DE102018104266A1 - Method and device for providing an aid to a workpiece processing zone - Google Patents

Abstract

Methods and apparatuses for providing an auxiliary device (1) to a workpiece processing zone (2) are given, which carry out at least the following steps:
a. Providing a lubricant (3) with a first pressure,
b. Providing a cryogenic coolant (4) with a second pressure,
c. Adding quantities of the lubricant (3) to the cryogenic coolant (4), the first pressure being at least equal to the second pressure,
d. Conveying the mixture of lubricant (3) and cryogenic coolant (4) in a common delivery channel (14) to a delivery point (5) near the workpiece processing zone (2).

Description

The invention relates to methods and apparatus for providing an aid to a workpiece processing zone. The aid is particularly suitable or intended to cause lubrication and / or cooling in the workpiece processing zone. In the workpiece processing zone, in particular, a removing material removal takes place on the workpiece, for. B. a machining production process.

The workpiece can be formed with a material which is difficult to process, so that high frictional forces and / or significant heat generation can occur during its machining. Such a situation may have adverse effects on the material properties of the workpiece or the tool, the dimensional accuracy and / or the wear, so that especially in such applications, a lubrication and / or cooling is considered necessary.

An intensive cooling and lubrication has been attempted by intensive rinsing of the workpiece processing zone with lubricant (eg oil). Such intensive use of lubricant is hardly feasible, especially with a small workpiece processing zone, possibly with sensory monitored or controlled processes. Furthermore, the intensive use of lubricants requires a complex treatment, so that considerable efforts are required for an environmentally sound implementation of such methods.

It is possible to perform a kind of minimum quantity lubrication. In this case, drops of the lubricant are added to an air stream and fed to the workpiece processing zone. A lubricant mist or aerosol is thus provided. The air can here with a pressure of 7-16 bar and the oil with a flow rate of 20-120 ml / hr. be supplied. However, it should be noted that this is accompanied by only a comparatively low cooling effect. Even attempts to work with cooled air or subsequently to perform a cooling of the aerosol, can hardly reach temperatures in the workpiece processing zone below -20 ° C.

An intensive cooling could be achieved if the workpiece processing zone is supplied with a separate cryogenic cooling means. Thus, liquid nitrogen, which has an evaporation temperature of -196 ° C, could be added. However, this requires a high outlay on equipment and is not suitable for small workpiece machining zones, because this separate supply requires accessibility of the workpiece machining zone through a plurality of nozzles and the channels of the fluid material require additional thermal insulation. Also, a miscibility of lubricant and coolant in the free environment of the workpiece processing zone is susceptible to interference and thus not set sufficiently reliable.

It is therefore an object of the present invention to at least partially alleviate or solve the problems described with reference to the prior art. In particular, methods and devices are to be specified which enable effective and environmentally compatible lubrication and / or cooling of a (thermally highly loaded) workpiece machining zone, and this preferably with little expenditure on equipment and applicable for very different, especially small workpiece machining zones.

This object is achieved with the features of the independent claims. Preferred embodiments of the invention are specified in the dependent claims. The features listed individually in the claims can be combined with each other in any technologically meaningful manner and indicate further embodiments. The description, in particular also in connection with the figure, illustrates the invention and provides further advantageous embodiments.

1. a. Bereitstellen eines Schmiermittels mit einem ersten Druck,
2. b. Bereitstellen eines kryogenen Kühlmittels mit einem zweiten Druck,
3. c. Zumengen des Schmiermittels zu dem kryogenen Kühlmittel, wobei der erste Druck zumindest dem zweiten Druck entspricht,
4. d. Fördern des Gemischs aus Schmiermittel und kryogenem Kühlmittel in einem gemeinsamen Förderkanal hin zu einer Abgabestelle nahe der Werkstückbearbeitungszone.

To this end, a method for providing an auxiliary means to a workpiece processing zone, which comprises at least the following steps:

1. a. Providing a lubricant with a first pressure,
2. b. Providing a cryogenic coolant having a second pressure,
3. c. Adding the lubricant to the cryogenic coolant, wherein the first pressure is at least equal to the second pressure,
4. d. Conveying the mixture of lubricant and cryogenic coolant in a common delivery channel to a delivery location near the workpiece processing zone.

In particular, a "fluid" means a liquid and / or gaseous fluid which may also contain particles. In particular, it "helps" to cool and / or lubricate a portion of the workpiece processing zone. A "provision" comprises, in particular, a predefinable conditioning or requirement-based composition with predefinable flow parameters and / or a specifiable physical state, in particular in the delivery channel, at the delivery point and / or in the (previously known) workpiece processing zone. In the workpiece processing zone can insbesondre also carried out a machining on a workpiece.

The steps are named a. to d. but it does not mean that these steps are performed in a sequenced order of this kind. In particular, it may be the case that all steps (at least temporarily) run in parallel.

According to step a. a lubricant is provided at a first pressure. It is possible for the lubricant to be stored in a lubricant reservoir at about atmospheric pressure and then pressurized by means of at least one pressure intensifier, such as e.g. with a pump, is conveyed under increased pressure through a lubricant line. In particular, the first pressure is downstream of the pressure level or immediately before the concentration of the cryogenic coolant. The first pressure may also be monitored, adjusted or regulated. The first pressure may be the "injection pressure" towards the cryogenic coolant.

According to step b. a cryogenic coolant is provided at a second pressure. The coolant can be stored in a pressure vessel and then flow as needed via a pressurized coolant line.

In this case, the first pressure of the lubricant is set to at least the second pressure of the coolant. It can thereby be ensured that the first pressure of the lubricant in the case of the quantity of lubricant corresponds at least to the second pressure of the carrier medium cryogenic coolant (step c.). The Zumengen can be done in a mixing volume of a mixing unit. In particular, the physical properties of lubricant and cryogenic coolant do not change significantly during the mixing process.

The lubricant, which is preferably finely dispersed in the cryogenic coolant, is then conveyed (as a mixture) to a delivery location near the workpiece processing zone, in a common delivery channel (step d.). In this case, there is preferably still a pressure which is significantly above the atmospheric pressure. In this case, a temperature is preferably present which is significantly above 0 ° C., ie at about room temperature, for example. In particular, the physical properties of lubricant and cryogenic coolant do not change significantly during production.

After leaving the mixture from the delivery point, ie after leaving the common delivery channel, the mixture can relax to form a fluid flow at temperatures well below -30 ° C to atmospheric pressure.

As a lubricant, an oil or a dry lubricant can be used. So-called "dry lubricants" comprising particles and / or liquids that dry quickly and thus virtually no (permanent or oily) wetting of the surfaces of the tool and / or the workpiece cause. Examples of "dry lubricants are: molybdenum disulfide (MoS ₂ ), polytetrafluoroethylene (PTFE), graphite, boron nitride, talc, calcium fluoride, cerium fluoride, tungsten disulfide, etc.

As a cryogenic coolant, carbon dioxide or nitrogen can be used. The cryogenic coolant provided is preferably a cryogenic liquid. The cryogenic coolant may be liquid carbon dioxide. It is possible that the cryogenic coolant comprises gaseous carbon dioxide, liquid or gaseous nitrogen.

The second pressure of the cryogenic coolant may be at least 50 bar, possibly even at least 55 bar or even at least 57 bar.

The (maximum) first pressure of the lubricant can before step c. at least 50% above the second pressure. This high first pressure can z. B. (spaced) from the Zumengung to the cryogenic coolant. The first pressure in the lubricant line can amount to at least 80% or even at least 100% above the (maximum) second pressure in at least one section.

If liquid carbon dioxide is used as the cryogenic coolant, the second pressure is preferably about 57 bar, wherein the first pressure in the range from about 57 bar to about 150 bar can be selected.

In step c. may be a pulsed addition of the lubricant. To control the flow rate, a pulsating addition mode can be used. Pulsed injection of the lubricant can be secured with a high speed solenoid valve that operates on a pulse width modulation (PWM) principle. This allows reaction times of up to 5 ms [milliseconds], which corresponds to the frequency of 100 Hz [Hertz or 1 / second]. The duration of the on / off times define the injection sequences of the lubricant into the flow of the cryogenic coolant and consequently its flow rate / consumption.

The amount of addition of lubricant into the cryogenic coolant and / or the work piece processing zone may be set in the range of 0.1 to 0.25 kg / min. [Kilogram per minute]. The actual value may vary depending on the Machining process of the workpiece can be specified.

It would be possible to add particles of the lubricant directly into the pressure vessel of the (liquid) cryogenic coolant, in which case this mixture is conveyed into the common channel.

In addition, a method for abrasive machining is proposed for a workpiece, wherein in a workpiece processing zone, an abrasive tool is brought into engagement with the workpiece, wherein a tool provided by a method described herein or with a device subsequently explained, issued gaseous from a delivery point becomes.

An abrasive machining process may include at least one of the following processes: turning, drilling, milling, grinding.

In particular, the invention finds application in minimal quantity lubrication for small milling or Bohrwerkzeige, z. B. with a maximum diameter of 5 mm [millimeters] or even a maximum of 3 mm.

• - ein Schmiermittelreservoir, eine Schmiermittelleitung und einen Druckerhöher,
• - ein Druckbehälter für kryogenes Kühlmittel und eine Kühlmittelleitung,
• - eine Mischeinheit, in die die Schmiermittelleitung mündet und von der ein gemeinsamer Förderkanal abgeht,
• - eine Abgabevorrichtung mit einem Ausgang hin zur Werkstückbearbeitungszone.

Furthermore, a device for providing an auxiliary means to a workpiece processing zone is proposed, comprising at least:

• a lubricant reservoir, a lubricant line and a pressure booster,
• a cryogenic coolant pressure vessel and a coolant line,
• a mixing unit, into which the lubricant line opens and from which a common delivery channel emerges,
• a dispenser with an exit to the workpiece processing zone.

The device is particularly suitable and / or adapted to carry out the method described here for the provision of aids.

In principle, the explanations regarding the method for providing aids to explain the device can be used, and vice versa.

The lubricant reservoir may be formed in a kind of tank, wherein the (liquid) lubricant is stored at about atmospheric pressure and room temperature. Starting from there, the lubricant can be conveyed via at least one lubricant line, for which purpose (also) at least one pressure booster is used. The promotion of the lubricant takes place towards the mixing unit, wherein if necessary also a return to the lubricant reservoir is provided.

The cryogenic coolant can be stored under high pressure in a container and optionally transferred via valves in a coolant line.

The mixing unit can be arranged on the pressure vessel and / or the coolant line, wherein in each case the lubricant line opens there.

If the mixing unit is part of the pressure vessel, the lubricant is mixed directly in the pressure vessel with the cryogenic coolant. This eliminates a separate coolant line outside the pressure vessel to the output device or coincide with the common delivery channel.

If the mixing unit is designed separately and at a distance from the pressure vessel, then a coolant line extends between the pressure vessel and the mixing unit, in which exclusively cryogenic coolant is conducted under high pressure to the mixing unit.

The (single) connection between the mixing unit and the dispenser is a common delivery channel for the generated mixture of lubricant and cryogenic coolant. The dispensing device is designed in particular in the manner of a nozzle with a (single) outlet. In this way, a promotion can be made such that a relaxation of the mixture and thus a significant cooling take place only after exiting the exit.

This evaporation can result in extreme cooling of the mixture of cryogenic coolant and lubricant, in the case of liquid carbon dioxide, for example to temperatures down to -78 ° C.

At least the coolant line and / or the common delivery channel can be designed as a capillary. As a capillary here is a channel with a maximum opening width of 1.0 mm [millimeter] understood. In this way, in addition to the low flow rates of the cryogenic coolant over z. As a capillary, also causes a good distribution and easy removal of the lubricant.

The lubricant line subsequent to the (first and last) pressure booster may comprise a throttle unit and / or a metering valve. With the (at least one) throttle unit, the first pressure can be set as desired for the mixing process or as required by the second pressure. With the (at least one) metering valve can the amount of injected lubricant to the cryogenic coolant is controlled as needed.

Further, the use of a cryogenic refrigerant under high pressure as a carrier for a lubricant for conveying by a common delivery channel is proposed. Further preferred applications or uses will become apparent from the explanations of the method and the device.

In particular, the invention thus discloses a method which enables one-channel CO ₂ -based high-pressure minimum-quantity lubrication in the machining. Thus, it solves the technical problem, lubricant and (liquid) coolant, both of which are important for the machining process to counteract mechanical and thermal loads, are performed efficiently and with low equipment costs and there z. B. can escape from the tool. Specifically, the supply of the minimum quantity lubricant is proposed under increased pressure and with the supply of z. B. pure liquid carbon dioxide combined as a coolant in a single channel.

According to the CO ₂ -phase diagram, carbon dioxide is in a liquid state at room temperature and a (second) pressure of around 57 bar. Thus, if liquid carbon dioxide is used as the cryogenic coolant, there is no need for special isolation of the coolant line and / or the delivery channel, which is an advantage over the use of liquid nitrogen, which requires vacuum insulation (T _{Evaporation_N2} = -196 ° C). With the room temperature of the liquid carbon dioxide as the cryogenic coolant, the injection of lubricant can be improved so that small amounts of lubricant (20-120 ml / hr. [Milliliters per hour] for oil or gr./hr. [Grams per hour] for Lubricant powder) can be introduced, and at the same time a good distribution and / or clogging can be avoided.

The developed system enables the supply of the mixture under high pressure, so that in the workpiece processing zone or at the cutting edge of the tool sufficient or desired cooling occurs and at the same time a lubrication with the desired amount of droplets or particles of the lubricant is realized in the coolant flow , Together with the continuous delivery of the mixture through a single conveyor channel to the cutting edge, the cooling and / or lubricating rate can be precisely controlled. The delivery or the delivery channel can also be made by the spindle to small (micro) cutting tools, such as cutters, drills, etc., with a diameter of less than 3 mm.

• - Einem (flüssigen) kryogenen Kühlmittel kann gleichzeitigen eine signifikante Schmierwirkung (Öl, Festschmierstoffe, etc.) beim Bearbeitungsprozess verschafft werden.
• - Eine platzsparende Einzelkanal-Lieferung von kryogenem Kühlmittel und Schmiermittel kann vorgesehen werden.
• - Eine Minimalmengenschmierung mit besonders kleinen Zugabemengen an Schmiermittel sind möglich.
• - Ein verbessertes Bearbeitungsergebnis am Werkzeug und/oder ein geringerer Verschleiß der (insbesondere kleinen) Werkzeuge sind möglich.
• - Eine umweltverträglichere Bearbeitung ist möglich.

Some achievable advantages are summarized here:

• - A (liquid) cryogenic coolant can simultaneously be a significant lubricating effect (oil, solid lubricants, etc.) procured in the machining process.
• - A space-saving single channel delivery of cryogenic coolant and lubricant can be provided.
• - Minimal quantity lubrication with particularly small amounts of lubricant added is possible.
• - An improved machining result on the tool and / or less wear of (especially small) tools are possible.
• - A more environmentally friendly processing is possible.

The invention as well as the technical environment are illustrated by the attached figure, which schematically shows a device for carrying out the method explained here. The technical features illustrated in the figure may individually be considered separately and combined with other aspects of the description or the claims, as far as this is not explicitly excluded.

1 shows by way of example an apparatus for carrying out a method for providing an auxiliary 1 to a workpiece processing zone 2 ,

According to a step a. there is a provision of a lubricant 3 with a first pressure. This is a lubricant reservoir 8th provided, which may be a tank which is exposed to approximately atmospheric pressure. From there, a lubricant line extends 9 through which the lubricant 3 can be promoted. For this purpose is in the lubricant reservoir 8th and / or the lubricant line 9 a printer's height 10 (For example, a pump) provided with which a first pressure of, for example, more than 50 bar can be adjusted. From the lubricant line 9 can be a return to the lubricant reservoir 8th be provided, as well as z. B. at least one shut-off valve, a check valve, a pressure, a mass flow, a volume flow and / or a temperature sensor. These components may be part of a (separate) lubricant supply unit.

The lubricant line 9 indicates below the Druckerhöher 10 a throttle unit 17 and then a dosing valve 18 on. With the throttle unit 17 can that of the printer 10 provided (first) pressure reduced or adjusted as needed. The metering valve 18 Farther downstream, in particular, is set up, as required, a predefinable quantity of the lubricant 3 into the (directly adjoining) mixing unit 13 to inject.

Furthermore, a pressure vessel 11 for cryogenic coolant 4 and a (possibly designed as a hose) coolant line 12 from the pressure vessel 11 towards the separate or spaced trained mixing unit 13 intended. This can (according to step b.) Cryogenic coolant 4 be provided with a second pressure.

The (needs-based) lubrication of the lubricant 3 to the cryogenic coolant 4 can by means of the mixing unit 13 be achieved so that the first pressure of the lubricant 3 at least the second pressure of the cryogenic coolant 4 equivalent. For this purpose, open the lubricant line 9 and the coolant line 12 (separated from each other) in a mixing chamber of the mixing unit 13 , Starting from there, the only common conveyor channel extends 14 towards the dispenser 15 ,

The coolant line 12 and the common funding channel 14 are designed as capillaries. The common conveyor channel 14 has no vacuum insulation.

In this way - according to step d. - The pumping of the mixture of lubricant 3 and cryogenic coolant 4 in the (single) common conveyor channel 14 to the delivery point 5 near the workpiece processing zone 2 respectively.

It is a (single) dispenser 15 with an exit 16 (here also the delivery point 5 ) to the workpiece processing zone 2 provided, the z. B. can be designed in the manner of a nozzle.

This is also a method for abrasive machining of a workpiece 6 , eg in a machine tool 19 , wherein, in a workpiece processing zone 2 an abrasive tool 7 with the workpiece 6 is brought into engagement, with the thus prepared aid 1 finally (after the aggregate conversion after exiting the dispenser) gaseous to the tool 7 or workpiece 6 is supplied.

It is possible for a controller 20 the machine tool 19 also actuates, monitors and / or regulates the active components of the device for the demand-oriented provision of the aid.

LIST OF REFERENCE NUMBERS

1

aid

2

Workpiece processing zone

3

lubricant

4

cryogenic coolant

5

delivery point

6

workpiece

7

Tool

8th

lubricant reservoir

9

lubricant line

10

intensifier

11

pressure vessel

12

Coolant line

13

mixing unit

14

delivery channel

15

dispenser

16

exit

17

restrictor

18

metering valve

19

machine tool

20

control

Claims (11)

Method for providing an auxiliary device (1) to a workpiece processing zone (2), comprising at least the following steps: a. Providing a lubricant (3) with a first pressure, b. Providing a cryogenic coolant (4) with a second pressure, c. Adding quantities of the lubricant (3) to the cryogenic coolant (4), the first pressure being at least equal to the second pressure, d. Conveying the mixture of lubricant (3) and cryogenic coolant (4) in a common delivery channel (14) to a discharge point (5) near the workpiece processing zone (2). Method according to Claim 1 in which an oil or a dry lubricant is used as the lubricant (3). Method according to one of the preceding claims, wherein as cryogenic coolant (4) carbon dioxide or nitrogen is used. Method according to one of the preceding claims, wherein the second pressure is at least 50 bar. Method according to one of the preceding claims, wherein the first pressure before step c. at least 50% above the second pressure. Method according to one of the preceding claims, wherein in step c. a pulsed addition of the lubricant (3) takes place. A method of abrasive machining on a workpiece (6), wherein in a workpiece processing zone (2) an abrasive tool (7) is engaged with the workpiece (6), wherein a tool (1) provided in any one of the preceding claims is gaseous from a delivery point (5) is supplied. Device for providing an auxiliary device (1) to a workpiece processing zone (2), comprising at least: - A lubricant reservoir (8), a lubricant line (9) and a pressure booster (10), a pressure vessel (11) for cryogenic coolant (4) and a coolant line (12), - A mixing unit (13) into which the lubricant line (9) opens and from which a common delivery channel (14) goes off, - A dispenser (15) having an output (16) towards the workpiece processing zone (2). Device according to the preceding claim, wherein at least the coolant line (12) or the common delivery channel (14) is designed as a capillary. Device according to one of the previous Claims 8 or 9 , wherein the lubricant line (9) below the pressure booster (10) at least one throttle unit (17) or a metering valve (18) is provided. Use of a cryogenic coolant (4) under high pressure as a carrier for a lubricant (3) for delivery through a common delivery channel (14).

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