Capabilities And Limitations Of Computer Based Models

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Before solid modelling software came into use, designers used to build prototypes for the purpose of evaluation of the product under design. The costs of such prototypes was usually prohibitive, taking into account the many details that had to be machined using steel. This scenario drove producers to seek more cost effective ways of coming up with prototypes. Computer based 3D modelling stood out as the best and most cost effective. Precise models of products or product parts are now able to be created using solid modelling software (Khemani, 2020).

Solid modelling involves an incremental process. First of all, designers specify points, lines and surfaces, and join them together to electronically represent the boundaries of the object under design. Designers may also choose to select models of simple shapes such as cubes and cylinders, dimension them as required, position and orientate them as needed and then combine the different models into a 3D model. The result is a complete and detailed digital representation of the geometry of an object. Two main approaches can be used to come up with the 3D models. The first approach is through the use of a graphical user interface. Alternatively, the designer can create 3D models through a programming interface. The graphical user interface approach is generally preferred by many designers because of its relative simplicity. Programming is not a discipline the majority of designers would like to get into (Dadi et. al, 2014).

Over the last 40 years, the art of 3D solid modelling has been constantly developing and increasing in complexity. As of now, solid modelling is one of the most used tools in representing products and product parts and so that design calculations can be performed on them. Dozens of commercial solid modelling software are now in the market. 3D modelling is now a multi-billion dollar market. Most of the software are founded on elaborate 3D graphic techniques. The main aim is to come up with photorealistic renderings of products or product parts. Applying animations to the 3D models is also possible, and this enables the design team to better visualize the object while still in the design stage (Dadi et. al, 2014).

Computer based 3D modelling has significantly reduced manufacturing costs. It has also improved product quality since engineers get to assess all the features of a product and alter the design as many times as they wish before embarking on the actual manufacturing process. With 3D models, engineers are saved the burden of engaging in low level and non-creative tasks in the course of designing products. 3D models also help engineers in evaluating the manufacturability and assemblability of products before going to the actual manufacturing. Such models help design persons to generate all the information required in the production of the products being modelled. They also enable engineers to concentrate on the conceptual high level decisions as regards designing. For any design decision the engineers make, the 3D modelling software is able to highlight the consequences of such decisions. In addition, the engineers are also able to get plan suggestions for the product under design (Dvorak, 1998).

One of the major advantages of 3D solid modelling is that it enables the designer to see the object as if it were the final end product. 3D solid models can also be viewed from all angles, thus enabling the designer to make it look exactly as he wants it to be. This way, the designer is nearly 100% sure of how the object will look like before moving on to the actual manufacturing process. By having a perfect idea of the final looks of the object, the designer can propose relevant changes to the design before it is too late (Dvorak, 1998).

Another advantage of 3D modelling is that it enables engineers to simulate real life conditions such as stress or live loading. One of the aims of designing is to come up with a strong structural components that can withstand the forces that will be subjected to it while in use. 3D modelling software makes it possible for design engineers to virtually load the component under design and assess its behaviour under loading. The possible failure modes of the object can be determined. It is at this point that the design engineer can decide how to alter the object so that it can perform efficiently. This can be through increasing the dimensions of the object or using an alternative material with better engineering characteristics (Yoshida and Shiiba, 2002).

3D models come in handy when making a presentation on the object to a team of the relevant stakeholders. One only requires a computer with the software installed, and the team can objectively critique the object by looking at its various design features. Instead of using a lot of words to explain, a 3-D rendering of the object speaks volumes of itself. 3D models can also be subsequently used for Computer Aided Manufacturing. Once the 3D design is complete, the same points, lines and surfaces can be used to generate the toolpaths that will machine the object into its desired shape, dimensions and configuration (Yoshida and Shiiba, 2002).

3D models allow for mass and volumetric analysis. For instance, the weight, mass, volume, and inertia of the object under design can be assessed. The behaviour of the object under different masses can be analysed and the best size selected. This is not possible with the older method of physically creating a prototype of the product under design. Another advantage of 3D solid modelling is its parametric nature. This means that changes to the size and other details of the object can be made retrospectively. The value of any given parameter can be altered and the effects of such alteration be analysed as they reflect through the entire system (3D systems, 2020).

3D models can be exported into a large variety of file formats for use in different scenarios. For instance, a PDF file of the modelled object can be created for incorporation into design briefs or reports. A JPEG image of the 3D model can be used to share the design across photo-sharing platforms (3D systems, 2020).

One limitation of 3D solid modelling is the large amount of computer memory it requires. The software for modelling in 3D are usually heavy. Many computers purchased in some 10 or more years back may not adequately support 3D modelling software. An upgrade is required of the computer or even better a fresh purchase of the new generation computers. The 3D modelling process can also be slow even for the competent designers. The level of detailing required is usually high and this consumes quite a lot of time. In addition, some manipulations may be complicated and may prove quite tedious to handle them. Also, the number of iterations in 3D solid modelling is just too much. One can only work one point at a time on the screen. Most 3D software require working with entity types. As such, a curve cannot be transformed to an arc nor a spline into a straight line. Also, there are instances where it is important to touch and feel the physical model of a product before production, to feel its texture and the composition of materials used. 3D models are only virtual and intangible. 3D modelling software is very expensive and can only be purchased by a few individuals and companies (Kimura, 2001).

Regarding the mounting bracket for the hydraulic pump, using the 3D modelling software is very effective. As mentioned in the above discussion, 3D modelling software have the ability to analyse how changes in a specific parameter affect the overall engineering properties of the object under design. For instance, in this mounting bracket, weight varies in direct proportion to the thickness of the bracket. Weight is a function of volume given that one can calculate the mass of the mounting bracket by multiplying the density by the volume, and subsequently multiply the result by the gravitational acceleration to obtain the weight. All these formulas are fed into the software, such that the alteration of any particular parameter changes all the other related values in the system. This is easy and very straightforward. It saves a lot of time. The design can be altered iteratively until the desired engineering characteristic is achieved. The mounting bracket in question only requires a change in the thickness while the cross section remains the same. The process is also very cost effective as compared to physically modelling the object for the team of designers to critique.

Computer based modelling has of late gained significant popularity in many engineering firms. Design engineers usually use computer based modelling to analyze 'what if' scenarios. It is particularly useful in situations where applying changes to the real system has high cost implications and is impractical. A good example is in the design of buildings. It is impractical to construct a concrete framed storey building and then physically apply the loads so as to study the behaviour of the structure under loading. This is more efficiently done using computer based modelling. The most obvious application is structural calculations. This is closely related to 2D and 3/D drawings. The combination is a very efficient way of analysing construction alternatives. The 3D software in use produces design data that can be used throughout the life cycle of the building - right from the project development to construction and further refurbishment of a building. Taking the example of a column, computer based modelling can be used to analyse the effect of reducing the column sizes below a particular minimum. Given the live loading on a building is constant, the cross section area of the column and the reinforcement bars determine whether the structure is capable of bearing the loads or will fail upon loading. The design team may want to reduce the column sizes arguing that they are overly sized and non-economical. Computer based modelling has the ability to prove them right or wrong by analysing the consequences of reducing the column dimensions. What happens is that drawing elements in the CAD software are vector based. This applies to points, lines, and surfaces. Linking all these elements results in a connected model with parts that are dependent on each other. Changes in one part of the model influence changes in other parts of the model (Khemani, 2020).

This is the major principle used in Building Information Modelling. BIM takes 3D modelling even further by linking the elements to costs (McFarlane, 2002). A change in the thickness of a particular reinforcement bars can show the changes in the overall cost of construction. The entire construction team is able to see such changes in real time provided they have the software with them. 3D computer based modelling is also useful in structural optimisation through the finite element method. It is also widely applied in cost estimation through quantity calculations. Such processes are iterative in nature and would be extremely tedious if they were to be done by hand. 3D computer based modelling has simplified these and many other construction design procedures.

References

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• Dadi, G., Goodrum, P., Taylor, T. and Maloney, W. (2014). Effectiveness of communication of spatial engineering information through 3D CAD and 3D printed models. Visualization in Engineering, 2(1).
• Dvorak, P. (1998). The advantages of solid modeling in product development. [online] Machine Design. Available at: https://www.machinedesign.com/archive/article/21818555/the-advantages-of-solid-modeling-in-product-development [Accessed 1 Feb. 2020].
• Khemani, H. (2020). What is Solid Modeling? 3D CAD Software. Applications of Solid Modeling.. [online] Bright Hub Engineering. Available at: https://www.brighthubengineering.com/cad-autocad-reviews-tips/19623-applications-of-cad-software-what-is-solid-modeling/ [Accessed 1 Feb. 2020].
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