Exam 2

Assembly Files

.sldasm 3D files composed of parts and other assemblies, info about how parts should be located in relation to each other, how the parts should be viewed within the assembly, and contains material properties and calculated properties

Drawing Files

.slddrw 2D representations of parts and assemblies, inform fabricators about the details of parts and files, info about how to make the physical parts and assemblies, contains tolerancing and machining notes, and material information

Part Files

.sldprt 3D objects created parametrically, contain information about how to make the part (like a recipe), contains material properties and calculated properties (center of mass, moments of inertia)

What information is necessary to reference a: 1. Coordinate system origin 2. Point 3. Line Segment 4. Quadrilateral 5. Circle on plane 6. Wireframe Cube 7. Solid Cylinder

1. 2. 3 dimensions 3. 6 dimensions (2 points) and a line 4. 2 points and 4 lines 5. Center and radius (2 parameters) 6. 2 points 7. Circle and height (3 parameters)

4 general methods to generate solids

1. Boundary representation 2. Constructive Solid Modeling 3. Parametric Feature-based Modeling 4. Direct Modeling

10 Principles of 3D printing (1-5)

1. Complexity is free - except high resolution is slow, trapped volumes are bad (solids) 2. Variety is free - except may require product design qualification 3. No assembly required - except tolerances defined by process, can only have single/like materials 4. Zero Lead Time - except most machines are very slow (1 in^3/hr), shoebox size = days of print time 5. Zero skill - except it takes experience to be proficient, lots of training required as complexity increases

4 Main Building Blocks

1. Extrusion - 1 profile sketch 2. Revolve - 1 profile sketch, 1 axiss sketch 3. Sweep - 1 profile sketch, 1 path sketch 4. Loft - 2 profile sketches, optional guide sketches

Hierarchy of file sharing

1. STEP file - all the info 2. IGES file - geometry in tact, can reconstruct to make solid model 3. STL file - basically only a picture, hard to map geometry to the surface

Fused Deposition Modeling Fortus 250 MC

10 x 10 x 12 inches 1 material type (ABS) Layers of .007, .01, .013 inches

Fused Deposition Modeling Fortus 400 MC

16 x 14 x 16 inches Several Material types Layers of .005, .007, .010, or .013 inches

10 Principles of 3D printing (6-10)

6. Zero constraints - except limited resolution, support structures required, size limitations 7. Compact & Portable Mfg - except big money things take big money machines 8. Less waste - except it depends on how many trials are required to get the part right 9. Infinite shade of materials - except they have to be compatible with machine, feedstock needs to be discrete 10. Precision Scanning (replicas) - except depends on resolution of scanning and printing systems

What is a story pole?

A kind of map for building one specific part; produces more accurate parts then using a ruler

Support Material

Abrupt overhangs require support material that will be taken off at the end (waste) Gentle slopes limited to less than 45 degrees off the vertical are possible Bridging small gaps is possible (microns to several inches)

Advantages of CAD

Accurate, quick, cheap to change designs, quickly modify views for presentations, keeps a record of the design process, enables communication to others

Binder Jetting

Binder Jetting - Liquid bonding agent is deposited to join powder material. Essentially it sprays out glue onto a layer of metal powder, has to be post-processed in a vat of brass so the finished product is a composite of metal like stainless steel and brass

Steps of 3D printing?

CAD Solid model, faceted model, virtually slice, layer-specific tool paths, build each layer on top of previous ones, finished part

General steps for 3D printing

CAD, STL convert, file transfer to machine, machine setup, build, remove, post-process, application

Constructive solid modeling

Contains a set of primitives (sphere, cylinder, prism) and constructs objects using boolean operations (union subtract, intersection)

Purposes of CAD

Design Analysis Communication Documentation

Laser Engineered Net Shaping (LENS)

Directed Energy Deposition - uses a high-power laser (500 W to 4 kW) to fuse powdered metals into fully dense 3D structures. The metal powder feedstock is delivered to the material deposition head by Optomec's proprietary powder-feed system, which is able to precisely regulate mass flow

Anisotropic mechanical properties

FDM parts are weakest between the layers, orient such that major forces are in the XY-plane so that not as much force is pulling between the layers

Advantages of additive manufacturing

Faster, cheaper, better Increased complexity, less material scrap, shorter design cycle, reduced part count, no drawings (all digital)

3D printing pros

Freedom of design - can produce an object of any shape Complexity for free - increasing object complexity will increase production costs only marginally Potential elimination of tooling - direct production possible without costly and time consuming tooling Lightweight design - enables weight reduction via topological optimization using FEA Part consolidation - reducing assembly requirements by consolidating parts into a single component, even complete assemblies with moving parts possible Elimination of production steps - even complex objects will be manufactured in one process step

What is the file name for wireframe modeling?

IGES

Always use pack and go when doing assemblies. What is pack and go?

It gathers all related files (parts, assemblies, drawings, references, design tables, etc) for a model design into a folder or zip file Reduces filing errors by creating a more organized system with everything you need in one folder

How to orient part to reduce support structure

Lay parts flat when possible Design overhangs with slopes >45 degrees from the horizontal

Aerospace applications

Leading Edge Aviation Propulsion (LEAP) Engine: Part count reduction from 20 to 1, 25% lighter, stronger and lower cost to manufacture, CoCr material fabricated by DMLS Just a single kg reduction of weight can mean $3000 in fuel savings per year - Rick Kennedy The GE90 is one of the world's most powerful jet engines

Fused Deposition Modeling

Material Extrusion - (think hot glue gun) plastic or wax material is extruded through a nozzle that traces the part's cross section geometry layer by layer. The build material is usually supplied in filament form. There are two nozzles, one for support and one for the plastic. The plastic hardens immediately and then the platform lowers and the extrusion nozzle deposits another layer in the x-y plane

Polyjet Printing

Material Jetting - similar to inkjet printing but instead of drops of ink onto paper, it prints layers of curable liquid photopolymer onto a build tray. Fine layers accumulate to create a precise model. Where there are overhangs, the 3D printer jets a removable gel-like support material It can blend materials and colors!

PC-ABS

Mixture of ABS and polycarbonate Tensile strength 68 MPa Max temp it can withstand: 138 C

Parametric Feature-based Modeling

Models are created using a historical approach (model tree), models are parametric based (they are defined), basic actions are defined (extrude, revolve, pattern), relational intelligence is added

Direct Modeling

No direct knowledge of parametric values are needed, no history recorded

Boundary representation

Often used for finite element analysis

Part files vs. picture files

Part files contain information about relationships instead of pixel information, less memory needed to store the information, more processing and memory needed to understand the information

Constraint Types

Plane to plane - 1 degree of freedom Line to plane - 3 Line to line - 2 Point to plane - 3 Point to line - 1 Point to point - none

Selective Laser Sintering SLS

Powder Bed Fusion - Uses high power CO2 lasers to fuse plastic metal, or ceramic powder particles together, to form a solid model that has small grain size due to the high temperature = good mechanical properties. System consists of a laser, part chamber, and control system. Developed under sponsorship by the Defense Advanced Research Projects Agency (DARPA) and acquired in 2001 by 3D systems

How to improve accuracy, precision, and print time

Printer is less precise in XY than in Z Time is wasted in transition between layers and since shorter parts print faster than taller parts of comparable volume and geometry, it is better to have short geometries if possible

Additive Manufacturing vs. Subtractive Manufacturing

Put new material where you want it vs. take away existing material where you don't want it

Layer thickness will affect:

Resolution, accuracy, surface finish, time Thicker layers = stair-step effect Thinner layers = better resolution

What file is used for solid modeling?

STEP

What is the file name for surface modeling

STL

Geometry Approximations use what file?

STL - Standard Tessellation Language (STereoLithography) Approximates geometry with facets or straight lines and no information of color, material, texture

Layered Object Manufacturing (LOM)

Sheet Lamination - uses carbon-dioxide laser to form layers of paper with a polyethylene coating on the backside.

3D Printing Cons

Slow build rates - various inefficiencies in the process resulting from prototyping heritage High production costs - resulting from slow build rate and high cost of metal powder Considerable effort required for application design and for setting process parameters - complex set of around 180 material, process, and other parameters Manufacturing process - component anisotropy, surface finish and dimensional accuracy may be inferior, which requires post processing Discontinuous production process - use of non integrated systems prevents economies of scale Limited component size - size of producible component is limited by chamber size

New challenges in design

Things are harder to conceptualize, tolerances, division of labor, mass production

Wireframe Modeling

Uses only vertices and edges (points and lines), nothing is recorded about open faces or interior/exterior, cannot measure any properties Advantages: uses less computing capacity

Surface Modeling

Uses vertices, edges, and faces; 3 points = a plane (surface normal vector can then be computed), object is built using only triangles; nothing is recorded about the interior/extorior Disadvantages: Seam between triangles sometimes gaps (not water tight)

Types of AM

Vat Photo-polymerization Material Jetting Binder Jetting Material Extrusion Powder Bed Fusion Directed Energy Deposition Sheet Lamination

Stereolithography

Vat Photopolymerization - A laser beam traces a cross-section of the part pattern on the surface of the liquid resin. Exposure to the ultraviolet laser light cures and solidifies the pattern traced on the resin and joins it to the layer below. Platform descends by a distance equal to the thickness of a single layer, typically 0.05 - 0.15 mm and then a resin-filled blade sweeps across the cross section, re-coating it with new material (uses thermostats so the plastic cannot be remelting after this process)

Solid Modeling

Vertices, edges, faces, volume, density, strength, conductivity Used for assemblies and analysis Disadvantages: requires more computing power,

What is surface modeling used for?

Video games, animated movies

3D geometries can be represented using these methods

Wireframe Surface Solid

"Additive manufacturing will become the most important, most strategic, and most used manufacturing technology ever"

Wohlers 2012

Critical geometries should be placed in the _________!!!!

XY-Plane (especially lettering) Orientation when printing determines surface quality

Topology Optimization

a mathematical approach that optimizes the material layout within a given design space, for a given set of loads and boundary conditions such that the resulting layout meets a prescribed set of performance targets

Assemblies give the ability to create larger items that are compartmentalized by keeping track of _____________

coordinate systems

Contours

lining the outside before filling it in, makes it look good for ya (good for ya oh oh)

Topology model must account for

material properties, spatial constraints, applied loads, boundary conditions, machine capability, tool paths, build orientation

XY- plane

most 3D printers print layer by layer which means the nozzle stays in the xy-plane

Rapid Prototyping (RP)

most popular term for this technology during the 1990's when prototyping was the dominant use - including design and concept modeling, form and fit testing. The materials and economics were generally not acceptable for use beyond the prototype stage (Freeform Fabrication)

Tall skinny parts have the tendency to topple due to the force of the ____________

moving print head

Other assembly functions include

number of instances, location of part files, display properties

3D Printing (3DP)

term initially coined by MIT and has been widely adopted by the popular press, especially when relating to polymer-based desktop models

What is additive manufacturing?

the official industry standard term for all applications of the technology. It is defined as the process of joining materials to make objects from 3D model data usually layer upon layer, as opposed to subtractive manufacturing methodologies. Essentially categorized by: any shape, digital data, and layers

What is CAD?

the use of computer systems to aid in the creation, modification, analysis, or optimization of a design; used by architects, engineers, drafters, artists, and others to create precision drawings or technical illustrations. CAD software can be used to create two-dimensional (2-D) drawings or three-dimensional (3-D) models; the use of computer technology for design and design documentation. CAD software replaces manual drafting with an automated process.

Build Volume

total cubic volume the part will take up (xyz)

Additive manufacturing

typically used by the scientific and technical communities to emphasize the increased capabilities to manufacture commercially viable and field-ready components with appropriate quality and reliability. The term "additive" is meant to differentiate AM from conventional subtractive techniques

Z-direction

usually the object being printed moves in the Z-direction so that the next layer can be added

Stereolithography is used for

very complex geometries that could not otherwise be machined, produces clear or non opaque objects

In-fill

weight is due to the density of the in fills, more in-fills = more material/time

Build Bed

what the object will be printed on