Hi Group
My CNC is nearly done. I have noticed a problem with twisting of the Y axis.
I set a dial-indictor against the 4 x 4 uprights that support the Y axis. I pushed against the uprights in the X axis direction and got a movement of .010 + -. I then setup the thk rails on top of the machine frame with wood brackets clamped to the uprights. I tried my test again and I have .005+ -. This test helped to confirm I should add the second set of rails to the machine. My questions to the experts in the forum is should I mount the THK rails to the top of the machine frame. And two, what is the best bearing spacing for the sliding THK elements.
I like the top mount location because they will be very easy to mount. These THKs are very small so they don`t take up allot of the table surface. I plan to add a work surface to the top of the machine so I can hide THKs under the work surface. Its my idea this will help to shield them from dust and metal chips.
Another reason for mounting on top of the machine is I`ve noticed a oscillation of the X axis as it comes to a stop. By the looks of the test it seems to reduce the oscillation with the rails set at there current location..
At the moment for the test theTHKs are spaced at a overall measurement end to end of 5.5 inches. I`m wondering if anyone could confirm if the 5.5 spacing is a reasonable distance to eliminate the twisting that I`m experiencing with the Thomson round rails.