SX3, Comedy of errors, fixes, suggrstions and information

[Old Megawatts]

This whole scenario started after I watched Richard's video on how to set the e-stops on my SX3. I have had my machine about nine months and had never really never understood how to set the stops and had always worked without them.
While zeroing the e-stops, my x travel suddenly stopped working and the stepper acted like it wanted to run in both directions at once. I traced this down to a bad crimp on one of the pins in the plug. After reparing this, I proceeded to zero all of the axis. I was feeling really good as I was able to hit the e-stop switches and then get the DRO readings to set the ends of travel. I went to the config. menu and set in the readings then proceeded to try out my new settings. The X axis worked great but when I tried out the Y axis, I guess I had made a mistake and had put the measurements in the wrong side of the switch. When the Y axis was moving the table towards me, I was watching the DRO and not the table and thought it was sure taking a long time to hit the end of the travel. When I glanced down, the table wasn't moving but the stepper was still running. Oh No! The ball screw had stripped the keeper from the end of the ball screw and had just kept going. I had only been moving about five inches per minute and I don't know how many times I had done that without any problems. I looked down and there were little balls on the base of the machine.
I had read about removing the end bearing supports and stepper motors mounts and that they came off fairly easy. I don't think so! Whoever put them on and doweled them in place thought that the dowel pins were nails and to be driven in until the heads were below the surface. This is one of the things that I hate about taper pins unless they can be knocked out from the back side. I much prefer a straight dowel with a thread on the end so it can be removed. Driving on the casting or having to wedge it apart is bad business.
Someone here asked how to reload the ball nuts. I can now tell you, very carefully. As you can see in the picture, there are two ball nuts in each setup. These are screwed towards each other with a spacer between them. These spacers set the pre-load on the nuts. The spacers are locked in place by the two tabs that are fastened to one of the nuts.
First , I washed all of the parts in kerosene and made sure that there weren't any metal chips etc. on anything. I don't recommend removing the little plastic plugs that make the balls re-circulate in the nut as you may have a hard time getting them in the correct place again. Then I coated the inside of the nuts with Dow Corning 44 grease. Any good grease would do. Then I used a small jewelers screwdriver that was slightly magnetic to place the balls in the groves in the nut. After the nuts were full, (About 50 in each nut.) I turned the little plastic rod about five thousands under the minor diameter on the ball screw. I bored one end of the rod to accept the turned down end of the ball screw and would butt up against the shoulder of the screw. Insert the rod into the ball nut then screw the ball nut onto the ball screw. The wipers can be placed on the screws and fixed in place after the nuts are in place.
I was so puoud of myuself after the nuts were on the screw and buttoned up. But why does the screw turn so stiffly? I pondered this question overnight and the next day I decided that I had better take everything apart again. One of the nuts turned freely and the other one didn't. I wondered why! Well, I discovered that the two nuts didn't have the same size balls in them. I had loaded about half of the wrong balls in each nut. I guess that in the manufactuing process, if one of the nuts is ground a little larger, they use oversize balls to correct the clearance. The small balls in the oversize nut will work OK but the oversize balls in the smaller nut doesn't work so good. I had to use my mike for a go/no go gauge to sort out the balls then get them into the correct nuts. After reassembling everything, it worked great. I also drilled and tapped the end of the Y axis screw for a 10-32 allen head cap screw and made a new retaining washer so that won't happen again.
While everything was torn apart, I decided that I might as well fix the machine so I can get full travel from the Y axis. You can see in the picture the setup that I used. As you can see, I used a piece of steel to make the bearing for the boring bar. I would recommend making it out of brass. The bar was turned from a piece of 1 1/16" OCR for a loose fit in ball nut fixture. The ID of the fixture isn't too critical as the ball nut itself is quite a bit undersize so I didn't worry about using it as a bearing. The end of the boring bar is bored to accept a .750 end mill and it is locked in place with a 1/4 - 20 set screw. The other end was turned to .500" to accept a 1/2" drill motor. This gained me a good .500 inch of travel. Total travel on the Y axis is now 6.750".
Another thing that I found when disassembleng the machine was that the coupling on the X axis was broken. I had wondered why I had picked up some slack in the drive. I couldn't see the darn thing with the cover on and it didn't run bad or make noise either. After some investingation, I found the reason. When the couplings were bored, the bug end bores were good and ranged from .316 to .3165 end to end of the bore. The shaft measured .3148. The small end bores were a different story. The hub is about .500" through the bore and ranged from .2526 to .265 through the bore on one of the couplings and the other ranged from .2515 to .269 through the bore on the other. As can be seen in the picture, this made the coupling run out an indicated .035. No doubt this is what broke the coupling. This kind of coupling won't stand that kind of misalignment! I had to purchase one new coupling from McMaster Carr (P/N 620-8K133, 1/4" x 5/16") $30.00 delivered. You will have to ream the 5/16" end a little to fit the 10 mm shaft. I believe this is a better coupling as it clamps around the shaft rather than using set screws. I salvaged the other coupling by boring the small end oversize, bushing and drilling and reaming it to .250".
I would suggest checking your couplings for run-out on the face of the hub. If there is run-out, sooner or later the coupling will part company.
Sorry this was so long. I hope that it may impart fome information to some and be of interest to others. I would be happy to answer any questions. My world is good again and I am happy. My machine is running again.

OM

[bullseye]

Can I see a better pic of your Saddle Mod on Y axis (to get more stroke)

I have a part 6.5 that I have to try to make and have been trying to figure out how to cut into the back of the Saddle as you did.....

Thanks

[Greolt]

OM, sounds like you had fun with all those little balls.

I always thought that the little circlip and washer on the end of the Y axis screw was a fairly inadequate hard stop.

I did not want to do your trick with the balls so I added a hard stop as last resort.

Greg

[Old Megawatts]

Bullseye,

Unfortunately, I have the whole thing back together. I have taken a picture of the bar and bearing. The bearing was fastened to the base of the machine with 1/4-20 x 2 Allen Hd. cap screws. I squared the bar parallel with the ways using a tri square. On my machine the center of the bearing hole was .658 above the base of the bearing. After I had made the bearing I inserted the boring bar through the ball screw nut mount and the bearing that I had made then squared everything with the ways. Then using a transfer punch, marked the location of the two 1/4-20 holes in the base. Then drilled and tapped them and bolted everything together.
Hope this helps.

OM

[jinu117]

I heard from Richard that Syil America implemented hard stop on newer machines... I've ran into same problem before (actually, I don't know why but direction of my y-axis was reverse and of course, the homing got me). Y axis... I had so many little problems it's not even funny... (Z-axis was catastrophic though, I have nice little 3/8 hole in my table thanks to that... the set screw came lose and the whole thing just... drilled in)
X axis is about the only thing I really didn't have to do much with at this point...
(keep in mind I am one of the very first buyer of Syil X3 from China directly...
Recently I gained enough time to get back to some machining, little modifications to make the machine run bit better for me and been enjoying it chipping.... (actually, need to clean up the damned area with bunch of copper chips all around...)
Richard's suggestion on cold air gun was right on spot for things I do. Bit noisy but no mass no fuss and after hard cut of job, when metal is colder than ambient, all is good.
Steep learning curve at first for me but right now, couldn't be happier with machine over all Get the feeling the machine will pay off itself in next 2 months tops with amount of R&D I conduct here

[syil]

so you have a suggestion use hard stop protect y axis out of range moving?
i saw a pic,and will discuss engineer.

[neilw20]

Originally Posted by syil so you have a suggestion use hard stop protect y axis out of range moving? i saw a pic,and will discuss engineer.

I am going to make a spacer plate, precision ground, and jack up the tower about 100mm. Then I can us more of my longer drills.
The extra Y travel hole will be in the spacer block, which will also be the attachment point for some bellows.

[jinu117]

Didn't want to make it too permanent

[syil]

maybe we can use this idea to defend later problems.

[Old Megawatts]

Greolt,

I like your idea for a solid Y travel stop. I was thinking about it today and with your stop, the only thing that is required to gain .400 travel is to saw off the turned down end of the ball screw. This could be done without even removing anything from the machine. With your stop, it won't be used for anything.
The thing that limits the Y travel towards the column in my modification is when the frame comes up against the allen head cap screw heads on the Y ball nut mount. You can only gain another .100 with a lot more work.

OM

[Greolt]

.
OM for a description of what I did to get full Y axis travel see this old thread.

http://www.cnczone.com/forums/showthread.php?t=23517

Posts 25, 26, and 57 relate to Y axis mods.

These just might give you some ideas. See pics showing travel extent.

Greg

.

[phidab]

Hello OM,
I have recently dissassembled my SX3 and the parts of the Syil CNC kit for this mill.
I have made a stupid mistake with the Y axis ballscrew ( unscrewed the nut a bit too much and 3 balls escaped from the nut )
I have completely unscrewed one of the two ballsrew nuts and tried to reengaged the balls in the grooves inside the nut. A bit tricky...
Then I have engaged the leadscrew in the nut. Bad result : I have now nine balls outside the nut !!!!!
Could you give precise explanations how to place the balls inside the nut. I am quite sure I could succeed with some patience and your advices.
Thanks a lot.
Philippe ( french hobbyist )