optimized gate and runner layouts to ensure uniform cavity filling and prevent defects like air entrapment and weld lines. Critical tolerances, venting systems, and ejection mechanisms are refined for high-yield medical-grade production, ensuring dimensional accuracy and structural integrity throughout the manufacturing process. Figures 2 illustrate a novel 3D CAD model of an injection mold assembly designed for single-step fabrication of articulated artery forceps and all the labels are depicted accordingly. The Mold configuration includes pre-aligned cavities for the left and right halves, ensuring precise geometry and hinge integration. The design eliminates the need for post-molding assembly, optimizing manufacturing efficiency and structural consistency. This innovation streamlines production while preserving the functional integrity of the surgical instrument.
Jaw Members and Precision Features
[0040] The custom mold is precision-machined to form two elongate jaw arms (1) with a wall thickness of 4.2 ± 0.05 mm, tapering to pointed distal tips (2) for vessel occlusion. The jaw cavity incorporates micro-serrated texturing (3) with a tooth pitch of 1.13 mm and depth of 0.35 mm, ensuring high-fidelity replication of anti-slip gripping surfaces. The mold halves are aligned via interlocking guide pins (4) with a positional tolerance of ±0.01 mm to maintain parallelism between opposing jaws. A uniform draft angle of up to 0.5° is applied to non-critical surfaces to facilitate ejection while preserving dimensional stability in the clamping region.

Hinge Mechanism and Articulation System
[0041] In the present invention, the mold is designed to incorporate a self-contained hinge assembly (5), configured using a box and socket architecture to allow precise and durable articulation between the jaw components. Specifically, the lower (LH) jaw includes an integrally molded hemispherical protrusion (6). This protrusion is designed to mate with a complementary hemispherical recess (7) formed on the upper jaw (RH). A critical clearance gap ranging between 0.05 mm and 0.10 mm is maintained between the mating surfaces to enable smooth, friction-free articulation of the jaws upon assembly.
[0042] To facilitate post-molding mechanical engagement, a cylindrical pivot channel (8) is integrally formed within the hinge assembly. This channel is dimensioned to a diameter of 2.33 ± 0.01 mm, which is sufficiently precise to accept a stainless-steel hinge pin via direct insertion, thereby eliminating the need for secondary machining steps. The high-precision nature of the molded pivot channel ensures accurate alignment of the hinge pin and contributes to the long-term mechanical reliability of the joint.
[0043] Further structural reinforcement of the hinge region is achieved through the integration of radial ribs (9) strategically positioned around the socket area. These ribs, each having a thickness of approximately 1.65 mm, serve to enhance the rigidity and mechanical stability of the hinge during both the molding process and in-service operation. The combination of the socket geometry, precision-molded pivot channel, and reinforcing ribs enables the production of a robust, articulating hinge assembly in a single Metal Injection Molding (MIM) step, without requiring post-mold assembly or machining interventions.
Integrated Ergonomic Features and Molded Mechanisms in Proximal Handle Design
[0044] The proximal portion of each handle includes a cavity configured to define an oval finger loop (10) having an inner diameter of 25.0 ± 0.15 mm to accommodate gloved fingers during surgical procedures. The finger loops are formed in mold without any post processing or forming (11) and four ejector pins (12) of 1x4.2mm and 3x1.6 in diameter, thereby facilitating to eject the part from the mold. A ratchet mechanism which has self-locking mechanism (13) is integrally molded on one handle, comprising three incremental teeth (14) with a pitch of 2.33 mm and a tooth angle of 50°, while the opposing handle incorporates a spring-arm pawl (15) configured with 1.0 mm overtravel protection to mitigate the risk of over-engagement. The elongated shaft section (16) of each handle follows a curved contour defined by a 523.0 mm radius and includes 1.5±1° draft angles (17) along with integrally formed stiffening ribs (18) having a thickness of 3.2mm providing enhanced resistance to bending during operational use.

Ejection, Venting, and Material Flow Optimization
[0045] The mold employs a cold runner type gating system (19) to ensure balanced fill of the thin-walled jaws (1.4 mm) and thick hinge regions (5.6 mm). Vent slots as per the trail run (20) (depth: 0.02 mm, width: 5.0 mm) are positioned at weld-line-prone areas, including the jaw roots and ratchet engagement zone. Ejector pins (21) are distributed in balance along non-critical surfaces to prevent warpage, with additional facilitating air trap assists (12,21) at the hinge socket to aid release. The tool is constructed to achieve surface finish and withstand up to 300,000 cycles with the given MIM feedstocks.

iii) Injection Molding (103)
[0046] The molding phase involves the injection of a molten metal-polymer feedstock into precision-engineered mold cavities, designed to replicate the intricate geometry of the target surgical component. An advanced injection molding machine was employed to ensure process repeatability and dimensional accuracy. Extensive experimentation was conducted to optimize the injection parameters and enhance flow behavior as shown in Table 2 below, especially across critical regions with varying cross-sections and complex geometry.

Table.2 Optimized Injection Molding Parameters
Molding Parameters
Temperature Profile
Nozzle (℃) 175 Nozzle Diameter(mm) 2.5
Barrel Zone 1 (℃) 175 Plunger diameter(mm) 28
Barrel Zone 2 (℃) 170
Barrel Zone 3 (℃) 165
Barrel Zone 4 (℃) 155
Injection Profile
I II
Speed (%) 30 26
Pressure(bar) 130 130

[0047] The injection profile was divided into two stages to control material flow and packing within the cavity. In the first stage (I), the injection speed was set to 30% with an applied pressure of 130 bar. In the second stage (II), the injection speed was reduced to 26%, while maintaining the same pressure of 130 bar. This two-step injection ensured uniform cavity filling and minimized internal stresses or defects within the molded green part. These optimized conditions contributed to defect-free replication of fine features, reduced warpage, and precise dimensional control, which are critical for subsequent debinding and sintering stages in the metal injection molding process.
Catalytic Debinding (104)
[0048] This method ensures thorough binder removal by leveraging catalytic decomposition in a thermally stable, oxygen-deprived settings. The process is conducted in an inert nitrogen atmosphere at a precisely controlled temperature of 120°C, blending aspects of thermal and solvent debinding but operating primarily as a solvent-based system. A 98% nitric acid catalyst is introduced at a controlled feed rate of 3.1 g/min into the debinding chamber, which is continuously purged with nitrogen to maintain a low-oxygen environment. The debinding cycle runs for 10 hours, ensuring uniform and complete binder degradation through controlled chemical breakdown reactions, thus forming debound components. Real-time monitoring tracks weight loss percentage, serving as a critical metric to verify debinding efficiency and uniformity while preventing part distortion. The process parameters temperature, acid concentration, nitrogen flow rate, and duration are methodically optimized to achieve repeatable binder elimination without compromising structural integrity to enable high precision for complex, high tolerance devices and is shown in Table 3.
Table 3: Catalytic Debinding Parameters
Parameter Value
Debinding Temperature 120°C
Acid Used 98% Nitric Acid
Acid Feed Rate 3.1 g/min
Debinding Duration 10 hours
Debinding Gas Nitrogen (N₂)

iv) Sintering and Final Treatments (105)
[0049] The debound metal injection molded (MIM) components undergo a precisely regulated sintering process in which the brown-state parts are thermally treated within a high-temperature furnace to induce densification and optimize mechanical characteristics. The sintering operation is performed at a temperature of approximately 1300 ℃ under an inert argon atmosphere.
[0050] Initially, the brown part is gradually heated to 500 ℃ over 60 minutes, allowing for the controlled removal of residual volatiles. The temperature is held at 500 ℃ until stabilizing the part geometry and initiating particle bonding. Subsequently, the component is heated to 800 ℃ by 330 minutes and maintained at this level to enhance atomic diffusion and neck growth. The cycle then ramps rapidly to 1300 ℃ by 390 minutes, where the part undergoes primary densification, achieving relative densities between 96–99% and mechanical hardness of approximately 35–40 HRC. The multi stage sintering cycle is shown in the Figure 3. The cooling phase begins with a reduction to 800 ℃ followed by a final descent to 50 ℃, ensuring dimensional stability and minimizing thermal stress for advanced engineering thereby mitigating oxidative degradation and maintaining a non-corrosive environment favorable to homogeneous thermal diffusion throughout the part geometry to facilitate the development of critical material properties, including enhanced hardness, ductility, wear resistance, and tensile strength, while simultaneously reducing residual porosity to near-theoretical density levels.
[0051] Post-sintering, the components achieved a relative density within the range of 96% to 99% of their theoretical maximum, with a measured density of approximately 7.60 g/cc and a hardness value between 35 to 40 HRC. The forceps are configured in accordance with the present disclosure to achieve improved control, durability, and user comfort during clinical use.
[0052] The final artery forceps are precisely aligned, for secure locking, lightweight (having a total weight equal to or less than 30 grams, compared to conventional 40-gram models), and ready for use without the need for secondary machining. This method enables reproducible, distortion-controlled manufacturing of high-precision surgical instruments suitable for scalable industrial production.

[0053] The present invention presents the following novel features and advantages:
• The invention enables direct manufacturing of articulated surgical instruments including jaws, hinge, and locking ratchet through a Metal Injection Molding (MIM) process.
• The present invention aids in the single-step manufacturing process for articulated instruments, by eliminating the need for secondary machining.
• The present invention utilises the Mold flow optimization and strategically augmented gate placement effectively reduce distortion associated with elongated geometries, ensuring stable component shape after sintering.
• The present invention aids in accurate alignment of mating components such as jaws and locking ratchets is achieved through precise mold design and shrinkage compensation techniques.
• In the present invention, the mold is specifically engineered for articulated surgical instruments, minimizing risks of misalignment and eliminating weld line formation.
• The present invention allows in the Sintering parameters that are fine-tuned to yield high-density parts with superior mechanical strength, avoiding the need for additional surface finishing or reinforcement.
• The method supports scalable mass production, offering high repeatability in dimensional precision, structural integrity, and product quality.
• The lightweight design and selected materials improve ergonomics and handling during surgery, minimizing operator fatigue without compromising performance.
• The present invention allows the surface treatment steps such as passivation and thermal aging are incorporated into the process cycle, enhancing corrosion resistance and surface finish without requiring post-processing.
• The present invention enables the manufacturing, wherein controlled shrinkage behaviour across complex and moving features ensures consistent adherence to critical dimensional tolerances.
• The present invention allows to deliver cost-effective, reliable, and high-performance solution, marking a significant technical and commercial advancement in MIM-based surgical tool manufacturing.
[0054] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
, Claims:We Claim:
1. A method for manufacturing articulated surgical instruments in a single metal injection molding cycle, the method comprising:
• preparing a feedstock (101) comprising a metal powder volume fraction optimized for moldability and green part integrity;
• injecting said feedstock into an optimized mold (102) having features corresponding to articulated forceps, said injection conducted in two stages at 130 bar pressure and barrel temperatures ranging from 175°C to 155°C (103);
• utilizing a hot-runner gating system to ensure balanced cavity filling across variable cross-sections;
• incorporating collapsible cores to form ergonomic loops and internal structures;
• performing catalytic debinding (104) using 98% nitric acid in a nitrogen-purged environment at 120°C for 10 hours;
• sintering (105) the debound part in an argon atmosphere, with a thermal profile ramping from 500°C to 1300°C;
• applying controlled cooling from 1300°C to 50°C to reduce residual stress and oxidation;
wherein the resulting surgical instrument exhibits dimensional accuracy, integral articulation, and eliminates the need for secondary machining or assembly.
2. An articulated artery forceps manufactured according to the method of claim 1, wherein the forceps comprises:
a monolithic structure incorporating micro-serrated jaws, spring-pawl ratchet with overtravel protection, and ergonomic loops;
hinge sockets with structural ribs of approximately 0.8mm thickness for articulation stability;
critical tolerances including ±0.02 mm for the hinge socket, 0.5 mm ratchet pitch, and 1.2 mm jaw wall thickness;
wherein the ergonomic loops are integrally formed using collapsible core sections within the mold;
wherein the ratchet mechanism includes a spring-pawl design with overtravel protection configured to allow precise locking and release;
a final mass of ≤30 grams and relative density between 96–99%.
3. The method of claim 1, wherein the injection is performed in two sequential stages:
Stage I at 30% injection speed, and
Stage II at 26% injection speed.
4. The method of claim 1, wherein the hot-runner system comprises a three-point gating configuration adapted to accommodate section thickness variation from 1.2mm to 3.0mm.
5. The method of claim 1, further comprising venting slots of 0.02mm depth to evacuate trapped gases during injection.
6. The method of claim 1, wherein ejector pins with air-popper assist mechanisms are used to prevent warpage and facilitate clean demolding of green parts.
7. The method of claim 1, wherein the hinge alignment mechanism comprises a precision-guided interface configured to maintain consistent structural integrity under dynamic operational loads within the locking system.
8. The method of claim 1, wherein the mold supports over 300,000 injection cycles while maintaining dimensional accuracy and surface finish.
9. The method of claim 1, wherein the metal powder feedstock comprises 17-4PH stainless steel or any other sinterable metal alloy selected from a group consisting of austenitic and martensitic stainless steels, titanium alloys, cobalt-chromium alloys, tool steels, and nickel-based superalloys, thereby enabling production of high-strength, corrosion-resistant components.
10. The method of claim 1, wherein the optimized mold configuration and calibrated injection parameters enable the formation of a fully articulated, structurally complete metal component in a single injection molding cycle, without requiring post-molding assembly or secondary machining, thereby reducing production time and increasing process efficiency.