Design Realization/Detailed Design - Medical Device Design: Innovation from Concept to Market - page 178

changed must be made. Also you need to make sure that everyone is using the correct
versions, probably more so than in any other part of your processes, otherwise all will
fall apart. Hence make sure you control the release of engineering drawings and part
specifications with the utmost care.

8.6.6 Part Numbering
Some countries, such as Germany, demand that all parts of a medical device (if they are
removable) should be individually numbered. Logical part numbering is a bone of contention
with everyone. You need a sensible part numbering system that does not just suit your stores
but also suits your packers and the end-user. Once devised most CAD packages will allow you
to use the part numbers as your filing system. But it is so easy to go down an illogical path.
You will find part numbers that are totally intelligible for the stores, but the end-user has no
idea what is going on. My advice is to think of the end-user, or the person putting it together.
If the part numbering is logical it should help assembly. If the part numbering is simply
sequential (in the order drawn) it is not much better than useless. Choose wisely.

One part numbering system I have seen that seems fairly simple for the designer and the end-
user (but not all) is to use outlining as with textbook chapter titles. First you need to allocate
an overall identifier for the main device, say, X1; thereafter, just as with outlining, the number
grows in length. Hence:
X1000 is the part number for the overall device;
X1100 would be the part number for the 1st subassembly;
X1200 would be the part number for the 2nd subassembly, and so on.
If X1400 also had sub-subassemblies then these would be X1410, X1420, and so on (as
illustrated in Figure 8.15 ).
Notice that the last number in the first four digits is a zero - this indicates it is an assembly.
You need to decide how many digits there are in this sequence to allow you to accommodate
all of your subassemblies.

X1000

X1100

X1200 X1300

X1400

X1100.1

X1420

X1410

X1100.2

X1100.3

X1100.4

Figure 8.15
Illustration of the concept of part numbering.