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How Intensive Deformation Roll-forming method helps to reduce length of machines

“The longer – the better” will say anyone you ask regarding rollformingmachine design. Having more than enough quantity of rollforming stations, you can gradually make anykind of profile with no stress, waives and ripples. However, each additionalfeet of the machine is not only about machine cost and delivery terms but alsorising demands for the workshop space, power requirements, handling weight, and lack of mobility. Intensive method of therollforming design helps us to build small machines with better budget, termsand gives a chance to small businesses to do the things that only big guyscould afford before. Below you can read engineering …

 As a sample we’ll useregular 1.5” double standing seam roof panel.








Pic. #1 1.5” standing seam profile drawing.

To show the differencewe designed rollers for this profile in 7 passes with Regular Rollforming (RR)method and Intensive Deformation (ID) method.

 With Regular Rollforming (RR) design bends gosuccessively one by one starting from the edge to center of the material(pic.#2). 


Pic. #2. Flow forming flower for Regular Rollforming design method.

Intensive deformation method undermined forms several bends on each pass (pic. 3.)  
 
Pic. 3. Flow forming flower for Intensive Rollforming design method.


As raw material we use 24 Gauge steel ASTM A653-96.
The tensile strength is 210 MPa, the Poisson's ratio is 0.3, the yield strength is 350 MPa, the hardening modulus in the plastic region is 587 MPa. Modeling of the deformation process was carried out in the Ls-Dyna program. Modeling the working tool only simulated the working surface of the calibrated rollers. In this case, the drive has only lower rollers, and the upper ones not propelled. In modeling, the feeding rollers used as first pass with no bands on, therefore eight stands are present in the model.
The shape of the material in formed state during the molding process is shown in Pic. 4, the upper rollers were hidden. Simulation results demonstrate loss of stability is on both edges of the workpiece. Pic. 4b shows the formation of ripples on the left edge between 4 and 5 passes. Pic. 4c demonstrate formation of a kink at the right edge as workpiece goes between 6 and 7 passes.
 
а – general view    b – loss of stability of the left edge    c – loss of stability of the right edge
Pic. 4.  Formed state of material at the process of forming according to the Regular Rollforming Method.


Pic. 5 shows the values of equivalent stresses according to the Mises theory. It can be seen from the picture that the largest equivalent stresses occur at the edges of the workpiece and its values are 367 MPa, which is higher than the yield point, which is 350 Mpa.  That means in places with the greatest values of equivalent stresses will occur plastic deformations, and as a result, edges of the material will be elongated in the longitudinal direction forming ripple defects along the edge shown in Pic. 4.



Pic. 5. Equivalent stresses in the workpiece during the forming process according to the conventional scheme.

Picture 6 shows the values of longitudinal stresses. You can see on the figure that the greatest longitudinal tensile stresses act in the edges of the workpiece as it passes through the second and third passes.

Pic. 6. Longitudinal stresses in the workpiece during the forming process according to the Regular Rollforming method.


Picture 7 shows the strain values in longitudinal direction. The greatest deformation values reach 2%. Such a value is higher than the elastic limit, therefore residual deformations will appear in the workpiece, which will subsequently lead to undesirable deformation of the edge in the form of a ripple.

Pic. 7. Longitudinal deformations in the workpiece during the forming process according to the Regular Rollforming method.


 04/09/2020
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