Technical note

The products of the AMF, SMF, SGF and series are modern cooling lubricant concentrates for metalworking that are free of mineral oils, vegetable oils, their esters, synthetic esters and/or organic solvents. Although these products are used like conventional emulsions, they differ in some areas of handling. The possible problems presented here, their most probable causes and the possible solutions given are intended to provide the user with a guide to help with 'first aid' on the spot. Of course, your dealer or the application technology department of DPI Metalworking GmbH is also available to answer any questions or clarifications you may have.

Special features

AMF, SMF and SGF products are real solutions. As such, they are easily mixable with water without the need for special mixing equipment or the need to follow a specific mixing sequence.
After mixing, one obtains homogeneous, transparent solutions that show through whitish to yellowish, depending on the colour of the initial concentrate. (For problems with mixing - appearance of the solution, etc., see Troubleshooting Guide).

Today, modern cooling lubricants are also expected to have excellent cleaning properties in order to ensure the long-term functionality of the machine tool. For this purpose, it is necessary to reduce the surface tension of the medium by means of suitable surfactants or similar.
This has an effect on the foaming behaviour of the cooling lubricant. In conventional emulsions, the calcium hardness of the make-up water in conjunction with the emulsifier package controls the defoaming. By forming so-called lime soaps, a foaming behaviour is achieved in which the foam produced more or less quickly disintegrates again and operating faults are avoided. However, this requires a medium water hardness range (approx. 10 to 20 degrees of German hardness according to DIN 38 409), which cannot be achieved everywhere without effort.

Since no emulsifier is needed for AMF, SMF and SGF products and, moreover, use with fully demineralised water is recommended, defoaming additives are added to these concentrates. Therefore, one concentrate addition is usually sufficient here to combat any foam that occurs (see also problem solver).

Corrosion protection on machines and plant components, tools and workpieces is one of the major challenges for any water-miscible cooling lubricant, since as a rule at application concentrations of between 3% and 10%, more than 90% of the water has an effect on the machine and the workpiece. Dissolved anions such as chlorides and sulphates, but also mechanically introduced atmospheric oxygen and the aqueous medium itself create ideal conditions for oxidation of the metal surfaces. The electrical conductivity of the cooling medium and the use of metallic materials with different electrical potentials entail the risk of pitting and electrocorrosion, and in the case of non-ferrous metals also of staining. Condensation and unfavourable object geometries exacerbate the problem. To ensure corrosion protection, modern cooling lubricants are equipped with several protective mechanisms. The high pH value of approx. 8.8 to 9.5 in the cross-section prevents normal iron and steel corrosion (iron oxide formation), as this does not occur in an alkaline environment (pH value > 8.5). In addition, more or less large quantities of corrosion inhibitors are added to the products. These are so-called oxygen blockers that are deposited on the metal surfaces in a small layer thickness and thus effectively prevent direct contact between oxygen and metal. Mineral and vegetable oil components, which also have excellent wetting properties and a high affinity to metal surfaces, function according to the same active principle.
metal surfaces. However, since corrosion inhibitors leach out (discharge via chips and workpieces) and the pH value can be subject to fluctuations (see problem solver), corrosion phenomena can never be completely avoided when using water-miscible cooling lubricants.
For this reason alone, we strongly recommend using demineralised water for the preparation of our products in order to keep the conductivity of the solution under control and to avoid the entry of corrosion-promoting salts and ions. (For more information, see the Problem Solving Guide).

Water is one of the basic prerequisites for life. In damp rooms, kitchens, but also in machine tools with water-miscible cooling lubricants, the conditions for strong bacterial growth are therefore particularly favourable. Conventional cooling lubricants and emulsions, but also the so-called 'fully synthetic' products, contain energy-rich hydrocarbons ('carbohydrate' is another name for a compound of hydrogen and carbon) and emulsifiers in their formulations. These substances are metabolised by microorganisms.

This 'biological degradation' is not only relevant to consumption, but also technically problematic, as metabolic products lead to odour nuisance, allergies, formation of corrosion-promoting substances, pH value reduction and other unpleasant phenomena. (see guide to problem treatment). To prevent these phenomena, cooling lubricants are usually equipped with biocidal agents to keep the growth of bacteria and moulds under control. It depends on this so-called preservation whether cooling lubricant circuits have to be changed and cleaned frequently or rather rarely. The preservatives and biocides commonly available on the market are additives that require labelling and are consumed through metabolism when infestation occurs. Microbial infestation often also leads to complete separation of the emulsion, as the emulsifier is also attacked. Subsequent disinfection and preservation of the equipment is often difficult and associated with the use of further substances that require labelling and are hazardous to health.

Unlike conventional products, the 'food supply' in our AMF, SMF and SGF products is almost zero. Therefore, we can get by with much smaller amounts of preservatives.

In addition, ingredients are used that prevent the multiplication of germs and fungi. If the products are used as intended according to the manufacturer's instructions, there should therefore also be no problems with odour formation. In contrast to emulsions, it is also not necessary to completely replace the solution in the event of microbial infestation, as sufficient addition of concentrate usually eliminates the problem. (For more information, see the problem-solving guide).

Although the cleaning effect of our AMF, SMF and SGF products is generally described as very good, there are some comments to be made about the residue behaviour of our cooling lubricants. Basically, the products are reversibly soluble, i.e. dried residues can be completely dissolved again with water. Notable residues only form where the product can dry on horizontal surfaces. In case of overdosage and/or contamination with emulsions or emulsifiable oils, such residues can also be sticky. As a rule, only an extremely thin anti-corrosion layer adheres to well blown-off workpieces, i.e. the parts can usually be welded, anodised and galvanised without further elaborate cleaning.
Anodising or powder coating is possible (however, we recommend appropriate preliminary tests). The ideal use of our products is therefore oil-free, which saves considerable costs and effort in the area of parts cleaning. Due to their special properties, the mineral or vegetable oils contained in the emulsions have a tendency to
affinity to metal to coat all surfaces in the engine room with a fine film of oil. While dust and dirt can also adhere well to it, water is effectively prevented from drying directly on the surface. This makes it difficult for dissolved salts and limescale to deposit. DPI products are different. Lime-containing mixing water causes the same phenomena as normal tap water.
Tap water in the kettle in the kitchen. Owners of glass shower cubicles also know what we are talking about.
These phenomena can be avoided by using fully demineralised make-up water. Large consumers of cooling lubricants, such as the automotive industry, have been using water treatment plants for their process water for a long time. (further information in the problem guide).

In connection with cooling lubricants, many users often explicitly ask about the lubricating effect of the product.
higher lubricating effect would also mean higher product quality. In fact, the processes and sequences between tool and workpiece during machining have not yet been described and researched in all details, but there are strong indications that in many machining processes the cooling effect of the production aid is of far greater importance. In modern tools, a uniform temperature profile during machining is far more important than reducing frictional energy. Specially coated carbide tools are sensitive to strong temperature fluctuations. Here, the excellent cooling effect of AMF, SMF and SGF products can lead to significant service life extensions and higher metal removal rates. On the other hand, the wear-reducing effect of lubricant components such as additivated mineral oils, esters, fatty alcohols, etc. of the usual emulsions is often bought by poorer cooling and lower dimensional stability. The high pressure absorption capacity of the common anti-wear and EP additives leads to a Cutting" of the oil/additive film on the cutting edge. This can lead to tolerance shifts up to the hundredths range, which are not always tolerable and have to be corrected. All in all, it can be deduced from practical experience that in processes where high temperatures arise (machining of titanium or high-strength steels, grinding, honing or similar) the use of our products can lead to better tool life, faster production and higher process reliability if the optimum application conditions are created. In summary, it can be said that optimal conditions, such as the use of demineralised water, cleanliness of the coolant system, freedom from entrained hydrocarbons (oil or emulsion residues) lead to optimal wetting properties and cooling effect of the solutions, while the presence of additional 'lubricating' components and salts dissolved in the water negatively affects the performance of the products and shortens the life of the solutions. (For more information, see the Problem Solving Guide).

General maintenance

DPI coolants do not require any special treatment under normal conditions. If the water quality is OK, enough concentrate is replenished and there is no contamination from dirt loads and emulsifying oils, DPI coolants can maintain their performance for a very long time without problems such as corrosion or unpleasant odours. Not to mention skin problems or other health issues. Under these conditions, we can guarantee a service life of the cooling lubricant of at least two years.

The prerequisite for this is a clean machine. This means that the cooling lubricant is free of emulsified oils and greases or other lipophilic substances, free of lime deposits and corrosion-promoting salts such as chlorides and sulphates.

DPI coolants clean the machines during machining by cooling and chip flushing. The duration of this process is difficult to predict and depends on the age of the machine, the type of coolants and lubricants used in the past and the amount of lime deposits in the pipes and hoses. The general construction and design of the machine also play a role.

When converting from oil-based products to DPI, if the machine is generally suitable for water-soluble products, there are some facts that should be considered.
The first and most important point is the fact that DPI cooling lubricants do not contain oil or similar substances. Despite the many disadvantages of these substances (health, parts cleaning, microbiology, etc.), their surface-active action provides additional corrosion protection for metal surfaces by completely covering them, preventing oxygen from interacting with the metals. Due to the affinity of the oil to metal surfaces, even in areas without direct contact with the coolant, a thin film covers metal sheets and covers and prevents them from being attacked by condensation, for example.

Knowing this particular difference, we strongly advise maintenance personnel to check where the periphery of the machine comes into contact with condensation and to use suitable rust preventives.
Tools and tool holders should not be touched with sweaty hands or these parts should also be treated.

We recommend our CORROPROTECT 210 as a drainage and corrosion protection agent. This versatile machine protection is a newly developed product without H 304 marking.

It is a non-water-miscible corrosion inhibitor that protects machines behind covers and other machine parts from oxidation.
The product is used as supplied and can be applied by spraying (normal spray bottle) or dipping. The exact duration of the corrosion protection is difficult to estimate. However, according to our assessment and experience with similar products, at least three to six months should be achieved. The product does not contain wax additives.
With regular filtering of the DPI coolant, we avoid too many elements such as chlorides, sulphates and organic substances that can promote corrosion. In combination with the use of CORROPROTECT 210, we are sure that any oxidation problem is greatly reduced.

Troubleshooting guide

Preliminary remark

This guide addresses frequently asked questions and ambiguities in the application of our products and suggests possible solutions.
Suggested solutions are given. It is intended to serve as a guide and to help you solve minor problems yourself. However, the following explanations do not claim to be complete and cannot replace advice from our application technicians. In particular, no legally binding guaranteed properties can be derived from this guide, nor does it give rise to any claims for damage caused directly or indirectly by the implementation of the following instructions. In cases of doubt, please contact us in confidence:

DPI Metalworking GmbH Application Technology
Siemensstr. 6
88048 Friedrichshafen, Germany
Phone 07541 591224
Fax 07541 591225
E-MAIL This email address is being protected from spambots. You need JavaScript enabled to view it.
Homepage: www.dpi-metalworking.de

Your authorised dealer or DPI field service.

Frequently asked questions

• Question: Can DPI cooling lubricants be mixed with other cooling lubricants or are residues of other cooling lubricants tolerated in the cooling circuit?
  Answer: DPI cooling lubricants have a unique operating principle and cannot be compared with other cooling lubricants on the market, regardless of whether they are 'fully synthetic', 'biological' or contain conventional mineral oil. Admixtures of foreign cooling lubricants can not only negatively influence the machining performance, but also lead to germination and odour formation.
• Question: How can you recognise admixtures or introductions in DPI cooling lubricants?
  Answer: Mixed DPI cooling lubricants form transparent genuine
  Solutions with a pH value of 8.8 to 9.5. The colouring can vary between colourless and slightly to strongly yellowish. Any turbidity or deviation from the pH range mentioned as well as a change in colour indicate contamination with foreign substances. Likewise, dirt, suspended matter and leakage oils can change the appearance. The latter can be removed by filters and skimmers. A turbidity ('becoming milky') indicates a
  Contamination with emulsifiable substances (emulsions, emulsion residues, emulsifying bed track or hydraulic oils as well as corrosion protection oils or thread cutting pastes or similar). Changes in the pH value can be caused, for example, by cleaning agent inputs, high iron ion inputs or microbial contamination.
  In the case of all the above phenomena, take a precautionary sample (fill approx. 500 ml into a clean, sealable sample vessel, either directly from the coolant tank or from the machine's coolant supply. In the latter case, please let the coolant run for a few minutes before taking the sample).
• Question: The cooling lubricant has taken on a different colour than when it was first filled. How should I react?
  Answer: In case of sudden colour changes, the last processed material should be documented and a sample taken. As long as the pH value is within the prescribed normal range, there is nothing to prevent further use until the matter is clarified. In particular, non-ferrous metal alloys, plastics and materials containing graphite such as cast iron or similar can change the appearance of the solution. The processing of already painted or powdered parts can also be responsible for colour changes. Remedy can be found after clarification of the causes by filtration or addition of non-ferrous metal inhibitors are created. Some colour changes can and must be accepted if all other relevant data are in order. For further information, please contact our application technology.
• Question: Do DPI cooling lubricants have a strong inherent odour?
  Answer: A perceptible inherent odour of the products can be observed at most shortly after the first filling. This odour dissipates after a few days. Overall, the smell of a DPI cooling lubricant can be described as inconspicuous and neutral.
• Question: How to react if the smell changes?
  Answer: A change in odour always indicates a change in chemistry and therefore a problem. Please take a sample and contact our technical field service or your dealer. In case of odour changes that indicate microbial infestation, the immediate measure is the addition of The addition of concentrate is recommended as an immediate measure. An increase of the measured concentration by approx. 1-2% is usually problem-free and eliminates the odour nuisance and the associated drop in pH value.
• Question: What should be done if the pH value rises above 9.5?
  Answer: A rise in pH above 9.5 indicates an input (e.g. strongly alkaline cleaners or degreasers) or a chemical reaction (e.g. when machining magnesium or machining brass containing lead). When machining magnesium or leaded brass). In any case, the application technology of DPI should be contacted. Precautionary sampling is recommended.
• Question: The pH value has dropped below 8.8. What should be done now?
  Answer: In most cases, the problem can be solved by adding a sufficient amount of concentrate.
  addition of a sufficient amount of concentrate. First, the concentration should be determined with a calibrated refractometer. Then the concentration can be increased by approx. 1 % in one or more partial steps.
  The cooling system should be set to maximum circulation to ensure good mixing. If 30 minutes after the last addition of concentrate the pH value has not risen into the normal range and the concentration is above 5 ° Brix, our application technology should be contacted. In this case, too, it is recommended to secure a sample before taking any action.
• Question: The measured concentration is above the target value and the pH value is still too low. What could be the reason for this?
  Answer: The refractometer, which is usually used to determine the concentration of water-mixed cooling lubricants, actually only measures the degree of contamination of the water. Provided that the
  refractive index (refractometer factor!) of the emulsion or solution is known, I can determine the concentration of fresh emulsions and solutions quite accurately with this device. If there is a lot of dirt and/or detergents, leakage oils and emulsion residues from the machine are mixed in, the refractive index of the preparation and thus the concentration to be determined will of course also change.
  refractometer factor. It is therefore quite possible that a heavily contaminated solution will indicate a high concentration in the refractometer, although there is actually an underdosage. Contamination of any kind will tend to push the refractometer factor towards a value of about 1, which is why this phenomenon is less likely to occur with conventional emulsions, whose factor is between 0.9 and 1.1 anyway. In case of doubt, always try to keep the pH value within the normal range.
  Nevertheless, the pH value can be undesirably lowered, e.g. by the introduction of acidic cleaning agents (glass or lime cleaners), the emulsification of foreign oils or by germ and fungal infestation. In case of doubt, it is recommended to take a sample and add concentrate.
  If there is no improvement, you should contact your DPI partner.
• Question: We have freshly filled a machine with DPI cooling lubricant, the product foams a lot. What to do?
  Answer: DPI cooling lubricants do not contain emulsifiers or similar.
  This leads to a very low foaming tendency, which can be reduced by a special defoamer is added to the recipe. This is what makes it possible to prepare our solutions with demineralised water in the first place, as we do not need the natural lime hardness of the drinking water for defoaming like conventional emulsions.
  Low foaming during initial filling may indicate too high a concentration or residual system cleaner in the coolant circuit. Heavy foaming, on the other hand, is unusual for DPI cooling lubricants and indicates a problem. It is known that residues of emulsions can affect the boric acid compounds, lead to a strong foaming of our product. Since these boric acid compounds form tough residues that are difficult to remove, complete cleaning of the machine with our cooling lubricant can take several weeks. The use of suitable filter fleeces supports and accelerates this process. Your DPI partner will advise you on the use of a suitable defoamer.
• Question: We have been using DPI for some time. For some time now, we have been noticing sudden foam appearing again and again. What could be the cause of this?
  Answer: Since you have been using the product for a long time, the refractometer factor of the solution may have changed due to entrainment and contamination. As a result, a too high concentration is measured although there is already defoaming. Since the defoamer in the concentrate is also discharged via chips and parts, it may be that there is simply not enough defoamer available. In this case, adding concentrate causes the foam to disappear immediately. If this is not successful, please contact your DPI partner.
• Question: What is the best way to keep DPI cooling lubricant solutions clean?
  Answer: Even after thorough machine cleaning and careful filling of the coolant circuit, it is precisely the excellent cleaning properties of DPI cooling lubricants that often lead to an increasingly dirty coolant solution. Boric acid compounds, dried lime soaps and oily contaminants etc. stubbornly settle in the unfavourable geometries of the machine and the coolant circuit and, over time, get into the coolant tank where they impair the performance of our products. Added to this are leaks and contamination from the workpieces being machined.
  Basically, every machine tool should be equipped with suitable filters. In our opinion, belt filter systems with suitable filter fleece have proven best in practice. DPI cooling lubricants do not cause any problems with fine or ultrafiltration processes due to their solution character. All application restrictions that have arisen over time due to the special structure of emulsions containing mineral oil no longer play a role with our products. Use a more expensive but effective fine-mesh filter fleece; your machine and the cooling lubricant will thank you.
  The machine and the cooling lubricant will thank you.
  Skimmers have proven their worth for removing leakage oils.
  Your DPI partner will be happy to advise you on the choice of equipment and procedures suitable for your operation.
• Question: Are all commercially available bedway and hydraulic oils suitable for use with DPI cooling lubricants?
  Answer: If DIN-compliant HLP and CGLP grades are used that do not emulsify themselves, no problems are to be expected.
• Question: How can I tell if the hydraulic or bed track oils I am using emulsify or not?
  Answer: A simple quick test can be done with a small transparent bottle (sealable). Simply mix the oil with an equal amount of tap water, close the bottle and shake vigorously. The two liquids mix and form a cloudy mixture. Now the bottle should be placed in a quiet place. The liquids should now begin to separate again. If after about one hour the water content is still clearly cloudy, one must assume that the product used is emulsifying.
• Question: Ever since I started using DPI cooling lubricant, I have had squeaking noises in the machine. What could be the reason for this and what can I do about it?
  Answer: Almost all machine tools were designed on the premise that they would later work with oil or emulsion as a cooling lubricant. For this reason, there are machine elements such as wipers, cover or telescopic plates and
  other moving parts designed to be lubricated by the machining medium. The cleaning and oil-displacing properties of DPI cooling lubricants remove old layers of grease and dirt, so it may be necessary to treat moving machine parts additionally and regularly with a grease or Teflon spray. (For suitable products and recommendations, please contact your DPI service partner).
• Question: Despite thorough cleaning of the machine before filling with DPI metalworking fluid and using fully demineralised water, deposits formed in the machine after a short time and the viewing panels became dull and milky. What happened?
  Answer: Due to the complicated object geometry of modern and also older machine tools, it is unfortunately practically impossible to clean all corners and angles so thoroughly that all deposits etc. are removed.
  Limescale in particular settles in the coolant lines and pipelines of the machine and is dissolved again by our particularly cleaning-active products. Since there is no longer an oil film wetting the surfaces, the dissolved limescale can settle on them as it dries, just like in a kettle.
  deposit on surfaces. This phenomenon can be eliminated by the careful use of acidic cleaners or the addition of suitable additives (ask our application technology).
• Question: How long can I store DPI metalworking fluids and under what conditions?
  Answer: As genuine solutions, our metalworking fluids are generally very stable in storage. For legal reasons, however, we can only provide a guarantee for a maximum of one year when stored in the unopened original container under roof at a permanent temperature of at least 5 °C to a maximum of 50 °C. In case of doubt, please send a sample to our laboratory.

Friedrichshafen, 14.03.2023