Why Lifting Bars Are Necessary
While eye bolts provide the attachment point for crane slings, lifting bars provide the critical function of keeping mold plates locked together during crane transport. Without a lifting bar, mold plates can separate under their own weight during the lift, creating a plate-drop hazard.
Lifting bars are mandatory for three-plate molds and strongly recommended for all molds above 500 kg. For our complete lifting bar catalog, see the lifting bars product page.
Two-Plate vs Three-Plate Lifting Bar Configurations
| Factor | Two-Plate Lifting Bar | Three-Plate Lifting Bar |
|---|---|---|
| Plates to secure | Fixed half + moving half | Runner plate + cavity plate + core plate |
| Clamping mechanism | Clamps across parting line | Extended clamps spanning all 3 plates |
| Separation risk without bar | Low — plates self-close by gravity | Critical — runner plate can fall out |
| Clamp travel required | Mold height (2 plates) | Total mold height (3 plates stacked) |
| Typical bar weight | 5-15 kg | 8-25 kg |
Sizing the Lifting Bar
- Span width: Bar length must exceed the mold width by at least 100mm (50mm overhang on each side) to ensure the clamp arms have adequate leverage. Measure the mold at its widest point including any protruding cooling connectors or hydraulic fittings.
- Weight capacity: The lifting bar's SWL must exceed the total mold weight. Do not factor in crane capacity or sling ratings — the bar must independently support the full mold weight. Calculate the SWL per the guide on SWL calculation for eye bolts.
- Clamp opening: The clamps must open wide enough to straddle the mold's total height (all plates stacked). For a three-plate mold, measure from the top of the runner plate to the bottom of the core plate.
- Center lifting point: The lifting bar should have a center ring or eye for crane hook attachment. Verify that the ring is rated for the full mold weight and positioned at the mold's center of gravity.
Pre-Use Inspection Checklist
- Weld integrity: Inspect all welds for cracks, porosity, or separation. Any weld defect means the bar must be retired or professionally repaired and re-tested.
- Clamp mechanism: Clamps must open, close, and lock smoothly. Sticking clamps may release during the lift. Lubricate clamp pivots with machine oil.
- Center ring/eye: Check for wear, deformation, or cracks. The ring must rotate freely. Replace if wear exceeds 5% of the original cross-section.
- Bolt tightness: All assembly bolts must be torqued to specification. Vibration from crane travel can loosen bolts over time.
- SWL marking: The rated SWL must be clearly marked on the bar. If the marking is worn or missing, the bar cannot be used until it is re-tested and re-marked. For inspection standards, see OSHA 1910.184.
Common Mistakes to Avoid
- Using a bar that is too narrow: The clamp arms do not reach the mold edges, creating an unstable grip. The mold can slip out of the bar during the lift.
- Not locking the clamps: Clamps must be locked (bolted or pinned) in the closed position before the lift. Friction-only clamps can release under dynamic loads (crane acceleration, wind, or mold swing).
- Lifting from one end of the bar: The crane hook must be centered on the bar. Off-center lifting causes the mold to tilt, overloading one clamp and potentially releasing the mold.
- Using a two-plate bar on a three-plate mold: A two-plate bar only clamps two plates together. The third plate (usually the runner plate) is unsecured and can fall during the lift.