Die-casting and Precision Machining

Conventional die casting (CDC) is a net-shape manufacturing process
using a permanent metal al die casting  that produces components ranging
in weight from a few ounces to nearly 25 kg quickly and
economically. Traditionally, die casting is not used to produce
large products; past studies, however, have shown that very large
products, such as a car door frame or transmission housing, can
be produced using die casting  technologies.2 Conventional die cast
components can be produced in a wide range of alloy systems,
including aluminum, zinc, magnesium, lead, and brass.
Two basic conventional die casting processes exist: the hotchamber
process and the cold-chamber process. These descriptions
stem from the design of the metal injection systems utilized.
A schematic of a hot-chamber zinc die casting machine is shown in
Figure 1.2. A significant portion of the metal injection system is
immersed in the molten metal at all times. This helps keep cycle
times to a minimum, as molten metal needs to travel only a very
short distance for each cycle. Hot-chamber machining Components are rapid in
operation with cycle times varying from less than 1 sec for small
components weighing less than a few grams to 30 sec for castings
of several kilograms. Dies are normally filled between 5 and 40
msec. Hot-chamber die casting  is traditionally used for low melting
point metals, such as lead or zinc alloys. Higher melting point
metals, including al die casting alloys, cause rapid degradation of the
metal injection system.
Cold-chamber al die casting machines are typically used to conventionally
die cast components using brass and aluminum alloys.machining Components
An illustration of a cold-chamber die casting machine is presented
in Figure 1.3. Unlike the hot-chamber machine, the metal injection
system is only in contact with the molten metal for a short period

Part Cooling Requirements
Once the part is extracted from the die casting, it may need to be cooled prior to further processing or transfer to other
equipment. This can be a liquid quenching or air cooled process based on the product and the desired material
characteristics. For liquid cooled operations, the equipment could be as simple as a quench tank into which the
robot dips the hot part once it is extracted from the al die casting. For air cooled operations, a small fixture or buffer stand
may need to be designed so that the robot can unload the parts. Robotic simulation is a great tool to validate
buffer stand reach and location.
Degating/ Flash Trimming
In some manufacturing operations like engine parts, thedie casting may have metal extensions known as gates or
runners that are deliberately created in the al die casting  process to eliminate air and porosity in the main casting part.
These gates can be removed by several different methods based on the quality and finish requirements of the end
product. In most cases, the gates are removed by using a “knock-off” stand. The degating process generally has
specific orientation and direction requirements to remove the excess material. Robotic simulation must be used to
ensure that the robot can access the desired knock-off position without any reach issues.zinc die casting
An extension of metal is formed on die castings at the parting line of the two die plates and where moving die
components operate. This is known as “flash” and is an unwanted by-product of the manufacturing process. This
flash is generally removed using a trim press or in some cases a CNC machine. The robot loads the casting into
the press or CNC machine, waits for the equipment to cycle before unloading the finished part. Using robotic
simulation to validate this load/ unload sequence is important to ensure that there is sufficient opening and clearance
to enter the machine.
Part Transfer/ Exit
die casting parts may be transferred out of the system in several different ways based on customer requirements.
Some parts may be transferred out onto conveyors for further processing while others may require robotic palletizing
into racks. Robotic simulation is again a
valuable tool to ensure that the robot can reach all
extremes of all pallets at all heights. al die casting,The simulation
can also be used to analyze cycle time based
on stack pattern requirements.zinc die casting
 

Floor Space
The amount of floor space required to automate a die casting operation depends largely on part processing
requirements as well as peripheral equipment design and sizes. The most effective way to ensure that appropriate
space is earmarked for the robotic automation
process is by performing a simulation of all the robotic
operations. Al die casting,This will ensure that equipment is placed
in locations that will suit all process requirements and
sequence of operations. A significant benefit of using
robotic simulation is the ability to test multiple product
styles and dies to arrive at a common layout configuration
which reduces changeover time and associated
costs. The simulation done in conjunction with
mechanical design and layout development will act as
a virtual three dimensional integrated cell.
Payload and Robot Selection
Robot selection is driven not only by environmental conditions but also based on payload, reach and part access
within the die. Al die casting,The mass, center of gravity and moments of inertia about the mounting face of the robot determines
the robot model based on payload capacity. The mass data for the payload analysis can be generated from
the mechanical design CAD package as long as the data entered into the system for material properties is accurate.
The mass data that is generated can then be entered into a payload calculation program to determine the
robot model that can withstand the payload requirements. die casting ,Apart from payload, other factors that help drive robot
selection are – die travel (horizontal vs. vertical), gantry vs. floor mounted robots based on equipment size and
access and cycle time requirements.
Cycle Time Validation
The main driver for production rate on a die casting system is the time it takes for one cycle of the press and the
unload time. Once this data is known, process design must focus on ensuring that the press spends a minimum
wait time on other pieces of automation. The time
spent by the robot after unloading the part from the
dies should not exceed the time required by the
press to cycle and generate a new zinc die casting.
Robotic simulation in conjunction with external robot
controller software (RCS) can be used to generate
accurate robot motion cycle time. The use of virtual
controls replicates real-world conditions and allows
for evaluation of both individual processes and
coordinated activities of robots within a system.