In recent years, die cast lubricants have changed greatly! Die casters who have been around long enough will remember "traditional oil-based die lube products" (1). Subsequent generations have seen a conversion to "water-based products" and in some limited applications a "dry powder."
With every generation, a better, faster, different product has been developed by the various manufacturers of die lubricants. The good news is that all of these manufacturers and universities have dedicated a great deal of time, money and effort into the pursuit of better products.
For the benefit of this discussion, the information contained will review advances in technology without reviewing the "traditional oil-based products" or the "dry powder" products. The discussion will review advances that have occurred in the "water-based technology". The "water-based technology" appears to be the predominately used product for applications where the die lubricant contributes to the external cooling of a die (2) Water has proven to be a great benefit to the characteristics of die coolant (3,4). Therefore, it is not necessary to review that aspect of die lubricant technology, as significant work has been completed at universities (such as Ohio State) and various manufacturers.
Die Casting Engineer Magazine, November 2003
Victor S. Lafay, Vice President Research and Technical Development
Stephen L. Neltner, Manager Product Development
Hill & Griffith Company
In the authors' experience, traditional die lubricants have been a complex formulation of waxes, oil, silicone emulsions, surfactants, water, minerals and other desirable materials. These products work very effectively but usually at the lower dilution characteristics with water (10:1 water to die lubricant up to approximately 60:1 water to die lubricant). Recent improvements in die lubricant formulations have suggested that higher dilution characteristics are not dependent upon the complexity of the lubricant formulation, but rely upon the selection of the ingredients (in many of the "next generation" die lubricant formulations, a lower number of these ingredients is required). These dilution rates can start at a 40: I water to die lubricant up to over 150:1 water to die lubricant dilution characteristics. It is important to point out that different dimensions of parts, complexity of part design, surface area, die condition, metal chemistry, and other considerations have an impact on the dilution characteristics.
The logical method of consideration of the improvement of the dilution characteristics of a die lubricant can be fairly simple. Given a specific part, on a specific die cast machine, in an existing application of a product that the consumer has accepted, a comparison can be made of a "new" product versus an "old" product. Every die caster realizes that their operation is unique! It is very simple for a manufacturer to suggest an application rate of a die lubricant at a different die casting operation. The real test comes from the application of a diluted die lubricant on a specific part in the operation under evaluation.
A traditional evaluation at this point would be to run for an extended period of time a die lubricant that meets or exceeds a customer's requirement. This could include: cooling characteristic of the die, application rate, desired dilution characteristic, the performance of the die lubricant, defects (during production and at the final analysis at the part consuming location), environmental impact (internal to the operation and disposal of residual material), and other considerations. Once the incumbent die lubricant has been completely evaluated, a comparison with the new die lubricant under the same conditions can be evaluated. It is so important that an "apple to apple" comparison is made so that a proper comparison can occur.
So, What's New In The Die Lubricant Formulations?
First, the changes in die lubricants have become "simpler formulations." So often formulators of die lubricants have the tendency to put everything and anything into a formulation to enhance the performance characteristics of a product. In most formulations, simpler is better! The next generation of die lubricants must be: environmentally friendlier (to be discussed later in detail); easy to mix, tolerable of water variations (dissolved salts and water treatments); in addition to the key concept of high performance.
In order to accomplish the demands of the consumer, products are made up as simple as one or two ingredients dispersed in water, to formulations containing waxes, oils, alkali metals, and other ingredients. As previously stated, historical formulations were oil-based products that generated smoke and other negative side effects - the result was the first generation of water-based die lubricants. The recent generations are a simple adaptation to the waterbased die lubricants.
Fortunately for the consumer of die lubricants, there are a number of high quality manufacturers of die lubricants. The die lubricants from these manufacturers are diverse in that they offer a variety of materials. The advantage to the consumer is that they can draw from a wide variety of chemical compositions and performance related advantages. A recent article in Die Casting Engineer pointed out the advantages of the newer generation die lubricants (5). As stated, the newer generation products have excellent cooling and wetting properties at higher temperatures.
Recent experience has shown that certain high technology based silicones when blended with water and a few minor ingredients can perform very effectively as a die lubricant. The advantages to these families of products is a less complex formulation, higher dilution characteristics, less build-up on the die surface, excellent cooling characteristics of the die, and significant performance in production of die cast parts. In addition to these performance characteristics, these materials can be easily dispersed in water and have a reasonable tolerance to water variations at the consumer's location. The reason that the consideration of water tolerance is so importance is because there is a great deal of variation in North America and few die casters have sophisticated water treatment systems for the "in-bound" water used in the dilution of die lubricants. Die casters have in many cases invested in sophisticated water treatment systems for the wastewater in their facility. The important note to consumers of die cast lubricants is that the "in-bound" water can be critical to the success or failure of a die lubricant at their facility.
Another direction that die lubricants has taken is based upon the concept of a slightly different formulation of materials that takes advantage of high technology based silicones, and other ingredients. These materials have resulted in higher dilution characteristics, less build-up on the die surface, excellent cooling characteristics of the die, significant performance in production of die cast parts, and increased tolerance to variations within the die cast facility. These products have the advantages of utilizing silicones and alkali metals in addition to the other materials formulated into the product at optimal concentrations to enhance the performance characteristics of the die lubricant.
The primary reasons that there are two product families (silicones and alkali metals) that are targeted for the next generation of die lubricants is to meet or exceed customer's expectations. There is so much diversity in application, cooling requirements, variations in the water sources used in diluting the die lubricant, wettability of the die lubricant on the die, and many other considerations that multiple products have the advantage of meeting the requirements of multiple consumers of die lubricants.
The topic of environmental considerations is always at the forefront of today's industrial world. Historically, most die casters consider waste and disposal the primary topic of conversation. Waste and disposal always needs to be at the forefront of discussions at any industrial location. However, there are other considerations that must be taken into account. These include the analysis of emissions associated with die lubricantss, materials formulated into die lubricants that will have a strong impact on the disposal of waste material from a die casting facility, and ultimately the cost associated with these considerations.
Emission associated with die lubricants is an important consideration when a die lubricant is formulated by a manufacturer. Certain ingredients can decompose to organic materials that will impact the threshold limit values (TLV) that is allowable in a die cast facility. A key element to remember when a die cast facility reviews a Material Safety Data Sheet (MSDS) from a manufacturer is that it relates to the die lubricant "as shipped" not "as consumed". The decomposition by-products that occur during the metal casting process are usually not included. The reason that this information is not included is because in most cases the decomposition by-products are either not known or vary based upon the specific conditions in the die casting facility. For example, the die temperature, the dilution ratio with water, the "type of water", ventilation within the die cast facility, and other conditions vary. Die casters should review the impact of decomposition by-products with the supplier of the die lubricant.
The other environmental consideration discussed is the impacts that die lubricants have on disposal of waste materials that die lubricants have on disposal of waste materials from a die casting facility. As "new and improved" die lubricants are introduced into industry, an important consideration should be the impact the die lubricant has on the waste and disposal of materials. One definite advantage that has been observed is the high dilution ratio of the next generation die lubricants. Since the products are diluted at much higher levels (these dilution rates can start at a 40:1 water to die lubricant up to over 150:1 water to die lubricant dilution characteristics) the disposal consideration is minimized. However, if any of the ingredients in the next generation materials has a disposal issue it may have not been taken into consideration.
Manufacturers of die lubricants have spent a great deal of manpower and resources in the development of die lubricants. The "next generation" materials have many advantages over historical materials; increased dilution characteristics, excellent cooling properties at higher temperatures, and improved performance of the lubricants in general. In addition, the environmental considerations and application characteristics are under investigation. The bottom line is; improved die lubricants that can be formulated to meet or exceed any die casters requirements!
1. Smith, J., "Don't let the new kid bully your dies': Die Casting Engineer, January 2003 page 46.
2. Piskoti, C. R., "New study turns up the heat on die spray cooling': Die Casting Engineer, January 2003 page 44-45.
3. Ticknor, A. D., External die cooling considerations': Die Casting Engineer, January 2003 page 38-41.
4. Piskoti, C. R., "New study turns up the heat on die spray cooling': Die Casting Engineer, January 2003 page 44-45.
5. Ibid, page 44-45.
6. Camel, Starnes, Wilbur, Eppich, and Hill, "Analysis of emissions associated with die lubricants on a 1400-ton machine': Die Casting Engineer, January 2003 page 28-33.
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