Method for the process management of a mold-filling process of an injection molding machine

A method for the volumetrically correct filling of a cavity of a mold with a melt of a material to be processed in an injection-molding process, said method comprising a learning phase and a production phase:

• performing said learning phase comprising the steps of:
• providing an injection molding machine equipped with a mold and set up for producing a usable part in a cavity of the mold;
• carrying out at least one learning injection-molding cycle to obtain the usable part and recording a pressure curve correlating to a mass pressure curve;
• determining a viscosity index, which characterizes a melt of the learning injection-molding cycle, during an injection phase of the learning injection-molding cycle or during a plasticization phase preceding the learning injection-molding cycle;
• determining a filling index as an index for the volumetrically correct filling of the cavity of the usable part in the learning injection-molding cycle, wherein the following equation applies:
• FIL
• =
• L
• t
• ⁡
• (
• s
• =
• CPi
• )
• t
• (
• s
• =
• C
• ⁢
• ⁢
• 0
• ⁢
• ⁢
• Pd
• ⁢
• PLMass
• ⁡
• (
• t
• )
• ⁢
• d
• ⁢
• ⁢
• t
• wherein
• FIL is the filling index,
• COPL is a changeover point in the learning injection-molding cycle,
• (s=COPL) is a screw position at the changeover point in the learning injection-molding cycle,
• (s=CPL) is a screw position at the start of integration for determining the filling index,
• t(s=COPL) is the time at the screw position of the changeover point in the learning injection-molding cycle,
• PLMass(t) is the pressure curve, and
• t(s=CPL) is the time at which the screw position has reached a position at which a predefined pressure PLMass(t)=PcP is applied, or has reached a position at which the filling of the cavity begins, wherein the following equation applies:
• s=CPL>s=COPL;
• and
• forming a molded-part volume equivalent
• MPVeq=FILNIL, wherein VIL is the viscosity index,
• performing said production phase comprising
• the steps of:
• carrying out a multiplicity of production injection-molding cycles using the mold;
• recording at least one pressure curve correlating to the mass pressure curve during a current cycle of the multiplicity of production injection-molding cycles;
• determining a viscosity index, which characterizes the melt of the current production injection-molding cycle, during the injection phase of the current production injection-molding cycle or during a plasticization phase preceding the current production injection-molding cycle,
• after determining the viscosity index, calculating a required filling index for the current production injection-molding cycle in accordance with the equation:
• FIp=MPVeq*VIp
• and
• adjusting a changeover point of the current production injection-molding cycle and/or an injection rate profile in such a manner during a remaining injection phase (EP) of the current production injection-molding cycle that the following equation applies:
• Flp
• =
• J
• t
• ⁡
• (
• s
• =
• CPp
• )
• t
• ⁡
• (
• s
• =
• COPp
• )
• ⁢
• PPMass
• ⁡
• (
• t
• )
• ⁢
• d
• ⁢
• ⁢
• t
• =
• MPVeq
• ·
• Vlp
• wherein
• COPp is the changeover point in the production injection-molding cycle,
• (s=COPp) is a screw position at the changeover point in the production injection-molding cycle,
• (s=CPp) is a screw position at the start of integration for determining the filling index,
• FIp is the required filling index,
• PPMass(t) is the at least one pressure curve,
• VIp is the viscosity index.