Operation Instructions for Sheet Metal Fabrication

1. Purpose

In order to standardize the operation of sheet metal, improve the quality of our products, so that our products can satisfy customers.

2. Scope of application

It is applicable to sheet metal operations such as MPX178 digital distribution frame, TYWZ outdoor cabinet, broadband box, JPX-250 main distribution frame components, GXF5-106 stainless steel optical cable junction box, etc.

3. Equipment

QC12NJDK CNC hydraulic shearing machine, WD67NJDK double cylinder hydraulic press brake machine, J23 series punch press, ZXJ bench drilling machine, AC/DC arc welding machine, polishing machine and scale, etc.

Operation Instructions for Sheet Metal Fabrication 1

4. Operation process

1. Collect materials

Go to the warehouse to collect materials according to the order and technical requirements.

2. Take materials

According to the requirements of the design drawings, the raw materials shall be taken according to the specifications, and the materials shall be checked for compliance with the requirements of the process.

In order to reduce consumption and improve the utilization rate of materials, the nesting method shall be reasonably calculated.

First, measure the distance between the steel plate and the two ends of the retaining plate (as specified in the process card), repeat the measurement several times, and then try to cut a small piece of material to check whether the size is correct.

If the size tolerance is within the correct range, the feeding shear can be carried out;

If the size does not meet the tolerance requirements, readjust the positioning distance until it meets the requirements.

When shearing, check whether the blade is sharp and firm, and adjust the blade gap according to the thickness of the sheet.

3. Punching

a) Check whether the material, width, length and thickness of materials meet the requirements of drawings.

b) Select the appropriate press according to the process.

c) Adjust the positioning device according to the sequence and requirements of process requirements, and punch out qualified process holes.

Related reading: How to Calculate Punching Force?

4. Bending

a) Check whether the material, width, length and height of the materials meet the requirements of the drawings, and the plates shall be clean.

b) Select the appropriate press brake according to the drawing.

Operation Instructions for Sheet Metal Fabrication 2

c) Adjust the positioning device according to the sequence and requirements of the process requirements, and perform bending.

d) Table of material thickness, bending fillet and die depth during bending.

(The dimensions in brackets are those of CNC press brake machine)

e) Minimum bending radius of various materials

f) Dimension table for bending fillet expansion.

Related reading: Press Brake Bending Basics

5. Welding

Operation Instructions for Sheet Metal Fabrication 3

a) Check whether the semi-finished parts transferred from the previous process meet the requirements of drawings and other technical documents, and timely adjust if they do not meet the requirements.

b) Prepare the required welding devices and tools.

c) The welding sequence shall be arranged according to the requirements of the drawing, which is generally key first and then general.

d) Select the type and specification of the welding rod and welding current according to the material and weld requirements of the workpiece.

The following current selection methods can be used for reference.

① Welding selection shall be considered from two aspects:

a) The general category of welding rods shall be selected according to the requirements of welding rod materials and welds.

b) The electrode diameter shall be selected according to the workpiece thickness, weld geometry, welding specification and other factors.

In order to improve labor efficiency without affecting the welding quality, it is recommended to use larger diameter electrodes.

The data listed in the following table can be used for reference:

AC/DC electric welding machine

Thickness of weldment (mm)234~56~12>13
Electrode diameter (mm)233~44~55~6

C02 protective cover

NameIron plate
1.0-1.2mm
Iron plate
1.5-2mm
Electrode diameterφ0.8φ0.8
Wire feeding speed5th5th
Current regulation3rd6th

② Selection of welding power source and welding current

a) Selection of welding power source

The welding power supply shall be selected according to the type of welding electrode.

Generally, the welding of ferrous metals, such as low carbon, can be used by AC and DC motors.

AC welding machines are cheap, so it is better to use AC welding machines to save electricity.

Some materials have poor welding performance, so DC welding machines are better than AC welding machines, such as cast iron, stainless steel, heat-resistant alloys, copper, aluminum alloys, etc.

b) Selection of welding current

The selection shall be based on the type and specification of welding rod.

Under the premise of ensuring the welding quality (such as the weldment does not redden early, the weldment shall not be penetrated, etc.), it is recommended to use high current welding.

Under the condition that electrodes with a diameter of 4~8mm are generally used, the welding current can be roughly calculated with the following formula:

 I =K*D

Where:

  • I=current intensity
  • K=coefficient (chalk coated electrode K=36~50, high-quality electrode (thick coating), K=40~60);
  • D=electrode diameter (mm)

According to the calculated current value, consider the following factors to determine the current.

a) The weldment has fast heat transfer, low operating current, high circuit resistance, and high operating current.

b) If the electrode diameter is unchanged, the current for welding thick steel plate is greater than that for welding thin steel plate.

Vertical welding and overhead welding shall be 15~20% less than flat welding, and the current of fillet welding shall be greater than that of flat welding.

6. Grinding

After welding, the machined parts shall be polished properly to make the components smooth and even without missing welding, cracks, splashes, burrs, etc.

Operation Instructions for Sheet Metal Fabrication 4

7. Detection

The machined parts passing the above processes shall be comprehensively tested according to the technical specifications, and can be transferred to the next process after passing the inspection.

8. Plastic spraying

a) The machined parts shall be sprayed with the required color according to the requirements of the drawings.

b) Processed parts after plastic spraying shall have uniform and smooth surfaces, no air hole, no sagging, and uniform color.

9. Inspection of semi-finished products

The formed semi-finished products shall be comprehensively tested according to the technical specifications, and can be transferred after passing the inspection.

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