Sieg/Arc X3 CNC conversion

I have an older Sieg/Arc X3 CNC mill conversion. In fact one of the first I believe. It has developed some backlash in the X axis. It appears to be in the ballnut area or the ballnut housing. There is no backlash in the connector between screw and stepper. - I seem to remember that something here is prone to coming loose. But have checked everything I can see short of dismantling. If any of you guys can shed any light on the problem. I would be extremely grateful for your advice,

Possibilities:

• Play in the thrust bearing that stops the feed screw from moving to and fro.
• Dirt in the ballnut - Dick Stephen I think mentioned this in an article in MEW describing how to clean them.
• Worn ballnut and/or balls and/or screw.

Most/all of these you would have to dismantle to fix. How much backlash is there? Have you got backlash compensation enabled?

Hi Rod,

Further to your discussion with Ian this morning, here is some more information which 'might' help you.

ARC only sold kits for the conversion.. say about ten years ago. I believe you purchased a converted machine second hand from someone. Are you able to find out if they installed the kit themselves?. We do not have any information about it now. All I can tell you is that if the kit was from ARC, it had NSK - Class 7 ball screws, and unless the previous user ran the machine hard, or failed to lubricate the nut, the probability of wear on the nut was low.

If the previous user had the kit installed on his machine by the late John Stevenson, then the installation contract was specific between him and John, in which case, ball screws other than NSK could have been used depending on that persons agreement with John at that time. Similarly, Rimo based in Scotland used to also buy manual machines from us and do his own conversion, using THK or SKF class 5 or 7 ballscrews, depending on what the customer was prepared to pay.

Other than above, to figure out whats going on, you will need to dismantle the machine.

Ketan at ARC.

Well I have fixed it. Thank you gentlemen. There are two small 5mm screws that "secure" the X axis bearing block to the Y axis carriage. These were "like something in an old fashioned piece of headwear".

As the Y axis screw was covering them, the screw needs to be wound back to the Y axis block after removing the stepper, the two aluminium keeper blocks and unscrewing the coupling shell. The two bearings are pulled off and the Y screw can then be rotated back to expose the 5mm screw positions. It is required to pull the loose table assembly forward about another 2", to clear completely.

Fully degreased the screws and the sockets before fitting star washers and copious thread lock.

Hard to believe that the integrity of my machine relied on two 5mm screws and no washers?

I am a bit protracted here for the sake of any other owners. - If you have exposed spindle steppers, clamp something on there and rock the shaft while checking underneath at these two screws above the Y axis ballscrew.