Functional Description: Overview; Functional Description: Injection Control - REXROTH VT-HACD-DPQ Series Technical Data Manual

Functional description: Overview

Overview
The VT-HACD-DPQ is a digital controller card. It optimizes
the control of hydraulic injection axes.
▶ The rate of injection profi les are completely realized by
a position control system. A position command value
profi le is automatically created on the basis of the
velocity profi le entered by the operator.
▶ As the VT-HACD-DPQ controls the position, a position
transducer is required. Both analog (0...10 V; ±10 V,
0...20 ad 4...20 mA) and digital position transducers
(SSI; INCR) are supported by the VT-HACD-DPQ.
▶ The VT-HACD-DPQ comprises limitation of the injection
force. For the limitation, 1 or 2 pressure transducers or
one load cell can be used.
▶ The rate of injection and the pressure profi les can be
regulated using a proportional directional valve or
separate valves for fl ow and pressure.

Functional description: Injection control

Injection profile
In order to fill the mold, a velocity profile with up to
10 steps is provided.
For every profile step, a maximum pressure/force limit can
be set. The injection cylinder is moved in a regulated form
using the velocity profile (position control).
At the beginning of the injection, the internal position
command value is set equal to the current actual position
value and then moved forward by means of a ramp which
corresponds to the relevant step in the velocity profile.
The steps are run through one after the other. Switch-over
to the next step is effected as soon as the position com-
mand value has been reached. The repetition accuracy of
the profile is determined by the highest setting of the
proportional gain possible so that the injection cylinder
follows the internal position command value as closely as
possible, also under varying load conditions. This system
is used as changes in the material properties of the plastic
and in the temperature have hardly any influence. As the
position control is a ramp of the position command value
over the time, variations of velocity between the profile
steps take place smoothly and do not require any special
ramp adjustment.
Digital control electronics | VT-HACD-DPQ
▶ The command values for the motion profi le can be
(analogously) transmitted by the PLC to the
VT-HACD-DPQ. The profi les can, however, also be input
into the VT-HACD-DPQ using the Bosch Rexroth
BODAC software.
Function
The VT-HACD-DPQ is a complete solution for controlling
hydraulic injection axes. The injection profile is created by
different parameters which are entered by the machine
operator. All process parameters for the injection cylinder
are stored on the card. Parameter changes can be loaded
onto the VT-HACD-DPQ individually or as complete profile.
The VT-HACD-DPQ keeps the last stored profile in a non-
volatile flash (memory). On the card, one single injection
profile is stored. To enable the VT-HACD-DPQ, a discrete
input (enable) is required.
Transition to the holding pressure
The VT-HACD-DPQ starts with the holding pressure profile
as soon as one of the specified transition criteria is met.
The transition criteria available in the stored profile are
hydraulic pressure and cylinder position, internal mold
pressure or digital input 3 (DI3). All transition criteria are
monitored on a permanent basis. Transition criteria which
are not used are to be set to values which cannot be
reached during the travel profile. The hydraulic pressure
command value is only activated if the cylinder position is
smaller than the set hydraulic transition position parameter.
So acceleration pressures higher than the set hydraulic
transition pressure are also possible without triggering of
the holding pressure profile. The machine control can start
the transition by means of a digital input (DI3).
Via the digital output DO1, the machine control is signaled
that the process has been completed.
Holding pressure phase
For the holding pressure, a pressure/force profile with up
to five steps is available.
As soon as the holding pressure phase is activated, the
VT-HACD-DPQ switches to pressure/force control with
superimposed velocity control. All other steps in the veloc-
ity profile are ignored. In every step, pressure, (force)
RE 30146, edition: 2013-10, Bosch Rexroth AG
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