What makes a great Technical Drawing?

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This is a question that comes up frequently. We all have our own opinion - often based on our industry and our companies needs.

What makes a good technical drawing a great technical drawing? I’m interested in hearing your views.

Is accuracy important? Or is it a given that all drawings should be correct? Should drawings be done to a standard? Is it more important that your drawing are done on time, or within the budgeted hours? Does the CAD part of the job matter? If the information you need to communicate is on the page – that’s good enough right?

I asked the same question in the AUGIAutodeskCADtutor and MCAD Forums and I had some fantastic responses.

Here are a few that really caught my eye. You can read my summary of the answers at the end of the post.

Here is a great response from Doug Barense On G+

Thoroughness, Readability and Accuracy, in that order.

https://plus.google.com/u/0/104641315693902919761/posts/AtAye7Ck9vc

 

And these in the AUGI CAD Manager’s forums:

From Tedg:

  1. Drawings need to be created to good drafting standards, lineweights, clarity, accuracy, to a given Cad Standard.
  2. Only enough detail for the purpose of scope and/or deliverables (ie: concept, 35% review, issued for bid, etc.).
  3. Keep within time/budget if possible, if the scope outweighs the budget; bring it up to the PM before you go over budget.
  4. Don’t over-dimesion! Dimension in one location like the plans, and reference them on details and sections, easier to change once instead of chasing them all.
  5. All disciplines’ drawings should match if possible, at least have the same building orientation. Of course there are exceptions like Civil will have grid north and Arch, Struct, MEP would have Plan North.

From Jaberwok:

Accuracy, Standards, Layout, Spelling.

http://forums.augi.com/showthread.php?141689-What-makes-a-great-technical-drawing&p=1184534#post1184534

 

Here’s a thought provoking response from Dean Saadallah on the Autodesk forums:

No set is perfect and a professional office providing the service should help manage a client’s expectations of this item

A client deadline should never be missed: do what it takes to meet it and ensure it’s a complete and accurate set

http://forums.autodesk.com/t5/CAD-Managers/What-makes-a-great-Technical-Drawing/td-p/3567228

 

Charles Bliss left this neat and succinct list on MCADforums:

Rule #1: The drawing should convey enough information to create the correct part without asking any questions.

Rule #2: The drawing should not have any ambiguity that leads to making too expensive of a part. This usually means the correct use of GD&T, proper finish call outs etc…

Rule #3: Add call outs to improve clarity. (leave nothing to chance)

http://www.mcadforums.com/forums/viewtopic.php?f=3&t=13051

 

This question as raised some great debate on CAD tutor forums. My favourite is his quote from Cecil Spencer, which was written in 1956 and supplied by ReMark:

[Our Drawings] must be so clear and complete that every one of the users arrives at exactly the same interpretation

http://www.cadtutor.net/forum/showthread.php?71629-What-makes-a-great-Technical-drawing/page2

 

I had this response from Jim Trujillo via Email:

‘Never, never let any outside force e.g. engineering, marketing ever have any input in establishing drawing content. What you will get are a lot of self proclaimed experts vying to justify their existence, without any thought as to the consequences.

I assume that  comment is tongue in cheek Jim (But I know how you feel!)

 

Summary

Here is my attempt to sum up all of our thoughts.

‘What makes a great Technical Drawing?’

Thoroughness

Technically correct, accurate, complete, consistent and unambiguous.

  • Check the brief (a lot – and at all stages of the drawing process).
  • Check your measurements.
  • Check your spelling.
  • Leave no questions unanswered.
  • Leave nothing for someone else to sort out or work out later.
  • If an extra hour spent checking the drawing pushes you over budget, it is still worth doing to ensure that no mistakes leave your office.
  • Don’t make the same mistake twice.

Brevity

Have you put too much information on the page? Less is more.

  • Only put on the drawing what needs to be on the drawing.
  • If you can get the point across with a written note – do that.
  • If you can get the point across with a hand drawn sketch – do that.
  • If a 3D model is going to be required to fully understand and explain the design – do that.
  • Don’t draw/model anything twice (Don’t leave yourself having to make the same edit in multiple places).
  • Don’t over dimension. Dimensions are an instruction – not a label.

Clarity

Will everyone who reads the drawing have the same interpretation? Does the drawing leave anything open to misinterpretation? Technical drawing is a method of communication – It’s a language.

  • Follow your National/Industry/Company CAD Standard.
  • Imagine your drawing has been dropped on the floor, stomped on, screwed up, had coffee/grease/lubricant split on it and then photocopied. Will the drawing still be clear and easy to read?!
  • Plan your drawing set in advance. Lead the reader through the set of drawings with call-outs and references.
  • Plan each drawing in advance, make sure that the layout is clear and logical – don’t be afraid of white space.
  • Don’t assume that the reader will understand your favourite abbreviations, hatches or lines colours. Include a legend or notes to explain non industry standard annotations.
  • Be certain that each drawing is easy to understand and easy to read.

Consideration

Fit for purpose drawings, on time and on budget!

  • The drawings shouldn’t leave any ambiguities or include any extras that will make the end product cost more that was expected.
  • Understand what it is your customer (the end user or users) needs from the drawings.
  • Understand what your client (your Boss) wants from the drawings.
  • Mange expectations of what you can realistically deliver.
Thanks very much to all who participated. The comments section is still open if you think of anything I’ve missed.
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Comments

  1. Nice topic Paul!
    In my opinion, technical drawing should be accurate, conform industry standards, well annotated and created in reasonable scale.
    We understand what objects are in the drawing because it is the industry standard.
    I’ve seen people plotting their drawing to smaller paper size, but don’t adjust the scale. So the drawing is very dense and hard to read. Unless you provide the drawing/dwf file, which is very easy to read on mobile device now.
    In the end, the technical drawing should be easy to understand and easy to read.

  2. So, first you mentioned accuracy, correctness, using standards, being on time, and being on budget. I’d say that it’s not a question of “either or” for any of these items. Ideally, they all should happen in a best case scenario, on any project.

    Then you mentioned just listing data/information in any fashion vs. taking care in the CAD presentation of data/information. I’d say that this item could be lumped into the category of linework. And nice linework is really what I think makes a good drawing great.

    Linework is a bit of an art form, and like I said, it is what comes to my mind in making a good drawing great.

    • Thanks Brian.
      Linework and Layouts can be tricky things to standardize if the projects you work on are not similar.

      ‘Drafter’s license’ is still required!

      Thanks for your comment.

  3. I think all of the points made so far are great. Hard to say anything different. I don’t buy into industry standards for drawing in some cases. However, there should certainly be a company standard so all drawings out of one company look the same. You shouldn’t be able to tell who produced the drawing without looking at the title block. So here are a few key points in no particular order:

    1. Don’t over dimension
    2. If it has no obvious purpose don’t put it on the drawing.
    3. Clear & Concise, so no fancy fonts.
    4. An easy to follow drawing numbering system, if your drawings are used outside the company a lot then there should be a key explaining how the numbering system works.
    5. Use Colour! <(Paul your comment editor says this is spelt incorrectly)
    6. Hatch sections relate to materials and are detailed in a legend.
    7. Accurate
    8. No point being on time & under budget if the drawing is going to cause costly mistakes. Its about balance, so everyone needs to have a clear understanding of what information needs to be presented. which brings me back to points 1 & 2.

  4. Chris H says:

    Disagree about use of colour. I’m one for use of correct line thicknesses and compliance to ISO standards. If drawings are reproduced i.e. photocopied then colour can be lost. Keep it simple.

    • I sort of side with Chris on that one.

      We swap a lot of PDF’s these days – so colour shouldn’t be a problem. Being able to stick colour views from an Inventor model on a sheet certainly helps explain what it is we are making.

      However, copying drawings (especially on site) is still an issue. I’d like to think that colour can be used intelligently – like in hatches where is wouldn’t matter too much if there was some loss of clarity due to reproduction.

  5. Ollie M says:

    This is really interesting because it’s the essence of what we are all striving to do. It’s a question I ask when interviewing potential CAD technicians and it’s also a question I ask myself when re-evaluating or setting up a new CAD system. It’s not static and what is right for one company may not be right (or less of a priority) for others. I always try to focus on the fundamentals of what we are trying to achieve. Communication, accuracy, unified production, stakeholder’s needs, the list goes on. I learned technical drawing with pens and a parallel motion and sometimes I think new versions of software are designed to save time but sometimes they cause make people think less, which doesn’t always make for a good CAD drawing. Thanks Paul, good post.

    • Thanks Ollie.

      In my new role as CAD manager at Halstock, I’m getting a lot of questions about ‘standards’. I have to make the point that everything we do is bespoke, so every project has it’s own requirements.

      It’s important that the drafters ask ‘is this good enough’, rather than simply following a prescribed route.

      It really helps me to bounce these sort of questions around. Thanks for your comments.

      Paul.