Quality control

• Quality Control


  Checking a product works and looks right before selling it
• Quality Control


  1. Ensures products are manufactured to a high enough standard

  2. Involves testing materials, products or components to check they've been made to a high enough standard and they meet the manufacturing specification
• Usually, only a sample of the materials, components or products are tested, as it would take too much time to check them all
• Tolerance


  The margin of error that is considered to be acceptable
• Tolerance


  • 20 mm measurement with a tolerance of ±0.5 mm has a lower limit of 19.5 mm and an upper limit of 20.5 mm
• Tolerances should be included on working drawings (in the manufacturing specification) to show the limits within which the product should be manufactured
• Components must be within the tolerance to pass through any size checks in quality control
• Go/No Go Fixtures


  • Check whether the size of a part is within its tolerance
  • Usually double-ended with one end machined to the lower limit and the other end to the upper limit of tolerance
  • Much quicker than measuring the actual dimensions of a component
• Registration Marks


  • Used to check the quality of colour printing onto paper and board
  • Used to make sure the printing plates are aligned in the right position
• Depth Stops


  1. Control the depth of drilling and cutting

  2. Allow you to drill to an exact depth in whatever material you're working with

  3. Adjust the drill depth by aligning the depth stop in a specific position
• Laser Cutters


  1. Need to be programmed with the right information including the size of the parts to be cut, the speed of the laser, and the power of the laser (depending on the material)

  2. A sample needs to be checked to make sure the machine has cut correctly
• PCBs


  Manufactured through photo-etching where the PCB is exposed to light, developed and an etching process removes the copper needed to form the tracks
• Exposure times need to be carefully selected when manufacturing PCBs
• A board needs to be 135-180 mm with a tolerance of 3 mm
• Depth stops are used to control the depth of drilling