Computer Aided Design, Manufacturing, and Engineering

In the electronics industry of today, companies emphasize betterquality, lower cost, and shorter lead time on their products in order tokeep up with their competitors. ACI Technologies (ACI) has beenutilizing Computer Aided Design (CAD), Computer Aided Manufacturing

(CAM), and Computer Aided Engineering (CAE) in its development ofadvanced electronics systems. CAD utilizes computer systems toassist in the creation, modification, analysis, and optimization of adesign [1]. Some of the more common programs to perform this type

continued on next page

Figure 1: The product cycle from design to production.

DESIGN PROCESS

MANUFACTURING PROCESS

CAE

Customer needDesign

definition andspecifications

Feasibility studyDesign

conceptualizationModeling Simulation

Design communication

and documentation

Design selection

Evaluation Optimization Design analysis

CAD

CAM

Process planning

Production planning

Design and procurementof tools

Material orderGeneration of NC, CNC

and DNC programs

Packaging

ShippingMarketing

ProductionQuality control Testing

of design work are SolidWorks, Creo, NX, and AutoCAD. CAM softwarewill check for interference between parts in an assembly and allowthe real time editing of the part from the assembly if necessary. Thereare many computer design tools for printed circuits as well. Most ofthese enable the designer to lay out a circuit, define integrated circuitparameters (package and pinouts), and then go directly to the printedcircuit board (PCB) layout and check that all circuits are completedaccording to design rules. Cadence and PADS are common tools inthe circuit design and PCB layout arena. CAM allows a manufacturerthe ability to use computer systems to plan, manage, and controlmanufacturing operations with internal or external plant productionresources. Mastercam and Autodesk Inventor are popular CAMsoftware tools. CAE is focused on using Finite Element Analysis (FEA)to analyze CAD geometry in its operational environment in an attemptto refine and optimize the design in pre and post production form.ANSYS, COMSOL, and Creo Simulate are examples of CAE software.Almost all of the CAD/CAM/CAE software available has the ability tocreate 3-D models of each part in an assembly, and then place theparts together using the proposed “mating” surfaces. Figure 1illustrates design through production of the product cycle.

Benefits

Product development costs can be reduced in pre-production designverification. The creation of engineering samples and the coordination

of the various engineering disciplines can help verify all phases of theproduct before committing to costly tooling costs. This reduces the timeand costs associated with rework due to unforeseen interferences. Thedesigners can check assembly tolerances and perform stack up analysesof the final assemblies using solid models of the individual components(Figure 2). Commercial off-the-shelf (COTS) parts are frequently availablefrom the component manufacturers in multiple 3-D formats in orderto seamlessly use their components in new customer designs. Designengineers can also use these models to perform stress and thermalanalyses by including actual material properties of the components.

3-D CAD software can also be used to make additive manufacturedprototypes using a process called stereo lithography. Stereolithography works by utilizing a laser to solidify a liquid polymer on thesurface. A platform moves the hardened polymer down about a tenthof a millimeter and the laser hardens the next layer. This process isrepeated until a full three dimensional model of the part has “printed.”There are many stereo lithography companies that can import a 3-DCAM file and print a full size polymer model of the component. Thequick turn ability of this process allows a functional prototype to be inthe hands of the design team within a day of laying out a part. Thespeed and low cost of the stereo lithography process can allow thedevelopers to mock up an assembly and check form and fit beforecutting metal or making expensive molds. Minor changes can beimplemented even before pre-production runs are started.

continued on next page

Figure 2: CAM assembly model containing COTS and custom parts tocheck for interferences.

Figure 3: Three dimensional model showing how board shape (green)was designed to fit with other COTS components (grey).

ACI Technologies, Inc. 1 International Plaza, Suite 600 Philadelphia, PA 19113 phone: 610.362.1200 web: www.aciusa.org

Training Center phone: 610.362.1295 email: registrar@aciusa.org

Helpline phone: 610.362.1320 email: helpline@aciusa.org

With the use of CAD/CAM/CAE software, the ACI design team hasbeen able to build prototype electronics to prove out designs. Thefollowing section gives a brief overview of a past project whereCAD/CAM/CAE were used to layout the components and set theoverall dimension requirements of PCBs. The considerations andprocess that was followed are described here.

Project Design Constraints

This project modeled some COTS components in detail usingSolidWorks to create a 3-D rendering of the parts. Some 3-D modelswere available from the manufacturer; some were created from 2-Ddrawings, and when there were no drawings or models available, ACIcreated models by measuring the actual components.

Custom components that were needed to interface with our housingand COTS parts were then designed. Using the overall sizerequirements for the system, the preferred form factor for eachsubsystem, and the size and material constraints of the COTScomponents, the layout of the custom assembly components couldbe completed (Figure 3).

Using the solid models to define the spacing of user interfacecomponents, PCB outlines, keep out areas, and mounting locationswere defined and documented. The board’s physical dimensions wereforwarded to ACI layout engineers along with the circuit schematicsand bill of materials for each board. Using this method, even the PCBlayouts were completed with a significant cost and time savings overthe three to four turns usually required.

Originally, the boxes that housed the systems were to be made fromsteel. Weight restrictions that were later imposed on the projectrequired the material to be changed to aluminum. The computermodels were then changed to reflect the material change. Afterchanging the three dimensional model of the assemblies, a simulatedstress analysis was done to find any stress points that may causepremature failure (Figure 4). The weak points that were found wereredesigned and strengthened, and the stress analysis was run again(Figure 5). Once the components were found to be strong enough,drawings were created from the models and the parts were fabricatedin aluminum.

As the project developed, customer-added requirements were quicklyevaluated by ACI and changes which impacted other components werefound using the modeling software’s interference detection feature.Sometimes a clearance hole was needed or electronic componentswere moved on the board. Other times it meant finding a place tomount a hardware part that did not interfere with the current layoutof a printed circuit board. The PCB layout software used in the projectallowed quick modification of the circuit boards and verification of theinterconnections between electrical components.

Conclusion

The use of Computer Aided Manufacturing requires thesynchronization of the many different engineering disciplines that gointo a preliminary design of a new product. Each member of the teammust be aware of the constraints of their section of the design,whether imposed by the customer requirements or by another’sdiscipline. The ACI team was in constant contact with each otherthroughout the design phase to ensure that any changes from onegroup did not adversely impact others.

For more information regarding Computer Aided Design (CAD),Computer Aided Manufacturing (CAM), and Computer AidedEngineering (CAE) at ACI, please contact the Helpline at 610.362.1320or via email to helpline@aciusa.org.

Reference:

[1] Groover, M.P. and Zimmers, E.W. CAD/CAM Computer-Aided Designand Manufacturing. Prentice Hall, Englewood Cliffs, NJ. 1984.

ACI Technologies

Figure 4: Stress analysis of aluminum bracket showing overstress atmounting tab.

Figure 5: Stress analysis of redesigned bracket showing less stress insolid model.

4 5