Design Realization/Detailed Design - Medical Device Design: Innovation from Concept to Market - page 175

about a design without the need for everyone to have an expensive copy of your software
(EDrawings is free). However you should be aware of two types of collaboration:
Asynchronous : This is commonly someone looking at a document, drawing, or file, then
commenting and sending it back or sending it to a group. This is the most obvious type of
collaboration if the partners are on opposite sides of the world. This is the most common
form of collaboration with CAD.
Synchronous : This is where partners look at each other, at the device, and comment at
the same time. This is clearly easy if all are in the same (or similar) time zone. Some
CAD systems come with this capability but most are asynchronous. Once again the
Internet comes to our rescue and software such as Skype enables us to have collaborative
meetings with relative ease.
One thing to be sure of, however, is data transmission. While programs such as EDrawings
help with communication they do not help with trials. If your manufacturer wants to try out the
design, this type of file does not help. Normally you would have to send your design in another
format. The most common type is an IGES file. This file contains a solid model of your design
and most CAD packages can import them with ease. Equally, most CAD packages also import
everyone else's file, but this is often more troublesome than using an IGES file.
Don't forget that this is still a meeting. As such you need documentary evidence for your DHF!
8.6.4 Reverse Engineering
I think you can see that the introduction of CAD is really starting to do wonders. Modern
CAD systems have the ability to import a digital “point cloud.” This point cloud is a
collection of x-y-z coordinates that describe the outer profile of a 3D object. Some typical
sources of such data are coordinate measuring machines, laser scanners, and CAT scan
data. If you are designing things to fit a human body then knowing the actual dimensions of
that body part is really useful. This point cloud data brings that shape into life; it is easily
converted into a surface model, which can then be converted to a solid. If you think this is all
far-fetched consider that maxillofacial surgeons are using this technique to develop implants
that are unique to the patient. Figures 8.11-8.13 illustrate typical devices to generate a point
cloud. Figure 8.14 demonstrates the transition from a point cloud to a solid model. Most CAD
packages do this automatically, to lesser or greater effect.
8.6.5 Engineering Drawings
At the very end, something has to be made. Therefore no matter how pretty your component
looks in CAD, an engineering drawing will be required for your DHF. Your CAD system
must have the ability to produce engineering drawings (to the relevant standard) with
relative ease (see Figure 8.10 ). Remember these are controlled documents so they need
revision numbers and if they change, just as with any document, a record of what has