I don't know if there is an "official" definition for the terms; I'll give you the usages I'm familiar with.
In electrical design, "front end" is commonly used to refer to data acquisition and "back end" usually refers to user interfaces.
In mechanical design, "front end" usually refers to elements that are included in the initial design work, prior to manufacture. "Back end" usually refers to elements incorporated as retro-fit or after manufacture has begun.
I am sure the usage is different in other industries (and maybe even within these), but I hope this has helped.
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Front end engineering design FEED is simply the engineering design of a project at the macro level. It is used by a contractor to develop detailed engineering design and calculations for final implementation of the project.
Generally we don't use the term back end design but assume it has to do with the "as builts" and design changes during implementation.
In mechanical design, "front end" usually refers to elements that are included in the initial design work, prior to manufacture. "Back end" usually refers to elements incorporated as retro-fit or after manufacture has begun.
I agree with the above statement, but a variation on this would be for custom manufacturing or for a capital equipment build (often the same thing). That would be where the "front end" refers to the initial stage of engineering design, or pre-engineering as it is often referred to. This includes gathering all the input from customers and previous builds and synthesizing a new design. The initial design may then get reviewed, internally by other functions within the organization, and externally by the customer and any consultants he may employ. Revisions to the initial design may then be negotiated and incorporated into the "front end" and a firm manufacturing/build schedule can be created.
At that time we can, as the saying goes, drive a stake in the ground. Any changes from that point forward would be part of the "back end" design, long before actual manufacturing begins. Usually this has financial and/or scheduling consequences, with ripple effects occurring as changes in one area may drive or require other changes as well, delays causing other delays, etc., a sort of "anti-synergy" of fixes and add-ons for items and specifications which were newly created or overlooked on the "front end".
However, "back end design" can also be good, as new technology, alternative components or materials, or a better way of doing things might be discovered during the early stages of material and component acquisition or during finalization of the detailed design. There may still be a cost associated with these positive changes, but the result could be a product or schedule improvement, or a cost reduction in other areas, which might offset the added cost.
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