[ned_seven]

Hi all

I'm a hobbyist and I've come across a Chinese 'XYZ Magnum' machine that is very cheap, 2000 euros.

However it has a vibration in the Y axis that is stopping it from working properly. At the moment the company have the speed slowed right down but the vibration is still evident even at that speed.

What I know about the machine;

its old, maybe 2005

It's an 8x4 with a water cooled spindle

Its driven underneath with a ball screw / lead screw and two circular rails on either side of the gantry.










I'm new to the CNC game. I was going to build a table and I was gathering info and the tools required for the build, and then I came across this.

If it could be repaired it would save me six months build time. Any thoughts on what might be wrong with it, or tips regarding this purchase in general? Any and all insight / opinions welcomed.

is it worth a shot or should i avoid like the plague?

kind regards,
ned .

[the_hamturdler]

I would buy it if it were in my area. That's a big machine for the price. Something like that in my area would go for 6000 (USD though) easily. Ask them for a recording of the vibration, we might be able to tell what's wrong that way. Causes could be anything from a bent ballscrew, bad coupler, bad motor alignment, bad support bearings. Worst case you would have to replace the entire ballscrew assembly which is cheap from china, but shipping will probably be killer. Given it's length I would just retrofit the machine with a rack and pinion.

I would go to see the machine, watch it jog around and see what's up. Maybe have them disconnect the y axis ballnut and move the gantry around by hand just to make sure the problem is with the drive mechanism and not the linear rails.

[ned_seven]

thankyou thankyou thankyou thankyou

I showed your reply to my girlfriend, saying look its okay! ) I'm not wasting all our money...

I'm going to see it on wednesday, ill take some video then. I'll be handing over as deposit though at that stage, so its going to be do or die.

Appreciate the vote of confidence.

[awerby]

It would be good to determine what's causing that vibration. If it's mechanical, then it's probably either one or more of the issues Hamturdler brought up, or stiction, which can be cured with proper lubrication, replacement of bearings, or, at worst, replacement of the slides (probably rods, which aren't expensive). If those things all slide smoothly when moved by hand, then it's probably stepper resonance, which can be cured by replacing the drivers with more modern ones, replacing the motors with ones that have lower inductance, or changing the power supply to one with more voltage (or all the above).

[ned_seven]

cheers Awerby, thats load to go on, great stuff. Hopefully its one problem!

one thing i did not realise, before going to see this machine, is that the machine doesn't need to be hooked up to a computer. It has its own handheld controller, with a usb port for drawings. So effectvely, as soon as the vibration is fixed, its ready to start, with no more complication. That's pretty sweet.

[wizard]

Like other have said this is a steal at $2000 or even Euros. The being said and considering that it has issues I'd try talking the sellers down a bit in price. Just don't piss them off as the asking price is worth it just for a steel frame as it appears to be a quality frame.

As for the vibration your best bet there is to post a video so that we can have something to look at. There are many possible causes but I might suggest that you will want to replace the linear bearings if the machine has had years of production anyways. Which brings up something else, inspect extremely closely the linear rails for signs of wear or scoring. This can be a problem if the machine has lots of mile on it. You will want to factor in the condition of the rails into the machines price. Round rails are not extremely expensive to replace but you need to consider the possibility.

As for the CNC controller, its value is an unknown until you get documentation to understand its capabilities. A controller of that age may have significant limitations with respect to RAM for example. Also it isn't a given that the controller can convert a drawing file correctly in every case, so CAM software may still be in your future. You will also need to know if the controller can be feed from a PC in trickle mode. In other words how useful a piece of hardware is depends upon how you use its capabilities and if those capabilities meets your needs. There is no way for use here to say if the controller will meet your needs or not but you need to consider if it does for yourself.

Ideally you will want to know if the CNC controller is widely supported by established CAM software. Even if the unit reads most of your drawings fine, there is reason to believe that it might not be the best approach to getting your stuff carved out.

In any event if you have the money this is a bargain in my mind,evne if another 1-2000 is required to get it productive again.

[MajorTendonitis]

I've read many times that ball screws are not recommended for machines over 4' ,as there prone to whipping . This machines Y axis should be designed with a rack and pinion imho

[ned_seven]

Cheers Wizard, Major

I'm swinging by the place today and will grab some video of the vibration.

This is the controller



I googled the serial last night and came across a thread about replacing the controller with a computer, a break-out-board and a speed controller. Likely I will go down that road. Rack and pinion may well be in my future also, as well as CAM software.

Its a long road! This machine has certainly made it less daunting, building one from zero is a mountain of a challenge.

On the price - they were looking for 6000 for it. However they were very straight with me and so I'll presume they were straight with others, in saying it needed work, and that seems to have put people off.
I, on the other hand, viewed it as a windfall.

[ned_seven]

just a quick update to this thread. I went to see the machine, but, there were four other machines on the shop floor and it was pointless trying to take video with all the noise.
I did see it jog around and it seems to move okay, so the issue is not that severe whatever it is.

I paid a deposit of 1200 today, (its mine!) and paying the remainder when I get my wage packet. Once its home and the dust is settled ill take some video of the problem areas.

[hanermo]

No.
Machines with upto 5 m of travel are done with ballscrews.
High accuracy machines, rated to 2 microns feature size.

They just use thicker ballscrews.

I've read many times that ball screws are not recommended for machines over 4' ,as there prone to whipping . This machines Y axis should be designed with a rack and pinion imho

[ger21]

No.
Machines with upto 5 m of travel are done with ballscrews.

+1
I've been using $150,000 machine with 14' ballscrews for 20 years.
It's not what you use, it's how you use it.

[ned_seven]

Hi,

so I got the machine home and the bed off to try see whats wrong with it. There is indeed a pretty severe wobble along approx half the length of the ball screw / threaded rod.
Would love advice on what to do / try / buy next.

https://www.youtube.com/watch?v=WXv5breXGLw

regards.

[KH0UJ]

In your video I can hear the electrical ripples, by the way it`s a very nice machine you got there, changing the XYZ stepper motor harness to a bigger wires will help it stabilize the oscillating vibration coming from the steppers itself, while putting a ventilating fan on the control box will help stabilize the chips itself to make unstable noises that affects the motor output when rotating, stepper driver chips on your unit gets noisy and unstable when it reaches 60 celsius, if you can stabilize the temperature on it then even if you work 16 hours a day it will not give you problems of instabilities.

I know it`s kinda odd but one of our brand new 6090 unit made exactly like your symptoms (vibrating XY) I solved it with just a little modification. so if the noise oscillation is not there the long shaft will not vibrate.


Lubricating the ball screw and the sliders would also help ease the movement to ease the friction it gets while moving. (gear oil C90)

[the_hamturdler]

Hi,

so I got the machine home and the bed off to try see whats wrong with it. There is indeed a pretty severe wobble along approx half the length of the ball screw / threaded rod.
Would love advice on what to do / try / buy next.

https://www.youtube.com/watch?v=WXv5breXGLw

regards.

I can't listen to the audio so I'm not sure, but it looks like it's just run of the mill ballscrews whip. As it gets closers to the center of travel it seems to get better which is consistent with whip. If the machine hasn't always had whip, the seyup is likely fine. I would replace the bearings in the ballscrews supports and maybe the ballnut. If one of the rolling elements is bad, it can lead to whip on a setup that is otherwise fine.

I still recommend to switch over to rack and pinion but bearings can be had for cheap so you may deem it worthy to try replacing them. The machine should be fine to use in the meantime, you may have some issues with surface finish on harder materials though.

[ger21]

Ideally, you'd want a larger diameter screw, with a higher pitch, so the machine would move faster, and the screw would spin slower.
The screw may be bent a little bit, but I'm not sure that it would be OK if it were perfectly straight.
You might be able to make some spring loaded supports that would steady the screw, and swing out of the way when it passes. Use some type of slippery plastic to ride against the screw.

[ned_seven]

Thanks guys, really appreciate the replies and info.

There is no oil at all on the long ball screw rod, so im going to get some today and see if that improves things. If it does improve, I will look at replacing the bearings.

In the control box, the larger power supply (seen with the cover off below) , the fan in it is damaged, melted, it would make you wonder how such a thing can happen. Its very noisy on startup and moans for about 5 mins before becoming quiet. I'm after buying a fan for it on ebay today so will arrive soon.

KH0UJ there is a good chance that the fan is what you were hearing, or what was causing the electrical ripples. I'll replace the fan and see if it improves matters also.

I also think the idea of a ball screw support is a great one, I saw a very clever one on youtube so might have a look at building one.



damaged fan.

Is this the power supply for the Y axis?

And the smaller one to the right of it the power supply for the X axis?




Thanks for reading,

regards,
ned .

[KH0UJ]

Try to take out the center sticker on the 12VDC fan, put some engine oil in it, blow that circuit board with a 90 PSI compressed air, sometimes conductive dust particles will produce electrical ripples depending on where it is located, assemble everything and observe if it`s still wobbly

[ned_seven]

I will do that this evening and report back, thanks!

[ned_seven]

so i oiled everything with 75w90 sythethic gear oil that i had on the shelf. I also replaced the fan with a similar specced fan. Now the machine is quiet as a mouse when idle which is nice, but the wobble is still present. There are some clunky noises coming from the bearing at the bottom of the table, i think ill replace that. Are they easy to allign again? I think ill need a feeler gauge, and some education lol. I made a video of the clunking noises.

https://www.youtube.com/watch?v=4AaeEdBTFTQ

[KH0UJ]

Right now it`s as smooth as ice, about that slapping noise, I think if you put rubber dampers on the top and cable tie, it will eliminate that slapping noise, I think ace hardware sells that rubber dampers that is used for the legs of the chairs or try to cut some bicycle tires then cable tie it on the top, not too thick though because it may hamper the Y axis ball screw mount.

The most important thing on Y axis is it should not have a play if you hold on the center of the ball screw mount then try pushing Y+ then Y- with your hands, it should not have a play at all, even 1mm of play is considered inaccurate, sure you can compensate it on the codes though, if the play is coming from the edges of the ball screw then try putting some washers to eliminate or lessen the play. since you already have the oil try lubricating all the axis to ensure it will run smoother when you try cutting on the machine, our machine here in the shop we always lubricate it once every 3 days, if not then the saw dust will by and by be stuck on the ball screw thread then it can and will get stuck then the spindle will now be offset on the program loaded then damages the material, our machines are running 8 hours a day 6 days a week, so I oiled it (all the axis using an oiler) twice every week to ensure the machine`s stability.