Some standard content:
National Standard of the People's Republic of China
Foam-in-place packaging
Foam-in-place packaging
1 Subject content and scope of application
This standard specifies the classification, technical requirements, test methods, inspection rules, etc. of foam-in-place packaging. GB/T 15719—1995
This standard applies to the packaging procedures for various precision instruments, meters, computers, handicrafts, fragile, fragile, special-shaped products, etc. that use foam-in-place packaging.
2 Reference standards
GB 191
Pictorial signs for packaging, storage and transportation
Broad-leaved plywood
GB1349 Coniferous plywood
GB2828 Batch-by-batch inspection counting sampling procedures and sampling tables (applicable to inspection of continuous batches)GB/T4857.5 Packaging and transportation package drop test methodGB8167 Dynamic compression test method for cushioning materials for packagingGB/T15718 On-site foaming packaging materials
GJB145A Protective packaging specifications
3 Packaging classification
Separate packaging;
Foaming packaging in bags;
Foam container;
Sealed packaging;
Prefabricated molding.
4 Technical requirements
4.1 General requirements
4.1.1 Materials
Foam-in-place packaging materials shall comply with the requirements of GB/T15718. Reusable polyurethane foam shall comply with the requirements of this standard and the foam shall not exceed 30% of the total foam volume. 4.1.2 Sensitive products
Foam-in-place packaging shall not be used for products that are susceptible to electrostatic discharge unless anti-static measures are taken. 4.1.3 Unit protection
The unit protection of products before packaging shall be carried out in accordance with the methods specified in GJB145A. 4.1.4 Foaming equipment
Approved by the State Administration of Technical Supervision on October 18, 1995 122
Implementation on April 1, 1996
GB/T15719-1995
Should have a certain pressure and be able to control temperature, flow and mixing ratio. 4.1.5 Foaming environment
On-site foaming packaging should be carried out in the normal temperature range of 15~38℃. 4.1.6 Predetermination of foam thickness
If there is no other provision, the minimum foam thickness shall be determined in accordance with the provisions of this standard. For flexible foam, the thickness of the cushioning material shall be determined based on the static bearing force and brittleness value [see Appendix A (reference) Figure A1]. For elastic foam, the minimum thickness is 50mm. 4.1.7 Determination of the amount of foam
The amount of foam shall be determined based on the gap between the packaged product and the container. 4.1.8 Use of limiting device
The foaming mold frame shall be made of rigid material, and ventilation and other devices shall be considered according to the adopted technical procedures. If necessary, additional limiting devices shall be used. So that when the foam rises, a certain product can be limited to suspend or move in its specified direction. 4.1.9 Marking
The marking shall comply with the requirements of GB191.
4.2 Foaming technology
4.2.1 Separate packaging
This method is widely applicable, especially for small batches and products with irregular shapes. The technical requirements are at least two consecutive pourings. The time interval between each pouring should allow the foam to solidify normally. 4.2.1.1 Method (see Figure 1)
4.2.1.1.1 Select the specified container (see Figure 1-a): 4.2.1.1.2 Select the best orientation for the product. Use as little additional material as possible, except for plastic film to prevent the product from sticking to the foam (see Figure 1-b);
4.2.1.1.3 Use a polyethylene film with a thickness of 0.02~0.03mm and a width of 900mm (double width) to tightly cover the inner side of the container, cover the bottom and extend beyond the box mouth of the container, flatten each corner, and temporarily fix it with tape if necessary (see Figure 1-c). Use formulas (1) and (2) to calculate the size of the film:
Film length = 2×height + 1.5×length (inside the container)Film width = 2.5×height + width (inside the container) · (1)
4.2.1.1.4 Pour a certain amount of raw material into the container, fold the polyethylene film inwards and completely cover the foam (see Figure 1-d): 4.2.1.1.5 When the foam rises and solidifies to a point where it is sufficient to support the product, place the product in the center of the container (see Figure 1-e); 4.2.1.1.6 Cover the packaged product tightly with a second film and extend it Extend beyond the box opening and temporarily secure with tape if necessary (see Figure 1f):
4.2.1.1.7 Pour enough raw material into the container so that it can expand and tightly wrap the product and fill the container (see Figure 1g)4.2.1.1.8 Fold the film and cover the box lid. After confirming that it has solidified, check whether the foam fills the container. If the container is overfilled, trim the overflow part. If it is not fully filled, pour a small amount of raw material to fill it (see Figure 1-h).4.2.1.1.9 Seal the box appropriately. Before moving, allow the foam enough time to solidify (see Figure 1-i). 4.2.2 Foaming in bags
This method is applicable to a wide range of products regardless of size. For products with a length of more than 800 mm, multiple bag unit foaming methods should be used (see Figure 2)
4.2.2.1.1 Select a suitable container based on the size of the product to be prepared (see Figure 2-a); 4.2.2.1.2 Consider the available support surface and select the best orientation for the product. The method of selection should take into account the position of the protruding part of the dangerous product and the possible difficulties in moving the product out in the future. A gap area should be left (see Figure 2-b); 4.2.2.1.3 Determine the size and make or select a polyethylene film bag according to the required width (or diameter) and thickness. It should be fixed to the bag armor and cannot move. It should be heat-sealed horizontally on the center line of the bag to form two layers (see Figure 2-c). The unfolded size of the bag is determined by the inner size of the container. The following formula is used: Bag length (L) = 2×depth+width+100mm
+-**+* (3)
GB/T 15719--1995
Bag width (Wr) = length + width + 50mm
4.2.2.1.4 Pour a certain amount of foam mixed raw materials into the bag, heat seal it, and place it at the bottom of the container (see Figure 2-d); 4.2.2.1.5 Place the prepared product in the center of the container (see Figure 2-e); (1)
4.2.2.1.6 Pour a certain amount of foam mixed raw materials into each bag. When the foam rises to half, remove the clips or tapes that fix the bag (see Figure 2-f);
4.2.2.1.7 Fold the ends of the bag and cover the container to stop the foam from rising. Open the container for inspection and confirm that the product is firmly fixed before sealing the box (see Figure 2-g).
4.2.3 Foam container
This method is suitable for heavier and larger products and uses separate packaging boxes made with special manufacturing technology. 4.2.3.1 Method (see Figure 3)
4.2.3.1.1 Make a mold for a special foam container (a simulated product can be used). The mold design should be easy to fold to ensure that the foam container is not damaged when it is separated (see Figure 3-a);
4.2.3.1.2 Apply the separation material (polyethylene plastic film, wax coating, etc.) inside the mold and completely surround the product or apply it to the inner surface of the mold (see Figure 3-b). If necessary, use tape to temporarily stick the plastic film; 4.2.3.1.3 Place the pads, pallets, fastenings, and reinforcement base inserts in the mold and fix them (see Figure 3-c); 4.2.3.1.4 Place and fix the product in the correct position L in the mold. The product can be hung under a crane or supported by pre-made foam blocks (see Figure 3-d);
4.2.3.1.5 Pour a certain amount of foam mixed raw materials into the mold so that the total rising height of the foam reaches the agreed Half the height of the product should be poured continuously, and the time between each pouring should allow the foam to fully solidify (see Figure 3-e); 4.2.3.1.6 Apply release material or plastic film on the top surface of the rising foam (see Figure 3-1); 4.2.3.1.7 Pour a certain amount of foam mixture into the gap in the upper half of the product to completely fill the space, and continue pouring according to 4.2.3.1.5 (see Figure 3-g);
4.2.3.1.8 When you are sure that the rising foam can completely fill the mold, place and fix the cover. The cover should have holes to release excess expanding foam and gas. The foam should be allowed to cure for 15 minutes before moving or opening the mold (see Figure 3-h); 4.2.3.1.9 Remove the foam container from the mold and use edge protectors for bundling (see Figure 3-i); 4.2.3.1.10 Apply, install, fix and seal the outside of the foam container according to the requirements of the specification (see Figure 3-j). 4.2.4 Sealed packaging
The product is safely enclosed in foam with a thickness of at least 50mm to prevent water vapor. 4.2.4.1 Method (see Figure 4)
4.2.4.1.1 Consider the convenient support surface and select the best orientation for the product. The orientation should also consider the location of the protruding parts of the dangerous product and the gap area that may cause difficulties when moving the product in the future (see Figure 4-a); 4.2.4.1.2 Select the container and appropriate design based on the product size, weight, minimum foam thickness, packaging, protective cover and the orientation determined in 4.2.4.1.1. If necessary, slide plates and table plates can be added (see Figure 4-b): Use long nails with washers to nail through the table plate to the slide. The nails should be staggered in two rows, and the spacing between nails in each row should not exceed 125mm; a.
h. The wood used should comply with the relevant wood standards; c. All plywood used should comply with the requirements of GB738 and GB1349. 4.2.4.1.3 Make a foam block in advance to support the product in a stable position during the foaming operation. The thickness of the support block should be determined by the weight of the product and its shape. When using load-bearing materials such as fiberboard or plywood, the concentrated load should be distributed to the entire support surface, and prevent compression and damage to the foam support block before foaming (see Figure 4-c); 4.2.4.1.4 Determine the cutting line on the horizontal plane that is most convenient for handling the product (see Figure 4~d); 4.2.4.1.5 Make a product protective cover to show the outline of the product as much as possible. The protective cover is generally made of fiber material. Use tape to fix the protective cover. The protective cover should be designed to protect the product during the opening cutting operation and make it easy to move the product out. Mark the cutting line on the outside of the container to protect the product. If the product has protruding parts or easily damaged parts, plastic bags should be used for pre-foaming to protect these parts.12.4
GB/T 15719—1995
, or use fiberboard to protect these parts in advance to prevent the protective cover from being punctured by the expansion pressure of the foam during the foaming process and causing the foam to stick to the product (see Figure 4-e); 4.2.4.1.6 Wrap the protective cover with a plastic film, and the plastic film should have a certain strength (see Figure 4-f); 4.2.4.1.7 Use the continuous pouring method to inject a certain amount of foam mixed raw materials into the container to completely fill the container (see Figure 4-g);
4.2.4.1.8 Before sealing, check whether the foam is 100% full, and after curing for 12 hours, the plywood cover can be nailed to the top of the container. The plywood cover should be at least 10mm thick and should exceed the outer edges of the four sides (see Figure 4-h). 4.2.5 Prefabricated molding
This procedure uses specially designed molds or fixtures to form two independent mold halves, generally made of wood materials. It is best to cast the precast mold in one go. Precast mold molding is suitable for packaging large quantities of products. 4.2.5.1 Method (see Figure 5)
4.2.5.1.1 Make a workbench, open a circular hole in the center of the workbench (the hole diameter depends on the suction diameter), fix the film suction device on the bottom of the workbench, and align its hole with the circular hole of the workbench (see Figure 5-a); 4.2.5.1.2 Select a pre-made mold. Film suction holes should be made at appropriate locations of the mould so that the film suction device can tightly absorb the polyethylene plastic film into the mould (see Figure 5-b);
4.2.5.1.3 Cover the mould or the simulated product with a layer of polyethylene plastic film (see Figure 5-c);4.2.5.1.4 Turn on the film suction device and spread the plastic film as evenly as possible on the mould or the surface of the simulated product. In the following steps, the film suction device is always turned on (see Figure 5-d);
4.2.5.1.5 Evenly cover the rising bubbles in the mould with a layer of polyethylene film, press the film cover down tightly, and take out the foam pad only after the mould is fully filled and solidified for 15 minutes to ensure that the foam pad does not deform. If the filling is not full, pour a little more foam mixed material into the gap (see Figure 5-e).
4.2.5.1.6 Carefully remove the half-finished cushion from the mold and check the surface consistency (see Figure 5-); 4.2.5.1.7 Repeat the above steps to produce the other half of the cushion (see Figure 5-g). 4.2.5.1.8 Pack the foamed cushion into the packaging box (see Figure 5-h). 4.3 Foaming characteristics
Packaging formed by the foam-in-place technology specified in 4.2 shall comply with the provisions of this clause and pass the tests specified in Chapter 5. 4.3.1 Appearance
When inspected in accordance with the provisions of 5.1, the outside of the packaging container shall not have a surface deformation of more than 6mm in a straight line 300mm long. For packaging with wooden or special bases and weighing more than 65kg, the base shall be checked for deformation when it is placed on a flat surface. The surface deformation on the supporting surface at any point on the base shall not exceed 12mm. 4.3.2 Drop test
Before the drop test specified in 5.2, the packaging container, liner, and product should not have defects. When no isolation material is used, the inner wall of the container and the foam should be checked for signs of separation. After the test, the unpacking inspection shall not allow the product to move in any direction, the foam material to break or the product to break or deform, the installation to be loose, the wire to break, or the foam to penetrate the surface of the product. 4.3.3 Cushioning test (flexible foam)
According to regulations, when the product is subjected to an accidental impact above the specified brittleness level, the packaging should have protection capabilities. The cushioning capacity provided by the flexible in-situ foam material should be consistent within the temperature limit range of -30~+50℃. Moreover, when subjected to the free drop test specified in 5.3, it should not exceed the specified brittleness level, and it should not fail to meet the requirements of this requirement due to weight or size. 4.3.4 Unpacking inspection
The manufactured in-situ foaming packaging container should be easy to open and close and should not damage the product or foam material. Failure to meet this requirement should be considered as a basis for non-conformity.
4.3.5 Foam filling degree
The foam formed in the package should fill the air as much as possible. Severe rounded corners are not allowed. There should not be too many discontinuous contacts and large gaps on the product support surface. The pre-foamed preforms should not have any signs of complete non-adhesion. 4.3.6 Foam adhesion
There should be no signs of foam adhesion on the product. 4.3.7 Product removal
The product should be easily removed from the foam packaging and there should be no signs of damage to the package, isolation film or bag. 4.3.8 Product status
The product should not show signs of damage caused by the use of on-site foaming materials. Obvious damage includes: broken or deformed convex corners, loose mounting parts, broken wires or burnt surfaces.
4.3.9 Package pretreatment
When specified in the contract, the package should be pretreated at a temperature of -30℃ for 24 hours. 4.4 Foam quality
Packaging foam produced by foaming equipment specified in 4.1.4 using the foaming technology specified in 4.2 and the foaming materials complying with the provisions of 4.1.1. 4.4.1 Rigid foam
Foam packaging produced by on-site foaming technology shall be completely consistent with the uniform unit structure. There shall be no cracks, bubbles, gap openings or air pockets exceeding 13mm in any direction; there shall be no obvious wrinkles, depressions or other shrinkage marks on the foam surface, and there shall be no occlusions, cracks or separations. The foam formed shall not be soft, sticky or brittle after curing. 4.4.2 Flexible foam
Foam packaging formed by on-site foaming shall not be clumping, inelastic or brittle after curing. There should be no multiple holes, gaps or nozzles with a diameter exceeding 50mm. In the packaging, there should be no contaminated reused foam in the new foam. 4.5 Special markings and labels
There should be unpacking marks and labels on the container. 5 Test methods
5.1 Surface deformation
Check whether the packaging has surface deformation such as tearing of the sealing tape, bulging of the container wall or denting of the container. Use a ruler of sufficient length to measure the degree of surface deformation of the packaging.
5.2 Drop test
The packaging container should be tested in accordance with GB/T4857.5 to assess The impact resistance of the package and its ability to protect the contents when it is impacted.
5.3 Cushioning test (flexible foam)
Perform the test in accordance with GB8167 to determine the cushioning performance of the cushioning material under impact and its ability to protect the products contained in it during circulation.
5.4 Unpacking inspection
All on-site foam packaging should be unpacked according to the instructions on the outside of the packaging box to check the fullness of the packaging box. There should be no foam adhesion or loose particles, difficulty in disassembling the product, etc. The foam should fill at least 95% of the entire space. 5.5 Foam quality
Check whether there are cracks, burns, gaps, unevenness or fine grooves on the foam. Cut three samples of 100mm×100mm×50mm from the foam. Check whether the samples have soft collapse, sticky particles (unexpanded ester) or cracks, shrinkage and other signs. There should be no open gaps or grooves exceeding 12mm in any direction, burn marks, etc. Any of the above conditions will be regarded as reasons for rejection. 5.6 Marking and labeling
Observe whether the markings and labels on the outer surface of the complete package are correct. 6 Inspection rules
The manufacturer shall be responsible for completing all inspection requirements specified in this standard and may use its own 426
GB/T 15719-—1995
equipment or any other equipment suitable for completing the inspection requirements specified in this standard. The user has the right to inspect any of the inspection items described in this standard when it deems it necessary to determine that the supplied products and services meet the requirements of this standard. 6.1 Inspection classification
The inspection specified in this standard is divided into finalization inspection and quality consistency inspection. Quality consistency inspection consists of periodic inspection and delivery inspection. Finalization inspection and quality consistency inspection consist of groups A, B and C. Finalization inspection is carried out together with product finalization test. Delivery inspection consists of group A and group B inspection.
6.2 Inspection batch
The inspection batch should consist of all foam packaging produced under the same basic conditions and provided for inspection in the same way. 6.2.1 Group A inspection
Group A inspection should consist of the inspection items specified in Table 1. The sampling plan for Group A inspection shall be based on the secondary sampling plan in GB2828, with a general inspection level of I and an acceptable quality level AQL of 2.5%. Table 1 Group A inspection
Inspection items
Foaming materials and components
Foaming equipment
Foaming environment and foaming quantity
Foaming technology
6.2.2 Group B inspection
Group B inspection consists of the inspection items specified in Table 2. 4.1.1
Requirement No.
4, 1. 5 and 4. 1. 7
Group B inspection is carried out on the batches that have passed the Group A inspection, and its sampling plan is based on the single sampling plan in GB2828, with special inspection level S-1. The qualified quality level AQL is 4.0%.
Table 2 Group B Inspection
Inspection Items
Unpacking Inspection
Foam Adhesion
Foam Filling
Product Removal
Product Status
Foam Quality
6.2.3 Group C Inspection
Requirement No.
Test No.
Group C inspection shall consist of the inspection items specified in Table 3. Group C inspection shall be carried out together with routine product testing. The sampling plan for Group C shall randomly select three foam containers, and no unqualified products shall be allowed. Table 3 Group C Inspection
Inspection Items
Drop Test
Cushion Test
6.3 Rejection of Lot
Requirement No.
Test No.
If an inspection lot is rejected, the manufacturer may rework it to correct the defects or remove the unqualified products by screening. Then, resubmission is allowed. The resubmitted batch shall be subject to one-time sampling and strict inspection and testing in accordance with GB2828. This batch shall be separated from the new batch and shall be clearly marked as a re-inspection batch.
GB/T 15719-1995
Figure 1 Separate packaging
GB/T 15719—1995
Multiple units
Figure 2 Foam packaging in bags
GB/T 15719—1995
Figure 3 Foam container
Special marking
GB/T 15719--1995
Figure 4 Sealed packaging
GB/T 15719—1995
Figure 5 Preformed mold
GB/T15719-—1995
Appendix A
Flexible foam packaging design
(reference)
A1 Determine the static bearing pressure of each surface, kg/cm2 (weight/each surface supported by the cushioning material). Then, use the measured product fragility value (obtained from the manufacturer or engineering estimate). A2
A3 Observe the cushioning curve to determine the required foam thickness. The drop height of all curves is 760mm. Find the foam thickness of each side of the product. Use the method of drawing a vertical line from the horizontal axis upward at the static pressure point on that product surface. A4
A5 Then draw a horizontal line from the left point of the vertical axis equal to the pre-estimated fragility value. A6 The intersection of these two straight lines will be close to a curve in Figure A1. The closest cushioning curve below the intersection is the foam thickness required to protect that side of the product from a 760 mm drop. A7
48 Repeat the above process for each other side of the product, using these values for each side, or the thickest value for each side of the specially protected product.
A9 If the intersection of the two lines is below all the curves, do not install the product in the flexible foam of this group of curves. A10 The arrow points to the optimum load point, which can be called the lowest impact level obtained with a 5 cm thickness of a particular cushioning material. Obviously, the vertical line from this defines the optimum static stress. When the calculated static stress is greater than the optimum value, this is the case listed in the curve. In this case, the product fragility value is determined to be 0.5, and the calculated static stress is 0.5. If the "nearest cushioning curve below the intersection" is assumed to be 5 cm thick, there is a dangerous situation of cushioning overload. This situation will cause a serious loss of cushioning thickness during a continuous drop and increase the impact load. There are two solutions: (1) Distribute the load by adding support blocks to change the static stress to a lower value. (2) Using the lower buffer curve, the intersection point is neither the optimal point nor on the left side of the optimal point.3 Rejected batch
Required number
Test number
If an inspection batch is rejected, the manufacturer can rework it to correct the defects or remove the unqualified products by screening. Then, resubmission is allowed. The resubmitted batch should adopt one sampling and strict inspection and testing according to GB2828. This batch should be separated from the new batch and should be clearly marked as a re-inspection batch.
GB/T 15719-1995
Figure 1 Separate packaging
GB/T 15719—1995
Multiple units
Figure 2 Foam packaging in bag
GB/T 15719—1995
Figure 3 Foam container
Special marking
GB/T 15719--1995
Figure 4 Sealed packaging
GB/T 15719—1995
Figure 5 Preformed mold
GB/T15719-—1995
Appendix A
Flexible foam packaging design
(reference)
A1 Determine the static bearing pressure of each surface, kg/cm2 (weight/each surface supported by the cushioning material). Then, use the measured product fragility value (obtained from the manufacturer or engineering estimate). A2
A3 Observe the cushioning curve to determine the required foam thickness. The drop height of all curves is 760mm. Find the foam thickness of each side of the product. Use the method of drawing a vertical line from the horizontal axis upward at the static pressure point on that product surface. A4
A5 Then draw a horizontal line from the left point of the vertical axis equal to the pre-estimated fragility value. A6 The intersection of these two straight lines will be close to a curve in Figure A1. The closest cushioning curve below the intersection is the foam thickness required to protect that side of the product from a 760 mm drop. A7
48 Repeat the above process for each other side of the product, using these values for each side, or the thickest value for each side of the specially protected product.
A9 If the intersection of the two lines is below all the curves, do not install the product in the flexible foam of this group of curves. A10 The arrow points to the optimum load point, which can be called the lowest impact level obtained with a 5 cm thickness of a particular cushioning material. Obviously, the vertical line from this defines the optimum static stress. When the calculated static stress is greater than the optimum value, this is the case listed in the curve. In this case, the product fragility value is determined to be 0.5, and the calculated static stress is 0.5. If the "nearest cushioning curve below the intersection" is assumed to be 5 cm thick, there is a dangerous situation of cushioning overload. This situation will cause a serious loss of cushioning thickness during a continuous drop and increase the impact load. There are two solutions: (1) Distribute the load by adding support blocks to change the static stress to a lower value. (2) Using the lower buffer curve, the intersection point is neither the optimal point nor on the left side of the optimal point.3 Rejected batch
Required number
Test number
If an inspection batch is rejected, the manufacturer can rework it to correct the defects or remove the unqualified products by screening. Then, resubmission is allowed. The resubmitted batch should adopt one sampling and strict inspection and testing according to GB2828. This batch should be separated from the new batch and should be clearly marked as a re-inspection batch.
GB/T 15719-1995
Figure 1 Separate packaging
GB/T 15719—1995
Multiple units
Figure 2 Foam packaging in bag
GB/T 15719—1995
Figure 3 Foam container
Special marking
GB/T 15719--1995
Figure 4 Sealed packaging
GB/T 15719—1995
Figure 5 Preformed mold
GB/T15719-—1995
Appendix A
Flexible foam packaging design
(reference)wwW.bzxz.Net
A1 Determine the static bearing pressure of each surface, kg/cm2 (weight/each surface supported by the cushioning material). Then, use the measured product fragility value (obtained from the manufacturer or engineering estimate). A2
A3 Observe the cushioning curve to determine the required foam thickness. The drop height of all curves is 760mm. Find the foam thickness of each side of the product. Use the method of drawing a vertical line from the horizontal axis upward at the static pressure point on that product surface. A4
A5 Then draw a horizontal line from the left point of the vertical axis equal to the pre-estimated fragility value. A6 The intersection of these two straight lines will be close to a curve in Figure A1. The closest cushioning curve below the intersection is the foam thickness required to protect that side of the product from a 760 mm drop. A7
48 Repeat the above process for each other side of the product, using these values for each side, or the thickest value for each side of the specially protected product.
A9 If the intersection of the two lines is below all the curves, do not install the product in the flexible foam of this group of curves. A10 The arrow points to the optimum load point, which can be called the lowest impact level obtained with a 5 cm thickness of a particular cushioning material. Obviously, the vertical line from this defines the optimum static stress. When the calculated static stress is greater than the optimum value, this is the case listed in the curve. In this case, the product fragility value is determined to be 0.5, and the calculated static stress is 0.5. If the "nearest cushioning curve below the intersection" is assumed to be 5 cm thick, there is a dangerous situation of cushioning overload. This situation will cause a serious loss of cushioning thickness during a continuous drop and increase the impact load. There are two solutions: (1) Distribute the load by adding support blocks to change the static stress to a lower value. (2) Using the lower buffer curve, the intersection point is neither the optimal point nor on the left side of the optimal point.
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