DESIGN ELEMENTS TO AVOID
Sharp angles Thick walls Abrupt section changes Many sections coming together at one point Cast-in bolt supports
7 8
USE Brackets Effectively
Taper “L” shaped brackets and make the length of contact with the main casting as ample as possible. Brackets can often be cast separately and then attached, simplifying molding. T is will reduce the bending moments from brackets carrying off set loads that are localized and in the body of the casting.
CONSIDER Ribs
While ribs can increase stiff ness and reduce weight,
poorly designed ribs are ineff ective. It is better to use a hon- eycomb design (Fig. 5). T e thickness of ribs, which should be rounded at the edge, should be approximately 80% of the adjoining thickness. Ribs should be deeper than they are thick and solidify before the casting sections they adjoin. T e space between ribs should prevent any localized accumula- tion of metal. T e following are rib designs to avoid:
• thin ribs joined to a heavy section (leads to high stresses and cracking);
• cross ribs and/or ribbing on both sides of a casting (creates hot spots and makes feeding diffi cult);
• complex ribbing (complicates molding, creates hot spots and hinders uniform solidifi cation);
• ribs meeting at acute angles (causes molding diffi culties, increases costs and aggravates the risk of casting defects).
9
KEEP Communication Open
Be prepared to communicate
frequently during every step of the designing process. Communication between the OEM, engineer and met- alcasting facility is imperative so each party is clear on the expectations, qual- ity and feasible results of the casting. Having to make changes and redesign elements will result in a high-quality fi nal design.
Sept/Oct 2011 | METAL CASTING DESIGN & PURCHASING | 37
Fig. 5. Notice how each design is gradually improved by eliminat- ing structural weakness until honeycombing is achieved.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60