5.1 Introduction to Product life cycle management | unit 5 advanced manufacturing method

CAD

Unit 5

Advanced Manufacturing Method

5.1 Introduction to Product life cycle management

Product life cycle Management (PLM) is a system of managing the entire life cycle of the product.

Product lifecycle management (PLM) is the Business Strategy of managing the entire lifecycle of a product from its conception, through design and manufacture, to service and disposal.

It Supports the Extended enterprise (Customers, Design and supply partners). PLM Spans from the Concept to the last stage – the life of a product or plant.

The life cycle of the product includes:

Inception of product

Design of product

Manufacturing of product

Service of Product

Disposal of product.

Need of PLM

The traditional philosophy of product design is based on the principle of minimizing the design and manufacturing cost.

In today’s competitive environment, where market is flooded with large number of identical products, for a success of a product, it is not only important to minimize the design and manufacturing cost but also necessary to minimize the total product life cycle cost.

The product life cycle cost consists of: cost of product inception, design, manufacturing, service and disposal.

This had made it necessary to develop a plan to manage all the phases of product life cycle.

Hence there is the need of PLM to manage the entire life cycle of a product from inception to disposal.

Components / Elements of PLM

The following are the essential elements of PLM:

Document/ Data management

The document management component stores, tracks and manages all the data associated with product and product development process.

2. CAD/CAM Data management

This component enables complete management and control of CAD/CAM data from all CAD/CAM tools used in organization.

It is very important in design and manufacturing of product.

3. Project Task (Workflow) management

This component assists in establishing and standardizing the product development process.

4. BOM (Bill of Materials) management

This component of PLM system stores and manages vast data about BOM. It helps to assess the potential impact of any change of materials on product cost.

5. Collaboration management

Collaboration management ensures all internal as well as external partners can work concurrently on project with full data protection.

6. Confirmation and change management

This component makes sure that every stake holder of system is aware of each process and updated changes of in all phases of product lifecycle from inception to disposal.

Collaborative Engineering

“Collaborative engineering is defined for the study of interactive process of engineering collaboration wherein, in order for serving their mutual interests, multiple interested stakeholders or partners:

i) Resolve conflicts

ii) Bargain for individual or group advantages

iii) Agree upon course of action

iv) Attempt to achieve joint outcomes

The aim of collaborative engineering is to facilitate the individuals and organizations, across the boundaries of discipline, geography and culture, to work effectively with collaborative actions for achieving joint outcomes.

It is used most effectively in product design, manufacturing, construction, etc.

5.2 Introduction to Rapid Prototyping

Rapid Prototyping Technology is a group of manufacturing processes that enable the direct physical realization of 3D computer models.

This technology converts the 3D computer data provided by a dedicated file format directly to a physical model, layer by layer with a high degree of accuracy.

Rapid prototyping is an "additive" process, combining layers of paper, wax, or plastic to create a solid object. In contrast, most machining processes are "subtractive" processes that remove material from a solid block.

RPT can automatically construct physical models from CAD data.

RP is capable to fabricate parts quickly with too complex shape easily as compared to traditional manufacturing technology.

Fundamentals of Rapid Prototyping

The Rapid Prototyping Wheel depicting the 4 major aspects of RP

Input

Input refers to the electronic information required to describe the physical object with 3D data.

There are two possible starting points – a computer model or a physical model.

The computer model created by a CAD system can be either a surface model or a solid model

On the other hand, 3D data from the physical model is not at all straightforward.

It requires data acquisition through a method known as reverse engineering.

In reverse engineering, a wide range of equipment digitizer, to capture data points of the physical model and “reconstruct” it in CAD system.

2. Method

While they are currently more than 20 vendors for RP systems, the method employed by each vendor can be generally classified into the following categories:

• photo-curing,

• cutting and gluing/joining,

• melting and solidifying/fusing and joining/binding.

Photo-curing can be further divided into categories of

• single laser beam,

• double laser beams and

• masked lamp

3. Material

The initial state of material can come in either solid, liquid or powder state.

In solid state, it can come in various forms such as pallets, wire or laminates.

The current range materials include paper, nylon, wax, resins, metals and ceramics.

4. Application

Applications can be grouped into:

Design

Engineering, Analysis and Planning

Tooling and Manufacturing

A wide range of industries can benefit from RP and these include, but are not limited to,

aerospace,

automotive,

biomedical, consumer,

electrical and electronics products.

Basic Steps in Rapid Prototyping Process

CAD Model Creation:

First, the object to be built is modeled using a Computer-Aided Design (CAD) software package or coordinate measuring machine or laser scanner.

Solid modelers, such as Pro/ENGINEER, tend to represent 3-D objects more accurately than wire-frame modelers such as AutoCAD, and will therefore yield better results.

This process is identical for all of the RP build techniques.

2. Conversion to STL Format:

To establish consistency, the STL (stereo lithography, the first RP technique) format has been adopted as the standard of the rapid prototyping industry and acts as the interface b/w CAD software and machines.

The second step, therefore, is to convert the CAD file into STL format. This format represents a three-dimensional surface as an assembly of planar triangular facets.

STL files use planar elements, they cannot represent curved surfaces exactly. Increasing the number of triangles improves the approximation.

3. Slice the STL File:

In the third step, a pre-processing program prepares the STL file to be built.

The pre-processing software slices the STL model into a number of layers from 0.01 mm to 0.7 mm thick, depending on the build technique.

The program may also generate an auxiliary structure to support the model during the build. Supports are useful for delicate features such as overhangs, internal cavities, and thin-walled sections.

4. Layer by Layer Construction:

The fourth step is the actual construction of the part.

RP machines build one layer at a time from polymers, paper, or powdered metal.

Most machines are fairly autonomous, needing little human intervention.

5. Clean and Finish:

The final step is post-processing. This involves removing the prototype from the machine and detaching any supports.

Some photosensitive materials need to be fully cured before use

Prototypes may also require minor cleaning and surface treatment.

Sanding, sealing, and/or painting the model will improve its appearance and durability.

5.3 Classification of Rapid Prototyping

Based on initial form of material used, the rapid prototyping systems are broadly classified into three categories.

LIQUID-BASED

Liquid-based RP systems have the initial form of its material in liquid state.

Through a process commonly known as curing, the liquid is converted into the solid state.

Examples:

a) Stereolithography (SLA)

b) Polyjet Modelling

2. SOLID-BASED

Except for powder, solid-based RP systems are meant to encompass all forms of material in the solid state.

In this context, the solid form can include the shape in the form of a wire, a roll, laminates and pallets.

Examples:

a) Fused Deposition Modelling (FDM)

b) Laminated Object Modelling (LOM)

3. POWDER-BASED

In a strict sense, powder is by-and-large in the solid state.

However, it is intentionally created as a category outside the solid-based RP systems to mean powder in grain-like form.

Examples:

a) Selective Laser Sintering (SLS)

b) 3D- Printing

Stereolithography (SLA)

Stereo lithography is the most widely used RP-technology. It can produce highly

Accurate and detailed polymer parts. SLA was the first RP-process, introduced in 1988 by 3D Systems Inc.

Working Principle

SLA uses a low-power, highly focused UV laser to produce a three-dimensional object in a vat of liquid photosensitive polymer.

Features

Material type: Liquid(Photopolymer)

Materials: Thermoplastics(Elastomers)

Min layer thickness: 0.02 mm

Surface finish: Smooth

Build speed: Average

Model and specification of process

This is based on selective polymerization of a photosensitive resin using ultraviolet light.

In this system, an ultraviolet laser beam is focused on the top layer of photo sensitive resin contained in a vat.

The beam is positions and moved in horizontal X and Y directions to polymerize the resin within the boundary a particular cross-section.

The cured layer of polymer is lowered by a platform attached to it, so that a fresh layer of liquid resin covers the cured layer.

SLA Process

Working

A vat containing a mechanism whereby a platform can be lowered and raised is filled with a photocurable liquid-acrylate polymer.

The liquid is a mixture of acrylic monomers, oligomers (polymer intermediates), and a photo-initiator (a compound that undergoes a reaction upon absorbing light).

At its highest position (depth a), a shallow layer of liquid exists above the platform.

A laser generating an ultraviolet (UV) beam is focused upon a selected surface area of the photopolymer and then moved around in the x-y plane.

The beam cures that portion of the photopolymer and thereby produces a solid body.

The platform is then lowered sufficiently to cover the cured polymer with another layer of liquid polymer, and the sequence is repeated.

The process is repeated until level b is reached. Thus far, we have generated a cylindrical part with a constant wall thickness. Note that the platform is now lowered by a vertical distance ab.

At level b, the x-y movements of the beam define a wider geometry, so we now have a flange-shaped portion that is being produced over the previously formed part.

After the proper thickness of the liquid has been cured, the process is repeated, producing another cylindrical section between levels b and c.

Note that the surrounding liquid polymer is still fluid (because it has not been exposed to the ultraviolet beam) and that the part has been produced from the bottom up in individual ‘slices’. The unused portion of the liquid polymer can be used again to make another part or another prototype.

ADVANTAGES

Achieving accuracy in industries

Capable of high detail and thin walls

Good surface finish

High part complexity

DISADVANTAGES

Some war page, shrinkage and curl due to phase change.

Limited materials (Photo polymers).

Support structures always needed. Removal of support structures can be difficult

Requires post-curing.

Application

Visual Representation models

Functional and tough prototypes

cast metal parts

Fused Deposition Modelling

(FDM) is a solid-based rapid prototyping method that extrudes material, layer-by-layer, to build a model.

It was developed by Stratasys

Working Principle

A plastic or wax material is extruded through a nozzle that traces the part´s cross sectional geometry layer by layer

Features

Material type: Solid(Filaments)

Materials: ABS, Polycarbonate, Poly phenyl-sulfonite;Elastomers

Min layer thickness: 0.15mm

Surface finish: Rough

Build speed: Slow

Model and specification of process

The FDM technique relies on melting and selectively depositing a thin filament of thermoplastic polymer in a cross-hatching fashion to form each layer of the part.

The material is in the form of a wire supplied in sealed spools which is mounted on the machine and the wire is threaded through the FDM head.

The head is moved in the horizontal X and Y directions for producing each layer through zigzag movements.

The supporting table moves in the vertical direction and is lowered after the completion of each layer.

FDM Process

Working

In FDM process, a gantry robot-controlled extruder head moves in two principal directions over a table, which can be raised and lowered as needed.

A thermoplastic filament is extruded through the small orifice of a heated die.

The initial layer is placed on a foam foundation by extruding the filament at a constant rate while the extruder head follows a predetermined path.

When the first layer is completed, the table is lowered so that subsequent layers can be superimposed.

In some parts, the filament is required to support the slice where no material exists beneath to support it.

The solution is to extrude a support material separately from the modelling material. The use of such support structures allows all of the layers to be supported by the material directly beneath them.

The support material is produced with a less dense filament spacing on a layer, so it is weaker than the model material and can be broken off easily after the part is completed.

The layers in an FDM model are determined by the extrusion-die diameter, which typically ranges from 0.050 to 0.12mm. This thickness represents the best achievable in the vertical direction.

In the x-y plane, dimensional accuracy can be as fine as 0.025mm

Advantages

Durable parts can be made

Minimal wastage

Easy handling, material changeover and support removal.

No post curing.

Office environment friendly.

Low end, economical machines.

Easy material changeover and support removal.

Variety of materials

Disadvantages

Longer to build

Low accuracy compared to SLA

Not good for small features, details and thin walls.

Surface finish is rough.

Support design / integration / removal is difficult.

Weak Z-axis.

Slow on large / dense parts.

Supports required on some materials / geometries.

Application

Form/fit testing

Functional testing

Small detailed parts

Presentation models

Laminated Object manufacturing (LOM)

As the name implies the process laminates thin sheets of film (paper or plastic).

The laser has only to cut/scan the periphery of each layer

Working Principle

The build material is placed on a platform and a heated roller bonds it to the previous layer and the sheet is cut to required profile by laser and glued to previous sheet.

Features

Material type: Solid(Sheets)

Materials: Thermoplasticssuchas PVC; Paper; Composites(Ferrousmetals; Non-ferrousmetals; Ceramics)

Min layer thickness: 0.05mm

Surface finish: Rough

Build speed: Fast

Model and specification of process

The main components of the system are a feed mechanism that advances a sheet over a build platform, a heater roller to apply pressure to bond to the layer below, and a laser to cut the outline of the part in each sheet layer.

After each cut is completed, the platform lowers by a depth equal to the sheet thickness (0.05 –0.5 mm).

The laser cuts the outline and the process is repeated until the part is completed.

After a layer is cut, the extra material remains in place to support the part.

LOM Process

Working

Lamination implies a laying down of layers that are bonded adhesively to one another.

The simples and least expensive versions of LOM involve using control software and vinyl cutters to produce the prototype.

Vinyl cutters are simple CNC machines that cut shapes from vinyl or paper sheets.

Each sheet then has a number of layers and registration holes, which allow proper alignment and placement onto a build fixture.

LOM systems are highly economical and are popular in schools and universities because of the hands-on demonstration of additive manufacturing and production of parts by layers.

LOM systems can be elaborate; the more advanced systems use layers of paper or plastic with a heat-activated glue on one side to produce parts.

The desired shapes are burned into the sheet with a laser, and the parts are built layer by layer.

On some systems, the excess material must be removed manually once the part is completed. Removal is simplified by programming the laser to burn perforations in crisscrossed patterns.

The resulting grid lines make the part appear as if it had been constructed from gridded paper (with squares printed on it, similar to graph paper).

Advantages

Wide range of materials

Fast Build time

High accuracy

durability

High part complexity

Disadvantages

Requires post-curing

Overheated roller may damage sheet

Limited materials (Photo polymers).

Support structures always needed.

Application

Form/fit testing

Less detailed parts

Rapid tooling patterns

Selective Laser Sintering

SLS is a process based on the sintering of non metallic or (less commonly) metallic powders selectively into an individual object.

SLS was patented in 1989.

Principle of Working

It uses a moving laser beam to trace and selectively sinter powdered polymer and/or metal composite materials.

Features

Material type: Powder(Polymer)

Materials: Thermoplastics: Nylon, Polyamide and Polystyrene; Elastomers; Composites

Min layer thickness: 0.10mm

Surface finish: Average

Build speed: Fast

Model and specification of process

In this process a high power laser beam selectively melts and fuses powdered material spread on a layer.

The powder is metered in precise amounts and is spread by a counter-rotating roller on the table.

A laser beam is used to fuse the powder within the section boundary through a cross-hatching motion.

The table is lowered through a distance corresponding to the layer thickness (usually 0.01 mm) before the roller spreads the next layer of powder on the previously built layer.

The un-sintered powder serves as the support for overhanging portions, if any in the subsequent layers.

SLS Process

Working

First, a thin layer of powder is deposited in the part-build cylinder

Then, a laser beam guided by a process-control computer using instructions generated by the 3D CAD program of the desired part is focused on that layer, tracing and sintering a particular cross-section into a solid mass.

The powder in other areas remains loose, yet it supports the sintering portion.

Another layer of powder is then deposited; this cycle is repeated again and again until the entire 3D part has been produced.

The loose particles are shaken off, and the part is recovered.

The part does not require further curing-unless it is a ceramic, which has to be fired to develop strength.

A variety of materials can be used in this process, including polymers (such as ABS; PVC, nylon, polyester, polystyrene, and epoxy), wax, metals, and ceramics with appropriate binders.

It is most common to use polymers because of the smaller and less expensive, and less complicated lasers are required for sintering.

With ceramics and metals, it is common to sinter only a polymer binder that has been blended with the ceramic or metal powders.

The resultant part can be carefully sintered is a furnace and infiltrated with another metal if desired.

Advantages

No need of support structures

No post curing required

Variety and Flexibility of materials

The main advantage is that the fabricated prototypes are porous (typically 60% of the density of moulded parts), thus impairing their strength and surface finish.

Fast build times.

Disadvantages

Rough surface finish.

Additional powder may get hardened while solidification along border line

Mechanical properties below those achieved in injection mouldings process for same material.

Many build variables, complex operation.

Material changeover difficult compared to FDM & SLA.

Applications

Form/fit testing

Functional testing

Less detailed parts

Parts with snap-fits& living hinges

High heat applications

3D Printing

Three-Dimensional Printing (3DP) technology was developed at the MIT and licensed to several corporations.

It was Produced by Z Corporation, USA.

Principle

An ink-jet printing head deposits a liquid adhesive that binds the starch powder material.

Features

Material type: Powder

Materials: Ferrousmetalssuchas Stainlesssteel; Non-ferrousmetalssuchas Bronze; Elastomers; Composites; Ceramics

Min layer thickness: 0,05mm

Surface finish: Rough

Build speed: VeryFast

Model and specification of process

Spread a layer of powder

Print the cross section of the part

Spread another layer of powder

Parts are printed with no supports to remove

Post processed by cleaning the excess powder, air blow, gluing and sanding.

Paint coated by sprayers or brushers to get finished product

3D Printing

Working

In 3D printing (3DP) process, a print head deposits an inorganic binder material onto a layer of polymer, ceramic, or metallic powder.

A piston supporting the powder bed is lowered incrementally, and with each step, a layer is deposited and then fused by the binder.

3DP allows considerable flexibility in the materials and binders used.

Furthermore, since multiple binders print heads can be incorporated into a machine, it is possible to produce full-color prototypes by having different-color binders.

The effect is a 3D analog to printing photographs using three ink colors on an ink-jet printer.

A common part produced by 3DP from ceramic powder is a ceramic casting shell, in which an aluminium-oxide or aluminium silica powder is fused with a silica binder.

The moulds have to be post processed in two steps: (1) Curing at around 150ºC and (2) Firing at 1000º to 1500ºC.

The parts produced through the 3DP process are somewhat porous and therefore may lack strength.

3DP of metal powders can also be combined with sintering and metal filtration to produce fully dense parts, using the sequence.

The part is produced as before directing the binder onto powders. However, the build sequence is then followed by sintering to burn off the binder and partially fuse the metal powders, just as in powder injection moulding.

Common metals used in 3DP are stainless steels, aluminium, and titanium.

Infiltrating materials typically are copper and bronze, which provide good heat-transfer capabilities as well as wear resistance

Advantages

High speed

Versatile - used for automotive, aerospace, footwear, packaging, etc.

Simple to operate straightforward

Can recycle

Enable complex color scheme

No wastage of material

Disadvantages

Requires post-curing

Limited functional parts

models are weak

Limited materials -starch & plaster-based only.

poor surface finish

need post-processing

Applications

Concept models

Limited functional testing

Architectural& landscape models

Consumer goods& packaging

5.4 Rapid Tooling

Rapid-prototyping techniques have made possible much faster product development times, and they are having a major effect on other manufacturing processes. When appropriate materials are used, rapid-prototyping machinery can produce blanks for investment casting or similar processes, so that metallic parts can now be obtained quickly and inexpensively, even for lot sizes as small as one part.

Such technologies also can be applied to producing molds for operations (such as injection molding, sand and shell mold casting, and even forging), thereby significantly reducing the lead time between design and manufacture.

Several methods have been devised for the rapid production of tooling (RT) by means of rapid-prototyping processes.

The advantages to rapid tooling include the following:

The high cost of labor and short supply of skilled patternmakers can be overcome.

There is a major reduction in lead time.

Hollow designs can be adopted easily so that lightweight castings can be produced more easily.

The integral use of CAD technologies allows the use of modular dies with base-mold tooling (match plates) and specially fabricated inserts. This modular technique can further reduce tooling costs.

Chill- and cooling-channel placement in molds can be optimized more easily, leading to reduced cycle times.

Shrinkage due to solidification or thermal contraction can be compensated for automatically through software to produce tooling of the proper size and, in turn, to produce the desired parts.

The main shortcoming of rapid tooling is the potentially reduced tool or pattern life (compared to those obtained from machined tool and die materials, such as tool steels or tungsten carbides).

The simplest method of applying rapid-prototyping operations to other manufacturing processes is in the direct production of patterns or molds.

Conventional Tooling vs Rapid Tooling:

RT is distinguished from conventional tooling in that,

Tooling time is much shorter than for a conventional tool. Typically, time to first articles is below one-fifth that of conventional tooling.

Tooling cost is much less than for a conventional tool. Cost can be below five percent of conventional tooling cost.

Tool life is considerably less than for a conventional tool.

Tolerances are wider than for a conventional tool.

Need of Rapid Tooling (RT)

Minimize cost

Increase productivity

Increase dimensional accuracy

Decrease tool time

Advantages of RT

Quantity : large no of parts to be machined

Design : fabrication of complex parts

Material : for machining difficult materials

Speed : to increase the speed of machining

STL File Format

There are many different ways to 3D print an object. But nearly all of them utilize computer aided design (CAD) files.

CAD files are digitalized representations of an object. They're used by engineers and manufacturers to turn ideas into computerized models that can be digitally tested, improved and most recently, 3D printed.

In 3D printing or additive manufacturing CAD files must be translated into a "language," or file type, that 3D printing machines can understand.

Standard Tessellation Language (STL) is one such file type and is the language most commonly used for stereolithography, as well as other additive manufacturing processes.

Since additive manufacturing works by adding one layer of material on top of another, CAD models must be broken up into layers before being printed in three dimensions.

STL files "cut up" CAD models, giving the 3D printing machine, the information it needs to print each layer of an object.

What is STL File?

A STL file is a format used by Stereolithography software to generate information needed to produce 3D models on Stereolithography machines. In fact, the extension "stl" is said to be derived from the word "Stereolithography."

A slightly more specific definition of a stl file is a triangular representation of a 3D object. The surface of an object is broken into a logical series of triangles (see illustration at right). Each triangle is uniquely defined by its normal and three points representing its vertices.

The stl file is a complete listing of the xyz coordinates of the vertices and normals for the triangles that describe the 3D object.

When creating a stl file, the goal is to achieve a balance between unmanageable file size and a well-defined model with smooth curved geometries.

Often a stl file can be termed "bad" because of translation issues.

In many CAD systems, the number of triangles that represent the model can be defined by the user. If too many triangles are created, the stl file size can become unmanageable.

If too few triangles are created, curved areas are not properly defined and a cylinder begins to look like a hexagon (see example below).

STL File Format

There are two formats of STL File:

ASCII format STL file: It is larger in size than binary format STL file, but it is human readable.

Binary Format STL File: It is smaller in size than binary format STL file, but it is not human readable.

5.5 Concept of 4D Rapid Prototyping

3D printed materials can be more flexible and useful, the structures of the material can transform in a pre-programmed way in response to any external stimulus. In general, self-changing structure of 3D printed part after post process is called 4D printing process.

In 4D printing process, 1D strand or 2D surface having multi-material feature, is created using the same 3D printing techniques.

Joint and folding angle strands

Printing 4D joint includes multiple layers of material. Composition of rigid polymer, expanding material and digital material depicts the folding direction and pattern. Those materials are placed above or below of each other depending upon the type of transformation.

Custom Angle Surfaces

Similar mechanism as folding strand described previously, series of flat two-dimensional structures were generated with edge joints. The position and spacing of materials at each joint specifies the desired fold angle hence positioned accordingly.

4D printed self-folding truncated octahedron demonstrating the “transformation over time” when submerging in water.

References

1. Ibraim Zeid, Mastering CAD/CAM – Tata McGraw Hill Publishing Co. 2000

2. Segerling L. J. - Applied Finite Elements Analysis, John Wiley and Sons

3. Seshu P. Text book of Finite Element Analysis, PHI Learning Private Ltd. New Delhi, 2010

4. Rao P. N., Introduction to CAD/CAM Tata McGraw Hill Publishing Co.

5. B. S. Pabla, M. Adithan, CNC Machines, New Age International, 1994

6. Groover M.P.-Automation, production systems and computer integrated manufacturing‘ - Prentice Hall of India

7. Ian Gibson, David W. Rosen, Brent Stucker, Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing, Springer

8. Geoffrey Boothroyd, Peter Dewhurst, Winston A. Knight, Product Design for Manufacture and Assembly, Third Edition ,CRC Press

9. Antti Saaksvuori, Anselmi Immonen, Product Life Cycle Management -Springer, 1st Edition, 2003

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