Report on CNC Motor Couplings
What's better Solid or 3 piece ?
Building your CNC machine will involve a lot of different decisions, if you have decided to use a screw to drive your machine slide, the motor coupling is your next decision, but there are some important decisions that will effect the way your machine is setup designed, and how it will perform, please take a minute to read below,
The one piece
Solid Coupling is by far the easiest lowest cost and in our opinion the
best way to join a screw to a motor, for cnc routers and cnc lathes, they are easily available, are self aligning, do not damage the motor shaft, and make a 100% connection from motor to screw, one trick when using a solid coupling is to use a simple thrust washer, placed on the motor shaft between the motor face and coupling, using a thrust washer will take any linear load of the screw, allowing the motor, coupling and screw a total direct connection with almost zero end play
The 3 piece flex coupling , is just as it's name implies, it's made from 3 parts one rubber connector, and two hubs, using this style of coupling is "
not recommended" for a CNC machine, applications for numerous reasons, difficult to perfectly align, there also can normally be some backlash in the rubber connector, you also must use additional screw support bearings to hold the screw from linear movement, because the name "Flex Coupling" is used, a big misconception or mistake people make is they can have some misalignment because it's a flex coupling , this is a WRONG misconception, misalignment of this style of flex coupling is bad for CNC cutting, center and or axial misalignment can cause the screw to oscillate in a sinusoidal path, and or bind, another issue with this style of coupling is the set screw damages the motor shaft, and will always work there way loose, We just don't make this stuff up it comes from many years of experiance, and by watching people make this mistake a lot
see an example of issues with backlash with this style of coupling