1. Patterns
Full size model of shrink rule measurements used to produce a mold cavity

2. # of castings to be made from pattern determines pattern type of material
wood ‑ soft or hard - mostly pines and mahogany
metal ‑ superior to all ‑ used for shell molding (heat) - all types
plaster
plastic ‑ injected into a mold
styrofoam / wax
composites ‑ laminates (wear resistance and strength)

3. pattern layout ‑ made full size ‑shrinkage and taper allowance is added
contraction is volumetric ‑ correction allowance is expressed linearly
1/8 to 1/4" per foot ‑
Linear shrinkage allowances in Table 2‑1 (p. 18)

4. Shinkage depends on:
1. casting design 2. type of metal 3. pouring temp 4. resistance of the mold to normal contraction of the casting

5. Taper
Taper of 1/16" per foot for vertical walls on patterns drawn by hand
machine drawn patterns require about 1 degree taper
for pockets or cavities in the pattern, more taper needed

6. Machining allowance
when locations on the castings surface will be machined, excess material must be left for machining. This allowance is called "finish”
when possible, surfaces to be machined should be in the drag (bottom) side of the mold.
a. provides a cleaner casting surface on the bottom because impurities float to top b. Most shrinkage is on top

7. Table 2‑2 (p. 19) for machine finish allowances

8. Pattern Configurations:

9. 1. single or loose pattern:
for single copy of pattern
for hand molding
gates and risers cut by hand or loose pieces used
pattern is drawn from sand by hand

10. 2. Matchplate pattern: used for large quantities of small castings
cope and drag mounted to opposite sides of wood or metal plate
runners and gates mounted to plate
used to increase productivity

11. Matchplate (Cont.) usually use a molding machine
Flask slips off after mold making and slip jacket used to prevent movement of the mold during pouring

12. 3. Cope and drag patterns:
Larger castings
cope half mounted on cope plate
drag half mounted on drag plate
2 molders working on opposite sides of line
one makes drags
one makes copes

13. 4. Special devices: loose patterns with irregular parting lines
follow board or pattern bed (match) is used

14. 5. Two Dimensional Sweep Pattern - For Loam molding
rotate 2-D shape about an axis ‑ creates a complex 3-D shape

15. Color markings for wood patterns: by AFS
1. Black ‑ body of casting unfinished 2. Red ‑ surfaces to be machined 3. Yellow ‑ core prints and seats for loose core pints 4. Red stripes on yellow background ‑ seats of and for loose pieces on the pattern 5. Black stripes on a yellow background ‑ stop offs ‑

16. Stop off
portion of a pattern which produces a mold cavity that is later filled with sand so it doesn’t become filled with metal during pouring and appear on the casting.
A stop off may be a reinforcing member on a frail pattern the mold impression of the reinforcing member being filled in by a core

17. Should use fillets to avoid shrinkage cracks and stresses at intersections in patterns