Go for speed
At first, it’s not a good idea to get the perfect parts. Just go for what is good enough. What you need to do is get the maximum number of off-the-shelf parts. Actually, it’s faster, cheaper and gives you the freedom to change the parts when required. If possible, you may want to go for items with short lead-times and variety.
When using off-the-shelf components, you will find custom pieces as well. Fabricating these pieces yourself is also a good idea. Actually, this is the fastest way. You can also tweak them as you find out that your initial design was not the best one. For these parts, using rapid prototyping methods is not a good idea. At this phase, you don’t need to make custom injection parts, especially if rapid prototyping components get you what you want.
As far as rapid prototyping goes, nothing is worse than ignoring something that is part of your learning process. If you think that you may need a stronger component, you should take steps to make it happen. At this point, you should not worry about cost, design or simplicity. You can take care of that later on.
Get Ready to iterate
Following the points given above, it will be possible for you to learn and discover that you need to change or get rid of some of your work. While doing so, you will experience an unexpected scenario. So, what is the solution? The solution will be there if you become iterate and flexible.