Accurate Strong Gantry

[Boyan Silyavski]

I am planning to attach an easy removable really small, geared spindle driven by the HS one with belt or directly coupled. (EDIT: i see now that the belt not good at this speed) In this method the supposed extension of the original spindle would be only about 60-80 mm and the force not bother the main spindle bearings
With 1:0,5 ratio (12000-to 6000 rpm) and quite enough torque I probably can make a typical steel milling with DIA 4-5 mm mill.

Belts are not a problem here. HTD belts are rated for these speeds. Problems are the bearings. Conical roller bearings will not spin so fast. Hence the 6000rpm limit on the spindles they sell. You will have to use angular contact bearings, not roller bearings, so they have to be over sized. Though i am still not sure if they don't use ball bearings on the spindles. You will have to check this and find suitable bearings and i don't see why it will not work. I have thought about that many times, despite what i said before. Plus my gantry on the machine i am building is rock solid. Though you have to have tremendously strong Z, cause 60-80 mm are big difference when we are talking about Z travel. On a router i mean.

One thing to note is that when we say -"this is bad, can not be done, not like that, you need other type of machine" , its not that it will not work. It will work.But not consistently, not for a long time. No perfect finish. Not be able to hold consistently precision. Ruining some element with time , /bearings/, etc. I can drive a city car where 4x4 car goes, but for how long? So actually its not a discouragement, its a reality check. I will be more than happy to see it done. Cause i will do it also.

Why don't you sketch your idea for the spindle and investigate the bearings.


As for the motors you could fit cheap encoder to steppers and then feed the signal to the breakout board/you will need available inputs/ . When out of programmed way, the machine could stop so you don't damage material. I have a plugin on my PC that does exactly that. Though that's not a true closed loop. The closed loop motors will push till all is where is meant to be and stop only if they could not overcome the force. If you decide to go this way, i will send you the plugin. There are cheap normal steppers with integrated encoders. though definetely will be mistake for the sake of encoders to buy some steppers witch are not low inductance.

Just use good PSU, good board and motors and you will not need these. Though closed loop would be nice on a metal working machine.