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Production Process Guidance of Leaf Springs -Punching (drilling) holes(Part 2)

Views: 0     Author: Wondee Autoparts     Publish Time: 2022-03-17      Origin: Wondee Autoparts

Production Process Guidance of Leaf Springs

-Punching (drilling) holes (Part 2)

1. Definition:

1.1. Punching holes


Punching holes: use punching equipment and tooling fixtures to punch holes on the required position of the spring steel flat bar. There are generally two kinds methods: cold punching and hot punching.


1.2.Drilling holes

Drilling holes: use drilling machines and tooling fixtures to drill holes on the required position of the spring steel flat bar, as shown in Figure 2 below.


2. Application:

All spring leaves.


3. Operating procedures:

3.1. Before the punching and drilling, check the process inspection qualification mark on the flat bar, and check the specification and size of the flat bar. Only when they meet the process requirements, punching and drilling can be allowed.


3.2. Adjust the locating pin

As shown in Figure 1 below, punch the center circular hole. Adjust the locating pin according to L1, B, a and b dimensions.

Positioning schematic diagram of punching a center circular hole

(Figure 1. Positioning schematic diagram of punching a center circular hole)


As shown in Figure 2 below, punch the center strip hole. Adjust the locating pin according to L1, B, a and b dimensions.

Positioning schematic diagram of punching a center strip hole

(Figure 2.Positioning schematic diagram of punching a center strip hole)



3.3. Selection of cold punching, hot punching and drilling

3.3.1. Applications of cold punching:


1) When the thickness of spring steel flat bar h<14mm and the diameter of central circular hole is greater than the thickness h of spring steel flat bar, cold punching is suitable.


2) When the thickness of spring steel flat bar h≤9mm and the center hole is a strip hole, cold punching is suitable.


3.3.2. Applications of hot punching and drilling:

Hot punching or drilling can be used for spring steel flat bar that is not suitable for cold punching. During hot punching, the medium frequency furnace is used for heating to ensure that the steel temperature is 500-550℃, and the steel flat bar is dark red.


3.4. Punching detection


When punching and drilling a hole, first piece of spring steel flat bar must be inspected firstly. Only it pass the first inspection, the mass production can be carried on. During the operation, special attention should be paid to prevent the positioning die from loosening and shifting, otherwise the sizes of the punching position will exceed the tolerance range, resulting in unqualified products in batches.


3.5. Material Management


The punched(drilled) spring steel flat bars shall be stacked neatly. It is forbidden to place them at will, resulting in surface bruises. The inspection qualification mark shall be made and the work transfer card shall be pasted.



4. Inspection standards:

Measure spring holes according to figure 1 and Figure 2. The hole punching and drilling inspection standards are as shown in table 1 below.


Inspection Items

Length Direction Deviation

Width Direction   Deviation

Hole Diameter

Punching Burr

Punching Surface Quality

Technical Requirement

L1±1

︱a-b︱≤0.75mm

According   to the process card

≤0.3mm

There is no crack at the punching   edge and no overheating and overburning on the hot punching surface

Measuring and inspection tools

Name

Tape measure

Vernier Caliper

Vernier Caliper

Vernier Caliper

Visual   inspection

Accuracy

1mm

0.02mm

0.02mm

0.02mm

Sampling method

Each batch shall be inspected according   to the first piece,   middle pieces and   last piece   inspection, and the visual inspection rate of punching surface quality is   100%.


Compiled by  WONDEE Autoparts

2022-3-17


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