Hand Sketching
Ron Graham
with numerous contributors
This summary results from an inquiry to newsgroup sci.engr by Ben Crane for "alternatives in training mechanical design engineers in the art of hand sketching." As he saw it, the choices were as follows:
  • have an engineering instructor teach basic drawing classes on-site
  • hire an artist with perspective drawing specialty to conduct the training
His idea was based on seeing CAD as a liability for early, conceptual design. This comment of course generated a cacaphony of responses from folks with an almost religious point of view. :-) This was because the discussion took of on pro-CAD v. anti-CAD aspects, finally degenerating in some corners into a debate over what constitutes a "Real Engineer." (This debate surfaces in these groups, for various reasons, a couple of times a year.) Since there could be no consensus achieved on this subject, no doubt Crane would be satisfied just to expand his range of choices.

This summary concentrates on conceptual design -- the earliest stages of product development -- only. During that period of product development, a case can be made for hand sketching as preferable over CAD for these reasons:

  • CAD calls for more detail than is necessary
  • CAD doesn't convey the idea rapidly enough -- especially if there's no drawing station nearby
  • CAD doesn't allow for quick changes -- especially if there are multiple design possibilities to consider
  • there may be no significant parts viewable via CAD
  • accuracy and detail aren't important
  • having options in design is important
  • your group may not be able to (or want to) brainstorm in front of the computer (it's not dynamic enough)
  • the CAD time investment requires that you know what you're designing before sitting down to the computer
  • there may not be enough time to learn (or find someone who knows) the CAD program or the drawing management system
Your mileage may vary on this. Some of the recent parametric packages (e.g. Pro/Engineer, Mechanical Desktop) make it pretty easy to change dimensions -- but the fact is that even they require dimensions to start out, and some designs get to that point after the idea is conveyed. Although some of you can create a CAD drawing easily and quickly, engineers who've been around will generally sketch on the [whiteboard, chalkboard, pad, envelope, napkin -- pick one] before even turning the computer on. But this isn't a zero-sum game: in general, software encourages attention to detail and working by hand encourages awareness of the big picture.

Alternatives in Conceptual Design

  • Bring in a veteran who's been drawing sketches in your shop for years. If you have one. Chances are, if you do, that veteran doesn't like being shackled to the computer anyway. :-)
  • Turn to a college Design program (e.g. architecture, interior, fashion, etc.) for help -- either consultation or training.
  • Contact a technical illustrator. Here are some online sources:

  • Get some software. Here are two online sources:

Be aware that these software packages have more in mind than drawing. Intent! is for full conceptualization.

While the capability to sketch effectively is not needed by everyone in your organization, it's essential to have in someone. This is a tool, just like CAD -- and you would think it essential to have CAD expertise in someone.

Advantages to Having Hand-Sketching Capability

  • Drawing by hand can reinforce some fundamental engineering skills:

    • selection of appropriate coordinate system
    • grasp of spatial relationships
    • design to available space
    • prediction of interferences
    • consideration to mass balancing
    • consideration to load path planning

  • Hand drawings are readily understandable by all shop personnel, regardless of educational background. (Disclaimer: you still need the dimensions, in the right places, to ultimately machine the part. You can use the sketch to prepare for the details later, or you can include the details in the sketch.)
  • Hand drawings are readily passed around to draw out ideas.

There are various types of sketches, depending on where you are in design:

Type of Sketch Information Delivered
thinking clarifies ideas (e.g. the "cocktail napkin")
prescribing scaling (for designers); repeatability; eliminates discretion of trades, machinists
talking guides discussion of ideas (e.g. improvements, ambiguities)

Reptar sketch
This was a first attempt at a sketch describing how this Reptar toy works. You can do something like this too, you know. :-)

It's important for engineers, especially young ones, to realize the importance of visual communication, especially in the early stages of design. Specifically, some familiarity with the following would help:

  • different views (e.g. perspective, orthogonal, isometric, etc.)
  • simple geometry, especially 30, 45, 60 and 90-degree angles
  • what information must be communicated by a drawing to enable manufacture
  • the differences in career path between the engineer and the designer (and an appreciation for what the veteran designer knows and the young engineer does not)
  • the risks in overdependence on software before a solid understanding of the design fundamentals involved
    • a tendency to overestimate second-order effects
    • a tendency to miss fundamental effects altogether due to the large amount of program output
    • a tendency to make faster mistakes, instead of fewer
  • the benefits of clear visual communication of designs (e.g. early knowledge of serious design constraints)
  • the constraints placed on any design by limited space
Sketching is not the only skill supplied by designers. Few young engineers are given significant training in these areas before they reach the job market:
  • interpretation of spec sheets
  • selection of vendors
  • sizing of support equipment
  • tolerancing
  • interference
  • fastening and joining
Some drawing skill enhances the engineer's grasp of these areas, and helps the engineer both understand and intelligently discuss spatial relationships. Young engineers will sometimes find that drawing/drafting courses are available in other majors if not in their own (e.g. look in Civil if not in Chemical). It's worth the while of undergraduate faculty to work sketching into design courses (if they haven't already); it's worth the while of managers to see that such skills are passed on to new hires.

Design Symbology

There are already families of graphical symbols available to represent most common devices in most engineering disciplines. And most of those are simple enough to sketch. Some rules applicable to graphical symbols for fluid power systems are as follows:

  1. Symbols show connections, flow paths, and the function of the component represented only. They do not indicate conditions occurring during transition from one flow path to another; nor do they indicate component construction or values, such as pressure or flow rate.
  2. Symbols do not indicate the location of ports, direction of shifting of spools, or position of control elements on actual components.
  3. Symbols may be rotated or reversed without altering their meaning except in cases of lines to reservoirs and vented manifolds.
  4. Symbols may be drawn in any size. [...but choose a size that readers can follow without eye strain...]
  5. Each symbol is drawn to show the normal or neutral condition of each component unless multiple circuit diagrams are furnished showing various phases of circuit operation.

You can guess that symbols for other types of devices follow similar rules of thumb.

References

Hanks, et. al. Rapid Viz: a New Method for the Rapid Visualization of Ideas. Crisp Publications, 1992. ISBN 1-56052-055-8
Hanks, et. al. Draw! a Visual Approach to Thinking, Learning, and Communicating. William Kauffman, N/A. ISBN 1-56052-054-X
Basic Diagrams and Systems
Military Standard, Mechanical Symbols (Other than Aeronautical, Aerospacecraft, and Spacecraft Use), Part 1, MIL-STD-17B-1.
Military Standard, Mechanical Symbols for Aeronautical, Aerospacecraft, and Spacecraft Use, Part 2, MIL-STD-17B-2.
Common Electrical Symbols

Contributors

Patrick Asselman, Jonathan Barnes, Paul Butler,
Richard Chandler, Ben Crane, Kelista Donovan,
"Hobdbcgv," Tom Hyde, Kurt Jaeger,
Dave Lawson, W. Letendre, Bob May,
Eric Mieczkowski, Doug Milliken, Paul R. Mitchell,
Jim Papadopoulos, "Paul," Chris Pollard,
Jonathan Priluck, Tony Rizzo, "RUSK,"
Jim Shockey, Gerhard N. Thoen, Christopher Wright,
S. Yoder

What You Can Do

  1. Find a way to show concepts quickly early.
  2. Find a way to prove the analyses later.
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