Seized Z-Axis? Need Diagnostic Help

I recently purchased a Lagunmatic 3516-SX and am working on getting it running.

The current issue I am dealing with is that I can't get the Z-axis to move. I was unable to jog that axis, through some troubleshooting I found that he motor, servo amp, etc were all good.

I disconnected the motor from the Z-axis ballscrew hoping to turn it by hand. I can't!

The Z has a counterweight that was not secured while shipping. I don't see any brackets, lins, etc and I could hear it moving around while unloading. The spindle casting doesn't appear to have any locking mechanism.

So I'm at a point where I feel like I should be able to turn the screw and it won't budge. I tried rotating with some channel locks on the end and no luck.

Looking for ideas on what I might try next? I am considering using a bottle jack under the spindle casting to try to nudge it up - bad idea? Should I try removing the ballscrew first instead?

One thing I noticed is that I can rotate the screw a couple +/- a couple degrees without any movement in the axis. Not sure how important/critical/worrisome that is at this point.

Thanks for any help! Lagun support has been helpful so far but they are on break until 1/4

Patience - don't try to break anything that's still good. That's a box-way Z, correct? If so, you may have some rust or some dried coolant that's seized the head. If you can remove the mount that holds the ballscrew nut to the head casting (after supporting but not trying to break free the Z with a couple bottle jacks) that will allow you to move the head only restricted by the guide surfaces. You can also try to loosen the gibs, but not too much. Maybe try spraying PB Blaster or similar into the guideways, but try not to get it on the ballscrew. Make sure not to introduce force that could act directly on the ballscrew (in other words, if the ball nut flange is down, move the head up with the jacks).

Do check that the counterbalance is free moving, and that the cable or chain's not bound.

If you can get a helper to work with you that would improve safety and give you a second pair of eyes to watch for binding or other issues while you're moving things. Make sure to coordinate so no fingers get pinched or worse. Wear safety glasses during this work, and think before acting!

Thanks for the advice and direction. I was thinking the same thing as you re: rust or coolant causing an issue.

You're correct this is a box way machine. The counterbalance is freely floating right now.

I like your idea and it definitely seems wise to disconnect the ballscrew before trying to move the head.

It's not obvious to me yet how I can actually access the ballnut. I have schematics but no maintenance instructions. I'm going to have to look closer at this tomorrow. I've been trying to look up Fadal instructions as they seem like similar setups but haven't had much luck yet.

Post some photos please. Not everyone is familiar with this type of machine. Forget jacking it free. Is there a brake on the Z axis screw by any chance ?

Regards Tyrone.

I took off one of the covers this morning to expose the spindle motor, drawbar cylinder, etc. This gave me better access to the top wipers and also allowed me to see the Z screw and yoke.

You can see in the photos there is some evidence of slight rusting on the ways and some discoloration on the Z screw as well. I believe this machine was repainted shortly before I purchased it because there is overspray in some areas, including the ways as you can see. I've scraped some of it off but I obviously need to clean it better. My thinking has been that it wouldn't affect trying to jog/move the axis down so it hasn't been a priority.

I've tried to show photos from all directions. There is no brake or bracket anywhere that I can see in person or in the schematics. I rigged the counterweight myself this morning just in case I did something that would cause it to move up or down.

Access to the Z yoke is pretty tight... I might start by removing the wipers and spraying PB blaster as we suggested. I'll probably wait for some advice until I do anything further...

Front right


Close up of right box way, top front


Close up of right box way, top backside


Close up of left box way, top front


Close up of left box way, top backside


Z-Axis screw, directly behind spindle motor. Slight discoloration


Top view of spindle motor, Z ballscrew


This is where I tried to grab and rotate the screw


Looking down the backside of the column. Can see the counterweight and chain system


Counterweight with provisional safety rigging. The chain is loose and counterweight freely sways


Column schematic. No mention of brake or any other holding device that I can see.


BOM Page 1


BOM Page 2


BOM Page 3

That's a mess. Some crooked used machinery dealer saw you coming. Those ways are rusted and you can see the paint over spray on the rusty ways. You need to pull the head off and clean the ways. Who ever sold you the machine sold you a lemon. Buy some hardened chain and call a rebuilder to help you. If you saw this and didn't figure out the ways are no good, then you need some help..

Running the head over that rust and mess you will really screw it up.

If the Z heads are bad, I would assume the X & Y are bad too....better pull off the way cover and think of pulling those slides apart too, if you can't return the machine.

Yeah the head needs to come off without any more attempts to run it up or down. It's not that big a job. Give the ways a good stoning to get rid of the paint overspray and rust. Check the lubrication piping system is clear whilst the head is off.

Regards a Tyrone.

You should think about what your goals are. If you bought the machine as a project, and knew you'd be looking at a fair amount of work before it was running, then keep going with the repairs. If you wanted a machine to make parts with ASAP, perhaps you should stop and reconsider putting more effort into this machine. That you could twist the ballscrew a few degrees while the head was seized tells me it or the thrust bearings are likely NG also. And the same might be for the other axis too.

What's your background? Have you done significant machine repair before? Do you have the time to strip and rebuild this machine?

Thanks for all the input! Sounds like the repair is more involved than I was hoping for, but I do have the time and I think the ability to do it.

I was hoping the visible section wasn't an indicator of the rest of the way. It's clear the head hasn't moved since the painting was done. But there is very slight rust under the top wipers. The bottom section of the ways seems ok.

This is a hobby machine for me. It's in my garage and I don't have work lined up for it. I've just wanted a full size CNC mill for a long time and this seemed like a good candidate. It sort of is a dream machine for me... I bought it out of state from a rigging company and was told it was working when taken out of service. From the pictures it looked good. With freight and unloading costs I came in under $4k so I don't think I got taken too badly.

The X and Y axes jog ok and the Y ways appear good (I did remove the covers to diagnose another issue).

I've rebuilt a BP knee mill and other things like engines and transmissions so while this is physically larger than other projects it doesn't seem intimidating. Just more project than I was hoping for. My background is in mechanical engineering by the way.

You're right about needing help and advice... hopefully I can find all I need in this forum. Because it is a hobby for me the idea of hiring help isn't appealing...

I don't have any overhead lifting capability right now. I would have to build/buy/borrow a gantry crane of sorts. Gotta think about what the next step should be...

After supporting the slide I would be looking to remove the lead screw and nut if possible if not make a scraper use lots of penetrant and scrape off some rust try moving it then some more give the penetrant time to work it will come apart.

It sounds like you've done enough that you can handle this project, and it's good that you can spare the time. If X and Y seem workable, then concentrate on Z for the moment. You should try to estimate where the CG will be for the head when it's decoupled from the Z ways, and make sure your lifting apparatus is stable and will not allow swinging when the head's separated. I'd guess it's in the 400+ pound range, so you don't want to lose control of it. Be sure you can move it away from the machine smoothly, is the floor concrete and flat? Otherwise may have to set up steel tracks for the hoist to run on.

Once the head's off you can take pics of the ways and slides. While off, you might as well make sure the head components are OK, including tool retention if it's using belleville washers for the drawbar. Spindle bearings should be checked, but that might be easier when the head's mounted again. Lot of folks here with much more experience than me; Richard, Tyrone, etc., so see what they have to say.

giz said:

Thanks for all the input! Sounds like the repair is more involved than I was hoping for, but I do have the time and I think the ability to do it.

I was hoping the visible section wasn't an indicator of the rest of the way. It's clear the head hasn't moved since the painting was done. But there is very slight rust under the top wipers. The bottom section of the ways seems ok.

This is a hobby machine for me. It's in my garage and I don't have work lined up for it. I've just wanted a full size CNC mill for a long time and this seemed like a good candidate. It sort of is a dream machine for me... I bought it out of state from a rigging company and was told it was working when taken out of service. From the pictures it looked good. With freight and unloading costs I came in under $4k so I don't think I got taken too badly.

The X and Y axes jog ok and the Y ways appear good (I did remove the covers to diagnose another issue).

I've rebuilt a BP knee mill and other things like engines and transmissions so while this is physically larger than other projects it doesn't seem intimidating. Just more project than I was hoping for. My background is in mechanical engineering by the way.

You're right about needing help and advice... hopefully I can find all I need in this forum. Because it is a hobby for me the idea of hiring help isn't appealing...

I don't have any overhead lifting capability right now. I would have to build/buy/borrow a gantry crane of sorts. Gotta think about what the next step should be...

Click to expand...

That's not the biggest milling head the World's ever seen. I've done stuff like this before when I'd no means of lifting the head by using the table traverses. If you've got a supply of good quality timber you could build a secure wooden stillage under and around that head off the table and then you could wind the head away from the ways using the table " Y " axis. You should have enough room to carefully get in to clean the ways.

That's if you can move the table with the " Y " axis screw. You'll need to disconnect the wiring, release the balance weight chains, withdraw the ball screw and nut and remove the keeper strips, gibs etc.

Make sure the table is wound fully in and the head is blocked up and securely fastened first though.

Regards Tyrone.

scojen said:

After supporting the slide I would be looking to remove the lead screw and nut if possible if not make a scraper use lots of penetrant and scrape off some rust try moving it then some more give the penetrant time to work it will come apart.

Click to expand...

If he wants to preserve whatever bearing surfaces he's got on the Z ways he might want to not move the head - there's risk of getting the debris into the Turcite or whatever bearing material is used. If the head's got to be pulled might as well do it, but how to determine whether that's needed is up to the OP - rebuild now, or get it working with issues and deal with it later...

Take it from me, that machine is a complete teardown and rebuild. My Fadal wasn't a whole lot better, at least I didn't have to take the head and saddle off, but everything else has been off or apart.

I'd start taking heavy parts off that head and prepare to R&R the head and clean up the ways and/or inspect any wear/damage.

The way that ballscrew looks, I have to wonder if it's any good, there is rust in the ball tracks.

You say the X and Y are fine, well I bet with the amount of neglect seen on the Z, the X and Y probably need some help. I can almost guarantee the lube system needs the metering units replaced or cleaned.

You say this is a hobby deal for you and you have Bridgeport rebuilding/engine rebuilding experience.

I'd budget somewhere around $3-4k and 6 months to get this machine into running order.

I'm 3 months and some $$$ into my Fadal VMC40 and it's almost ready. I figure I saved about $1800 because I already had replacement motors on hand.

I also have a decent amount of experience doing CNC retrofits and repair.

Seems like the consensus is that the head needs to come off at minimum. I'm looking to do the safest minimum possible at this point...

I like the idea of using the table to move the head away, I was thinking along the same lines. I should be able to build a cradle that bolts into the t-slots and straps around the top. If I can get away from removing the spindle motor and move everything together that is a bonus in my mind.

Not sure I want to start rebuilding/replacing components without even testing them first. That's in regards to the spindle components. I've never even spun the motor...

Y does look good, don't know what I would do to improve it. X jogged fine but did have a squeak while jogging. I'll need a second hand before I can remove the half-enclosure and see the ways there.

Right now I'm cleaning the wipers and ways in prep to disconnect the ball nut from the yoke. I removed the lube manifold behind the spindle motor for clearance so I will clean that as well.

Sounds like you can do it. Over engineer the crib and take your time. Have a buddy there when you do it for safety. I suspect the back of the head has Turcite. I have rebuilt and help build Taiwanese machines with Rulon / Turcite. Im not sure about a Spanish made Lagun. Get it apart and take come pictures of the back of the head. Be sure to wrap some electrical tape around the ball screw so it won't screw out of the nut and you will have a thousand balls all over the floor. Replacing the metering units and inspecting the tubes is a good idea too. As we said if the be sure to check under the covers. Also tahe a .0015 feeler gage and try to slide it under the way wipers. They may look good, but are worn out.

Thanks Richard. Do you have any insight on how I should remove the Z screw? I don't think I can access all of the bolts on the yoke with the limited space I have between the spindle motor and ways. The only other way I can see is if I remove the bearing assembly from the top and use an extension to reach the bolts from above. But I'm not 100% certain I will be able to remove that assembly in-situ...?

Perry I think I just came across your Fadal videos while researching the ballscrew and thrust bearings. Good videos!

The screw and nut needs to stay in one piece, you don't want to separate them. I've used a " Jubilee " clip in the past fastened around the top of the screw where it meets the nut to prevent the screw running away. Looking at the drawing is it possible that could you remove the top lead screw bracket, screw the screw up out of the bottom bracket and then CAREFULLY bring the whole lot out using the table traverse without removing the screw and nut pair from the head ?

Having a pal there is a good idea but choose some one who can keep his mouth shut unless he needs to speak. I find people yapping on about nothing in particular a nuisance on jobs like this. I agree with Rich about the mating faces on the head, nowadays they are nearly always some sort of anti friction material. With a bit of luck they will be ok.

As you said using a stout wooden rig fixed to the table will minimise the amount of work you need to do to the rest of the head. How much table travel have you got front to back ?

Regards Tyrone.

You will need to remove the spindle motor and everything on top of the head. Leaving the motor will make it top heavy and make it dangerous when you move it out. Those ball screw brackets on the head are normally horse-shoe shaped so you use Allen sockets and a ratchet to get in there. and when you move the head out the ball screw will stay put. A few more pictures that are not close ups would help too. Here is a link to a Kitamara VMC head I just helped re-do the Turcite. Lots of pictures. Post # 25 shoes the Horse shoe bracket they use. You can see on picture 1 on how the Turcite rips off. It is glued on. If you run your head over rust it will know doubt rip of the turcite. Be sure to loosen the rear hold downs and center gib before trying to screw the head up or down.
http://www.practicalmachinist.com/v...mura-mycenter-head-way-turcite-repair-313068/

If you have to remove any wires or hoses, be sure to mark them with number tape.

Take your time and listen to guys like Richard who have been doing this for years. In the end you will be rewarded with the machine you hoped for just go slow and do it safely. Think ten times then act.

Ron