Break-in wear is what happens during the initial uses of the brand new machine. The moving components wear against each other to make the final shape and size adjustment that will help settle them into a stable relationship for the rest of the machine's operating life. This is an essential stage in the life of the machine that can greatly influence its performance throughout its lifespan.
There are many conflicting principles when it comes to breaking in new machines. Most machines are recommended to be broken in under light operating loads but there are also experts that advocate breaking in under normal or heavy load. There is also the issue of what lubrication products to use. There are industrial grease and lubricating oil that are specially formulated for breaking in engines and other equipment that some experts recommend against.
An argument for starting light and slowly increasing the power or load is to not work the machine too hard which can result to excessive wear. On the other hand, those that recommend heavy load argue that it is the best way to set the components, like pistons and cylinders.
With regards to the lubricant, those that are against the use of break in products argue that the break-in process should exposed the machines to its normal operating conditions, of which the special lubricants are not used on.
Because of how all evidences are mainly anecdotal, it can be confusing to know which method of breaking in best. The safest bet is to follow whatever is instructed by the manufacturer with regards to the break-in process so that if something goes wrong, you're likely protected by warranty.
