16.810 (16.682) Engineering Design and Rapid Prototyping Instructor(s) Lecture 6 Manufacturing - CAM January 14, 2004 Prof. Olivier de Weck Dr. Il Yong Kim 16.810 (16.682) 2 Outline ? Introduction to Manufacturing ? Parts Fabrication and Assembly ? Metrics: Quality, Rate, Cost, Flexibility ? Water Jet Cutting ? Video Sequence B777 Manufacturing ? Role of Manufacturing in a Real World Context ? OMax Introduction ? Computer Aided (Assisted) Manufacturing ? Converting a drawing to CNC Routing Instructions 16.810 (16.682) 3 Course Flow Diagram CAD/CAM/CAE Intro FEM/Solid Mechanics Overview Manufacturing Training Structural Test “Training” Design Optimization Hand sketching CAD design FEM analysis Produce Part 1 Test Produce Part 2 Optimization Problem statement Final Review Test Learning/Review Deliverables Design Sketch v1 Analysis output v1 Part v1 Experiment data v1 Design/Analysis output v2 Part v2 Experiment data v2 Drawing v1 Design Intro Due Wed, Jan 21 16.810 (16.682) 4 Introduction to Manufacturing ? Manufacturing is the physical realization of the previously designed parts ? Metrics to assess the “performance” of mfg ? Quality ? does it meet specifications? ? Rate ? how many units can we produce per unit time? ? Cost ? What is the cost per unit? ? What is the investment cost in machinery & tooling? ? Flexibility ? what else can be make with our equipment? ? How long does it take to reconfigure the plant? 16.810 (16.682) 5 Life Cycle: Conceive, Design, Implement 1 Beginning of Lifecycle -Mission - Requirements -Constraints Customer Stakeholder User Architect Designer System Engineer Conceive Design Implement “process information” “turn information to matter” SRR PDR CDR iterate iterate The Environment: technological, economic, political, social, nature The Enterprise The System creativity architecting trade studies modeling simulation experiments design techniques optimization (MDO) virtual real Manufacturing assembly integration choose create 16.810 (16.682) 6 Simple Manufacturing Plant Warehouse PF1 … PFn QA1 … QAn Parts Buffer Supplier Buffer Assembly Final Inspection Finished Goods PF = Parts Fabrication (focus of this lecture) QA = Quality Assurance Raw Materials Energy Supplied Parts Labor Money Sales Scrap Emissions 16.810 (16.682) 7 Raw Materials ? Material Selection ? Strength ? Density ? Cost ? … ? Form ? Sheet ? Rods, ... Refer to Ashby, M.F., Materials Selection in Mechanical Design, Oxford; Boston: Butterworth-Heinemann, 1999. 16.810 (16.682) 8 Parts Manufacturing ? example: deck components ? Ribbed-bulkheads ? Approximate dimensions ? 250mm x 350mm x 30mm ? Wall thickness = 2.54mm decks ? Fundamental Parts Fabrication Techniques ? Machining – e.g. milling, laser and waterjet cutting ... ? Forming – e.g. deep drawing, forging, stamping ? Casting - fill die with liquid material, let cool ? Injection Molding - mainly polymers ? Layup – e.g. Pre-preg composite manufacturing ? Sintering - form parts starting from metal powder 16.810 (16.682) 9 Metal Cutting/Removal Techniques Turning on a lathe Milling Planing Drilling Countersinking Slotting Grinding Reaming New Techniques: Laser Cutting (mainly for sheet metal) Waterjet Cutting Reaming 16.810 (16.682) 10 Quality: Engineering Tolerances ? Tolerance --The total amount by which a specified dimension is permitted to vary (ANSI Y14.5M) ? Every component within spec adds to the yield (Y) q p(q) L U Y y y) 16.810 (16.682) 11 Process Capability Indices ? Process Capability Index ? Bias factor ? Performance Index C UL p {  /2 3V CC k pk p {()1 k UL UL {    P 2 2()/ p(q) q L U UL 2 UL 2 16.810 (16.682) 12 Rate: Manufacturing ? Typically: #of units/hour ? The more parts we make (of the same kind), the lower the cost/unit ? Learning Curve effects ? Higher Speed - Human learning ? Reduced setup time ? Fewer Mistakes (= less scarp=higher yield) ? Bulk quantity discounts (=economies of scale) ? Better negotiating position with suppliers of raw materials and parts 16.810 (16.682) 13 Learning Curve Equation ? Credited to T.P. Wright [1936] ? Model cost reduction between first production unit and subsequent units ? Model the total production cost of N units () B total CNTFUN ? ln 100% 1 ln2 S B { S=90% Learning Curve 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1 3 5 7 9 11 13 15 17 19 Number of Units Produced Co s t / Un i t S=90% B=0.85 TFU=1 TFU = Theoretical first unit cost S = learning curve slope in % --> percentage reduction in cumulative average cost, each time the number of production units is doubled Recommended: 2<N<10 S=95% 10<N<50 S=90% N>50 S=85% 16.810 (16.682) 14 Cost: Driving Factors ? Cost/Unit [$] ? Depends on ? Manufacturing process chosen ? Number of Parts made ? Skill and Experience of worker(s), Salary ? Quality of Raw Materials ? Reliability of Equipment ? Energy Costs ? Land/Facility Cost ? Tolerance Level (Quality) 16.810 (16.682) 15 Process Selection tot fixed var ()CN C C N ? - Machine -Tools - Training -Time/part - Material -Energy Fixed cost process 1 Total cost process 2 Total Manufacturing Cost [$] N - number of parts produced Total Cost process 1 Fixed cost process 2 Choose 2 Choose 1 E.g. Waterjet Cutting E.g. Stamping 16.810 (16.682) 16 Flexibility: Uncertainties ? Short market cycles ? Distinct customers with changing needs ? Changes in laws, regulations & standards a Uncertainties in products and, therefore, in single parts! ? How to address these uncertainties? a Flexibility as ‘Magic bullet’? 16.810 (16.682) 17 Flexibility of process technologies High Speed Machining Forming technology Punching Casting Set-up time Output rate ? ? o ? ? a Fix Var C C Prototyping ? Flexibility is the ease with which a system can change from one state to another! ? Which process is more flexible than others? What type of flexibility? 16.810 (16.682) 18 Types of Flexibilities and their Linkage Component or Basic Flexibilities System Flexibilities Aggregate Flexibilities Organizational Structure Microprocessor Technology Process Routing Product Volume Expansion Machine Material Handling Operation Program Production Market 16.810 (16.682) 19 Waterjet - Brief history - Industrial uses of ultra-high pressure waterjets began in the early 1970s. Pressures: 40,000 ~ 60,000 psi Nozzle diameter: 0.005" - Special production line machines were developed to solve manufacturing problems related to materials that had been previously been cut with knives or mechanical cutters. - Examples of early applications Cardboard Shapes from foam rubber Soft gasket material 16.810 (16.682) 20 Waterjet - Brief history - In the early 1990s, John Olsen (pioneer of the waterjet cutting industry) explored the concept of abrasive jet cutting. - The new system equipped with a computerized control system that eliminated the need for operator expertise and trial-and-error programming. - Olsen teamed up with Alex Slocum (MIT) Used cutting test results and a theoretical cutting model by Rhode Island University. Developed a unique abrasive waterjet cutter. 16.810 (16.682) 21 Pumps Intensifier Pump - Early ultra-high pressure cutting systems used hydraulic intensifier pumps. - At that time, the intensifier pump was the only pump for high pressure - Engine or electric motor drives the pump Pressure: ~ 60,000 psi 16.810 (16.682) 22 Pumps Crankshaft pumps - Use mechanical crankshaft to move any number of individual pistons - Check valves in each cylinder allow water to enter the cylinder as the plunger retracts and then exit the cylinder into the outlet manifold as the plunger advances into the cylinder. Pressure: ~ 55,000 psi Reliability is higher. Actual operating range of most systems : 40,000 ~50,000 psi An increasing number of abrasivejet systems are being sold with the more efficient and easily maintained crankshaft-type pumps. 16.810 (16.682) 23 Nozzles Two-stage nozzle design [1] Water passes through a small-diameter jewel orifice to form a narrow jet. Then passes through a small chamber pulling abrasive material [2] The abrasive particles and water pass into a long, hollow cylindrical ceramic mixing tube. The resulting mix of abrasive and water exits the mixing tube as a coherent stream and cuts the material. Alignment of the jewel orifice and the mixing tube is critical In the past, the operator adjusted the alignment often during operation. 16.810 (16.682) 24 X-Y Tables Separate Integrated x y z Cutting table Gantry Cantilever 16.810 (16.682) 25 X-Y Tables Loading material onto the table can be difficult because the gantry beam may interfere, unless the gantry can be moved completely out of the way Because the gantry beam is moved at both ends, a very high-quality electronic or mechanical system must be employed to Well-adapted to the use of multiple nozzles for large production runs Y-axis is limited in length to about 5 feet because of structural considerations Gantry Cantilever 16.810 (16.682) 26 X-Y Tables Separate Integrated Inherently better dynamic accuracy because relative unwanted motion or vibration between the table and X-Y structure is eliminated More expensive to build than the traditional separate frame system Less floor space is required for a given table size because the external support frame is eliminated System accuracy can be built at the factory and does not require extensive on-site set-up and alignment 16.810 (16.682) 27 Waterjet in Aero/Astro machine shop OMAX Machining Center 2652 Integrated cantilever Image courtesy of OMAX Corporation www.omax.com 16.810 (16.682) 28 CNC - Control System The OMAX control system computes exactly how the feed rate should vary for a given geometry in a given material to make a precise part. The algorithm actually determines desired variations in the feed rate every 0.0005" (0.012 mm) along the tool path OMAX uses a PC to compute and store the entire tool path and feed rate profile and then directly drive the servo motors that control the X-Y motion. CAD Model SolidWorks (.prt) Drawing SolidWorks (.dxf) CAM Layout Omax Layout (.ord) Omax Make Image courtesy of OMAX Corporation www.omax.com 16.810 (16.682) 29 How to Estimate Manufacturing Cost? (1) Run the Omax Software! Overhead cost estimate in Aero/Astro machine shop 0 ( $1.25/minute)C (2) Estimation by hand manufac o manufac Cost C t , manufac cutting traverse cutting traverse cutting i i i ttttt t l u  !! # | - Break up curves into linear and nonlinear sections - Measure curve lengths and calculate cutting speeds - Solve for cutting times for each curve and sum Image courtesy of OMAX Corporation www.omax.com 16.810 (16.682) 30 How to Estimate Manufacturing Cost? [in/min] 471.42 15.1 ? ? o ? ? a q u linear ? Linear cutting speed, u linear ? Good approximation for most of the curves in the CAM waterjet cutting route ? Arc section cutting speed, u arc ? Assume if arc radius is less than R min ? Reduce manufacturing time ? Reduce the total cutting length ? Increase fillet radii ? Reduce cutting curve lengths >@[in/min]334.9866.1 15.1 4  eRu arc N/A0.30.20.1250.15R min (in) 12345Quality Index, q 16.810 (16.682) 31 Best applications Materials and thickness - Aluminum, tool steel, stainless steel, mild steel and titanium - Thicknesses up to about 1" (2.5 cm) Shapes - An abrasivejet can make almost any two-dimensional shape imaginable— quickly and accurately—in material less than 1" (25 mm) thick. - The only limitation comes from the fact that the minimum inside radius in a corner is equal to ? the diameter of the jet, or about 0.015" (0.4 mm). 16.810 (16.682) 32 Applications that are generally poor Low-cost applications where accuracy really has no value Using a precision abrasivejet as a cross-cut saw - Just buy a saw ! Applications involving wood - It's hard to beat a simple jigsaw. Parts that truly require a 5-axis machine - This is a much more specialized market. 16.810 (16.682) 33 Material Aluminum Aluminum is a light weight but strong metal used in a wide variety of applications. Generally speaking, it machines at about twice the speed as mild steel, making it an especially profitable application for the OMAX. Many precision abrasivejet machines are being purchased by laser shops specifically for machining aluminum. Aluminum is often called the "bread and butter" of the abrasivejet industry because it cuts so easily. A part machined from 3" (7.6 cm) aluminum; Intelli-MAX software lets you get sharp corners without wash-out Image courtesy of OMAX Corporation www.omax.com 16.810 (16.682) 35 References A comprehensive Overview of Abrasivejet Technology, Omax Precision Abrasive Waterjet Systems, http://www.omax.com/ 16.810 (16.682) 36 Spiral Development (DSM) 12345678910 1 1X X 2 X2 X X 3 X3X X 4 X4X X 5 X 5 6 X6 7 X7 8 X8 9 X9 10 XX X 10 1 – Requirements Analysis 2 – Concept/Sketching 3 – CAD Modeling (.prt) 4 – FEM Analysis 5 – Design Optimization 6 – Make Drawing (.dxf) 7 – CAM Layout (.ord) 8 – Manufacture (Omax) 9 – Structural Testing 10 – Accept Part