Carbon Orthotics from a CFRP Manufacturing Specialist Perspective

Contents

Introduction
What is Carbon? Delving into CFRPs
- Carbon Orthoses
Advantages and Disadvantages
CFRP and Carbon Fabrication Process
- “Autoclave Molding Method”: The hallmark of high-quality CFRP parts manufacturing
- CFRP Creation Requires a Specialized Environment and Facilities
Case Study: Development of the “C-FREX” Long Leg Brace (Exoskeleton) for People with Spinal Cord Injuries
Summary
- Reviewing CFRP and Carbon Orthoses (Braces)
- Consult with Us Now

Introduction

Carbon and CFRP orthoses (orthotic and prosthetic devices) have become buzzwords in recent years. Carbon fiber (referring to CFRP) is often employed in prosthetic limbs and other assistive equipment, but what precisely is this material? In this article, we will explore CFRP and carbon orthoses from the viewpoint of a carbon component manufacturing company—our perspective.

What is Carbon? Delving into CFRPs

While the term carbon fiber refers to thin strands of carbon, these fiber strands will not retain their form on their own. Thus, they are combined with a resin to retain the shape and maximize its distinct lightweight and strong characteristics.

Composite materials are substances composed of two or more constituents, such as carbon fiber and resin, to yield new functions. Carbon fiber reinforced plastic (CFRP) is the name given to a composite created from carbon fiber and resin.

Carbon Orthoses

The advanced “lightweight, strong, and non-corrosive” characteristics of CFRP have catalyzed its widespread use in diverse fields from aviation, satellites, and automobile to leisure and sports. Carbon orthoses refers to orthotic equipment that is made predominately from CFRP. Alongside prosthetic limbs for athletes, the use of CFRP has proliferated in adaptive equipment fields and assistive devices such as wheelchairs, canes, and crutches.

Advantages and Disadvantages

As an anisotropic material, the strength of CFRP is determined by its fiber orientation. Thus, unlike metals and other isotropic materials, CFRP requires detailed material design and planning. The high design versatility of resins and fiber, however, necessitates specialized knowledge for fabrication. Working with these materials is nearly impossible without expert knowledge of their characteristics and functions. While CFRP offers impressive advantages, high production costs due to the need for molds, expensive materials, and complicated fabrication processes are lingering issues.

CFRP and Carbon Fabrication Process

“Autoclave Molding Method”: The hallmark of high-quality CFRP parts manufacturing

CFRP fabrication uses a range of molding methods depending on the applications, form, and production lots. This article, however, will focus on the hallmark method for achieving high-quality products with exceptional design flexibility—”Autoclave molding.” High-quality CFRP fabricated with the autoclave molding method is known as dry carbon.

CFRP Creation Requires a Specialized Environment and Facilities

Each process demands specialized technicians with thorough knowledge of CFRP’s characteristics, and work personnel with know-how of the facilities and environment. These pinging factors are critical for yielding high-quality CFRP products.

Case Study: Development of the “C-FREX” Long Leg Brace (Exoskeleton) for People with Spinal Cord Injuries

About the C-FREX Exoskeleton

C-FREX stands for Carbon Fiber Reinforced Exoskeleton, a long leg orthotic brace for people with spinal cord injuries that we, Uchida, developed over seven years (from 2014–2021) in collaboration with the Research Institute of the National Rehabilitation Center for Persons with Disabilities (NRCD, Saitama, Japan). It acts as orthotic brace (exoskeleton) that augments walking mobility and maintains muscular and physical functions for people with spinal cord injuries. The development C-FREX heralds an entirely new orthotic device that achieves a similar gait to that of an able-bodied person without the use of external power.

Development Concept

1.Replace the transtibial (below knee) socket with CFRP to reduce weight and maximize elastic potential energy.

2.Realize knee joint flexion-extension motion without using motive force.

3.Fulfill user needs with a sophisticated design not found in conventional orthotics

C-FREX development was driven by our honed technical expertise and in-depth knowledge of CFRP and its strengths and weaknesses. The cost of CFRP remains an issue. In the mass customization fields, we are diversifying high-strength 3D printer parts to minimize the added costs (ultimately borne by the user) and lead times that arise from the need to create one-off molds specific to the physique and symptoms of the user.

Tokyo 2020 Olympic Torch Relay Marks the Completion of Development

C-FREX was used in the Tokyo 2020 Olympic and Paralympic Games Torch Relay on July 14, 2021, marking the completion of its development.

Tokyo Olympic and Paralympic Games: C-FREX and Kazu Takahashi, Olympic Flame Lighting Ceremony

Our Current Main Project

After completing development of C-FREX, we began working with prostheses and orthoses manufacturers and distributors to develop CFRP-based adaptive equipment. We are deploying our honed engineering and technological expertise and networks to advance the impressive powers of CFRP and share it with people on the local level.

Summary

Reviewing CFRP and Carbon Orthoses (Braces)

Carbon (CFRP) is an anisotropic material that demands highly specialized know-how in material selection (carbon fiber and resin), material design, and manufacturing methods.

A large-scale environment and facilities are required to produce high-quality CFRP products.

Costs due to mold fabrication and numerous complex processes that require hands-on labor by specialized technicians are still an issue.

Consult with Us Now

As CFRP specialists, we are advancing our experiences in C-FREX to progress low-cost development processes in adaptive equipment and other mass customization domains.

ABOUT UCHIDA - 55 years since our founding

We leverage a wealth of technical expertise as a CFRP molding and processing manufacturer using FRP, GFRP, and CFRP materials. We offer a one-stop solution, encompassing design, analysis, manufacturing, secondary processing, assembly, painting, quality assurance, and testing.

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UCHIDA's equipment

We have cutting-edge equipment to ensure that we can address even the most advanced challenges of our customers.

DMG森精機 - VS1000/40/2050
X軸：2,050mm（ストローク）／ Y軸：1,000mm ／ Z軸：600mm ／テーブル作業面：2,250×1,000mm

ASHIDA MFG Co., Ltd.
Autoclave Oven 2
Size : Ø1,150x1,000mm / Operating temperature : at normal temperature - 400℃ / Design pressure : 2.0Mpa (maximum working pressure) / Vacuum system : back suction system / Vacuum units : 5

ASHIDA MFG Co., Ltd.
Autoclave Oven 3
Size : Ø3,000x6,000mm / Operating temperature : at normal temperature - 200℃ / Distribution accuracy : ±2.5℃less / Heating rate : 4.0℃/min. (empty furnace) / Cooling rate : 4.0℃/min. (empty furnace) / Design pressure : 0.99Mpa (maximum working pressure) / Working pressure : 0.7Mpa less (if no specification from the manufacuturer 0.3Mpa around) / Pressure accuracy : ±0.02Mpa（for pressure setting of ０ - 0.99Mpa/cm²） / Boost pressure accuracy : 0 - 0.03Mpa/min / Pressure source : compressed air (regular use) / Vacuum system : back suction system / Vacuum units : 10

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Oven
Size : W1,000xH1,000xD1,000mm / Temperature range : Environmental Temperature +20 - 300℃ / Temperature elevation capability : Environmental Temperature (20 - 40℃) - 300℃ / 45min less / Vacuum system : back suction system / Vacuum units : 10

ESPEC CORP.
Temperature & Humidity Chamber

INSTRON
Static Universal Testing Machine 5985

Oven
Size : W7,000xH3,000xD2,000mm / Temperature range : Environmental Temperature +20 - 300℃ (Max) / Temperature elevation capability : Environmental Temperature (20 - 40℃) - 300℃ / 60min less / Vacuum system : back suction system / Vacuum units : 10

NEO
X axis : 4,000mm (stroke) / Y axis : 2,000mm / Z axis : 1,200mm / C axis : 0° - ±270° / B axis : 0° - ±110° / Table working place : 4,000x2,000mm

【開発】
3Dプリンター | Markforged

Painting booth
Various painting, and clear finish is done in dedicated painting booth

Adhesion, Finishing, Coating Room
Finishing process, such as trimming, drilling, and bonding, surface treatment of the molded product type and is done in a private booth

Toshiba Matrixeye EX (Ultrasonic flaw detector)
Matrix-Arrey : 32

AMETEK CREAFORM Metra
SCAN750 Elite (3D scan)

Olympus Corp.
Inverted Microscopes

Oven
Size : W450xH450xD450mm / Temperature range : Environmental Temperature +20 - 650℃ / Temperature elevation capability : Environmental Temperature+50 - 650℃/120min less

Cutting Plotter Table working place : W1,500xL3,500mm

SHIMA SEIKI MFG., LTD
Cutting Plotter

KUKA
Robot

Krauss Maffei
Epoxy resin injection machine Resin 60L ／ Hardener 25L

Krauss Maffei
630t Press machine Height total 5,200mm ／ Length max 1,500mm ／ Width max 1,200mm ／ Whole cycle time per component part 240sec

DMG森精機 - NV5000B/40
X軸：1,020mm（ストローク）／ Y軸：510mm ／ Z軸：510mm ／テーブル作業面：1,320×600mm

Big sized clean room
JIS B 9920 cleanliness class maximum concentration (Pcs/m³） / Class 5 : 100,000m³ / Capacity : m² (16,000x16,000mm) 760m² (16,000x16,000x3,000mm) / Temperature and humidity condition : Temperature : 23℃±3℃, Humidity 65% less / Ambient conditions : Temperature 35℃ during summer, Humidity 70% less / Ambient conditions : Temperature 35℃ during summer, Humidity 70% less / Temperature -5℃ during winter, Humidity 40% less