In a rebar bending machine, the bending bolts and sleeves (often functioning as the bushing on the stop/gauging shaft, or as the interchangeable mandrel sleeve on the bending shaft) is critical for adapting the machine to different rebar diameters and for protecting the machine’s core components.
Function When Bending Different Rebar Diameters
The primary role of Rebar Bending Machine Bolts and Sleeves is to act as an interface between the machine’s fixed shafts and the rebar. When the rebar diameter changes, the sleeve is changed or adjusted to match.
Diameter Adaptation and Support: The sleeve provides the correct contact surface for the rebar. According to safety regulations, the stop shaft must be equipped with a sleeve, and the diameter and strength of this shaft/sleeve assembly must not be less than the diameter and strength of the rebar being bent. This ensures the shaft can withstand the bending force without deformation. Furthermore, the mandrel diameter should be 2.5 times the rebar diameter. In practice, operators change the appropriate size mandrel and bend mandrel (which act as sleeves over the shafts) to match the specific rebar diameter and required bend radius.
Eccentric Adjustment (Specific Designs): Some advanced designs use an eccentric bending shaft sleeve. By rotating the sleeve, the gap between the bending shaft and the center shaft changes, allowing a single machine to accommodate different rebar diameters without repeatedly swapping out the entire shaft assembly.
Anti-Rotation and Stability: The sleeve helps prevent the rebar from rolling or slipping during the bending process. For instance, the bend mandrel (sleeve) is drawn snug against the machine case to prevent rotation, keeping the rebar stable.
Rebar Bending Machine Bolts and Sleeves Precautions
Correct Sizing and Matching: Never use a sleeve or mandrel that is undersized for the rebar. The mandrel diameter must be sized according to the rebar diameter and bend radius (typically 2.5 times the rebar diameter). When bending high-strength or low-alloy rebar, the maximum allowable diameter must be recalculated based on the machine’s nameplate, and the corresponding mandrel must be swapped in.
Inspection Before Operation: Before starting, check the sleeve, mandrel, and stop shaft for cracks, damage, or excessive wear. A worn sleeve can slip, causing inaccurate bends or dangerous kickback.
No Changes During Bending: Never attempt to change the sleeve, mandrel, or pins while the machine is running or under load. All adjustments must be made with the machine stopped and powered down.
Do Not Exceed Capacity: Do not bend rebar that exceeds the machine’s rated diameter. Even with the correct sleeve, overloading the machine can cause the shaft or sleeve to snap.
Secure Installation: Ensure the sleeve/mandrel is properly seated and secured (e.g., with retaining washers and bolts) before operation to prevent it from working loose during the bend.
