Magnetic Stir Plate 120mm

thingiverse

This is a magnetic stir plate based on a 120mm fan, powered by 12 volts. I wanted something larger and more stable than the 80mm units. It uses a PWM speed controller from eBay, either with or without an LCD. At high speed, it will throw the magnet, but that's much faster than the speed needed for a vortex to reach the bottom of a 2L vessel. With the 1.5" stir bar, the speed needed to keep a good vortex is well below 50%. It should work fine for larger vessels, given the rather large stir bar. I have only tested it with a 2000ml flask. So far, it hasn't thrown the stir bar, unless I really crank the speed far beyond what's needed. The magnets are N52 1/2" x 3/4". They're quite strong and require careful handling. If they slam together, they will shatter. The poles are on the flat ends, so alternate them when pressing them into the MagnetMount. One side of the magnet has a red dot; make sure it's facing up, while the other has its dot facing down. The 1.5" stir bar can be found on eBay. The 120mm fan features HBD bearings and is available on Amazon. The PWM speed controller uses a print template called NoLCDSideCar.stl, which can be found on eBay. The PWM speed controller with LCD uses a print template called LCDSideCar and can also be found on eBay. If you use this controller, you'll need to break the tabs off the side of the LCD module. It should fit tightly but may require some glue. The side cars are bolted on using 1" #4 screws. They have cutouts for nuts, but the screws are tight enough that they probably aren't needed. The 120mm fan is bolted to the base using four 2" #8-32 machine screws. The screws are attached to the base first using two nuts each. It needs the spacing from the two nuts, and three nuts hold the magnets a bit too far from the base. Test fitting the fan with the mag mount attached, adding washers until the mag mount stops touching the base, then add another washer. I ended up using two washers. Add a nut or two to keep the fan in place; there should be enough room for two nuts at the end of the screw. Both side cars have slots for Anderson Powerpole connectors. You can find these on Powerwerx.com. They're safe from vibration and properly fused, but make sure whatever you use is properly secured. The MagMountBase is super glued to the top of the fan. The fan hub is curved, with a matching curve in the printed base. This must be as well centered as possible; use a slow-drying glue to give yourself enough time to center it properly. The magnets are pressed into the MagnetMount, with alternating poles on the same side. The MagnetMount should slide onto the top of the MagMountBase. A little knife scraping may be necessary to fit them together without force. Either use a 3mm x 10mm screw to permanently keep them together or just use super glue. I created two parts in case I needed to alter the spacing of the magnets or change to different magnets without having to re-glue it to the fan. The four #8 screws actually support the entire stir plate, with the screw ends resting on the table. A non-skid mat will keep it from moving around, especially if the MagMountBase isn't well centered on the fan. I modeled this in Fusion 360, and you can find the source files as well as IGES included. I printed it in PETG since that's what was in the printer. The infill was 30% with three solid layers. Print Settings: Printer Brand: MakerGear Printer: M2 Rafts: Doesn't Matter Supports: Yes