[Cuis] Economic Design

[Juan Vuletich]

Hi Folks,

When I was a kid, my father worked for a company that is generally 
regarded as a world leader in the automobile market: Mercedes Benz. I 
remember in the early 80's, an ad for a Basic compiler with advanced 
structured stuff from Pascal. The ad presented it as "the Mercedes of 
Basics". These guys were so serious when it comes to product quality, 
that comparing anything with them was synonym with "top quality". I 
still read from time to time old stuff from them, because I find their 
attitude inspiring.

Today I found an article in a 1974 issue of an internal magazine for the 
sales organization. It is called "Economic Design", and I was astonished 
by how directly the ideas apply to our field. Here it is, sightly 
abridged and translated from Spanish into English (my comments follow 
afterwards). I hope you enjoy it as much as I do.

-----------------------------------
Economic Design
(Mercedes Benz "Información de Venta", VII./VIII. 1974/2 A/II/031)

Criteria from our development department on a hot topic, equally 
interesting to both customers and salesmen.

The "economic design" subject plays a big part in our house. On one hand 
we must design for economic manufacture, so we can sell at good prices. 
On the other hand, we must reduce as much as possible the maintenance 
and repair costs for our customers. Unfortunately, these objectives 
might contradict each other, so we need to find a balance between them.

In early design phases we already try to have a small set of different 
groups and elements (for example, engines, transmissions, suspension 
parts) be enough for many different car models and types. We solve this 
by applying a system of interchangeable elements for the whole series. 
In this way it is possible to use big quantities of each group or part. 
This reduces manufacture cost of each one, and also simplifies the 
storage and logistics of spare parts.

These groups and their elements are subject of intensive tests both in 
the test bench and in the real world. In this way we can guarantee the 
required robustness and service life, while saving unnecessary expense 
in materials and machining. Value analysis is done to try to make even 
cheaper parts. Here, the crucial part is to state what stress can be 
demanded on each part. Exaggerated demands are always bad! From all 
this, we determine what expense in materials and machining are really 
required to meet the requirements in the simplest possible way. Costs 
and benefits must relate in a reasonable way.

But for car owners, not only purchase price is important. Later expenses 
are important too. Besides consumption of fuel, lubricants and tires, 
maintenance and repair costs impact considerably on profitability. 
Because of this, we try to design a maximum number of parts without 
maintenance, or at least, that seldom require it. Repairs must also be 
possible in the simplest way.

Later, when the product is manufactured in series, a statistics of 
warranty failures and voluntary repairs tells which parts fail the most. 
These are subject of rigorous examination, to quickly take action, for 
example, by adjusting manufacture process or part design. These 
corrections are then applied to the serial manufacture.

Design also impacts on repair costs after an accident. As the front-side 
collision is the most common kind of accident, all Mercedes Benz cars 
have the front fenders held with screws, not soldered, so they are easy 
to replace. Even soldered parts are designed to be easy to be partially 
replaced. The relevant procedures have been described in Mercedes 
workshop manuals since 1962.

In short, the Daimler Benz house is doing big efforts to make design 
help reduce costs. Current world economics will require these efforts to 
be intensified in the future.
-----------------------------

I think this text is a great lesson on software design.

It agrees with Dan Ingalls' wonderful "Design Principles Behind 
Smalltalk" 
http://classes.soe.ucsc.edu/cmps112/Spring03/readings/Ingalls81.html . 
Dan says "Good Design: A system should be built with a minimum set of 
unchangeable parts; those parts should be as general as possible; and 
all parts of the system should be held in a uniform framework. "

The Mercedes article also sheds new light on why simplicity in design is 
of paramount importance: It allows us to ship stuff that is better 
tested and more robust. It makes for a system that breaks less often and 
is easier to repair.

It also states that exaggerated requirements go against quality, by 
raising costs for no reason. Do "the simplest thing that could possibly 
work". "Make everything as simple as possible, but not simpler". In 
short, it reduces both short-term and long-term costs.

Cheers,
Juan Vuletich