Case Study

Custom Component Solutions From Prototype to Volume Production

Item

Minimally Invasive Total Knee Arthroplasty System

Specification

ISO 7206 Orthopedic Implant Standard, ASTM F899, CE MDR Compliant

5-Axis CNC Precision Machining + Vacuum Aging Heat Treatment + Medical-Grade Mirror Polishing + Citric Acid Passivation + Cleanroom Packaging

Implant-Grade SS630 (17-4PH Precipitation Hardening Stainless Steel)

82.5 × 56.2 × 38.4 mm (Custom Patient-Matched Anatomical Curvature)

±0.02mm for Articular Surface Profile (ISO DIN 2768-f Standard)

Ra ≤ 0.02μm (Medical-Grade Optical Mirror Finish)

H900 Aging Hardening, Target Hardness HRC 38-42

Pre-Clinical Prototype Batch (12pcs) + Clinical Trial Small-Batch Production (180pcs)

7 days for prototype; 12 days for clinical trial batch

ISO 9001:2015, ISO 13485:2016 (SGS Authorized), ASTM A967 Medical Passivation Standard

Clinical Application

Core Design Standard

Manufacturing Process

Base Material

Part Overall Dimension

Critical Tolerance

Articular Surface Finish

Heat Treatment Condition

Order Volume

Lead Time

Compliance System

This project comes from a European orthopedic medical device manufacturer developing a new generation of minimally invasive knee replacement systems. As the core load-bearing articular component of the knee joint, the femoral condyle has extremely strict requirements for anatomical precision, long-term biomechanical stability, clinical safety, and regulatory compliance. The customer faced 6 core pain points that their previous supplier could not resolve stably:

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Ultra-high precision requirements for anatomical curvature and defect-free mirror finish to minimize post-implantation wear and osteolysis

High risk of dimensional deformation of the irregular curved structure after vacuum heat treatment, which cannot guarantee ±0.01mm profile tolerance

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Strict full-process traceability requirements for CE MDR regulatory filing, which the previous supplier could not meet with incomplete production records

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Uncertainty of batch stability from prototype to commercial mass production, with high risk of performance fluctuation after scale-up

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Urgent pre-clinical validation timeline, requiring fast prototype delivery and flexible R&D iteration support

Lack of transparent cost control scheme for the full product lifecycle from clinical trial to mass production

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To address the clinical performance, regulatory compliance, and mass production stability requirements, our medical device engineering team developed a full set of custom design solutions, fully aligned with global orthopedic implant standards and the customer's clinical validation needs.

Anatomical & Kinematic Design

Custom 3D anatomical curvature matching natural knee joint kinematics, with optimized articular surface profile to ensure uniform contact stress distribution, reduce post-implantation polyethylene insert wear, and extend the implant's long-term service life

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Precision bone-fitting interface design to ensure perfect osseointegration with the patient's femoral bone, reduce post-operative pain, and shorten patient recovery time

Smooth edge transition design to avoid stress concentration, reduce intraoperative fracture risk, and improve surgical adaptability for minimally invasive procedures

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Biomechanical Performance Design

Targeted material performance tuning: Specified H900 vacuum aging heat treatment for SS630, with hardness strictly controlled at HRC 38-42, to achieve the optimal balance of strength, toughness, and fatigue resistance required for long-term load-bearing knee implants

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Topology optimization of the load-bearing structure to disperse cyclic stress during knee movement, improve long-term fatigue resistance, and meet the 15+ year service life requirement of total knee arthroplasty

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Reinforced design of threaded mounting holes to ensure intraoperative fixation stability, avoid thread damage during implantation, and improve surgical safety

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DFM & Regulatory Compliance Design

We provide permanent free DFM review service for all orthopedic implant projects, with a response cycle strictly in line with global medical device industry standards:

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Standard structure projects: Full DFM report issued within 24 hours after receiving drawings and requirements

Complex anatomical structure projects: Full DFM report issued within 48 hours

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For this femoral condyle project, our DFM optimization includes:

Reserved uniform and symmetrical machining allowance for heat treatment and polishing, optimized one-time 5-axis clamping scheme to avoid secondary clamping tolerance accumulation

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Rationalized tolerance design: Strictly defined critical tolerance for the articular surface, balanced clinical performance requirements and mass production stability

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Full design traceability system: All design iterations, DFM reviews, and engineering changes are fully documented as Design History File (DHF), fully meeting CE MDR regulatory requirements

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Drawing on years of experience in precision orthopedic implant manufacturing, our team developed a closed-loop manufacturing process to address all customer challenges, with 100% qualified rate for both prototype and trial batches.

5-Axis CNC Precision Machining & Stress Relief

Adopted high-precision 5-axis CNC machining center, one-time clamping to complete rough and semi-finish machining of the full 3D anatomical contour, with uniform machining allowance reserved for subsequent processes

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Added low-temperature intermediate stress relief after rough machining to eliminate cutting-induced internal stress, and minimize post-heat treatment deformation risk

Pre-machined mounting holes with special high-temperature resistant protective tooling designed for the full process to avoid contamination and damage

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Vacuum Aging Heat Treatment for SS630

Adopted high-precision vacuum aging heat treatment (H900 condition) with furnace temperature control accuracy within ±3℃, to ensure uniform batch hardness within HRC 38-42, meeting long-term load-bearing fatigue resistance requirements

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Used custom anatomical fixture positioning during heat treatment to control post-heat treatment profile deviation within ±0.02mm, fully meeting the final design tolerance

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Full heat treatment process parameters and batch hardness test reports are archived for full traceability

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Multi-Stage Mirror Polishing

We formulated a 7-stage diamond abrasive graded polishing process for the articular surface:

Coarse grinding to remove heat treatment oxide layer and machining tool marks

Semi-fine grinding to level surface micro-defects and control anatomical profile accuracy

Fine grinding with medical-grade diamond abrasive to pre-control surface roughness within Ra 0.2μm

Pre-polishing to eliminate polishing lines and optimize surface uniformity

Ultra-precision mirror polishing to achieve final Ra ≤ 0.2μm

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Medical-grade ultrasonic cleaning to remove polishing residue

Medical-grade ultrasonic cleaning to remove polishing residue

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Passivation & Cleanroom Packaging

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Adopted citric acid passivation process fully compliant with ASTM A967 medical standard, non-toxic and meeting ISO 10993 biocompatibility requirements, to form a dense passive film and improve corrosion resistance in the human body environment

Final cleaning and packaging completed in a class 10000 cleanroom, with double-layer vacuum packaging to avoid secondary contamination, fully adapting to the customer's subsequent sterilization process

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All production and inspection processes strictly follow our ISO 9001:2015 and SGS-authorized ISO 13485:2016 medical device quality management system, with zero tolerance for non-conforming products.

Implant Material Full Traceability

Our implant-grade SS630 is sourced exclusively from long-term, annually audited qualified suppliers. Every batch of incoming material is accompanied by the original mill certificate of origin, full COA (Certificate of Analysis) including chemical composition, mechanical properties, and non-metallic inclusion test results.

Mass Production Batch Stability Control

We conduct 100% batch re-inspection via XRF metal composition analyzer to confirm compliance with ASTM F899 implant-grade standard before production, and assign a unique medical-grade traceability code to each batch for end-to-end tracking from incoming material to finished shipment. All material and inspection records are archived for a minimum of 10 years, fully meeting CE MDR's full lifecycle traceability requirements.

We openly acknowledge that absolute "zero defect" is not a realistic claim for Class III orthopedic implants across the global medical device industry. However, our closed-loop SOP system and in-process control framework enable us to limit the non-conformity rate to PPM level, and achieve 100% non-conforming product interception before shipment:

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Permanent Process Locking: All prototype-validated process parameters are finalized into locked SOP, with any changes requiring formal ECR/ECN process and prior customer confirmation.

Key Control Point (KCP) Management: 6 mandatory KCPs are set across the full production workflow, with "100% first article inspection + per 20pcs in-process inspection" mechanism, all data recorded in Device History Record (DHR)

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Pre-Shipment Full Inspection: cleanroom visual inspection of the articular surface, CMM full-dimensional inspection of each femoral condyle, and batch hardness and corrosion resistance testing

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Pilot Batch Validation: Before scaling up to commercial mass production, we will complete a 50-100pcs pilot batch to verify process consistency, and only start full mass production after customer confirmation

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CAPA Continuous Improvement: We have a formal Corrective and Preventive Action system in line with ISO 13485, to conduct root cause analysis for any abnormalities, implement permanent corrective actions, and update SOP to avoid recurrence

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Regulatory Compliance & Audit Support

Our ISO 13485:2016 system fully covers the entire production workflow of orthopedic metal implants, including CNC machining, vacuum heat treatment, precision polishing, medical-grade passivation, and cleanroom cleaning & packaging.

We can provide full supporting documentation for your CE MDR technical file, and fully cooperate with your annual supplier on-site audits and notified body regulatory audits, with all required system and production records ready for review.

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On-Time Delivery: Prototype parts delivered within 7 days, clinical trial batch delivered within 12 days, 100% meeting the customer's pre-clinical validation timeline, with no delay to the project progress

Stable High Quality: 100% of parts achieved Ra ≤ 0.02μm articular surface finish, 100% dimensional tolerance pass rate, and CPK of key dimensions ≥1.67, fully meeting clinical implantation requirements, with zero rework and zero customer complaints

Regulatory Compliance Approval: All material, production and inspection documents fully met ISO 13485 and CE MDR requirements, and the parts passed the customer's biocompatibility pre-test and friction wear performance test

Full Lifecycle Cost Control: We offer a transparent, flexible tiered pricing scheme tailored to the product lifecycle:

Pre-clinical small-batch phase: R&D-friendly pricing to minimize verification cost

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Commercial mass production phase: 3-5 tiered pricing levels based on annual order volume, with lower unit cost for higher quantities

Annual framework agreement: Locked pricing cycles to avoid raw material price fluctuation risks, with exclusive benefits for long-term partners including tooling cost waivers and production priority scheduling

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Long-Term Strategic Cooperation: We helped the customer shorten the pre-clinical development cycle by 35%, reduce comprehensive production cost by 22%, and became the customer's long-term designated orthopedic implant precision machining supplier

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1-24H Quote Response • No MOQ Required • 99.8% On-Time Fast Delivery • ISO-Certified Quality

Address: 303, 3rd floor, building A, No. 80 ChangJiang Road, Dong District, ZhongShan City, GuangDong Province, China 528403

Email: selina@marigold-rapid.com

Mobile: +86 18718750572