Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Program-control systems
  • G05B19/02—Program-control systems electric
  • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form
  • G05B19/4093—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form characterised by part programming, e.g. entry of geometrical information as taken from a technical drawing, combining this with machining and material information to obtain control information, named part program, for the NC machine
  • G05B19/40937—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form characterised by part programming, e.g. entry of geometrical information as taken from a technical drawing, combining this with machining and material information to obtain control information, named part program, for the NC machine concerning programming of machining or material parameters, pocket machining
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C3/00—Milling particular work; Special milling operations; Machines therefor
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/34—Director, elements to supervisory
  • G05B2219/34175—Overlap, between two blocks, continuous, smooth speed change, movement
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/49—Nc machine tool, till multiple
  • G05B2219/49077—Control of feed and spindle, cutting speed
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
  • Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Definitions

• the invention relates to a method for machining a workpiece with a milling tool, which is arranged on a rotatable spindle, wherein the spindle is displaced relative to the workpiece or the workpiece relative to the spindle along a machining path and the spindle rotates about a spindle axis, a speed and / or a phase position of the rotation of the spindle along the machining path is controlled as well as a device and a computer program for carrying out the method and a data structure for coding the computer program.
• Numerical controls are used in modern machine tools to control the positioning and movement of tools relative to a workpiece. In order to machine a workpiece according to a specification, it is necessary to move the tool relative to the workpiece on predefined paths.
• a path control The desired paths are defined in a part program that is processed by the numerical control.
• the numerical control converts the geometric instructions of the part program into instructions for the position control of the various feed axes of the machine tool.
• the milling spindle driving the tool is usually operated at a technological, constant speed during the milling process, which is specified in the parts program. (S word according to DIN 66025).
• a path speed is programmed in the part program for the tool (F word according to DIN 66025), which usually refers to the TCP (tool center point) or the location of the tool intervention on the tool.
• Generic milling methods are known, for example, from DE 10 2015 112 577 Al, DE 10 2010 060 220 Al, WO 2017/056025 Al or JP 2017-001153 Al.
• the spindle position is not exactly coupled to the path feed (e.g. with a speed-controlled spindle) or the path length integral in neighboring milling flanges is not a multiple of the tooth feed (misalignment even with a given position coupling between the feed axes and the spindle).
• milling workpieces that are manufactured according to the prior art typically show irregular cellular surface structures as shown in FIG. In Figure 8, the milling tracks run from left to right. It can be seen how the points of engagement of the tool cutting edges in adjacent milling tracks are randomly synchronized. However, there are always shifts, which then lead to an optically uneven appearance (wider stripes) of the surface. In the case of tools for injection molding or the like, this structure can be transferred to the end product.
• An object of the invention is to specify a method which makes it possible to produce a phase position of the tool cutting edge interventions in a targeted manner in adjacent milling paths. In particular, this is intended to improve the surface quality.
• the above-mentioned problem is solved in particular by a method for machining a workpiece with a milling tool, which is arranged on a rotatable spindle, wherein the spindle is displaced relative to the workpiece or the workpiece relative to the spindle along a machining path and the spindle about a spindle axis rotates, wherein a speed and / or a phase position of the rotation of the spindle is controlled along the machining path, and wherein the Machining path includes line-shaped parallel tracks.
• the processing path comprises parallel paths arranged in a cell next to one another and the phase position of the spindle along the processing path is the same or essentially the same in adjacent paths. Due to the same phase position, the pattern created in the surface by the milling process is the same in adjacent paths, so that the impression of a uniformly machined surface is created. The surface quality therefore makes it possible to dispense with polishing the surface.
• the phase position is controlled by varying the speed of the spindle and / or the feed speed of the spindle relative to the workpiece along the machining path.
• the speed and / or the phase position is controlled to a predetermined setpoint along the processing path at at least one synchronization point.
• the rotational speed and / or the phase position is controlled along the processing path at a plurality of synchronization points to a respectively predetermined setpoint.
• control of speed and phase position to the setpoint is started at a trigger point before a synchronization point is reached.
• the phase position is controlled by lowering or increasing the spindle speed.
• the phase position of the spindle can thus be controlled without changing the feed rate simply by regulating the spindle speed.
• the phase position is controlled by lowering or increasing the feed speed of the spindle relative to the workpiece along the machining path.
• an intervention in the feed is used to synchronize the phase position.
• the phase position is shifted by a multiple of the division of the cutting edges in a milling tool with multiple cutting edges.
• individual cutting edges are used synchronized. For example, if the milling head has 10 cutting edges, synchronization can take place every 36 ° (360 ° / 10).
• a device for carrying out a method according to one of the preceding claims which comprises means for displacing a workpiece relative to a milling tool arranged on a spindle and means for speed control and phase control of the rotation of the spindle.
• the spindle is driven by a position-controlled electric motor.
• the device comprises means for determining the angular position of the spindle.
• the problem mentioned at the outset is also solved by a computer program for executing a method according to the invention and a data structure for coding a computer program for executing a method according to the invention.
• FIG. 2 sketch of a speed limit profile as a cling to the
• FIG. 4 sketch for the joint scanning of the path speed profile and a spindle speed profile in the interpolation cycle
• FIG. 5 sketch for phase compensation of the spindle towards a block limit
• FIG. 7 sketch for the subsequent phase compensation in the case of dynamic trajectory planning for the programmed block boundary
• FIG. 8 sketch of a surface of a milling workpiece produced using a milling process according to the prior art.
• NC programs describe the milling path in a sequence of simple geometric elements. (Railway) bases or railway bases are the respective boundaries between two of the following geometric elements. These coordinates are taken from the NC program per line as an NC block.
• the path parameter also known as the path length integral
• the path parameter describes exactly one point on the path described in the part program, which may well lie between the support points of the NC blocks
• nSpdi n Prog (the speed of the spindle is at the value specified in the program)
• vb vp rog (the feed speed) it is at the value specified in the program)
• cpspdi cpprog (the angular position (phase) of the spindle is at the value specified in the program)
• the start (in time and / or path parameters) for planning a motion profile is based on a synchronous point.
• Each program line is designated in Figure 1 and in the text below based on Din / Iso or G code with N10, N20 and so on up to N100.
• a CNC control determines a maximum speed of the feed as a speed limit value profile for path planning.
• the speed limit value profile contains the feed programmed in the NC program or the feed speed w TM, pn> g and, as a result of the path profile analysis, the dynamically determined maximum values for the
• the task of the downstream so-called speed profile generator is to set a speed profile above the path parameter (or the time, depending on
• the speed profile calculated in this way is scanned by the so-called scanning interpolator in the cycle time of the so-called interpolation take as IPO scanning points and the position setpoints are calculated for all feed axes involved in the movement.
• This also means that not every NC interpolation point is output to the axis controller exactly as the position setpoint, because in the most general case the exact NC block limit comes to lie between two IPO sampling points.
• the scanning is shown schematically in FIG. 3. With a time interval T a, position values Sb were determined by corresponding displacement sensors of all axes and passed on to the control.
• the speed curve of a position-controlled spindle is determined and controlled via the path curve.
• the angle (phase) of the spindle is controlled to a predetermined value at certain points.
• a graphic representation is based on that of the web speed profile.
• the speed of a position-controlled spindle can be represented like a path speed profile in the same representation of a speed plan as the path parameter (or the time) as shown in FIG. 4.
• the cyclic position setpoints can then be scanned simultaneously by both profiles.
• an exact spindle orientation is assigned at at least one point on the path. According to the invention, this assignment takes place particularly advantageously in the NC program.
• the programming of such a synchronization condition leads to a fixed spindle orientation at least (FIG. 5) once per adjacent milling path.
• the object of the method according to the invention is first of all to determine whether trajectory planning is possible while observing the dynamic limit values. In the event that trajectory planning is possible, two possible methods for establishing synchronicity are described below. In addition, a method is specified as to how the case can be advantageously dealt with in that trajectory planning is not possible.
• a spindle angular position desired at this point is assigned to a specific geometric location on the path.
• This is achieved according to the invention by adding an additional NC block base (possibly redundant for the pure path description) to the part program in the CNC program.
• an additional NC block base possibly redundant for the pure path description
• the syntax extension provides a command G119, which expects a parameter S with the specification of an angular position of the spindle relative to a zero point (phase position).
• trajectory planning is possible, two methods can be used.
• a phase compensation takes place by means of the spindle.
• the definition of a synchronizing point shows that synchronizing points can only lie on the path (path parameters) at those geometrical locations in which a constant feed rate occurs.
• program line N70 contains the information that the spindle should assume an angle of 77 ° there.
• the created area in FIG. 5 is the speed-time integral, which corresponds to the required phase correction of the spindle position.
• the respective segment limits of the speed profiles are encircled.
• the process is time-optimized without influencing the feed planning and completely without negative influence on the total machining time of the part program.
• the calculation of the synchronization process is to be carried out as follows: After a (new) NC block with orientation condition for the spindle is found in the look-ahead buffer, the spindle speed profile becomes - similar to when a "normal" new NC block comes in - in addition to the path speed profile recalculated.
• the position setpoint output to the spindle in the last cycle is known, as are the exact path parameters and thus also the duration (in path and time) before reaching the synchronization point.
• the required amount of phase compensation is then the difference between these two angular positions in the modulo circle. In the case of multi-bladed tools, the required phase compensation can of course also be reduced to 360 ° angular positions / number of cutting edges.
• a spindle speed profile can be calculated that establishes the synchronization point exactly to the block limit. If the path feed (as in our example) is not constant during the phase correction of the spindle, it is important that the Synchronization process of the spindle ends exactly at the block limit.
• the phase compensation takes place by temporarily lowering the feed level, see FIG. 6.
• the method for the temporary lowering of the feed level of the speed profile is particularly efficient with high-speed spindles.
• the required height and duration of the feed lowering are small because the spindle takes practically every angular position in the range of milliseconds without varying the spindle speed.
• the calculation of the synchronization process is carried out as follows: The required phase correction amount is first determined as in the aforementioned method. After calculating the required phase correction up to the synchronization point, a modified piece of speed profile is calculated towards the synchronization point in such a way that the movement section takes exactly as much additional time (compared to the original planning) as the spindle needs to sweep over the required phase correction. Trajectory planning is always impossible if there is not enough time or time to find a trajectory.
• the method according to the invention provides for a downstream synchronization point to be determined which is a certain distance ... d away from the programmed synchronization point (downstream) on the path.
• the selected distance ... d is an integer multiple of the planned tooth feed, which is known from the S and F word.
• the S word controls the spindle speed, the F word the feed rate.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Geometry (AREA)
• Human Computer Interaction (AREA)
• Manufacturing & Machinery (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Mechanical Engineering (AREA)
• Numerical Control (AREA)
• Automatic Control Of Machine Tools (AREA)
• Milling Processes (AREA)

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Citations (4)

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• 2018
  • 2018-07-09 DE DE102018116553.6A patent/DE102018116553B4/de not_active Expired - Fee Related
• 2019
  • 2019-07-03 US US17/258,554 patent/US11507050B2/en active Active
  • 2019-07-03 EP EP19736669.3A patent/EP3821307B1/de active Active
  • 2019-07-03 JP JP2020569133A patent/JP7065213B2/ja not_active Expired - Fee Related
  • 2019-07-03 CN CN201980040339.5A patent/CN112513752B/zh active Active
  • 2019-07-03 PL PL19736669.3T patent/PL3821307T3/pl unknown
  • 2019-07-03 WO PCT/EP2019/067869 patent/WO2020011623A1/de not_active Ceased
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  • 2019-07-03 HU HUE19736669A patent/HUE064291T2/hu unknown
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