What is a excellent injection mold could you define them?

That is a loaded question. It depends on a lot of factors. A good tool for what requirements? EAU's, product life cycle, material selection, etc.
I have run aluminum prototypes that were good tools, but not for long life, and I have run hardened, nickel chromed tools that were good, but for millions of parts/year.
In molding, it has been said for generations that nothing beats a good tool. If you have to stand on one leg to get the process safe and stable, than your in trouble.
Make the process you want and change the tool to accomodate.

That depends of what purpose with the mould is and what you are producing. In my opinion an excellent injection mould is characterized by being designed with as few moving parts as possible. The shaping parts should more or less be interchangeable. Furthermore there should be high accuracy in parting lines, as you don't want them to be visible on your produce. Spare parts should be easy to insert and change. That goes for all moulds. If you make a mould for medical parts there are several other issues: The surface of the product shouldn't be of a kind that "attracts" dirt, that gives some demands to the surface of the cavities. If the produce is used internally there definitely shouldn't be visible or touchable parting lines or edges. It should be made with a hot runner as you want as small injection marks as possible and you will have a shorter lead time and therefore higher production rate. You will also benefit from less waste than from the old fashioned string inlet.

A good injection mold is the tool that provides a broad process window, woth dimensional accuracy for the product, mechanically robust, reliable and dependable. The last place to shave program costs is in your tooling I agree with most of the provious posts, however I would specify standardized components in the tool to simplify preventive maintenance (I think the previous post alluded to this) Other factors enter in such as the product's end use, production volumns, etc. but at the end of it a good mold is the mold that meets the criteria and runs painlessly when needed. One last comment, Gregg is on the mark, you develop a solid process and tune the tool to the process in the end you have the quality solution.

hello everyone
thanks for your advice. truthful being a professional mold maker we must ensure our injection mold 's quality.after all pay attention on the quality is more worth than the price.
the reason for excellent injection molds always perfect in line with the customer 's plastic products . special for his structures and functions.
best regards!

one that meets the customers requirements, and makes you money.

hey Everyone,
I think customer requirement's is best solution for excellent injection moulding. injection moulding is very quick way and the production of any designing in some ways like development, tool, designing ,repair,maintenance
etc.
Thanks