What we need to take into consideration when we design a product to get rid of tolerance problem.
When designing, here's a list of things to take into consideration or do as early in the design as possible in order to minimize tolerance issues:
1. Consider the process capability of the chosen production process for each custom part and how that affects the tolerance stackup.
2. Consider the tolerances of stock components.
3. Involve the suppliers, quality, and manufacturing people as soon as possible, getting tolerance and process buy-in earlier rather than later. Many times you will need to re-think a design because of process or assembly related tolerance requirements.
4. Base the datum reference frameworks of all your parts on 'functional datums' as much as practical in in order to minimize tolerance stack between mating components.
5. Design by default with overly generous clearance wherever possible.
Waiting until the end of a design effort to start thinking realistically about tolerances virtually guarantees that you will have tolerance related issues.
1. change dimension(s) and/or tolerance(s)
2. change dimensioning scheme
3. change design