A Tool-Changeable Robotic Part Manipulator Corey Stevens (RBE)

Advisors: Craig Putnam (CS), Stephen Nestinger, PhD (ME)

Abstract

The goal of this project was to design and produce a robotic part manipulator to be

used in a Vertical Machining Center. Project deliverables include a tool which is

capable of being swapped in and out of a Vertical Machining Center’s spindle, able to

flip a part over for a secondary machining operation, and operate autonomously to

enable continuous machine operation. A prototype tool was developed capable of

fulfilling each of these requirements as well as programming code to also handle a

variety of machine errors.

Project Goals

• Demonstrate successful tool changes in and out of the spindle

• Demonstrate part pickup and fixturing

• After one side of the part has been machined, pick up the partially-completed part

and flip it over for a secondary machining operation

• Provide robot software capable of handling errors and improperly placed parts

• Provide appropriate software and hardware documentation, including a user’s

guide

Mechanical Design Three initial designs were considered for the rotation and gripper functionality: electric

motor, pneumatic gripper and bevel gear driven by spindle orientation. The pneumatic

design was chosen because electric motors in a wet environment could lead to

electrical shock and fire, and bevel gears would prove too difficult to integrate

effectively. The chosen design features a rotary union, pneumatic coupling and

fastening to provide pneumatic logic control over a rotary gripper module.

Manufacturing • Nearly all components of the MQP required manufacturing

• Solid modeling using SolidWorks allowed simulation of entire

system prior to manufacturing

• Components machined on the WPI VF-4SS, VM-3 VMCs and

the SL-20 Turning Center

• Turning of the custom 2.5”-16 thread required precision single

point threading

• Focus on Geometric Design and Tolerancing to ensure parts

mate correctly when compared against the solid model

Programming To ensure that the robot does not crash, or cause the machine tool to

crash during operation, the program which controls the movement of

the robot must be robust, capable of handling a variety of unforeseen

circumstances, including, but not limited to:

• Part misalignment

• Out of parts

• Loss of air pressure resulting in a dropped part

• Broken tools

Analysis • Force analysis conducted on the gripper with a 5lb force yielded

0.0001” deflection downward

• Acceptable value because estimated part weight would never

exceed 5lbs

• The tool weighs approximately 10.5lbs, which does not exceed

12lbs, a weight restriction of the machine tool’s carousel

Offset Verification & Error Detection • Uses the Haas Wireless Intuitive Probing System (WIPS)

• Allows custom probing cycles to be designed such that the entire

process may be automated using macro programming.

• Verification of the X,Y,Z work coordinate offset to minimize error

and maximize total accuracy of the system

• Allows small errors present in the robot’s construction to be

corrected for before the manufacturing process begins

Rotary Union • Allows tool to rotate while the air supply remains

stationary

• Channels seal using PFTE (Teflon) O-rings

• Low duty cycle (estimated 10%) allows excellent

service life due to high o-ring lubricity and low

wear

• Custom 2.5”-16 thread design allows high

clamping force to compress o-rings and ensures

no rotation of the union’s free half while in the

tool carousel

Gripper • AGI Automation gripper unit AGM-10 allows

180°rotary movement and gripping motion in

one unit

• Compact form factor reduces weight and overall

tool diameter

• Future improvements could include wireless

sensor input to detect condition of the gripper

and/or rotary movement with proximity or similar

sensors

Toolholder • Turned in the Haas VF-4 Vertical Machining

Center to a custom 2.5”-16 thread

• Maximizes rigidity and reduces error

Offset Verification Using the

Haas Wireless Intuitive

Probing System

Offset Verification Using the

Haas Wireless Intuitive

Probing System

Prototype Gripper Modeled in

SolidWorks

Prototype Gripper Modeled in

SolidWorks

Rotary Union to Carry Sealing O-Rings Rotary Union to Carry Sealing O-Rings

Gripper Design to Grip 1” Round Bar Stock Gripper Design to Grip 1” Round Bar Stock

Sponsors Acknowledgements

• William Weir, PhD

• Torbjorn Bergstrom

• Adam Sears

• Peter Farkas

• Michael Gibney

• James Loiselle

• Alexander Segala

• Michael Fagan

Prototype Robot as of 4/12/12 Prototype Robot as of 4/12/12

Force Analysis Showing Maximum

Deflection Area

Force Analysis Showing Maximum

Deflection Area