Improving Productivity-When to Consider Automation Chapter 5

When Automation is Needed Automation considered cost reduction Assumed less operating costs Justified by the amount of labor that can be eliminated Doesn’t always reduce costs

General Motors case study 1960’s investing heavily in robotics and automation Tried to justify cost reduction by measuring work productivity Total labor hours needed to produce an automobile Discovered that automation doesn’t always improve productivity Doesn’t reduce waste

Automation makes sense when: The manufacturer needs to increase the rate of production substantially A human being needs to be removed from an unsafe/unhealthy production process

Pre-Automation Process Before automation waste areas need to be eliminated Review waste categories in all major departments

Examples of waste Category Example Non-value adding activities Inspections, repair/rework, taking parts in and out of storage Uneeded materials Parts that can be eliminated or have no function in the product Unneeded operations Making, using or assembling unneeded parts Delays and downtime Materials arriving late, broken machines, absence of workers Loss Spoiled, scrap, or unusable materials that are thrown away Duplication Making extra product in anticipation of defect/scrap. Making two or more styles of a product that have the some function

Design for Assembly (DFA) Simulates assembly of the product, to be evaluated in terms of its suitability to modern methods of assembly If followed most products can be assembled for less than with automation

DFA Guidelines Design parts that are symmetrical Doesn’t have to be oriented Makes automation easier If it can’t be symmetric, make it very asymmetric Obvious which way it is assembled Makes it easier for the operator to install correctly If a part tangles or jams together Slows down operators Eliminate parts that are hard to handle

Make insertion and fastening of parts simple and fast Design a fixture to hold the components during assembly Provide chamfers, insertion guides, and ample clearance for parts being inserted Create a sequence of assembly in one axis Design parts to be oriented properly before they are released Standardize on commonly available fasteners and fastening techniques

Reducing the number of parts Eliminate parts and reduce variety Least parts needed to make the product function Determine the minimum number of parts by asking: Does the part have to move relative to other parts in the assembly when the product is in operation? Does the part have to be made from special material different from the other parts of the assembly? Does the part have a unique function even though the answer to the first 2 questions was no?

Bathroom Scale case study Mechanical bathroom scale consisted of: 17 separate stamped metal parts 6 spot welds 7 fasteners Design was popular but overseas competition was making cheaper products Looked into automation Wouldn’t decrease their selling cost much Instead they went through DFA

Reduced design to 6 parts 5 fasteners (from 7) No spot welds (from 6) 2 were stamped and assembled in the press 5 fasteners (from 7) No spot welds (from 6) Cost of retooling was minimal compared to automation

Their DFA program was a team with representatives from: Product engineering Production engineering Purchasing Sales Cost accounting Plant personnel

Mechanization of Assembly 2 tasks of assembly: Acquiring a component Adding the component to the assembly Must establish a sequence for assembly that meets DFA guidelines Make assembly simple and fast Identify the part that will be a chassis Other parts are assembled into If no chassis, an assembly jig is used

Common mechanization: Mechanization-making or assembling things with machines and tooling to increase the rate of production Common mechanization: Screw guns Riveting machines Staplers Nail guns Part feeding (parts, fasteners) Positioning Clamping

Automated Manufacturing Systems Chapter 6

Automation Is a repeatable operation or process that relies on several components working together Building blocks of automation: Repeatable operation or process Control system Material placement system

Nature of Automation Primary goal is to increase productivity

Mechanization vs. Automation Increase rate Reduce cycle time of operator Enhances machine operator’s abilities Automation Relies on mechanisms Does not require an operator

Soft Automation Handle a wide variety of shapes and material characteristics Complicated control system Simple looking hardware (fewer details) Use of computers, software and sensors

Control Systems Operator controls the machine Start/stop Manual Control Automated control Operator controls the machine Start/stop Make adjustments Pushing a button Computer system monitors the operation Must also monitor quality

Numerical Control Automating manufacturing processes by describing tool paths Movement along an axis or vector 1801 French textile weaver used punch cards with their looms to control patterns 1949 Michigan machining company used punched tape to create contoured parts of helicopter blades Used information on punched tape 1952 Massachusetts Institute of Technology developed a machine and computer to actuate the machine motors 1958 Kearney and Trecker developed the first machining center Machine could change tools automatically

How NC Controls a Machine Tool NC program contains instructions for movement in each axis Instruction is sent to a control unit (MCU) that controls electric motors Motors are attached to lead screws When the motors turn the screw a sensor measures the movement

NC Programming The Code used to control the machine Computer software used to generate the code CAD/CAM system Use CAD model

Material Feeding Consists of orienting and providing a method of propelling components Used in automation to provide parts to assembly equipment