Simple Solutions That Work! Issue 13

Contact: JOHN HALL [email protected] 46 controlled. For example, where to place a thermocouple in a die so that it gives the relevant tool temperature. • Select measurement methods – selecting the proper measuring device specific to the casting process will ensure that the system will be accurate, stable, and cost effective. Tilt pour casting machine signal types include: – Electric – Pneumatic – Hydraulic – Light – Radio waves – Ultrasonic • Select control method – in order to control the casting parameters, selecting the proper control method is critical in controlling the casting process effectively. In the tilt pour process these method include: – On/off – Proportional – Integral – Derivative • Select control system – most permanent mold casting cells utilize local control, but a distributive can be utilized. • Set control limits – understanding the operating parameters gives the foundry engineers the ability to define the limits of the measurable parameters in the casting process. • Define control logic – most tiltpour casting machines use some form of ladder logic and in some cases must communicate with other machine languages such as robots or CNC. • Create redundancy – even the best control will have failures. It is important to design a redundancy system to avoid catastrophic failures or create an unsafe condition. • Define a fail-safe – fail-safes allow the casting machine to return to a safe state after a control breakdown. In a tilt pour casting machine these include: – Spring to center hydraulic valves – Normally closed water and air valves – In line hydraulic velocity fuses – Motor protection – Lock out tag out • Define lead/lag criteria – depending on the conditions within the casting work cell, there may be lag times associated with peripheral equipment such as ladlers, casting extraction devices, conveyors, and saws. Setting lead/lag times compensates for this effect and can reduce the possibility of creating a defect. • Investigate effects of changes before/after – as noted above, investigating casting process changes in the control system, unforeseen problems can be identified and corrected before casting defects are created. • Integrate and test with other systems - the proper integration of a casting process with the goal of eliminating defects in a work cell environment avoids conflicts between multiple systems with improved defect reduction, safety, cost and profitability. The single best way to prevent defects is to keep the casting process in control. The benefits of controlling or automating the casting process are not only defect reduction, but it also increases worker safety.