Design Tips

1. Design the component shape using the minimum wall thickness required to achieve the performance criteria for example

  • Tensile and proof strength
  • Impact strength and notch sensitivity
  • Corrosion resistance
  • Weldability
  • Fatigue resistance

2. Design the component shape using gradual and progressive blends to section changes

  • Minimise the number of section changes
  • Blend sections with tapers
  • Reduce stress concentrations
  • Allow feeding of sections

3. Design to avoid isolated heavy sections

  • Heavy sections can induce stress concentrations and tears
  • Lack of feed metal can cause shrinkage defects
  • Defects can result in reduced material properties

4. Design to avoid sharp corners and sharp re-entrant angles

  • Sharp corners induce high thermal gradients
  • Hot spots are caused by re-entrant angles
  • Corners produce differential cooling rates
  • Shrinkage, tears and distortion defects can occur

5. Design junctions to avoid heavy mass concentrations

  • Junctions between sections create mass concentrations
  • There are five types of junctions ­ L, T, V, X and Y
  • Drawing an inscribed circle identifies the mass concentration in a junction
  • Defects can be shrinkage, tears and cracks

6. Identify critical and special areas of the component

  • The design criteria and analysis data should be considered
  • Highly stressed areas can be identified
  • Critical surfaces need to be defined
  • Machined surfaces should be marked with machining allowance
  • Areas of high material quality should be specified
  • Cosmetic areas are important for process considerations

7. Identify the key dimensions and tolerances necessary for the component function

  • Specify dimensions only where required
  • Apply as high a tolerance as possible
  • Indicate datum points
  • Detail any weld ends

8. Identify any jigging or fixture points and place away from natural line of symmetry

  • Identify areas for jigging or fixtures
  • Locate these away from natural ‘casting joint’ lines
  • Advise if CNC machining is to be used to finish the part

9. Quantify the quality and material specification consistent with optimum economy and fitness for performance

  • Specify the surface quality
  • Specify the internal quality
  • Apply the approach of ‘fitness for purpose’
  • Do not over specify

10. Our engineers can also take into account such issues as:

  • Locations in a casting where shrinkage is possible
  • The influence of feeder design and location on the pattern of the solidification
  • The influence of insulating, exoltheumic or chill materials on the pattern solidification