6mm Belt Tensioners for Monoprice Select Mini 3D Printer

thingiverse

The Monoprice Select Mini has a pair of 6mm belts used for X and Y movement. These belts have cheap spring tensioners that can flex under rapid acceleration, leading to print artifacts. To fix this, replace the spring tensioners with constant-tension belt tensioners. To install these tensioners, you'll need small cable tie fasteners. The cable ties provide clamping force to hold them in place. Before installing, print and clean up the parts, then test fit them together. They should fit snugly. Start by removing the spring clips from your belts with pliers. Install the X tensioner first: take a cable tie and the smaller half of the tensioner from behind the machine. You'll see the belt through the large slot. Place the smaller half on the exposed belt, then add the second half on the other side. Engage the cable tie to its lock and draw it tight, but don't over-tighten. Next, slide the extruder hot end as far towards the tower as possible, holding it in place while you move the tensioner along the belt. Now fully tighten the cable tie lock using pliers. Trim the excess cable tie. To ensure proper installation, test the tensioner by sliding the extruder back and forth. If the tensioner hits anything, you may have installed the large and small parts incorrectly. Just cut the cable tie and correct your mistake. For the Y tensioner, lay the machine on its back and pull the build plate forward. Feed a cable tie through the slot in one half of the Y belt tensioner, then around the belt and through the other half's slot. Engage the lock but don't tighten it yet. Move the tensioner as far forward along the belt as possible, right up against the metal lip. Now tighten the tie wrap as tight as possible and trim off excess cable. Sit the machine upright and slide the build plate backwards, listening for the limit switch to engage when almost completely at the rear. If the tensioner interferes with the build plate's travel before engaging the limit switch, you didn't get it fully forward. If needed, use a clamp or locking pliers to compress the tensioner while tightening the cable tie. This worked great on my printer, eliminating slop on the linear rod bearings. I've provided enough tolerance in these parts for variations between printers, but feedback would be helpful.