Facing an unprecedented demand for parts, forging companies are being pressured to produce as fast as possible, causing operators to cut corners. But settling forpoorly mixed lubricant will only create unnecessary and costly problems down the line.
by Daniel Vila-Flor
COVID- 19 has hit everyone globally, regardless of country, in- dustry or company size. However, as countries, industries, and companies begin to recover, some companies—especially forging companies—face an almost unprecedented demand for parts. Press operators are pressured to run their machines as fast aspossible because of a global shortage of parts and the fact is that suppliers arestruggling to meet the demand.
While demand and production remain high, what must not be neglected arequality lubricant and die lubrication. The difference between proper systemsand bucket approaches can be as different as night and day. Using poorlymixed lubricant creates many problems and issues. If poorly mixed lubricantis compounded with a poor application, you get the ingredients for disaster:for the press, for the operator, and for the quality of the forged parts. DesignManagement Konsulting Oy, DMK, offers solutions to both lubricant-mixingand application which allow the forging shop, press, and operator to enjoy thebenefits of properly mixed lubricant that is properly applied—creating savingsthrough improving process conditions and increasing output.
The Bucket Approach
The problems associated with poorly mixed lubricant are numerous. Manyfirms across the industry use the bucket approach where they add water toraw lubricant, mix by hand, and apply it if it looks ok. Although the bucketmethod is simple and efficient, it’s an outdated practice that creates poor-qualitylubricant with solids that are either too high or too low. Both of which candestroy dies, create poor parts, and most importantly, waste time and moneyneedlessly.
If enough water is not added when mixing die lubricant, the amount ofsolids in the lubricant goes up increasing viscosity. High-viscosity lubricantis difficult to spray, regardless of whether a hand wand or an automatic spraysystem is used. High-lubricant viscosity requires better atomization of thelubricant. (Atomization is the transformation of a liquid into small, fine droplets.) If the lubricant is not properly atomized, the lubricant film in the diesuffers since it does not coat the die properly. This results in excess lubricantin some areas of the die and leaves minimal to no lubricant in other places.This will cause forgings to stick to the die, or worse, over and underfill thedie in different places of the same hit.
High viscosity and poor atomization are just the beginning of problemswith high-solid lubricant. The drying time of the lubricant increases due tothe high solids, resulting in lower press operating efficiency. In addition, thegreater the amount of graphite in the lubricant, the more polluting it will beto the surrounding environment. Since the high-solid lubricant pollutes theenvironment faster, the lubricant build-up increases and creates additionalproblems. All of the above contribute to reduced die life, an increase in die-change delays, and the added cost entailed in using too much lubricant.
The immediate and obvious answer to high-solids lubricant is to over-di-lute the lubricant in order to avoid all of these problems. This is not the bestsolution since over-diluted lubricant also has significant problems. The atomization of the lubricant will be better, but the coverage of lubricant in thedie will be poor. With less graphite in the lubricant, the protective graphitefilm in the die becomes poorer. If the graphite film is poor, the cooling of thedie will be lessened, producing an increase in friction. Poor cooling causesthe dies to undergo higher thermal cycling which, in turn, wears out the diesmore quickly. Additionally, with a poor lubricant film, the friction betweenthe forging and the die increases, and the forging may stick to the die. Evenif the forging does not stick to the die, there is the risk that the forging willunderfill the die due to reduced friction reduction. An underfilled die means