In the cast metals industry there are many differing kinds of casters. High volume sand, jobbing sand, investment, pressure diecast, centrifugal casters to name a selection. But even within one of these specific types there is subtle variations that mean each foundry needs a specific set of tools to do the scheduling job just as a plumber will use a different set of tools for each job that he carries out.To best schedule a foundry you need to be able to select the right set of tools for the job.
Each metal caster will have different processes that they will need to schedule and each process will have one or more constraints that need to be taken into account.This is a list of constraints that are most often used in the metal casting environment.The best capacity constraint to use in most cases is time as it is usually the most accurate. However in some cases, jobbing foundries as one example, time may not be the capacity of choice so any of the available capacity constraints can be used or a combination of capacity constraints
Rack moulding and Stack moulding require some unique capacity constraint measurements not found in other types of metal casters and as such the tools required here vary from the norm. In order to allow for scheduling these types of processes without compromising the systems ability to schedule other types of moulding these processes need to be treated as a one off.Two additional capacity constraints (blows and number of racks/stacks) are used in this case and in addition the calculation of time also needs to be changed.
Investment foundries have a need to store, and use in scheduling, both the quantity of wax moulds that go on one tree and the number of wax moulds made per injection of the wax die.No additional capacity constraints are required in this instant.
Pressure diecasters have a very similar situation to investment casters and the same approach will allow for successful scheduling.No additional capacity constraints are required in this instant either.
Scheduling by time requires 2 different times to be taken into account. Firstly there is setup time (if required) and this can be applied in different ways depending upon process. Then there is the run time which is only calculated differently for stack or rack moulding.An allowance can be required for efficiency when creating working times in the calendar, each process can be different in this case.An adjustment is required where scheduling by man hours to allow for the number of employees working in each department
Once a schedule has been created for a day it can then be broken down and/or prioritised by different criteria as required. There are many common methods for this and here are just a few.
An example of a schedule broken by metal and melt sequence.
It may be necessary to breakdown production runs for many different reasons, box availability, melt capacity and bottleneck process capacity to name but a few.
To make scheduling simpler the use of automatic highlighting of specific issues with colour is of great benefit.Common uses for this are to highlight jobs that are running late, jobs that were scheduled to have been processes but were not, jobs added to the schedule after the schedule is finalised and highlighting remakes.
Many other tools should be provided in the ‘bag of tricks’ to help with specific sets of circumstances and the slide above contains but a few.
This slide contains an example of scheduling while monitoring an additional bottleneck process. There is no limit to how many additional bottleneck processes can be monitored, the only limitation is the screen size, and this is a reason why most schedulers have large screens or dual screen configurations.
SCHEDULING REQUIRES A TOOLKIT NOT A TOOL
EACH FOUNDRY IS UNIQUE AND REQUIRES A UNIQUE
SET OF TOOLS IN ORDER TO SCHEDULE IT
TIME (INC SETUP TIME)
NUMBER OF MOULDS
WEIGHT (POURED or CASTING)
MOULDING BOX AVAILABILITY
FLOOR AREA (LESS COMMON)
OVEN CAPACITY (LESS COMMON)
Rack or Stack Moulding
MOULDING PROCESS MARKED AS SPECIAL CASE
STORE RACK OR STACK SIZE
NUMBER OF BLOWS CAPACITY
NUMBER OF RACKS/STACKS CAPACITY (SPACE)
CHANGES TO TIME CALCULATION
STORE 2 BIND QUANTITIES
BIND QUANTITY 1 USED FOR TREE SIZE
BIND QUANTITY 2 USED FOR DIE NUMBER ON
STORE 2 BIND QUANTITIES
BIND QUANTITY 1 USED FOR CASTINGS PER SHOT
BIND QUANTITY 2 USED FOR CASTINGS TRIMMED PER
SCHEDULING BY TIME
SETUP TIME PER DAY OR PER JOB
ALLOWANCE FOR EFFECIENCY PER SHIFT
MACHINE TIME Vs LABOUR TIME
PROCESS PRECIFIC CALENDARS
DEFINABLE SHIFT PATTERN
UNLIMITED NUMBER OF SHIFTS
SHIFT & PRIORITY
SHIFT & METAL GRADE
MELT & POURING TEMPERATURE
METAL & MELT NUMBER
MANY OTHER VARIATIONS