How to ensure the accuracy and maintenance of the die during the processing of stamping parts of electronic products?

In the processing of stamping parts of electronic products, the precision of the die directly determines the dimensional tolerance, surface quality and consistency of the product, while the maintenance affects the life and production stability of the die. Combined with the characteristics of precision, thin material and tiny structure of stamping parts of electronic products, the precision and maintenance of dies need to be systematically controlled from five dimensions: design and manufacture, installation and debugging, production process, regular maintenance and fault handling:

First, source control: mold design and manufacturing accuracy

Stamping parts of electronic products (such as terminals, shielding covers and connector pins) require extremely high clearance and positioning accuracy of the die, so it is necessary to eliminate errors from the design and processing stages:

Precise design parameters

According to the thickness and ductility of stamping materials (copper, aluminum, stainless steel sheet), the optimal die gap is calculated: too large a gap is easy to produce burrs, and too small a gap will aggravate the wear of the cutting edge and cause the material to stick to the knife. Usually, the gap value is 8%~12% of the material thickness (the thin material takes a small value).

Adding guiding and positioning structure: using guide post and guide sleeve to guide accurately to avoid the dislocation of upper and lower dies when the die is closed; For tiny holes and special-shaped structures, positioning pins or floating top pins are set to ensure accurate feeding step of materials and prevent hole position deviation and size deviation.

Selection of high-hardness die steel: Wear-resistant die steels such as SKD11 and DC53 are preferred at the cutting edge, and the hardness reaches HRC58~62 after quenching, so as to reduce the wear and deformation during stamping.

High precision machining technology

CNC machining center, wire cut cutting, mirror discharge and other precision equipment are used to process the mold cavity and cutting edge, so as to ensure that the straightness and verticality errors of the cutting edge are less than or equal to ≤0.005mm, and meet the precision requirements of tiny parts of electronic products.

Polishing or nitriding the die surface: reduce the surface roughness (Ra≤0.2μm), reduce the friction between the material and the die, and avoid scratches or sticky materials on the surface of the parts.

Second, installation and debugging: avoid human error and ensure accurate clamping.

Improper mold installation and debugging is a common cause of out-of-control precision, and standardized procedures should be strictly followed:

Matching inspection of equipment and mold

Confirm the parallelism of the slider and the flatness of the table before installation, so as to avoid uneven stress on the die due to insufficient equipment precision.

When lifting the mould, use a special spreader to prevent the cutting edge from collapsing or the guide part from deforming due to the collision of the mould; After installation, use a dial indicator to detect the parallelism of the upper and lower dies of the mold, and the error should be controlled within 0.01 mm.

Precise adjustment of clamping parameters

Adjust the closing height of the punch to ensure that the die is completely closed in the whole stroke, but it will not be over-squeezed to prevent the die from elastic deformation.

When trying to punch the first piece, gradually adjust the step distance and pressing force of the feeder, check the product size (such as aperture, bending angle and spacing) according to the drawings, and lock the parameters after confirming that they are qualified to avoid parameter deviation in the production process.

Third, the production process: real-time monitoring to reduce the loss of precision.

In batch production, process control should be done well to prevent the precision of the mold from decreasing due to wear and impurity entry;

Regular cleaning and lubrication

After stamping every 500~1000 pieces, stop the machine to clean up the iron filings, oil stains and material scraps on the surface of the die, so as to avoid the impurities from getting stuck in the cutting edge or guiding position, which will lead to the crushing injury or dimensional deviation of the parts.

For the moving parts such as guide posts, guide sleeves and blanking plates of the mould, special lubricating oil with high temperature resistance and wear resistance should be applied regularly to reduce the friction loss between parts and prolong the life of guide precision.

Real-time monitoring of mold state

In production, the first article inspection and process sampling inspection are double checks: the first article in each batch must be inspected in full size, and sampling inspection should be conducted every hour in the production process, focusing on the burr height and dimensional tolerance of the product. If it is found out of tolerance, the machine should be stopped immediately to check the wear of the die edge.

For the high-speed stamping die, an online monitoring sensor is installed to monitor the vibration amplitude and clamping pressure of the die in real time. If there is any abnormality (such as sudden pressure increase), stop the machine immediately for investigation to prevent the die from being damaged.

Standardize operation to avoid accidental injury.

It is forbidden to punch super-thick materials or mix foreign objects (such as metal lumps) to prevent the cutting edge from cracking or the mold from deforming.

Use special fixture or sucker when picking and placing parts, to avoid manual contact with the cutting edge of the mold, and to prevent the cutting edge from being scratched or injured.

Fourth, regular maintenance: graded maintenance to extend the precision life of the mold.

According to the use frequency and wear degree of molds, make a three-level maintenance plan of daily maintenance, regular maintenance and overhaul maintenance:

Maintenance level maintenance cycle maintenance content

Daily maintenance 1. Clean the mold surface and cavity after each shift.

2. Check whether the cutting edge is chipped or stuck.

3. Lubricate the moving parts

4. The mold surface is coated with antirust oil to prevent oxidation.

Regular maintenance every 10,000 ~ 50,000 pieces produced or 1. Dismantle the mold and clean the guide parts and exhaust holes every week.

2. Use a dial indicator to detect the wear of the cutting edge. If the wear is more than ＞0.02mm, repair it in time.

3. Check the clearance of guide post and guide sleeve. If the clearance is too large, replace it with new parts.

4. Calibrate the mold locating pin to ensure accurate positioning.

When overhaul and maintenance produce 100,000 ~ 200,000 pieces or the precision of the die drops seriously, 1. Re-grind the cutting edge to restore sharpness and dimensional accuracy.

2. Replace wearing parts such as spring and ejector pin.

3. Re-polishing or nitriding the mold cavity.

4. Check the mould accuracy as a whole, and carry out CNC repair processing when necessary.

Five, fault handling: timely repair, to prevent further deterioration of accuracy.

The minor faults of the mold should be handled in time to avoid the problem from expanding:

Wear or collapse of the cutting edge: slight wear can be repaired by manual whetstone, and serious collapse needs to be removed and repaired by grinding machine. After grinding, the clearance of the cutting edge needs to be re-tested to ensure that it matches the thickness of the material.

Loose guide parts: When the gap between guide posts and guide sleeves is too large, directly replace the new parts, and re-calibrate the parallelism after installation.

Die adhesion: Clean the surface adhesion of the die, polish the cavity, and adjust the type of stamping lubricating oil (select special oil with stronger oil) to reduce the adhesion between the material and the die.