I remember my first job after graduation. It was a small company that sold CAx (CAD/CAM/CAE) software. A few colleagues and I would visit construction departments, that used drawing boards or various 2D (two-dimensional) design software. Our offer was based on software working in a 3D (three-dimensional) environment. The fascination of young people with the possibilities of this approach to design was directly proportional to the resistance of a large group of designers with many years of experience working in a 2D environment. When I recall this conflict of sorts, I come to the conclusion that:

• designing in 3D was a natural step in the development of tools to support this process, 
• the reduction in the time it takes to create geometry, manufacturing documentation, numerical analysis and product manufacturing processes is undeniable,
• the process of early prototyping on 3D printers would not have happened without such tools,

at the same time, I note that:

• the creation of manufacturing documentation – technical drawings, is often treated as the last – marginalized stage,
• people who define their role in the organization as Constructor often have a very superficial knowledge of manufacturing processes, claiming that this is not their responsibility, but that of the Technologist,
• 3D design has greatly reduced the need to develop handwritten, rapid sketching skills and spatial imagination,

and that

• the role of technical drawing is still the same, whether you are creating documentation in 2D or 3D. It is the main communication tool in the technical environment, a kind of language. There are advanced attempts to replace the drawing by recording technical information directly in the 3D environment, (MBD – Model-Based Definition), but also in this recording it will be necessary to follow the good practices mentioned in this article. 

The title question about drawing review, and in fact the attempt to answer it, is the result of working with many project teams facing similar challenges, which in my opinion can be minimized by planning and performing a professional review of drawing documentation.

The challenges I have in mind are, for example:

• starting the production of a component with a sub-supplier who, after producing the first parts, provides a control measurement report that differs from the one we get after taking measurements in our own laboratory – challenge: which report is the basis for evaluation?
• drawings of components or products within the same family refer to mutually exclusive standards and norms – challenge: which are needed and which are redundant? Is there a practical justification for a complaint received about any of these entries?
• quotes based on drawings of the first prototypes ordered from external suppliers are significantly lower than the final ones ordered for series production – challenge: cost overruns in the project budget, reduction of the assumed margin. 
• drawings sent to suppliers or passed to in-house production come back with information that they are not feasible – challenge: increased time to prepare documentation, potential delays in the project,
• part received does not match the other parts in the assembly, attached report shows no discrepancies with the technical drawing – challenge: is the part made correctly or not? Do we have a problem with other parts? The team is figuring out how to fix it, at a time when they should already be working on the next stage. 

In each of the examples given, there is more than one reason for the problem. However, in most of the cases I have dealt with, they have been caused by drawing errors or inaccuracies (which are also ultimately errors). 

Since they affect so many design aspects, I think they are worth looking into. The good news is, that they figured out how to do this a long time ago. Below is the way my supervisor showed me, in my first R&D department. It is very versatile and could be applied to any technical sector.  

In practice, it boils down to a few questions to ask yourself when reviewing a drawing. Before I get to them, however, I want to describe the team that will be reviewing the documentation, how to prepare for such a meeting and when to hold it. I will also give three key principles whose application guarantees a definite improvement in the quality of the technical documentation produced. 

Team.

The most important thing is for the team to be diverse, both in terms of experience and expectations of the drawings being reviewed. The technologist responsible for manufacturing will look for something different on the drawing, the metrologist who will be measuring the product and the customer who will be using the product in his application will look for something different. The diversity in terms of experience allows, on the one hand, practical learning for those who are starting out in their careers, and on the other hand, the questions they will be asked, are often a good reason to think about whether there is definitely room to make important and sometimes minor but necessary changes. Inviting clients and suppliers to review – saves time – which is in short supply on every project – and money – which is wasted through deficiencies or errors on redundant drawings. 

Preparation.

As for any meeting, it is also worth preparing for this one. A meeting can be arranged remotely. However, if possible, I prefer physical meetings. In this case, it is a good idea to print out a set of drawings for each participant to review. The scale of the printout must ensure good legibility of the drawing. Colored pens and highlighters will also definitely be needed. One person, who is responsible for preparing the next revision, writes all proposed modifications on his or her copy. 

If the company has checklists, the most important preparation step is for the drawing author to review the drawing with such a list and make all changes before the meeting. This saves a lot of time and attention can then be focused on the essential elements.

The meeting itself should be an open discussion, focusing on arguments and proposals. When organizing such a meeting for the first time, the amount of time needed can often be underestimated. We will certainly need more if we are reviewing a new type of drawing, for which a standard does not yet exist or needs to be completed. Depending on the level of preparation, the team’s experience and familiarity with the subject matter, for moderately complex details this can be from 15 minutes, to as much as two hours per drawing. Often several sessions are required. Once the changes have been made, it is imperative to bring the team together again for another review. So, that everyone (using their notes) can finally verify that their expectations are in the drawing.

Time.

As I have already mentioned, these types of meetings are time-consuming and require the team to come together. I suggest, that such reviews should be organized before each release of the next major revision of the drawing. In the case of product drawings, this could be a drawing:

• prepared for making the first prototype, 
• planned for the start of production of parts to be subjected to verification tests, 
• being the basis for the design of the manufacturing process, tools and machines,
• planned for handing over to the customer.

Rule 1 – use only one source of information 

EVERY piece of information contained in the technical documentation, MAY only be given in ONE place. 

This is a universal principle used in information management, that should be applied to technical documentation – including drawing documentation (SSOT – Single Source Of Truth or SPOT – Single Point Of Truth). 

For the moment, I will limit myself to drawing documentation only. I will give some examples that illustrate the most common errors caused by not applying this principle:

• the position of the hole was given on the main view and on the section. On the section, a tolerance has been added to the dimension, on the view it has not. Thus, there are two dimensions on the drawing relating to the same feature. One is tolerated, the other is not. Which notation should be respected? If we assume that a standard for general tolerances is given on the drawing, it may be, that the tolerance given next to the dimension and the one resulting from the standard are different. In both cases, the problem is the same: Which standard should be respected? The only good answer to this question is to leave one definition of the hole position on the drawing,
• the same situation as above, but the dimension is given with a tolerance on the detail drawing, and without a tolerance on the assembly drawing. The problem of ambiguous notation is the same. Except that in this case it is more difficult to find because the dimensions are placed on two different drawings,
• the material of which the detail is to be made has been defined in the detail drawing. The same material was referenced in the assembly drawing. After consultation with the supplier, it was decided to change the material definition. The change was only made on the detail drawing. Even, if we assume that the documentation was correctly supervised in the supervising system (PDM – Product Data Management), the system enforced the creation of a new index of the assembly drawing, but did not ensure (because this is not its function) that the material definition in this drawing was updated. As a result, there are two material definitions for the same part in the documentation. Which is the correct one? Without knowing the history and circumstances of this change, it is difficult to answer this question.
• The cited situation with a change of material definition may apply to any other feature referenced several times in one drawing or in several drawings.

Rule 2 – treat existing drawings as inspiration, not as a basis for copying

EVERYONE who releases a drawing (i.e. decides that a particular revision of a drawing is complete and can be used in the next design stage) is RESPONSIBLE for ALL information contained in the drawing, including that which they COPYED from previously released drawings. 

Those creating drawing documentation can start working on a new drawing in two ways: 

• create a new drawing or 
• use an existing drawing as the basis for a new one. 

The risk of not applying this principle is significantly higher for the second option. Those basing a new drawing on an existing drawing assume, that the drawing already released in the system is 100% correct and content can be copied from it without verifying its correctness. This is often not the case. A drawing treated as a base drawing is part of other documentation. Taken out of its context, it may be stripped of important information. Some of the information contained therein may have become outdated. One must also assume that someone may have made a mistake and released documentation with errors. Information from ‘base’ drawings can be taken as inspiration. It is absolutely necessary to verify their correctness and consistency with the newly created documentation. 

Rule 3 – as the author of the drawing you know everything about its content

EVERYONE who releases a drawing (i.e. decides that a drawing revision is complete and can be used in the next design stage) MUST be able to answer ALL of the following questions.

The following questions apply to each drawing element i.e. dimension, tolerance, plan, view, section, note, referenced standard, etc. 

• Why is this on the drawing? 

If no one on the team knows, perhaps it is irrelevant information and should be removed?

• What does it mean? 

Is the notation unambiguous? Does everyone on the team reviewing the drawing interpret the notation (dimension, tolerance, comment, note, ….) the same? If not, what should be added or removed to make the interpretation unambiguous?

• Who needs/who will use this information that is on the drawing? 

If no one needs it, perhaps it is irrelevant information and should be removed?

• What technology will the detail be made in?

Are the shape and manufacturing quality requirements feasible with the planned technology?

• Is the requirement measurable? 

Has the planned method of measurement/verification been confirmed by the person who will perform the measurement or has experience in performing such measurements? If the requirement is not measurable, what other requirement should it be replaced with?

• Has a dimensional chain analysis been performed for the key dimensions?

Analyses are worth reviewing, from the point of view of the components taken for analysis. This is often the last moment for possible changes. 

• Does the record comply with the required standards?

A standard can be a standard, an internal instruction or a customer specification. It is important that the necessary standards are referred to in the drawing and that all notations in the drawing comply with them. If the standards contradict each other to some extent, the author’s interpretation should be stated on the drawing. 

These are very general questions, that can be applied to virtually any type of technical drawing. For specific trades or types of drawings, it is worth considering the following questions. Dedicated checklists with questions can be prepared for the types of drawings, that are done the most, which definitely make the work easier and faster, both for the drawing authors and for the teams reviewing the documentation. 

To summarize. By applying a planned drawing review process and the few principles mentioned above, we can:

• easily ensure high, reproducible quality of technical documentation without the need for multiple revisions (FTR – First Time Right or RFT – Right First Time),
• produce unambiguous documentation that is understandable to all who use it (by allowing expectations and opinions to be exchanged),
• protect the documentation from mistakes that may be made during future modifications (single-source-of-truth principle),
• make the maintenance of a reproducible standard of documentation independent of the author and the location in which it was created (checklists and group reviews of documentation).