One of the first things to consider when using a horizontal bending machine is the bend radius. The Bend Radius is something that can cause a lot of problems if it is not set correctly for the job in hand. This can result in damaged material, rejected parts and may even mean that the machine is unable to complete the task at hand.
Minimum Radius and Material Thickness
For mild steel, the minimum inside bend radius is roughly equal to the thickness of the material being bent. Thus a 5 mm thick plate would require a minimum inside bend radius of 5 mm. In fact, attempting to bend the material at a radius less than this could result in tearing of the outer surface of the metal.
Material Grade Affects the Minimum
Materials of softer ductile nature, such as annealed aluminium, will bend at tighter radii than harder work-hardened grades. Higher tensile steels are required to bend at larger minimum radii, sometimes up to 2 or 3 times the material thickness.
The Former Size Sets the Radius
In horizontal bending the former is used to form the bend. The former has a nose to the former which forms the inside of the bend. This is often referred to as the bending die. The Euromac range of Bending Machines are designed with the ability to change formers quickly to allow for the selection of the appropriate bending tooling to achieve the required bend radius as detailed on the drawing.
Measuring an Existing or Required Radius
A set of radius gauges can be used to determine a formed radius very quickly. Compare the bend with the appropriate gauge to confirm the required radius has been formed. Typically a required radius is measured from the inside of the bend.
Allow for Springback
Springback – The material springs back after the bend has been formed due to the material returning to its original shape after the forming pressure has been released. The bend will therefore open up slightly and increase the inside radius. The amount of over-bend required will depend on the material being bent and is typically in the region of 1 – 3 degrees. There is more on Euromac Bending Machines at https://www.cotswold-machinery-sales.co.uk/euromac-bending-machines/horizontal-bending-machines.
Measuring an existing radius or checking for a specific required radius on a drawing for your bending job is easy using a set of radius gauges to check the bend.
