Simple Solutions That Work! Issue 7

amount of resin to be delivered to the chamber as well. Do this using the recommended resin/ pound percentage – for example, “1.5% per pound/minute” – available from your resin supplier. To translate the resin percentage into a resin amount, multiply this percentage by the pounds of sand/minute. For example, if the resin percentage is 1.5% for 80 pounds of sand per minute, the resin amount is 1.2 pounds per minute (0.015 x 80 = 1.2). Before beginning resin calibration, determine the proper amount for each resin (typically Part I and Part II) to be used in production operations, also available from your resin supplier. Optional third-part resin – If your mixer includes an optional third pump used to supply the catalyst for a three-part resin system, also determine the proper third-part resin amount. Typically, this is a percentage of the part-1 and/or part-2 liquid total. 1. Locate an empty container suitable for holding the amount of liquid you expect the mixer to process during calibration. 2. Weigh the container selected using an appropriate calibration scale. Note this weight for later use. 3. Place the container level with or above the mixing chamber’s inlet ports. Note: It is important that the container is level with or above the inlet port. If the container is below the port, liquid can run out of the hose before and after the calibration test, which can dramatically affect accuracy. 4. On the mixing chamber, remove the liquid delivery jet of the liquid supply you are calibrating. 5. Place the liquid delivery jet, nozzle pointing down, over the calibration container. 6. If the mixer is equipped with a Calibration Timer, start the timer now and catch the resin that is ejected from the nozzle. If the mixer does not have a calibration timer, it is best to have a helper use a stopwatch and run the selected pump for a specified amount of time (1 minute is best, but a shorter time can be chosen in order to avoid resin waste) 7. Weigh the container of resin and subtract the weight of the empty container weighed previously. 8. If the amount dispensed matches the amount desired, the mixer is ready for production. If the amount does not match the amount desired, adjust the speed of the pump and retest until at desired range. The method for adjusting pump speed will vary based on mixer age and manufacturer, but it is usually via a potentiometer or a PLC Touchscreen input. Refer to your specific mixer manual for detailed information. 9. Repeat this process for each resin component. First and Last Sand Once properly calibrated, the sand from the middle of a cycle is usable, but operators will sometimes have issues with the first and last sand at the beginning and end of a cycle. In order to make this sand usable, we recommend setting up a board test and then making adjustments to the start/stop speed of your resin and/or sand to balance them. To perform a board test, obtain a long board, such as a 1’ wide strip of plywood 8’ long, and a helper. Start the mixer and catch the first sand out of the mixer at one end of the board. Move the board under the mixer discharge catching the sand from the mix cycle. Shut down the mixer in time so that the last sand discharge from the mixer will be on the opposite end of the board from the start point. Set the board down and observe the sand: Continued on page 52 51