What makes a great Technical Drawing?
August 2012 | Filed Under: Personal Posts
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?
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.
And these in the AUGI CAD Manager’s forums:
- Drawings need to be created to good drafting standards, lineweights, clarity, accuracy, to a given Cad Standard.
- Only enough detail for the purpose of scope and/or deliverables (ie: concept, 35% review, issued for bid, etc.).
- Keep within time/budget if possible, if the scope outweighs the budget; bring it up to the PM before you go over budget.
- 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.
- 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.
Accuracy, Standards, Layout, Spelling.
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
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)
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
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!)
Here is my attempt to sum up all of our thoughts.
‘What makes a great Technical Drawing?’
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.
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.
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.
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.