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Roll forming process design of racking column (upright)
Sep 21, 2018

1. Design principle

First guarantee upright tolerances relative to racking assembly, the pores distances, taking account of different plate thicknesses.

For example, take the average thickness as standard and meanwhile consider the differences of other thicknesses, or emphasize the biggest yield and highest precision requirement thickness.

The radial clearance is easily adjusted by adjusting the distance between punching axis caused by different plate thicknesses, but not easy to adjust axial pore clearance caused by different plate thicknesses. It should be highly noted that this adjustment is important to make sure finished profile precision.


2. Design and adjustment of roll forming process:

1) Radial gap of roll forming is easily adjusted and the gap of upper roller shaft and lower shaft can be adjusted to different thicknesses. But the axial gap and plate differences are difficult to adjust, should with adjustable axial structure to solve this issue.

Roll forming adopts certain bending radius and waist to let bending point gradually outward move. In this way, the waist, leg as well as bending parts are changing with the bending angle. The advantage is to get precise waist within fewer forming passes and some rollers are common use.

The adjustable pre punching pores distance can help guarantee the perforation precision of finished column. Each row pores adjustable range 4-8mm.

2) 

the opening widths of same profile size at different thicknesses are a little different, so when the common rollers are used, the punching moulds of adjustable pores gaps should be used to make sure the same profile precision of different thicknesses.

based on the basic thickness and series of perforation drawings, to take full advantage of possible perforation design to ensure punching precision.

After design, making and testing, to know the exact incoming steel strip size, you should not calculate out the punching moulds by theoretical width. Because the pore positions gaps will change with the plate thickness increase, the thicker and the pore positions should be closer, this increase the adjusting difficulty in actual production.

different thickness plates will bring different offset of neutral layer and thus plate width different and the pore positions offset on open width plate. To ensure constant punching position and pore positions on finished profile, you can design the offset on less important position(for example, to adjust the pore position differences caused by plate thicknesses on the middle coming-up height).

3The open width of incoming strip: 

checking from reference table to know the modification coefficient K(like 0.45), K x t is the offset of neutral layer of steel plate, Rz=R +K xt is the bending radius of neutral layer, t is plate thickness. On AUTOCAD can make profile diagram and making out the neutral layer offset.

4) Distribution of forming angles

Horizontal rollers are the main force to form profiles, average forming angle on each pass is good for stable forming. After the bending angle is over 45°, by vertical rollers can strength the result of horizontal roller forming passes. Considering the resilience of steel material, the bending angle can plus 2°.

5)

The entry vertical roller guide at the first several stations can stop steel plate from transverse transferring from center line.

The first horizontal roller station are parallel rollers to press steel strip not to slip, and transmission ratio is 1.

The final one or two rectifying rollers can guarantee the finished precision.

The roll forming design process should fully consider the characteristics of each profile and the affectation to rolling processes and roller shapes.

The steps such as cutting and punching before roll forming also affect roll forming process, like the pre punched hole is on or not on the roll forming line will make hole deform during roll forming.

6)

Take full use of computer design software: we adopt fixed radius, at given bending angle like 30°,we know that the total length of neutral layer offset is fixed, we can check out the arc center, arc length, straight line length, etc to find out tangent line as roller design reference. If we design the upper rollers at same radius and width, meanwhile design the lower rollers considering axial tolerances, roller clearances, coming steel strip tolerance, material resilience, the total margin of all rollers and exchange clearances, surely perfect racking upright can be made out.

Good forming passes decide the finished product quality, number of forming passes, roller shape, roller life, roller installation and adjusting, producing speed, producing cost and loss.


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