Fox Rundown and Torque Automation Project

This project shows the design process being used to create a machine to aid a FOX Factory assembly process. This machine automates the rundown and torque of a linear bearing into a shock body, reducing cycle time, and more importantly, reducing ergonomic strain.

meet the team

DavidDaleyCircle

david daley

Project manager

I’m David, and I’m a transfer student from Watsonville, California. What I most enjoy about engineering is manufacturing, whether it be design for manufacturability & assembly, or physically making parts. I am involved in Formula SAE designing aero structures and worked for FOX Factory last summer where I designed assembly tools and fixtures. Next school year I’ll be back at Cal Poly for the blended master’s program in ME. Outside of school, I enjoy cycling and hiking. 

EricForresterCircle

eric forrester

drivetrain lead

I’m Eric, and I am from Long Beach, California. I enjoy engineering because it’s all about the methodology for solving all kinds of problems. As the theory portion of my engineering education comes to an end, I am looking forward to applying my knowledge to real world problems to design the best products possible. Outside of engineering I enjoy biking; road biking, mountain biking, and bike collecting are my favorite activities.

 

 

ChrisHansen2Circle

chris hansen

controls lead

I’m Chris, and I am from Torrance, California. I have grown to love engineering and specifically enjoy designing solutions to problems. I have been involved in robotics in high school and college and am currently a project lead in the Cal Poly Robotics Club. I enjoy drawing, playing the piano, and 3D printing as many cool things as I can. 

RileyOConnor

riley o'connor

Structures lead

I’m Riley, and I’m a transfer student from Antioch, California. I’ve been involved in Baja for two years as a powertrain design lead and as a CNC machinist making gears and shafts. I worked at Tesla this past summer doing process improvement at the Lathrop factory. Outside of school I enjoy all things metalworking and recently 3D printing. I’m also designing and building my own desktop CNC mill.

Our Sponsor: Fox factory inc.

link to run the numbers video: https://www.youtube.com/watch?v=R4BXLoZLBEU

sponsor advisors

WillCrawfordCircle

will crawford

fox factory

My name is Will Crawford and I’m the current Manufacturing Engineering Manager at the Fox Factory in Watsonville, CA. I’ve been working at FOX for over 10 years and have been through the explosive growth of our industry and efforts. My career at FOX began as a Sr. Manufacturing Engineer whose focus has been in tooling and equipment design. My background has always been on the mechanical side of Manufacturing Engineering. I’ve always encouraged co-educating peers on design techniques and found mentors helpful. Being a native of Pennsylvania, I’m a PENN STATE and then Arizona State graduate. It’s been a pleasure to work with Cal Poly and the students on this project.

Our thanks to Dr. Peter Schuster for bringing this together for the Team.

TomMullrooneyCircle

tom mulrooney

fox factory

I’m Tom, and I’m a manufacturing engineer at Fox. I’m from Wilmington, Delaware and studied mechanical engineering at the Univeristy of Delaware. I’ve previously worked in aerospace manufacturing, but now at Fox I design assembly tooling & fixtures and program automation systems. At home, I enjoy cycling and hanging out with my dog, Huey.

Project Video

Project poster

Problem Statement

FOX Factory Inc. is looking to automate the assembly process of a linear bearing into the shock shaft. The bearing must be manually rundown with a spanner tool and then torqued to spec. Currently the process is an ergonomic strain on the line associates and requires multiple tools for the operation. 

Initial Designs

The team performed a functional decomposition to determine the fundamental functions the design must perform. Those functions and concepts to meet those functions were organized into a Morphological matrix. Different combinations of concepts were chosen to generate several initial designs. A sketch of the overall system layout, and a sketch of the hex adapter is shown below.

System Sketch
Adapter Sketch

Structures

Analysis

Deflection in the horizontal motion shafts due to a 50-pound vertical load applied at the drivetrain output gear

The deflections of the horizontal motion shafts were analyzed to determine if a 1” OD and .6” ID cross section was sufficiently stiff to provide minimal deflection at the drivetrain. Minimal deflection is needed to ensure the drivetrain does not bind or damage the shock. Using static analysis, it was determined that each shaft would deflect about less than 2.5 thousandths of an inch. The team decided this was sufficiently stiff.

Structures Render

Shock Fixture

The main goals with the shock fixture were: 

  • Prevent the shock from tipping towards the operator 

  • Align the shock with the drivetrain gear 

  • Allow the shock body to slide up as the bearing threads in 

These goals were accomplished with a toggle clamp and delrin v-block at the top of the shock body, and a carriage sliding on linear rails & ball-bearing carriages at the base of the machine. A pneumatic cylinder under the sliding carriage supplies the compressive force needed to engage the first thread on the bearing. 

Shock Fixture Render

Adapter

Adapter Bottom View
Adapter Iso View

The adapter piece transmits torque from the output gear of the drivetrain into the bearing housing. The adapter has a male hex feature that fits into the female hex cutout in the output gear on the drivetrain. The adapter also has 3 dowel pins that fit in 3 holes in the bearing housing. 

Project Sponsor

Final Design

Features

  • Little to no ergonomic strain on line associate through the use of a tool balancer
  • Visual feedback about process shown on HMI display
  • Line associates can troubleshoot proccess with HMI
  • Data collection through PF6000
  • Safety measures such as an E-stop and dual engagement safety buttons

Instructions for Use

  1. Load shock into machine
  2. Lock shock into place with toggle clamp
  3. Place adapter onto bearing housing
  4. Move drivetrain so the adapter engages with the output gear
  5. Use buttons on handles to begin torque and rundown
  6. Machine will torque the bearing to spec.
  7. Remove drivetrain from adapter
  8. Remove adapter from shock
  9. Remove shock from machine

(See video for details)

Controls System

The control system for this machine is comprised of three programmed elements: 

  • Atlas Copco’s PF6000 torque driver controller 
  • A touchscreen human-machine interface (HMI) panel 
  • An Allen-Bradley MicroLogix 1400 programmable logic controller (PLC) 

The combination of these control elements takes several external inputs, along with some closed-loop feedback from the torque driver, and moves through a cycle of operation steps to rundown & torque the shaft bearing into the shock body tube. The main I/O with brief function descriptions are as follows: 

Inputs:

  • Two buttons & a safety relay for normal operator input  
  • Torque & position feedback from the Atlas Copco torque driver 
  • Several HMI reset options in the event of an operator error 
  • An emergency stop to cut power to the driver and activate an emergency & maintenance mode 

Outputs:

  • Several programmed tasks for an Atlas Copco Tensor ST torque driver 
  • Three pneumatically actuated Amlok linear rail brakes, preventing drivetrain motion 
  • A pneumatic cylinder to supply o-ring compression force while engaging the bearing threads 
  • Information for the operator, to be displayed on the HMI 
RS Logix Ladder Diagram

Design Requirements

  • Torque Repeatability
  • Operator Safety
  • Ergonomic
  • Manufacturable
  • No Witness Marks
  • Reliability
  • Maintainability
  • Drivetrain

    Gear Analysis

    The most critical portion of the drivetrain was the gears themselves. Given the shaft size required to hold onto the gears, the bearings themselves were massively oversized for the loads that will be experienced. The biggest concern was with the gears themselves.

    FEA of slotted gear
    FEA of standard gear
    Drivetrain Render

    Handles

    Handles Render

    The Handles assembly is responsible for the interaction of the operator with the machine. The operator uses the handles to position the drive train as needed. There is a button at the edge of each handle that the associate operates with their thumb. The button is used to progress through the states of the rundown and torquing process.

    Torque Driver

    The torque applied to the bearing housing will ultimately come from an Atlas Copco Tensor ST Torque Driver. The driver is controlled by a PF6000, which both communicates with the torque driver and the PLC.

    Atlas Copco Torque Driver and PF6000

    Moving Forward

    Initially, one of the goals of the project was to physically build and test the designed system. The outbreak of COVID-19 lead to the shutdown of Cal Poly’s campus, which eliminated the possibility of the team manufacturing any parts in the campus machine shop, Mustang ’60. As such, the team pivoted and created new goals for the project. Now the goal has been to provide our sponsor with all the necessary documentation and software so they can build the machine at their factory on their own.

    Project renders

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