CAD Design Hiring Contractors Good vs Bad Design Practices

8/10/2019 CAD Design Hiring Contractors Good vs Bad Design Practices

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CAD Design - Hiring Contractors, Good vs. Bad Design Practices and relateddownstream cost impacts.

Finding a qualified CAD Designer to Develop Your New Product Design Ideas can be a realchallenge. With the market penetration of CAD Software programs designed specifically for ease

of use and with all of the new Freelancer portals its become difficult for clients to distinguishbetween industry professionals and outright imposters. The cost implications of making thewrong contractor choice, especially for novice inventors can have terminal consequences on anyproject effort. The information provided within this guide will give the client somewhat of anoverview of what to look for when selecting a qualified CAD Designer who can help bring newproduct ideas to market.

Intro - The successful development of products can rely heavily on the fidelity of theengineering design files and the legacy produced by them. Overall programdevelopment costs and downstream functions like manufacturing necessitate goodworkmanship and a level of quality delivered by the service providers selected to createthe initial CAD data. As within any industry, there are qualified professionals and thereare lower level enthusiasts . Capabilities or lack there-of, may not be truly apparentuntil after having contracted with a service provider and after having commenced aninitial program effort. Sometimes poor decision s arent apparent until after havingreached or exceeded some proposed budgetary limit. With online contracting andfreelancer websites like oDesk, metrics of quality rely upon a system of feedback basedupon client experience, contractor claims of workmanship in the form of a portfoliowhich may not even represent their own workmanship and lastly, an automated systemof standardized testing which can be cheated. This type of qualification system is by nomeans a substitute for real world, traditional credential and resume building where skillsand workmanship are qualified by career superiors that have worked within the field forlonger periods of time and have acquired these very same skills which are beingclaimed. With the market availability of highly user friendly CAD software programs likeSolidworks and Google Sketchup it has never been easier for beginners and recreationalCAD users who lack formal training, real world experience and engineering knowledge toattempt to author original designs and subsequently offer product design services tounsuspecting clients. In the CAD Design world it's not uncommon to hire contactorswhich promise to engineer the original product ideas while the client waits expectantlyfor a "Picasso" but then receives a "paint by numbers" design instead. Sometimes theclients due to unfamiliarity with the development process can't tell the difference andpay for data that is ultimately rejected by the manufacturers selected to produce theend product. Building upon the right or wrong foundation of CAD Data can mean thedifference between a sustainable development effort and one that deadlocks against anexpended budget with nothing to show for it. This guide provides an overview of threeareas of proficiency to assess when identifying a qualified contract CAD Designer. Byusing these areas of assessment you will increase your chances for success while savingmoney and ensure the creation of a data legacy to support subsequent efforts.


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4 Sufficient wall thicknesses which support integrated features like recessed areasfor labeling, fastener attachment points and "reveal lines". Reveals are cosmeticfeatures that allow for assembly mismatch between parts due to dimensionalvariations in manufacturing processes. Having sufficient walls will also insurethings like durability, impact resistance and "mold flow" which is an aspect of themolding process that can affect overall part quality and eliminate the risk ofproduction scrap. Certain products or part geometries and materials will haveminimum requirements or "thumb rules" that dictate things like wall thicknesses.

5 Coring (if applicable) which is critical for controlling the dimensional stability ofmolded parts. Coring is the removal of excess material on otherwisenonfunctional / non critical geometries that may otherwise "sink", distortadjacent features when cooling or impede material flow into the injection moldcavity resulting in "shuts" or "non-fills" and scrapped production lots.

6 Draft is required for the successful removal or "ejection" of parts from themolds. This is a "taper" feature applied to all surfaces which are "in the line ofdraw" or the direction of separation of the mold. Some draft features can befairly complex and require a great deal of creativity and understanding of moldconstruction in order to integrate into a part design.

7 Snaps, Living Hinges and Assembly Features require a certain skill level in orderto implement successfully into product designs. A skilled designer will know howto integrate these attachment features within "steel safe" tolerance limits whichis a term used to describe molded parts as having these features designed in away such that they can be optimized to best performance by making simple and

cost effective adjustments to the molds. This is a fairly standard practice.

When evaluating a CAD design of molded parts and assemblies, examples of things tolook out for and that signify poor quality workmanship

8 Missing or improper use of rounds, stress risers and hard edges in areas thatmay see higher mechanical stresses when the parts are in use. A good designwill employ a liberal use of rounding and surface transitioning which strengthenparts and improve moldability.

9 Knife Edges are as the name implies sharp, narrowly terminated features that

should not be present unless they are absolutely critical to function which is nottypical.

10 Non-Uniform Wall Thicknesses are usually the first clue to poor workmanship.Molded parts should have uniform material thicknesses throughout the partdesign.


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11 Undercuts and Die Locks are features that literally cannot be molded. These arefeatures that require the mold steel to be evacuated from the part features usingelaborate mechanisms (slides, walkouts, hand loaded cores, side actions, etc.)that can make the tool cost prohibitive. Undercuts can be done using passthrough "shut off" features but integrating these into a design requiresknowledge that quite frankly is esoteric to the novice designer.


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Part 2 Familiarity with CAD Software Programs, Native and Advanced Functionality

Clients often select contractors based solely on cost and simply because that person isequipped with a workstation, a CAD program and some basic knowledge of thesoftware. This is flawed thinking and is often costly. Some CAD applications can behighly sophisticated and programmed with advanced design functionality that only asmall percentage of it's users ever become proficient with. These are the real,experienced experts that not only bring concepts out and into the visual realm but canactually bring them successfully into the manufacturing space as well. Having access toa CAD program no more qualifies a user to design products than owning an automobilequalifies a driver to compete in the Indy 500. In many cases, so called expert usersmay not even have legal and licensed software installations which should be a red flag.

The CAD software market is vast with an array of applications, native functionalities,

modules and ad-on extensions that facilitate a broad range of engineering and designtasks. In an attempt to capture market share and increase sales, products likeSolidworks were introduced and marketed to newer users who were seeking a cost-capable solution with a user friendly icon based graphical interface. The intuitive natureof this interface alone has simplified basic CAD Modeling operations to the point thatanyone with little to no experience at all can build simple to intermediate geometriesand present primitive concepts. The drawback to having a market saturated with theseuser friendly CAD applications is that it becomes increasingly difficult to identify andconnect with the kinds of specialized and talented service providers that a client mayneed to actually bring their specific products successfully and economically to a

commercialized state. Simple laws of supply and demand have basically left freelancedesigners with a growing pool of competition, declining hourly rates and consequently ahigher incidence of low quality workmanship.

When seeking out qualified individuals to design your original products consider thekinds of tools a CAD Designer uses or has had experience with. If a client is seeking thedevelopment of plastic injection molded parts and designs that incorporate elaborateand aesthetically complex shapes then perhaps Solidworks or Google Sketchup are notthe ideal tools for this kind of work. There are a number of higher end applications likeUnigraphics, CATIA and PTC's Pro Engineer which are used to author complex surface

geometries and allow the seasoned user to create very robust and stable engineeringdata. Most reputable manufacturers in China are still using ProE, UG and Catia due totheir more robust platforms. If a user has been designing products successfully with aprogram like Pro E it's likely that you are dealing with a professional since proficiencywith this type of system and it's functionality is not easily acquired by recreational usersor enthusiasts that lack hours of design time.


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Part 3 CAD Modeling Technique and Methodology

The effective modeling of 3D CAD Designs requires a mixture of three things

1 art - the creative ability to rationalize forms within a 3D spatial environment

2 engineering - a basic academic or even intuitive knowledge of physical structures

3 programming - an understanding of algorithms and conditional parameters

Many self-proclaimed "expert" CAD designers fly under the radar with basic artisticability but lack the engineering experience to support intelligent design decisions. Theartistic element is important especially when developing consumer products that requirea degree of aesthetics but without a practical knowledge of how certain structures reactto things like mechanical stresses and strains then the CAD Data produced by these "3D

Generalists" may be nothing more than virtual paper weight. The programming aspectof valuable CAD Designs has more to do with database flexibility and how easysubsequent design changes will be once a 3D CAD Model or database is constructed.Most CAD Designers are not deeply versed in building clean, flexible, stable models andassemblies. This is a proficiency that is relegated to the top flight of talent in this field.The main advantage to working with a well thought out and algorithmically solid CADdatabase is that a little forethought with respect to anticipated changes means thatthose subsequent changes can be quickly and easily implemented without incidentfurther into the design cycle. This can save on considerable labor costs and lead timeespecially when scheduling becomes more critical.

The modeling of parts and assemblies in 3D CAD can be done by such a wide variety oftechniques and the uniqueness to which any individual CAD Designer appliesmethodology that no two databases are ever alike. Two designers could be givenidentical sample parts to model in CAD and the result will be identical 3D geometries butthere could be a major discrepancy between the data and features used to "program" orbuild the CAD files. In the programming world "good code" is often a description givento a program or sub routine that performs a desired function while utilizing the fewestlines of code, least amount of memory and is easily interpreted and edited by otherusers. Efficient CAD Modeling necessitates the use of these very programming

principles and a "good database" will have fewer, more intelligent features and isportable meaning it's easy to navigate when handed off to other users for furtherdevelopment functions.


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3D CAD Models can be comprised of a number of different classes of geometry. Aproficient CAD Designer will have a skill set that involves having worked with all of theseand knows how to apply the mixture of proficiencies to create good, clean, flexible yet

stable CAD Files. The general classifications are boundary representations and wireframes that lack surface or volume

characteristics

surface models or skins that have surface characteristics but lack volume

boolean and IGES solids that have volume and surface characteristics but aredifficult to edit

Feature Based Parametrics which can have a significant degree of intelligenceand can be highly flexible and editable

The majority of products developed in 3D CAD are built using Feature Based ParametricModeling programs. A feature is a physical attribute command applied to a 3D PartModel that either results in material volume being added or subtracted to/from a largerindependent base parent geometry in order to produce some final net dependent

child geometry. The associative relationship between the parent / children meansthat changes applied to the parent will affect the child but not the other way around. Ifyou delete the parent feature the child feature is deleted with it but the child may bedeleted and the parent structure remains. These geometries are known as

associative. The information used to derive the feature geometry can be either pre-

programmed using native functionality of the software or the information can be drivenby sketched orthographic sections using 2D functionality. The proportionality andnumerical dimensions controlling orthographic sections, shape and size of features arereferred to as parameters and can slave off of equations or table data managed within aspreadsheet.

Feature based parametric modeling when fully utilized can be extremely powerful withrespect to modifying designs and making changes efficiently. But again, the right tool inthe wrong hands can produce undesirable results. For example, if an inexperienceduser fails to establish appropriate values for settings like model accuracy then an

entire database c an crash under rebuild or regeneration errors when prototypersrequest higher precision to drive their processes and the database must be modified.Model accuracy controls the precision to which a system mathematically calculatestheoretical boundary intersections and vertices within CAD geometry. These data basecrashes can occur even after countless labor hours have been invested developing theCAD geometries for the final product design. These are serious problems that do occuroften requiring the need for additional labor or CAD File Repair.


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A good clean CAD database will incorporate features like advanced rounds in place ofsurfaces made up of many intermediate features, complex curve networks and boundarycontrols to approximate tangencies and edge transitions. Instead of using theseadvanced functionalities, some designers will spend exorbitant amounts of time trying tobuild these types of non- flexible and complex surface patches and literally boxthemselves into non-flexible and unstable models that cannot be further edited withoutrework. In some cases designers have been known to abandon project efforts afterboxing in with unstable data and then expect the client to absorb the loss and to changeservice providers in the midst of the project. Its not uncommon for a designer to sendcorrupted or unstable export files to vendors, manufacturers or other service providersas a result of bad modeling practices. If a CAD model fails to solidify on export forexample then it cannot be used to support volume calculations needed for things like

shot sizes. Mold Flow and Finite Element Analysis functions also require good, cleansolid models. Again, the fidelity of these CAD file geometries will impact subsequentdevelopment, engineering, analysis and manufacturing functions and can either savetime and money or require costly CAD Data Repair.

In summary there are certain skill requirements to consider in determining whether aservice provider is capable of producing the kind of data legacy required for a successfulproduct development effort. The right kind of talents can improve the communication ofideas, establish a platform for revision control in modifications and concept refinement,and will give the client deliverables that integrate seamlessly into the manufacturing andassembly processes. In almost all cases, economic feasibility is always of concern and inorder to stay within budgetary limits it's imperative that the service providers selectedare able to perform within the three major areas of proficiency outlined in this guide and

can deliver quality at every phase of development.

CAD Design Hiring Contractors Good vs Bad Design Practices

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