[xander18]

First, I apologize if this has been brought up before. I tried the search function but couldn't find much.

Any info on adjusting the way screws on the Z axis? I moved my mill recently and am concerned they're not set properly.

[rpovey]

The way screws just adjust the slop between the head and the column.
I suspect what you are looking for is information on tramming? (ensuring the column is perpendicular to the table), there are a lot of threads on that.

[xander18]

No, I've already trammed it, that's fine. The issue right now is that while travelling up or down the Z axis pulls to the left or right. With a long drill bit installed I can see the tip of the drill pulling left while the Z axis is travelling up and pulling right while it's moving down. That's why I think that it's the head's fit into the Z axis ways that's not tight enough.

[TXFred]

That could well be a gib tightness issue. Have you got a CNCFusion kit with the ballscrew off to one side of the head? With loose gibs, that setup will make the head twist as you describe.

Frederic

[xander18]

Yeah, the ballscrew is off to the side. But I tightened the gibs all the way down until it couldn't move, backed them off about an 1/8-1/4 of a turn and it still pulled from side to side. So I was wondering what I was missing.

[LUCKY13]

Thats probably to much to back it off. It just need to back off ever so slightly, just eniough so it can move again, and it should be faily hard to move not to stiff though).



There is also a good chance your gib is not flat. This does make ajuasting abit harder. I dont know what the X2 has for gibs but if its just a flat gib sand it on a flat surface with sandpaper and this will help. Might even have to take a hammer and flatten it some first if its real bad. Using the axis locks does tend to bend them and with CNC you dont need to use the locks anymore. When reajusting remember dont crank the screws down real tight or you might bend them again. A flat gib will lock the axis real easy compaired to one that is bend which doesnt have much surface contact to give holding strenth ( a bent one doesnt).



Jess

[TXFred]

Thats probably to much to back it off.

Yup. I think those screws are m6x1, which means that backing off 1/8 to 1/4 of a turn creates 0.005" to 0.010" of slop. That's too much.

It's an iterative process to get those gibs set right. Make small adjustments and keep at it until you're satisfied.

I dont know what the X2 has for gibs but if its just a flat gib sand it on a flat surface with sandpaper and this will help.

The X2 gibs are made of paper mache, margarine, and just enough iron filings to make them look like actual metal. Sanding them flat will help, but a better solution is to make new gibs out of brass or silver steel. Then they won't flex as much when you tighten the gib screws, giving you more contact surface and less friction.

That seems counterintuitive, but it works. Think of snow skis. Longer skis with more contact surface are faster because they spread the load out more.

I did brass gibs on my X2. With the stock gibs, if I tightened them to remove all slop from the axis, it wouldn't move. With good gibs, I could eliminate all the slop and it would still move.

Fred

[MystRacing]

The head on the X2 is 2 pieces, one possibility is that the 2 castings for the head are miss-aligned. There are threads on here that explain adjusting that. I'm not much good with the search but I'll see if I can find one.

[xander18]

Hi everyone, I guess I had email notifications turned off and I didn't see all these replies! Thanks for the help, I'll pull the gibs and see what I can see.

Since I made this post I have moved the mill into my Formula SAE team's shop where I'll be making the bellcranks so I'm looking back into boosting that Z accuracy. MystRacing, I'll look into that miss alignment issue. I didn't build this mill (extremely lucky craigslist find right before I started my own build) so I'm really not sure what quality it was built to.

[Dano523]

When first working with the X2, the problem that I had was that when milling, the spring arm support that was to hold the head neutral, didn't hold the head, and it would walk down and crash a tool(between the weight of the head, and slight chatter, the lock down was slipping as well.

So what I did was added the 2258 Air Spring Conversion Kit with the spring loaded arm still on the machine, so if the head was going to move, it was going to be upwards.

Next mod since the gears bit the bullet when I crashed a tool, belt drive, and then motor control board since it allowed the motor to run full voltage.

Now that I could put power to the work piece, back supported the column to get ride of all of the chatter (column to the base).

With the column now supported, went back and trammed the Z axis head to the column, and make sure that the column was trammed to the bead.

With these mods, it allowed me to tighten up the head gibs tighter to take a great deal out of the head to column track, an since the column had more support to get rid of a lot more chatter, the stock hold lever now does it job (and if the head moves, it going up, instead of down, and will not crash the machine).

So back to Opt, out the gate, you need to tram the head to the column, and column to the base. This is easy to do with laser in the spindle, since you can take the make a piece of stock with the head all the way down, then move the head up on the column to make sure that the laser is still pointing at the same spot on the work piece. Not only may you find that the head to support block may need to be adjusted, but also shimmed as well so the spindle always tracks the same place on the table, no matter what the head is in it's Z travel. And yes, it's bear tramming the head to table, since you have to leave the bottom head to block bolts hand tight, then bring the back head support up above the column top so you can tighten/loosen the top bolt when tramming. Throw in needed shimming of the head to block, and the fun just gets a lot deeper. For this reason alone, get the column to bead square first, then go back and attack the head to back block afterwards.

As for the head/gibbs tracking the column, lapping with help, but if you just Lube the bearing areas on the column track with Mobil 1, will find that you can tighten down the jibs a great deal more and still allow the head to move.

Bottom line, the machine is not half bad once modded for light/small work, but in stock form, even trying to get a clean cut on plastics is just too much of a headache.

[Johann ohnesorg]

If you can see that the drill point travel sidewards when you lower the head then your column is not perpendicular to the table.

Take a 2" long piece of aluminum, 1/2" square. Drill it on one side, press or glue in a steel rod, maybe 1/4" so you can grab it in a chuck. Drill and slot the other side, too so you can put in a dial indicator and lock it in position. Make sure the DIs plunger moves freely. Now put this fixture in the chuck and lower the head to the table and set it to a reading of a 1/4 inch or something like this so it won´t lift off the table when you swivel it around. Swing it to the left, make a note of the reading. Swing it 180° to the right and see if it shows the same. I doubt it. Now adjust the column so it´s perpendicular and then, both reading should be the same. The last setting to 0,001" or five tenth is done with the big column screw set to a little bit more than snug, move the column with light knocks from a lead or rubber hammer. Now tighten it down and check again. You can do the same in relation of the Y to the Z axis, here it´s more of a hassle because you have to shim the column to zero.

Adjusting gibs: loosen all up, then start with the outer screws. Set one tight, open it again until you can move the Z-axis with the quick action. Now tighten the other and then open it until you can feel a slight drag again. Do the same for the other two. Check if the head moves with the same drag over the whole dovetail length. If not, you may have to rework your dovetails or switch the column for a new one. You can only check for drag without the lift spring/gas spring . It´s done best with the column to it´s back on your work table. So maybe do this first, then set up for a perpendicular column. Clean everything throughly before and use copious amounts of oil during the process, it really makes a difference.

One last thing, when you make the DI jig make sure you choose a length that will not go into the slots of the table when you use it to check for X to Z axis rectangularity. Or use a 1-2-3 block to rest it in the case this happens.

Cheers,
Johann

[xander18]

The column is currently trammed to the base. The issue can be quantified this way; I put an indicator in the spindle and touch it up against a 123 or ground block set on the table. Now, with the indicator on the block just touching the Z axis up and down jumps the indicator .005" back and forth. Moving it up and down doesn't adjust the reading until I change direction, then it throws it about .005" off again. This leads me to believe the head isn't tight in the ways so it's torquing in a rotational manner. The mill (I didn't build it) has something similar to a CNC Fusion kit - though on the opposite side - so it's putting a moment force on the head.

Last night I pulled out the gib and sanded it flat and smooth. Johann, I'll try that gib adjustment method tomorrow evening and see how it looks. The writing on the wall is that I should make a brass gib and get better way lube before I expect anything significant in accuracy. It will have to be a very tight fit to stay true with the ballscrew where it is.

Also, dano253, the previous owner put a counterweight with pullies on the machine. Hoping that will do the job of that spring kit.

[MrWild]

The problem is that the head is put together misaligned. The <i>only</i> way to get things right is to disassemble the head and loosen the four bolts holding the halves together. Been there, done that. Any messing around without tearing the head down will NOT fix things.

[MystRacing]

Read this thread. I haven't looked here in a while but I think this is where your problem lies.


Mini-Mill Spindle-Column Alignment