Carriages

Overview

The purpose of the carriage is to ride on a linear rail and provide smooth motion in one direction. If the carriage wobbled on the rail, then clearly, the motion of the carriage is not restricted to only the direction of the rail. It is near impossible to account for this extra motion while 3D printing, so a carriage that rides loosely on its rail can cause 3D print failures and at the very least can decrease print quality.

This brief section on carriages will focus on the V-Rail carriages supplied by the company OpenBuilds. There is not much to say about “traditional” rail carriages because typically there is little variation in these pre-assembled components. V-Rail carriages, on the other hand, do not come assembled, but instead are sold as kits that include a plate, wheels, and the hardware to connect the wheels to the plate. There are different options for the carriage plates and wheels that are compatible with different shapes of V-rail. This flexibility in the V-Rail system makes it possible to use a large carriage for the print bed while using a small lightweight carriage to move the extruder. The wheels can also be handpicked for your printer as they are available in a couple different sizes and materials. Depending on how often you expect to be running your 3D printer, you can save a little money by picking delrin over polycarbonate wheels. The wheel size will depend on the plate and rail chosen.

Assembly of a V-Rail Carriage

Assembly of the v-rail carriages is straightforward. A M5 bolt is used to connect the wheel to the carriage with a spacer in between. However, it is up to the user to find the balance between having the carriage ride snug enough on the rail to avoid wobbling while not riding too snug, which would impede the free motion of the carriage. The eccentric spacer is what allows for the ride stiffness to be adjusted. Rotation of the eccentric spacer, which is found between the plate and the wheel, will change the distance of the wheel to the rail. Bringing the wheels closer to rail will result in a stiffer ride while backing the wheels away from the rail will result in the opposite.

Limitation of V-Rail Carriages

I am personally a huge fan of V-Rail. This opensource linear system is intuitive, which makes it easy to assemble and explain to others. However, some of the more advanced DIYers shy away from V-rail, which is why it is important to highlight some of the limitations. The ability to adjust the ride stiffness of the carriages is both a pro as well as a con to this system. Over many hours of printing the eccentric spacers can slowly start to rotate which could cause wobble in the carriage. For this reason, V-rail requires more maintenance than “traditional” rail. Further, the longevity of plastic wheels will never match that of the ball-bearings found in other carriages.