For turning, grinding and milling machines
The new oil emulsion separator from HENGST frees contaminated air from cooling lubricant mists from cutting machines. By creating a slight negative pressure in the machining area of the machines, the device effectively prevents excessive release of cooling lubricant aerosols during operation and when the doors are opened. This innovation results in a significant reduction in exposure throughout the shop.
The three-stage filtration has been perfectly adapted to cooling lubricant aerosols and ensures compliance with the limit values according to DGUV 109-003. Thanks to the extremely efficient EC fan, energy consumption is significantly lower than that of many comparable units. The first filter stage can also be cleaned several times, which contributes to low operating costs. A safety mechanism or “anti-shear” mechanism reliably protects the seal of the main filter during installation.
In metal cutting on machine tools, cooling lubricants (MWF) are used to increase machining speed, quality and end product efficiency.
There are two main types of coolant:
It is important to note that both direct skin contact with MWF and inhalation of cooling lubricant aerosols are considered hazardous to health. Therefore, it is the employer’s duty to conduct a risk assessment for the handling of cooling lubricants. This is particularly important with regard to health protection, as the extensive variety of possible ingredients makes classification difficult. The VKIS-VSI-IGM-BGHM substance list provides a useful overview.
In some cases, compromises are unavoidable. For example, the emulsions of water-mixed MWFs provide a breeding ground for undesirable microorganisms. This problem is counteracted with biocidal additives, but this in turn brings other burdens.
During machining in machine tools, cooling lubricant aerosols are inevitably generated, which may occasionally contain small amounts of material particles. The particle size distribution of these aerosols typically shows a peak in the range of 1.5 to 2.5 µm. When minimum quantity lubrication (MQL) is used, these peaks can even be less than 1 µm, while in certain processes such as grinding they can rise well above 2.5 µm. Due to the heat at the machining point and the evaporation of fine aerosols, part of the emission also always passes into the gaseous state.
The emissions can leave the machining area through remaining gaps and often represent diffuse pollution in the workshop and work area. When the doors are opened after the machining process, there may also be brief peak concentrations directly in the area of the machine operator. To limit these effects, it is now state-of-the-art to equip machine tools with oil mist extraction systems, also known as oil mist separators or emulsion mist separators. Nevertheless, there is still a large stock of machines without air filters, although there are clear efforts to retrofit them.
The integrated fans in oil mist extractors create a negative pressure in the machining area and guide the extracted air through several filter stages. The cooling lubricant (coolant) filters play a crucial role here, as they can significantly reduce the release of aerosols and thus significantly reduce the potential hazards posed by cooling lubricants. This helps to prevent occupational illnesses and reduce the number of days of absence due to illness. In addition, recirculating air operation is energy-efficient and does not lead to heat losses.
FREQUENTLY ASKED QUESTIONS ABOUT THE MULTI-CNC
Here you will find answers on the subject of healthy air in your CNC production!
Cooling lubricants can contain various substances, including biocidal substances. Employees are continuously exposed to these substances, which is why the concentration of oil mist and emulsion mist in the air must be reduced for health protection reasons.
An oil mist extraction system is a filter system used to remove cooling lubricant vapors from the work areas of machine tools. These cooling lubricants (coolants) normally contain oil, with the oil either being the main component of the coolant (non-water-mixed coolants) or, in most applications, being present as an emulsion in water.
The average particle size in terms of mass is usually around 1.5 µm to 2.5 µm, and in certain grinding processes it can be even higher. An ePM1 80% filter (according to ISO 16890) removes aerosols of this size for the most part. It may be necessary to use filters with higher classifications, especially when processing critical materials where additional particle filtration is required. In cases of minimum quantity lubrication, particle sizes tend to be somewhat smaller, so filters with higher classifications are occasionally used.
As a rule, ISO 16890 is used as a reference. This standard specifies the efficiency for atmospheric aerosols, the finest fraction of which is about 0.3 µm. This is significantly smaller than the typical particle sizes in cooling lubricant mists. In fact, the actual efficiency (ePM1) for the separation of cooling lubricant mists is usually significantly higher than the standardized classification value. EN779 is no longer relevant for classification. Occasionally, HEPA filters are also used, which are standardized according to EN 1822 and the similar ISO 29463. These standards determine the efficiency for the so-called “Most Penetrating Particle Size” (MPPS), i.e. the particle size that can be filtered out most poorly by the filter.
HEPA filters may be available as a retrofit option for the Hengst MultiCNC. When retrofitting, it is recommended to replace the standard Lotex 1704 pre-filter mat with a Lotex 1805 pre-filter mat to extend the service life of the HEPA filter. These pre-filter mats are already included in the HEPA filter set. Due to the higher pressure drops when using this filter combination, the initial volume flow is reduced by about 100 m³/h.
The MultiCNC is extremely versatile and handles a wide range of applications. With normal cooling lubricant mist concentrations and proper extraction, it has very long filter life. Even at higher concentrations, the MultiCNC remains reliable in operation, but requires more regular filter changes. The filter principle of the MultiCNC shows its strengths especially in connection with emulsions, but can also be used effectively in lighter applications with oil mists. Further information on the expected concentration of MWF mists can be found in Annex 1.3 of DGUV Regulation 109-003.
The Hengst MultiCNC is ideally suited for retrofitting. Many existing facilities do not have a filter unit. In these cases, the unit is not included in the machine manufacturer’s CE Declaration of Conformity. According to the Machinery Directive, it is considered a stand-alone machine and comes with its own CE marking and a mandatory main switch with emergency stop function.
The Hengst MultiCNC can in many cases be mounted either on rails and vibration dampers on the machine housing or on a small stand next to the machine. A practical option is the connection via a suitable flexible hose. It is advisable to position the unit ideally above the suction point to ensure a possible backflow of the cooling lubricant from the suction hose.
The extraction point should preferably be placed at a sufficient distance from the actual machining point to prevent direct entry of coolant spray and chips. On lathes, the opposite side of the lathe chuck is often well suited. At the connection point of the extraction system, a metal mesh is ideal for filtering coarse contaminants. However, it is necessary to clean this regularly to avoid clogging. If it is foreseeable that maintenance could be problematic, at least a baffle plate should be used in front of the extraction point to trap coarse particles. If you have any further questions about this, please do not hesitate to contact us.
Many oil mist collectors operate effectively without the need for special filter condition monitoring instruments. Excessive filter loading or blockage of the extraction point usually results in noticeably reduced airflow rates. Alternatively, a pressure gauge can be used to monitor pressure differentials across the filters. Optionally, a differential pressure switch can be used to send a message to the machine tool if necessary. In any case, it is advisable to include the filter check in the machine’s maintenance schedule.
The connection diagram can be found on the product page. In general, the Hengst MultiCNC only requires a 230 VAC power supply with the appropriate power (170 W / 500 W). The unit can therefore simply be switched on at the beginning of the shift using the main switch provided and switched off again at the end of the shift. If required, it is possible to control the fan power via a potentiometer, a 0…10 V input or pulse width modulation (PWM).
When considering control of the Hengst MultiCNC, it may be wise to reduce power slightly when the machine tool machining area door is closed. Once the door is opened, the system should immediately ramp up to full power to best protect the operator from escaping coolant vapors. If the door remains open, it might be considered to regulate the MultiCNC to “0” after a certain time. However, the run-on time should be well thought out, as the unit also plays a role in subsequent processes such as blowing off the workpieces with compressed air.
Do you have any questions? Please do not hesitate to contact us.
The impressive production facility of WIAG Antriebstechnik, a leading manufacturer of gear cutting technology and gear assemblies, houses three state-of-the-art halls equipped with the latest CNC machining equipment. These halls in Lippstadt play a crucial role in the production of large components that are later integrated into the products of well-known and extremely demanding customers.
The company emphasizes the significant position of high-quality machines from the upscale market segment in its operating environment. In order to amortize the investment costs, the plants must be operated continuously in two to three shifts. Therefore, WIAG Antriebstechnik relies on first-class filter technology and efficient production to meet the demanding requirements of its customers.