I have recently run into a problem with my x axis on my x3. To reduce chatter and to improve surface finish I was told that it is a good idea to tighten down my gibs. The z axis tightened down quite a bit which has helped immensely with chatter when plunge cutting. However, when i tightened down my x axis it would cause the stepper motor to stall. I am using one of the multi-hex wrenches where they all turn out of a handle. If I back off just 1 or 2 degrees it will run fine. Am I just tightening down too MUCH? Is there something else I can do so I can tighten a little further and still have it run smoothly. Thx

Hi,

Does your X axis bind through out its entire movement or just in certain places?

If the axis is binding anywhere in it range of movement then it would be over tightened gibs , under powered stepper or both.

If the stepper is powerful enough for the axis then you would need to look for other possible causes for chatter.

There is one other possibility and that would be “slipstick” or “sticktion” (both the same thing). This is caused by two very flat surfaces rubbing together which can suddenly stick (very tightly) to each other causing your stepper to stall. Are the X axis bearings finished on a surface grinder without scraping marks?

John

It will bind right after I tighten down the gibs. The stepper is a 500 so thats not the issue and the screws are the ballscrews that come with the cncfusion kit. I may be just tightening down the gibs a bit much then. Im not sure how the bearing are finished nor am I sure how the ways are finished. Thx oldman.

May be needing more waylube?

What kind of lube are you using?

Do you lube it every few hours of running?
(the "single-point" lube systems are usually setup for every few hours of running)

Pres

The x3 isnt setup for a oneshot system. I use a lightweight mobil one gear oil. Its the same stuff that gets used at my previous college. I lube it every few usages. It doesnt get used continously yet.

The best way IMO to adjust the gibs is by disconnecting the screw. Then you can adjust the table for a nice smooth movement by sliding it back and forth by hand. It's difficult to adjust the gibs with a ballscrew connected as you have very little feel.

Are you running preloaded ballnuts? If you are not running preloaded ballnuts the machine will be prone to chatter as the backlash allows the table to slop around very easily from cutting forces.

Steve

Then you can adjust the table for a nice smooth movement by sliding it back and forth by hand.

That was a very interesting statement to me. As you may remember I set up my X axis with a stepper motor and got the rapids I described and had no binding or stalling issues. While I was dismantling my machine I tried to slide the table off the saddle but could not move it. The only way to remove it was to slacken off the gib. Your statement and my experience suggest to me that my scraping and lapping is going to make a big difference where machine rigidity is concerned. The down side for me is that my dovetails will ware faster than yours. It also tells me that the 0.1” pitch screws would be a better choice over 0.2”.:)

John

John, My machine will rapid at 60 ipm with a table tight enough to not move by hand with the screw disconnected. But it also will have very high "stiction".
My test that I use to make sure my table has low stiction is to setup a indicator in the spindle and a block or vise on the table to reference from. I then command .010" movement in both directions. Since I have preloaded dual ballnuts If I see more than .001" backlash I know my table has to much stiction to be accurate and repeatable.
In any case you have me convinced, I am going to scrape in my x3 ways in the future after I finish off my lathe project.
Steve

how does one scrape the ways on an x3, this is an unfamiliar term to me, but i figure if its something that i might outta consider doing, might as well do it while i have the table and saddle off....(i'm mid stroke on my cnc fusion kit install)

I've seen a report where the X3 gib strips were lapped on a flat surface, and it lowered the sliding effort of the axis. If this is to be done, I would think that it should be done well.

http://www.arceurotrade.co.uk/projects/X3-CNC/X3_Article_Part_1.pdf

Myself, I would not touch the ways, though.