V slot Wheel tester

thingiverse

If you need a way to check if your V-Slot wheels are running straight, this tip might be helpful. You will require a Dial Gauge and some 5mm bolts, nuts, and washers to set the height properly. Wheels that don't run true can make it extremely difficult to get the first layer down, and depending on where the wheel is located, the error will grow larger and larger as the print gets taller. Check out my image for an example of how small the error is at the bottom, but how much bigger it becomes as the print rises higher. You can also see this by placing the nozzle just above the print surface, then moving the bed and getting the impression that the glass is wavy. In fact, the wheels are raising and lowering the nozzle (when the wheel on the X rail is faulty) or maybe even tilting the level of the bed when the Y axis wheels are at fault. To test a wheel, fit it under the nut and tighten to finger-tight, then lower the dial stem against the sloping edge of the wheel as that's the running surface. Discard any wheels that don't run straight.