The critical can opener usability features and manufacturing process necessary to achieve them are as follows:
*Ease of cutting:A hard blade makes cutting easier.The desired hardness can be achieved by proper heat treatment of the blade.
*Smoothness of lid cutting:The cutting edge should be sharp enough to rip through the can lid.This can be achieved by appropriate swaging of the blades edge.
*Slip-free operation:This characteristic depends on how tightly and smoothly the drive sprocket rolls on the outside of the can rim.
*Safety in handling:The can opener should be free from sharp edges and burrs.
*Comfortable grip:A comfortable grip is ensured by smoothening the surface of the handle and radiusing the edge.
*Appearance and durability:This depends on the surface preparation and coating.

PRODUCT DEVELOPMENT for the USABILITY of a TOASTER:

USER REQUIREMENTS
Some Primary usability requirements:
1.Functional requirements:
*a toaster should produce a toast of ideal golden brown.
*a toast should be uniformly browned over the entire slice on both sides.
*a toasting action should not take too long.
2.Ease of use:
*the controls such as push down lever and sliding knob should be easy to operate.
*the controls should be conveniently located(some designs,the slide down lever is placed along the slide panel.)
3.Aesthetics:
*the overall external appearance should be pleasant and stylish.
4.Maintainability
*removal of bread crumbs should be easy.
*the outside of the toaster should not stain permanently
5.Reliability:
*since a toaster is intended for daily use by the entire family,it should be sturdy enough to perform reliability.It should be durable.
6.Energy consumption:
*the electrical energy consumption should be minimized.Although a toaster does not cost too much in terms of energy cost,it does draw a fairly large amount of current.
7.Safety:
*the outside of the toaster should not be so hot as to burn the skin.
*the toaster should protect the user from being electrocuted.
8.Recyclability:
*at the end of its useful life,the toaster should be easy to dismantle and dispose of.The parts of the toaster should be recyclability.


Some of the more commonly used fastening methods include:
>Integral fasteners:this constitute formed areas of the component part or parts that function by interfering or interlocking with other areas of assembly.
>Threaded fastener:separate components having internal or external threads for mechanically joining the parts.
>Rivets:used for fastening two or more pieces together by passing the body through the hole in each piece then clinching or forming a second head on the other head on the other end of the rivet body.
>Industrial stitching and stapling:fastening methods in which U-shaped stitches are formed from a coil of steel wire by a machine that applies the stitch.
>Shrink and expansion fits:composed of two normally interfering parts in which the interference been eliminated.
>Snap fit and slide fit:commonly used in plastic parts when frequently disassembly is needed for pats replacement.