How do engineers design products?

Your teacher was right. Designers use the right brain, engineers use the left brain. I see it every day at my job, and engineers know nothing about "design". Function first, and then let the designers try to package it.

Dependence of product. Product can be in various forms as some can which is making in million pieces or one factory which is build as one item. Engineers often have a requirement list and budget, designers haven't budget and it's main difference which squeze engineers mind.
Today is a lot of information and main problem is that that engineers education is focused on one branch and usually neglected other disciplines as botany, zoology, medicine ... In infoworld we cannot know all but where is a truth information.

There are many things to think about:
1. The working parts need to be designed to perform the function required (stress analysis may be used to ensure sufficient strength).
2. Lubrication of moving parts with bearings, low friction materials, oil etc.
3. Supporting structure. To withstand forces of the function, environment and foreseeable abuse (stress analysis may be used)
4. Assembly (deciding where one part ends and another begins and deciding which fasteners to use)
5. Manufacture. It should be easy to make each part and to assemble the parts using appropriate tools.
6. Compliance: Regulatory requirements such as Health and Safety and EMC.
7. Ergonomics. It should be comfortable to use and easy to understand (this is often neglected).
8. Aesthetics: If it looks wrong, it probably is. Good looks can be important to marketing but not always.
9. Generally maximise the ‘selling points’, reliability and durability.
10. Generally minimise the cost. This can be dependent on the quantity required. The cheapest solution to make one product can be very different to the cheapest solution for a thousand.
11. Sensible compromises. Improving the product on one respect usually means making it worse in another.
As you can see, there is much to think about (usually all at once). Aesthetics plays a part but is only one consideration amongst many and a balanced view needs to be taken.

Hi Racehouse
to much to write about but have a read here....
http://en.wikipedia.org/wiki/Design_engineer

I see more complicated than I though. I used to think engineers did things the way they did because thats how they though but you are restricted to think about many things and dont have the freedom of design designers do. thanx a lot guys your input is much appreciated.

Engineers make things work where as designers can only conceptualize it. Also it is often found that people think a good design means good aesthetics but it is not so. Say you are designing a refrigerator a good design ensures that the refrigeration cycle is perfect, its not necessarily important to make it look good.