Most extruder work on a Cartesian printer starts with a screwdriver: loosening screws, swinging the body aside, wrestling with the filament path. MihaiDesigns has taken a different route with the PitStop, a two-part extruder where the front section pulls off the carriage and hotend magnetically, with no screw turning. That detached half houses the drive gear, stepper motor, cooling fan and print-cooling duct, and the magnetic split is what allows rapid access to the filament path and drive gears.
The build itself is thought through. The printed parts come in bright yellow or orange and mount on the X-axis rods and belt of a Cartesian printer, shown installed both on a Prusa i3-style machine and on an aluminum extrusion Bear frame. A full-sized Noctua fan replaces the smaller stock fan and pushes air through internal ducts over the stepper motor, heatsink and gears. There is an integrated X-belt tensioner tightened with an Allen key, internal slots made for square nuts, a metal finned hotend heatsink wearing a blue silicone sock, and an inductive bed-leveling probe. IGUS bearings are used, though the maker says any bearings will do. MMU2S support is built in, and two multi-material unit assemblies have been demonstrated.
Printing it takes about 150g of plastic and roughly 20 hours, and the assembly comes out about 20% heavier than stock, a figure corrected down from an earlier 30% estimate. The maker printed it in ASA, deliberately the cheapest filament available at the time, to confirm the design works from lower quality material, and reports a year of reliable printing with no visible change in print quality.
One open question: stock frame compatibility follows the Prusa MK3S CAD drawings but has not been physically tested, and whether it works with the Bear 2.1 frame is unknown. Free STL files for personal use are promised soon, and a bill of materials preview is already up on the maker's website.
Project by MihaiDesigns. Watch it on their YouTube channel: