Why is checking so important for a design – but so difficult to do?

By 23 August 2018 News No Comments
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3D CAD Models – Self Checks

Risk management throughout a project is a key factor to consider for it to be both commercially and technically successful. There are lots of tools – whether it’s Project Timeline Management, Failure Mode Effective Analysis, Failure Tree Analysis, Vendor Supply Review or Engineered Design Management etc.

However, the most common risk to any project is a result of human error. The further along the development road map you are, the bigger the headaches from simple mistakes! Design engineers often employ various checking techniques to ensure their drawings are thorough and error free. However, it’s common that the checking process just verifies the drawings are compliant to a system, as opposed to whether the design and drawing are truly correct for the design intent.

Here at Haughton Design we employ a highly structured checking process for all of the work we output. Whether its CAD design, engineering drawings or product design specifications. There’s potential for a slip up in them all! So how can each output be checked effectively without it taking too much time?

There are several types of reviews and checking processes which should be considered below but this article is mainly about effectively checking a 3D model:

  • Project Input Document – Check the design and drawing delivers to the input?
  • Preliminary Design Review – Does the early design meet the basic brief?
  • Finite Element Analysis – Is the design robust, can it handle it’s intended use?
  • Critical Design Review – Does the design meet the required specification?
  • Manufacturing Drawing Check – Can someone make the design to the design intent?
  • Manufacturing Data Check – Are the 3D file outputs correct to the 3D model?
  • Output Check – Are the correct parts and quantities being ordered?

One of the most effective methods to speed up the above process is a design self-check. Prior to requesting formal approval, it is essential to check your own work. A lot of time can be wasted by missing a view, or even forgetting to put a critical height/width/depth dimension onto a drawing. Doing a thorough self-check on each and every output can seem tedious but both the 3D models and 2D drawings should be self -checked. If done effectively, it can save you and the checking team lots of time in the long run.

Human error will always be present if just using a manual self-checking process. Therefore, we often use another tool, called an Augmented Self Check. An augmented self-check is a verification technique using the digital tools available in 3D modelling. At Haughton Design, we generally use SolidWorks as our main CAD platform for design development. SolidWorks contains incredibly useful, built in checking tools that, when used effectively, can save time and money on any project.

The typical SolidWorks evaluation tools HD use are:

  • Interference detection
  • Hole alignment
  • Thickness analysis
  • Draft analysis
  • Clearance verification
  • Geometry compare

Interference detection

Cross sectional views are often used to check for these types of errors. However, it’s typical for engineers to check only in two planes, around key areas of interest and forget about sometimes even the most simplest of component mates. Interference Detection identifies collisions between components and helps to examine and evaluate those collisions. It is also useful in complex assemblies, where it can be difficult to visually determine whether components interfere with each other. Other useful applications of this tool are to detect and verify sealing surfaces and analyse the compression of sealing O-rings or gaskets, or checking the interference fits between shafts and holes.

Hole Alignment

Hole Alignment checks whether holes are misaligned in assemblies. This is usually a quick 30 second check to verify that all the fasteners in the assembly will align up. These types of mistakes can sometimes be the most embarrassing to designers and engineers, especially when they’ve designed simple parts, not verified them in a prototype scenario, committed to production, and then found out that they don’t fit together. One of the most common errors, despite alignment, is mismatching tapping or fastener sizes.

Thickness Analysis

Thickness Analysis is a tool typically used for plastic moulded components. It analyses the model created and outputs a report based upon deviation in material thickness. The general rule of thumb is to keep a consistent wall thickness when designing moulded components, however it’s common for this not always to be possible. Highlighting these areas using this tool can be useful when presenting these areas to a senior/experienced engineer for approval.

Draft Analysis

Draft analysis is a tool typically used for plastic moulded parts to check the correct application of angular draft to the faces of the part. This check can quickly verify any anomalies with split lines and check that the core and cavity surfaces are designed correctly.

Clearance Verification

Clearance Verification checks the gap of acceptable designed clearance between multiple components within an assembly. This tool can quickly measure minimum distances between components – a good tool to use when designing dynamic assemblies with lots of moving parts.

Geometry Compare

Geometry Compare is a useful tool in the output stage of the design process. It can compare two components side by side and check the feature tree or overall geometry to analyse if they’re the same model, or if changes have been made. This tool can be used to check that your export model matches your native CAD file model, a design change has been implemented in a later revision, or that the manufactures production CAD data matches your latest released revision.

These are only a handful of the design checks that HD use to ensure our outputs are error free and that our designs work out of the box. The design reviews and the checking processes have been refined over the years of HD’s operation, and as our output grows, our quality of workmanship increases throughout all our work.