1. The calculation principle of expansion:
During the bending process of the sheet, the outer layer objectively exists to the tensile stress, and the inner layer is subjected to compressive stress. The transition layer under pressure-the neutral layer. The length of the neutral layer remains the same after bending as before the bending, so the neutral layer is the basis for calculating the unfolded length of the bent part. The position of the neutral layer is related to the degree of deformation. When the bending radius (the R angle shown in the figure below) is larger and the bending angle (the angle θ shown in the figure below) increases, the degree of deformation increases, and the position of the neutral layer Gradually move to the inner side of the bending center, the distance between the neutral layer and the inner layer of the sheet is <90>
2. Calculation method:
strong2.
unfolded length=in-material+in-material+compensation amount
unfolded length=out-of-material+out-of-material-compensation 0 1 (R≤2.0 θ=90).L=A+Bk, (see attached table 2 for k value)
2. (R>2 θ=90) L=a+b+K
K=(R+λ)*π/2
Note: When R≥5T,λ=0.5T.
When R<>
ab is the strong straight edge value of the tangent point of R. _sp7p4pspan strong _sp7p0 pspan0 obtuse angle bending:
1 (R≤2.0 θ>90):
_span L=A+B+k_span 4 (see attached table for k/90)
2 (R>2 θ>90 ): L=A+B+K
K=(R+λ)*πθ/180 _span_span1 span4 pspan_span_span0 span4 Note: When R≥5T, λ=0.5T.
When R<>
_span. 
sharp angle bending:
2 (R≠0 θ<90):>
L=A+B+KK=(R+λ)* πθ/180
_span4_span_span4 p_span_span1 When R≥5T,λ=0.5T.when R<>
AB is the straight edge value of the tangent point to R. _span4p img4pspan _span1 strong_span2p _span2 0p Z-fold (straight side segment difference)
1. When H≥4T, it is formed in two times and calculated as two 90-fold bends.
2. When H<4t,>
L=A+B+K (K value is shown in Table 3)
strong_strong_strong_strong_span114 .When H<2t,>
When H≥2T,Spread in two bends (θ≠90)
Reverse bending and flattening _span_span_imgA4sp-span0.
N-fold
1. When the N-fold processing method is gasket reverse folding and flattening, then press + p7pLspan+ p7pLspan + span
. (The value of K is shown in Table IV).When the N-fold is processed in other ways, it is calculated according to the general bending (R≠0 θ≠90)”
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2.2. The dimension design value of the marked tolerance: take the middle value of the upper and lower limit dimensions as the design standard value
strong_span strong_spanspan4 strong2spanspan strong_span4p 3.1. During the unfolding process,In addition to the expansion of the shape, for some such as threading (flanging) tapping, tapping (extruding teeth. Cutting) flanging expansion rivet nuts (Z products). Flower tooth pressure riveting nuts (S products). Pressure riveting Screws (FH products). Pressure riveting screws (NY products). Pressure riveting nut posts (SO, BSO, SOO, SOPC products) (note the difference between 3.5M3 and M3 bottom holes). During the unfolding process, it must be carried out first Pre-opened bottom hole (see appendix 5 for details) 4. Opening process holes For some products that require less precision, we can bend and polish the corners. Open a bending process hole. The size is determined by the thickness of the plate. It should be larger than the plate thickness and should not be too large. Try to choose a suitable mold that has been used during the programming process. (Easy to reduce mold and processing time).
1 There are three situations in the picture: full package, half package, and overlap.
①All the overlapped edges do not need to open the process hole;
②For the thickness T<1.5mm>0 For edge wrapping and plate thickness T≥1.5mm, process holes need to be added at the corners.
There are two ways for craft holes: round and U-shaped; the center of the long round hole is on the bending line.
as shown in figure ab
1. After unfolding, it will be the part of the line segment, and process it into the process hole form shown in the figure below: as shown in figure c _span4 The width of process hole is 0.5 (LASER) or 2.0 (NCT).
2 When the distance between the drawing edge and the bending edge (internal dimension) is less than 2.0mm, the bending process will be affected. At this time, the corresponding bending deformation zone is cut or changed Shape size, as shown in Figure e:
1) Under the following circumstances, it is not allowed to open process holes:
① has no external appearance or assembly requirements Allowed workpieces;
②Single shipment, without the customer's permission.
③Japanese customers did not require craft holes:
2) Under the following conditions,The programmer can decide to open the craft hole by himself:
① Open the corner of the craft hole to weld the filled work piece;
② non-functional surface assembly Workpieces shipped inside the complete machine.
3) In the following cases, the engineer needs to negotiate with the customer to open the process hole
affects the bending or mold forming of the workpiece.
The unrounded part (LASER) after unfolding of the product will be rounded according to R0.5.
4. It is worth noting that when we are in the process of unfolding, we find that there is a hole that is close to the bending edge, and the hole will bend after bending. Ream after opening the bottom hole.
In general, we have two calculation formulas for reference:
LMIN=(2.0-2.5) T+D/2 _span0 span _span2 It is the lower mold V groove)
5. smooth and burr surface: During the unfolding process,Glossy and burr surfaces are one of the important things we must consider. Generally, there is no indication on the drawings and the customer does not specifically request, such as folding a box. We usually use the inside as the burr surface and the outside as the smooth surface. For customers (such as Japanese customers such as VGI, TBS, Seiko, etc.) have special requirements, the drawings clearly indicate, we will all develop according to the drawings.
6. The requirements for the unfolding of the press processing:
The general form of the bending process of the press is shown in the figure. The choice of V groove is related to the thickness of the material, and the minimum folding size is limited by the V groove. , Its relationship (as shown in the attached table)
Note: The minimum bend L in the table must be a sharp knife upper die; _p7span span _p7sp span
Forming (H≥5T).
For Z-folding one-time forming (H≤5T), use a breakage die to bend, the maximum breakage difference is 835mm (2pcs), and it is a one-time breakage, and there can be no obstruction in the middle.
The thickness of the broken plate T: 0.5-2.3, the height of the broken plate H: 0.5-10 mm.
7, material-saving placement: after expanding and checking OK,We also need to choose a reasonable placement method (generally X value>Y value) to see how to save the most material, rotate the expanded image to a reasonable position (don't mirror it, the burr surface will be reversed.), and then arrange the knife.
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