After the stamping dies used in manual line production in the early stage were transferred to automatic line production, the rework and scrap rate of stamping parts has been high due to the problem of iron chips falling off the edges of dies, which seriously restricts our quality, cost and efficiency.
To this end, we set up a technical research group on the problem of trimming and iron chip falling, and carried out technical research on the problem of iron chip falling, and achieved good results.
The goal of the automobile main engine factory is to pursue high quality and low cost.
The production pace of the stamping manual production line in the old production base is 3 ~ 5spm.
After being upgraded to an automatic production line, the production pace can reach 6 ~ 10spm, the production efficiency can be doubled, and the production and operation cost can be greatly reduced.
However, the following problem is that the mold of the manual line is not enough to support the production of the automatic line, and the mold used in the manual line must be transformed and upgraded to meet the production requirements of the automatic closed line.
The problem of iron chips falling from the stamping die
The key point of changing the stamping manual line mold into automatic mold is to solve the problem of iron filings falling off during trimming.
Because the iron filings in stamping production are easy to adhere to the surface of the mold and parts (Fig. 1), and then dents will be pressed out on the surface of the parts (Fig. 2).
When the quality inspector at the end of the line identifies the indentation defects, at least 7 of them have been reworked or scrapped.
It not only seriously affects the appearance quality of stamping products, but also increases the later operation cost.
How to eliminate the iron filings produced by trimming dies is a major problem perplexing stamping production.
Through the optimization and transformation of the die structure of the manual production line, we can effectively reduce the iron filings produced in production, and there is no obvious crushing problem of waste iron filings on the surface of stamping parts.
Fig. 1 iron filings accumulation of lower die block
Fig. 2 crushing on the outer surface of stamping parts
Optimization and rectification of blade structure
Through the optimization and rectification of the trimming knife block and punch, it can meet the standards, ensure stable production, reduce the production of iron filings, and fundamentally solve the problem of iron filings.
⑴ The optimization and improvement of the straight repair tool block include (Fig. 3 and Fig. 4):
① Smooth the “wave” part of the datum;
② The positive cone of the cutting surface is changed to a 90 ° vertical plane;
③ The edge is gnawed and repaired sharply;
④ The datum plane shall be controlled at 10mm.
Fig. 3 before the rectification of the direct repair tool block
Fig. 4 after the rectification of the direct repair tool block
⑵ The optimization and improvement of the punch include (Fig. 5 and Fig. 6):
① Change the original intake from 10mm to within 5mm;
② The peripheral edge of the upper part of the punch is low, and the middle bulge is trimmed to be flat;
③ Push and polish the edge and circumference of the punch.
Fig. 5 excessive punch intake
Fig. 6 reasonable punch intake
⑶ The optimization and improvement of the blade gap and its gap with the pressing plate include:
① Grind and match the blade gap with red lead to make the gap even and reasonable (Fig. 7 and Fig. 8);
② Adjust the gap between the cutting edge and the pressing plate from 0 ~ 0.1mm to 0.5mm ~ 0.7mm (Fig. 9 and Fig. 10).
Fig. 7 the blade clearance is too small
Fig. 8 uniform blade clearance
Fig. 9 the clearance between the cutting edge and the contour of the pressing plate is small
Fig. 10 the clearance between the cutting edge and the contour of the pressing plate is uniform
(4) The optimization and improvement of waste knives include (Fig. 11 and Fig. 12):
① The gap between the waste knife and the knife block is adjusted from 7mm to 1mm;
② The intake was adjusted from 12mm to 4mm;
③ Adjust no empty knife to empty knife.
Fig. 11 waste knife before rectification
Fig. 12 after waste knife rectification
Rectification of pressing core structure
The optimization and improvement of the pressing surface of the pressing core include (Fig. 13 and Fig. 14):
① The pressing control surface of the pressing core is adjusted from a maximum of 40cm to less than 20cm.
Reducing the pressing area helps to reduce the indentation, because even if there is a small amount of iron filings, they will not be brought into the mold;
② The lapping rate of the pressing core is from 75% to more than 95%;
③ All pressing surfaces are smoothed and polished.
Fig. 13 before rectification of pressing core profile
Fig. 14 after rectification of pressing core profile
A vent hole with a diameter of 30mm is added in the local closed area inside the pressing core to keep it consistent with the external air pressure, so as to avoid the problem of iron scraps absorption caused by the negative pressure inside the mold during production, as shown in Fig. 15 and Fig. 16.
Fig. 15 before adding vent hole to pressing core
Fig. 16 after adding vent hole to the pressing core
Add vent hole to punch
The optimization and improvement of adding vent holes in punch include:
① The number of vent holes on the surface of the punch is increased from 230 to 290, with an increase rate of 26%.
The vent hole is selected at the part with large area and small arc transition.
The size of the vent hole is φ6mm, which is consistent with the original size (Fig. 17 and Fig. 18);
② The convex model surface is smoothed and polished.
Fig. 17 punch before adding vent hole
Fig. 18 after adding vent hole to punch
Through the optimization and improvement of the cutting edge, pressing core and punch structure, its process parameters meet the requirements of trimming process, reduce the generation of trimming iron filings, and then avoid the iron filings from crushing the parts and molds.
In the last 8 months of production, the indentation rate has been reduced from 8.5% to 3.1%, and has remained stable for three consecutive months, with obvious effect.
In terms of consolidating the achievements and continuous improvement:
On the one hand, we apply the typical cases with obvious success to the structural design stage of the new mold, so as to eliminate the problem of trimming and falling iron filings to the greatest extent.
On the other hand, we have formulated the norms for the maintenance of stamping dies with iron filings falling off the edges of stamping dies, which are controlled from the system and process, so as to ensure the production stability of stamping dies during the production and operation period and reduce the unqualified products caused by iron filings.