so i decided to post this here instead of the novakon forum because might be interesting to anyone who's bought or wants to buy a kx1 variant machine. mine happens to be an early first gen sieg kx1 bought from novakon.
i should note i bought this as a demo machine for a good price, and that combined with being an early version it has some strangeness about it. the new versions have many improvements.
i was having some issues with spindle deflection, and wanted to find the root of the problem so i took the whole machine apart. as it turns out, there are several contributing factors - some fixable, others design problems.
1st thing is the z axis gib. there are 4 screws hidden in behind the electrical cover, and difficult to adjust. new versions have tapered gibs so this is a non issue. once apart, i was able to lay the column on its back and adjusted the gibs nice and snug. its a bit challenging because you get the gib screw gut right, then tighten the lock nut and it adds a 1/8 of a turn to the screw, making everything too tight. what this did for me is remove any play in the head, and this helped a great deal with deflection.
wit that fixed, the numbers are as follows with the head at the highest point:
pulling up on head against machine weight (110lbs) - .004" movement in Z.
pushing down with all my weight (165lbs) - .003" movement in Z.
pushing in the X direction with all my strength - less than .001" movement in X.
pushing in the y direction - .001" backward, .002" forward. curiously, .003" Z motion results in both directions.
so i went searching for areas of flex. the head flexes very slightly, but most of the movement was coming from 2 locations. pushing in the Y, the movement was from the base of the column. its not a very secure mount because theyve milled most of it away to run the motor in the back. i may try to fix this a little by adding a bracket that connects the lower part of the column to the rear motor mount, bracing it. the new mill has a deeper column, but the base is the same, so i dont think it will be much improvement here.
pulling up and down, the movement was from the ball screw conneting plates. the drawback with this is that the head tends not to settle in precisely the same spot each time. its out by about .001". it appears to be consistent though, in that it returns to the correct location after the ball screw is moved. the new version of the mill has a counterbalance strut. this probably doesnt help however because its in the back of the column. to be effective, it should be supporting the head. i may add one as a test.
along the way, i found that the spindle had some play as well. enough to move .001" side to side at 8" from the nose. the nose bearing is angular contact, so this should be fixable with some tightening, but i need the spanner tools first.
i will post some photos later on of the rebuild.
other than the column quirks though, the machine is really amazingly well built.  |