Redesigning Inefficient Multitools

This project demonstrated the importance of assembly efficiency in a manufactured product. It began in February 2016, and ended in May 2016. The new design had improved assembly efficiency and reduced labor and production costs.

Problem: When a product is designed, there are two considerations which are of the utmost importance: Ergonomics and Cost. This is due to the fact that almost anything manufactured is meant for human usage or more appropriately, human-centered usage.

Many manufactured products are designed to aid during a emergency situations. However, sometimes, they have unwanted parts which make their assembly and hence manufacturing a lengthy task. The idea is to eliminate unwanted parts or merge multiple parts and increase assembly efficiency and decrease the cost.

Goal: The aim of this project was to redesign a 7-in-1 multi-tool using Boothroyd and Dewhurst Design for Assembly Method (DFA / BDI), and Hitachi Assembly Evaluation Method (AEM). The purpose is to eliminate unnecessary parts, increase the ease in assembly, decrease the material cost and increase the design and assembly efficiencies.

Tools: Solidworks, Rhinoceros, Reverse Engineering, Tool Design, Design for Manufacturing, Design for Assembly, Cost benefit analysis

Impact: After disassembling, analyzing, reassembling, and brainstorming about the product. The project proposes a new design which reduces the total parts from 39 to 23. The new design is estimated to decrease the total assemble time from 325.86 seconds to 159.45 seconds. The new design is also estimated to save labor production cost of $2.08 per unit and material cost of $3.38 per unit. The part count design efficiency is increased from 46% to 83%. In BDI analysis, the assemble efficiency is increased from 36% to 43%, and the design efficiency is increased from 17% to 36%. In AEM analysis, the assemble efficiency is increased from 65% to 67%, and the design efficiency is increased from 30% to 56%.


The BodyGard® 7-in-1 Emergency Tool is a key-chain rescue tool that combines an automatic glass breaker, a seat belt cutter, sonic alarm, bright LED flashlight with both a high beam and low beam and an emergency flasher in a device small enough to fit on a key chain or in a pocket. In addition to these safety devices, the BodyGard 7-in-1 offers a digital tire pressure gauge and a thermometer. For convenience, the product from hence forth will also be known as multi-tool. The tool was invented by Bennett S. Rubin and Richard C. Adamany. The product, is made in China and has pending patent — US patents 7,557,720 and D575,182.

The automatic glass breaker is a spring-loaded, high-carbon steel pin designed to break automobile glass when pressed flush against the surface. The seat belt cutter blade is housed securely within the casing to prevent accidental or intentional cutting. With the push of a button, the sonic alarm signals trouble with a high-decibel output. Its bright, flashing red distress light is also push-button activated to signal for, and direct help to, your location. The high-intensity flashlight can be used for night sight and safety.

  1. Automatic Glass Breaker

  2. Safety-Blade Seat Belt Cutter

  3. Sonic Alarm

  4. LED Flashlight w/ High and Low Beam

  5. Flashing Red Emergency Flasher

  6. Thermometer

  7. Digital Tire Gauge

After disassembling the product, we got 39 parts. We gave each part a name and showed the structure tree of the product. We performed Boothroyd and Dewhurst design for assembly method, and Hitachi assembly evaluation method to determine the efficiencies of the original product. The production and labor costs were also determined.

Part Count of the Original Model


A new design was made and the same methods of analyses were used on it. The new model improved efficiency and had better features. At the same time, it reduced the manufacturing and design costs.

The original and the redesigned models are very different in terms of aesthetics, part count, assembly time and economics. As the main goal of this project was to reduce the cost, number of parts and increase efficiency, it is incredible how a patent pending product was redesigned to accomplish all of these.


  • The total number of parts was reduced from 39 to 23 parts. Many parts were combined with other parts and few unnecessary parts were eliminated. The part count design efficiency was increased from 46% to an amazing 83%! The total assembly time was reduced from 325.86 seconds to 159.45 seconds.

  • In the case of DFA, the assembly efficiency was increased from 36% to 43% is and the design efficiency was increased from 17% to 36%. In the case of AEM, the assembly efficiency was increased from 65% to 67% is and the design efficiency was increased from 30% to 56%.

  • The labour cost was decreased from $ 4.07 to $1.99, a saving $ 2.08 per unit and the production cost was reduced from $ 17.94 to $14.56, giving a great unit saving of $ 3.38!