1. Design Process, DFM/DFA, and Rapid Prototyping Techniques
Tech/ME 140 Lecture 3
Design Process, DFM/DFA, and Rapid Prototyping Techniques

2. Product Development Process

4. The Design Process Has 5 Steps: Step 1: Conceptualization
Step 2: Synthesis
Step 3: Analysis
Step 4: Evaluation
Step 5: Documentation

5. Step 1: Conceptualization Or Recognition of Need & Definition of the Problem
Divided into two:
Typical design and
Atypical design
Typical design relates to repetitive design
Atypical design is for new product:
May involve market study or research to determine customers’ need or other need
May also emerge from request from customers
Brainstorming
Can be other unexpected opportunities

6. Step 2: Synthesis
Literally means the combining of the constituent elements of separate material entities into a unified entity, to include:
Specification of material
Addition of geometric features
Inclusion of greater dimensional details to conceptualized design
Removes (filters) cost-adding features and materials
Employs DFM and DFA to ensure good design
About 70% of manufacturing cost is fixed in steps 1 and 2 activities

7. Step 3: Analysis
Analysis means determining/describing the nature of the design by separating it into its parts to determine the fit between the proposed design and the original design goals
Two categories of analysis are:
Mass properties analysis, and
Finite element analysis
Can be performed manually, but the computer increases analysis capability and reduces its time

8. Step 4: Evaluation
Checks the design against the original specifications
Often requires construction of a prototype to test for conformance
Often employs rapid prototyping technique
Rapid prototyping techniques to be discussed

9. Step 5: Documentation
Creating all necessary product and part views in the form of:
Working part drawings,
Detailed and assembly drawings
Addition of dimensions, tolerances, special manufacturing notes, and standard components
Creation of:
Part numbers,
Bill of materials, and
Detailed part specifications
Creation of product electronic data files used by manufacturing planning and control, production engineering, marketing and quality control

10. Design Process

11. Design for Manufacture (DFM)
Definition: DFM is the method of design for ease of manufacturing of the collection of parts that will form the product after assembly.
Easy and cost efficient to manufacture
Applies to all manufacturing processes
It is relative to:
Material Type
Material Form and Shape
Dimensional Tolerances
Design and Shape
Manufacturing Process
Others

12. General Design Principles
Symmetry eliminates reorientation
The square part at left is not fully symmetric, since it is not identical in all four orientations (Exhibits 180 degree symmetry only).
Asymmetric Part
Symmetry of a part
makes assembly easier 31

14. Design for Assembly (DFA)
Definition: DFA is the method of design of the product for ease of assembly.
A process by which products are designed with the following in mind:
Ease of assembly
Contains fewer parts
Takes less time to assemble
Reduces assembly costs
Easy orientation and insertion of parts

15. Design for Assembly Principles
Minimize part count
Design parts with self-locating features
Design parts with self-fastening features
Minimize reorientation of parts during assembly
Design parts for retrieval, handling, & insertion
Emphasize ‘Top-Down’ assemblies
Standardize parts…minimum use of fasteners.
Encourage modular design
Design for a base part to locate other components
Design for component symmetry for insertion
Here are Key Principles which simplify and minimize assembly operations 29

16. Component Elimination Example: Rollbar Redesign
‘..If more than 1/3 of the components in a product are fasteners, the assembly logic should be questioned.’
This rollbar assembly was greatly improved by combining parts and adding self-fastening features.
Point out the “quote” at the top of the slide and then ask the class what percentage of components in a Cummins Engine are typically fasteners?
24 Parts
8 different parts
multiple mfg. & assembly processes necessary
2 Parts
2 Manufacturing processes
one assembly step 30

17. Eliminated Parts are NEVER…
Designed
Detailed
Prototyped
Produced
Scrapped
Tested
Re-engineered
Purchased
Progressed
Received
Inspected
Rejected
Stocked
Outdated
Written-off
Unreliable
Recycled
late from the supplier!
Emphasize the impact on part count in a system….
Don’t just flash this slide and move on. It’s worth reading every bullet point. You’re trying to stress the number of things that go wrong with a part. I typically “speed” up as I get into the second column and then take a “big breath” and state the last one regarding “late from the supplier”…

19. Eliminate Secondary Operations
Re-orientation (assemble in Z axis)
Screwing, drilling, twisting, riveting, bending, crimping.
Rivet

20. Eliminate Secondary Operations
Welding, soldering, gluing.
Painting, lubricating, applying liquid or gas.
Testing, measuring, adjusting.
Eliminate painting of engines: Not feasible for all markets, but Daimler-Chrysler has been requesting it at CMEP as a cost reduction (they currently “clear-coat” the Ram engines at CMEP).

23. DFM and Machining Not all designs can be machined by all machines
Design must align with machining process
Machining process must align with part form
Material must match machine selected
Material size must fit machine selected

24. DFM Ideas In Turning Processes
Consider Turning:
Solid cylindrical parts with multiple shapes
Solid tapered parts with multiple shapes
Prototypes of few orders
Automated process for small hardware items like screws, nuts, bolts etc.

25. DFM Ideas In Milling Processes
Milling is for solid prismatic parts
Ideal for multi-axis machines
Ideal for multi-sided parts
Ideal for complex prototypes

26. Some DFM Ideas in Plastic and Composite Forming
Consider:
Simple designs
Best/simplest available process
Avoid too complex designs when possible
The need for rounds and fillets
The fact that plastic materials are in various forms and shapes
Using biodegradable plastics when possible
There is a difference in thermoplastics and thermosets
Using only recyclable plastics when possible

27. Rapid Prototyping
Rapid prototyping uses modern technology to produce a physical prototype from a CAD (Computer Aided Design) file in a matter of hours instead of days or weeks.
These techniques shorten the time required for product development.
The ability to translate a 3D computer model into a physical model in a very short time enables you to quickly evaluate your products to ensure a basic fit, form and function.

28. Sample Prototypes from Rapid Prototyping

29. Advantages
Rapid prototyping techniques shorten the time required for product development.
The ability to translate a 3D computer model into a physical model in a very short time enables you to evaluate your products to ensure a basic fit, form and function.

30. Applications
Prototyping
Rapid tooling
Rapid manufacturing

31. Rapid Prototyping Principles

32. Some of the Methods/Techniques
Stereolithography (SLA)
Solid Ground Curing (SGC)
Laminated Object Manufacturing (LOM)
Fused Deposition Modeling (FDM)
Selective Laser Sintering (SLS)
Ballistic Particle Manufacturing (BPM)
3D Printing and Deposition Milling (3DP)
Direct Shell Production Casting (DSP)

33. Stereolithography (SLA)
Stereolithography (SLA) is the most widely used type of rapid prototyping. Stereolithography produces 3D parts by curing successive layers of UV-curable resin. The parts of the resin that the laser cures in each layer are defined by a CAD model of the part. Because of the accuracy and ability to produce highly detailed parts, Stereolithography is excellent for concept models, masters, assemblies, and patterns for investment casting.

34. Stereolithography (SLA)

35. Solid Ground Curing (SGC)
Solid Ground Curing (SGC), is somewhat similar to stereolithography (SLA) in that both use ultraviolet light to selectively harden photosensitive polymers. Unlike SLA, SGC cures an entire layer at a time. First, photosensitive resin is sprayed on the build platform. Next, the machine develops a photomask (like a stencil) of the layer to be built. This photomask is printed on a glass plate above the build platform using an electrostatic process similar to that found in photocopiers. The mask is then exposed to UV light, which only passes through the transparent portions of the mask to selectively harden the shape of the current layer.

36. Solid Ground Curing (SGC)
 After the layer is cured, the machine vacuums up the excess liquid resin and sprays wax in its place to support the model during the build. The top surface is milled flat, and then the process repeats to build the next layer. When the part is complete, it must be de-waxed by immersing it in a solvent bath.

37. Solid Ground Curing (SGC)

38. Laminated Object Manufacturing (LOM)
Profiles of object cross sections are cut from paper or other web material using a laser. The paper is unwound from a feed roll onto the stack and first bonded to the previous layer using a heated roller which melts a plastic coating on the bottom side of the paper. The profiles are then traced by an optics system that is mounted to an X-Y stage.
After cutting of the layer is complete, excess paper is cut away to separate the layer from the web. Waste paper is wound on a take-up roll. The method is self-supporting for overhangs and undercuts. Areas of cross sections which are to be removed in the final object are heavily cross-hatched with the laser to facilitate removal. It can be time consuming to remove extra material for some geometries, however.

39. Laminated Object Manufacturing (LOM)

40. Fused Deposition Modeling (FDM)
FDM is one method to develop rapid prototypes or models. The FDM machine builds the part by extruding a semi-molten filament through a heated nozzle in a prescribed pattern onto a platform. ... available from Stratasys, the inventor of Fused Deposition Modeling technology

41. Fused Deposition Modeling (FDM)

42. Selective Laser Sintering (SLS)
In Selective Laser Sintering (SLS), thermoplastic powder is spread by a roller over the surface of a build cylinder. The piston in the cylinder moves down one object layer thickness to accommodate the new layer of powder. The powder delivery system is similar in function to the build cylinder. Here, a piston moves upward incrementally to supply a measured quantity of powder for each layer.

43. Selective Laser Sintering (SLS)
A laser beam is then traced over the surface of this tightly compacted powder to selectively melt and bond it to form a layer of the object. The fabrication chamber is maintained at a temperature just below the melting point of the powder so that heat from the laser need only elevate the temperature slightly to cause sintering. This greatly speeds up the process. The process is repeated until the entire object is fabricated.

44. Selective Laser Sintering (SLS)

45. Ballistic Particle Manufacturing (BPM)
Developed by BPM technology, it sprays
material (wax) in 0.002" drops at rates of 12,500 drops per sec to build up slices. The elevator drops as slices are formed. Variable slice thickness is set by changing the flow rate. Part material supports are made from water soluble wax (polyethelene glycol) and are removed after completion by placing the model in water.

46. Ballistic Particle Manufacturing (BPM)

47. 3-D Printing and Deposition Milling (3DP)
3D Printing and Deposition Milling (3DP) is a low-end version of additive fabrication technology. One variation consists of an inkjet printing system. Layers of a fine powder (either cornstarch or plaster) are selectively bonded by "printing" a water-based adhesive from the inkjet printhead in the shape of each cross-section as determined by a CAD (computer aided design) file. Alternately, these machines feed liquids, such as photopolymer, into individual jets that deposit tiny droplets as they are scanned to form a layer of the model. The liquid hardens after being deposited. Materials available for spraying include glue, wax, and photopolymer. Photopolymer Phase machines employ an ultraviolet (UV) flood lamp mounted in the print head to cure each layer as it is deposited.

48. 3-Printing and Deposition Milling (3DP)

49. Direct Shell Production Casting (DSPC)
Direct Shell Production Casting (DSPC) is a revolutionary patternless casting process for metal parts in which the casting molds are generated automatically, directly from 3-D CAD data. With DSPC there is no need for physical patterns, core boxes or any other tooling, and no part-specific setup. The only "pattern" is the CAD design itself. DSPC enables production of a functional metal prototype or parts without a production tool. DSPC works by producing ceramic molds directly from a CAD file, which are then poured with any metal alloy, obtaining a fully functional part in a matter of days. A ceramic mold can be made with an integral core, which separates it from other rapid prototyping methods that have no way of incorporating complex cores in their plastic, wax, or paper patterns. DSPC is a proprietary technology developed at Soligen. Its core technology is based on Three Dimensional Printing (3DP) a patented technology invented at the Massachusetts Institute of Technology (MIT), and licensed exclusively, on a worldwide basis, to Soligen for the metal casting field of use.

50. Direct Shell Production Casting (DSPC)

51. DFM/A Ideas in Rapid Prototyping
Use environmentally friendly RP systems and materials
Use affordable RP systems (do cost analysis for justification)
Selected RP systems must accommodate your design needs: size, materials etc.
Consider software issues/needs
Consider contractual issues (maintenance) with manufacturer/dealer