NM-200s2 Y-Axis Jamming?!

[webgeek]

Ugh; seems my good luck has run out. Right when I get an order for 50 sets of parts my machine starts giving me fits.

This last weekend I used to machine to make some parts - all went great. I used my flood coolant like always and by the time I was done my coolant was looking murky so I decided to change it with my next run.

Today I go out to the machine and home it. The y-axis makes a metal-on-metal squealing noise a bit but homes OK. I'm good about giving it a few squirts of oil with the oiler before milling anything every time. So I figure it might need more oil so I give it a good number of squirts (6 or 7) and start running the axis back and forth to spread the oil around. It keeps making the squeal but the noise is quieter except every couple of times in several different spots it jams and I lose steps. I go back and try and oil those spots specifically by squirting on them and traveling back and forth other them and it seems to get better, almost totally eliminating the sound and no more jams. I go over the whole travel giving it a squirt every inch or so (going though all the oil in the oiler and then some in the process) and then do a few more full travels. Either no sound or minimal sound and no jams consistently.

I go eat lunch and come back in 30 minutes. It's back to jaming again worse than before. Now I'm really nervous something bad is wrong and honestly, I don't even know where to begin. We've had several days of cold and hot alternating weather and I'm worried my bad coolant somehow got into the ways and rusted something but I've looked under the covers and everything looks ok (and is totally swimming in oil). I'm going to get a small screw driver so I can actually remove the way cover in the front (without removing the enclosure) to really see but from everything I've seen, it looks good.

This is a new problem for me, any suggestions on where to start looking? When it jams, a little bit of hand pressure and it un-jams, so that's odd too. Thanks in advance for the help!

-Mike

[JoeBean]

It could be a piece of swarf between the non-bearing section of the saddle & table (if that makes any sense). Comparing the inverted saddle in the picture here:


With the base here:


You can see the part that is lubricated & that the saddle rides on, as well as the higher (height-wise) section that doesn't support the table but where there's very little clearance between the saddle & base.

In any case, whatever the problem is you're probably going to have to take the table & saddle off to fix it. You don't want to leave it if it's damaging the ways!

It's not that big of a deal to remove the table & saddle, thankfully. I've had mine off & on 4 or 5 times now. With the proper tools around it takes about an hour or so (plus the time to do whatever job prompted your removal of the table). Here's the (rough) outline of the procedure from memory:

1. Remove the front & rear way covers by removing the screws against the column and the screws holding the mounting plate on the front, and then removing the screws against the saddle from under the covers (alternatively you can wait till the table is off to take these out). I have my way covers sealed with double sided tape because I was worried about swarf getting in, so it takes me a few minutes to separate the parts. It should be quick for you though.

2. Remove the cover plate over the X axis stepper. I think there are 3 or 4 screws holding it in place.

3. Remove the X axis stepper- 4 bolts & 1 screw in the motor coupling that you can see here:


4. Remove the bunch of screws that mounts the X gib. Use a screwdriver or similar to push the gib slightly out of one end. Then you can grab it and pull it right out, like so:


5. Disconnect the bearing mounts from the table. There's one mount on each end of the table. They're attached by 2 hex cap bolts & 2 alignment dowels. The bolts are simple. The dowels, on the other hand, give you 2 options: Originally I slowly raised the table and use a pry bar to separate the bearing mount from the table, but it was tedious. Then I realized that the dowels are tapped for a screw. I can't remember the exact size, BUT, cap screws used in various places on the mill have the same thread (I believe the ones that hold the cover on over the motor is one example). At any rate, I had bought some known-grade bolts of various sizes for the mill and used a 10.9 one to screw into each dowel and carefully get it to turn, lightly tapping on the head of the bolt if it seemed to be jammed to jar the dowel pin loose. They all started to turn fairly easily, and once they turn they can usually be turned & pulled out at the same time. Alternatively it would be easy to make a little puller to do the same job, or if you had some threaded rods/crap bolts to screw in to each of them you could probably grab them with visegrips and pull them straight out. In any case, if you decide to slowly raise & ply MAKE SURE you take the dowels out before you reassemble, as you won't get them lined up while lowering the table. Here's the holes for the bolts & pins in the bottom of the table:


And here's a bearing mount:


6. Use some chain & some T-nuts & bolts screwed down until they jam to lift the table off with a crane or hoist above the table. The table tilts up from the front. It lifts like this:


7. Remove the X ballscrew from the saddle after first removing the oil line to the ballnut. Then disconnect the main oil supply line from the saddle.


8. Remove the Y axis motor & mount. It's just bolted down. Then unbolt the bearing mounts from the base. You can see where they bolt to here:


9. Remove the Y gib as you did the X, making sure to remove the gib before lifting the saddle.

10. I ran some straps around the whole saddle and lifted it with them. It's heavier than it looks! Just don't get something caught in the ballscrew.

11. Have a beer.

It goes together in the reverse order, and it's usually faster than taking it apart. As you can see the job is pretty simple. As you're taking it apart whatever the fault is should become pretty obvious.

By the way, if you haven't already now would be a good time to reroute the oil lines to allow the table to fully travel to the right (facing it). See here for more details & a picture.

Hope that helps!

[webgeek]

Hi Joe - your post is incredibly helpful, I appreciate it! Sadly, I'm desperately trying to avoid removing the table as I simply don't have either the room or any way to lift it. Just getting the machine on it's base in my garage was a nightmare I'll never repeat. Next time I'll build a dang A-frame crane around the machine (totally serious) to move it again.

I've got the way covers off and everything is nice and clean. While jogging the machine I can see the entire surface on both sides and it looks great. There is some uneven wear way up in the front where the gib and saddle are wearing the suface inconsistently but it's only in the last 1" or so of the way and so not related to what I'm seeing. It appears to be a bit of an inconsistency in the casting.

First question: is it possible to remove and reinstall the gib without removing the table?

There are two sets of screws on the gib - the black ones that appear to screw into the gib itself (different than my last mill so a little confused on these) and the allen screws used to tighten and loosen the gib. Everything except one of the allen screws was VERY loose. The nuts on the allen screws were mildly tight but the allen screws themselves were barely finger tight. I'm assuming this isn't normal.

Once I loosen everything the rest of the way all jamming stopped immediately but I still get a tiny bit of the squealing sound in specific spots. The ways are perfect in those spots so I can't figure out what's causing it. Re-tightening the gibs causes the squeeling to get louder. There are some weird accumulations of "gunk" in spots on the ways which I've cleaned off but it didn't appear to impact anything. I've gone ahead and added penetrating oil everywhere I can to see if that makes a difference and it's sitting now. I'm also going to use my compressor to blow the oil in deeper just to be safe to see what happens.

Final question: what is the proper procedure to re-adjust and tighten the ways on this machine. The two screw thing is different than my last machine and new to me. Additionally, the gib adjustment on my last machine was both finicky and critical to accuracy but it also weighed a LOT less.

Thanks again for the great help.

-Mike.

PS: I'm irritated that my call to Novakon support didn't get returned. First time I've tried to talk to someone in the support group and apparently it's proving to be just like people have said. Very annoying, I'm just glad this forum exists with so many great people!

[JoeBean]

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[webgeek]

Thanks for the info! After letting the oil sit for a bit and slightly moving the X axis to take pressure off the gib I was able to slide it right out. I was hoping for it to show some reason for the jamming, but it was spotless and showed effectively no wear at all. It's in great condition.

I'm getting more and more concerned that the whole table is going to have to come off

-Mike

[StillLearning]

Hi Mike,

Is it possible that the gib has enough movement to lock up during operation? Seeing as the gib is tapered, is there is enough slack between the set screws that allows the gib to slide back and forth and intermittently lock up the axis? Just an idea. It may be a directional dependent issue, but it would then lock up when traveling in one direction and may or may not release when moved in the opposite direction.

[Frogblender]

If the jamming occurs only during rapids, you could slow it down as an interim measure.

I, too, am semi-paranoid about sufficient oiling - lots of pumps on the one-shot, plus manual oiling often and everywhere. Make sure coolant isn't getting anywhere it shouldn't and washing away oil.

[ihavenofish]

Hi Mike,

Is it possible that the gib has enough movement to lock up during operation? Seeing as the gib is tapered, is there is enough slack between the set screws that allows the gib to slide back and forth and intermittently lock up the axis? Just an idea. It may be a directional dependent issue, but it would then lock up when traveling in one direction and may or may not release when moved in the opposite direction.

the gib is not tapered on this machine, its a very large block. it is unliklely to be the issue. baside on the description, i think theres something caught in the dovetails somewhere, or possibly in the ball screw though thats less likely.

short of removing the table, you might be able to pull off all the guards and see something. i woul dnot try to run the machine til you find the source, because it could be causing damage to the ways.

[urbanimports02]

this sounds more like a stepper problem then a gib issue. try powering off the steppers and rotating the ball screw by hand and see if it all moves nice and easy. mine has done this a few times and sounds like it is stalling out and all that jazz and ended up being a break out board once, a stepper motor another time and loose wires on the gecko for that stepper another time. all sounded like something was physically binding. i think all of my issues were interrelated and the loose wire was the culprit for failing the others, as since the wire repair i have been running flawlessly 10hrs a day for a few months now. anyway, worth a look

[webgeek]

Hi all; sorry for the horribly late update. I reached the Novakon support guys and it took them all of 20 seconds to diagnose the problem by hearing it over the phone. The front block that holds the bearing for the Y-axis ball screw was gummed up. It was packed with grease and jammed up a bit. I just had to clean it out with some penetrating lube and then hit it with some good grease. The problem vanished instantly! Thanks all for the good advice everyone! I certainly know the mechanics of my mill more now than before!

-Mike