Hi, I have recently aquired an orac and I have a problem I cant track down. The problem is that when cutting steel with any cutting tool there is an under lying vibration tone from the tool just like it is going to chatter and when it gets to the end of the cut I get a heavy chatter/vibration.
When inspecting the turned item apart from chatter lines on the shoulder of the part, the surface looks good as you would expect.
I have checked the tool height and the toolpost and the jibs adjustment.
I have replaced the chuck with a new one.
I have tried different speeds and feeds.
I have now reduced the end chatter on stock material of 5/8" and smaller.
Anything of greater diameter produces end chatter and I still get a vibration tone when cutting.
I am now suspecting the spindle bearings but not knowing how to tell if they are worn I am just guessing.
I would have assumed that loading the billet with a revolving center on the tailstock would show a difference but the vibration tone is the same and so is the end chatter.
I've listened closely to hear if the bearings are making a noise and when turning at 500 rpm and above I can hear a jingle of the races revolving and also once in a while I do get a grumbling sound which lasts for a second or so.
I would appreciate if anyone has some knowledge that they can pass on and also advice of the correct bearing numbers so I can purchase some without stripping the machine to find out.
Many Thanks
Orac spindle bearings
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davidimurray
- CNC Expert
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- Joined: Thu 24 Aug , 2006 9:45 am
Hi John
Fancy seeing you over here! Have you tried greasing your headstock bearings? Did your machine stnad idle for any significant amount of time. The reason I ask is a friend bought a toolchanger for his Orac and it refused to turn - on stripping we found that the grease had solidified!
Did your new computer not completely solve the problem?
I might be able to take some sound recordings of our one at work if that helps.
Cheers
Dave
Fancy seeing you over here! Have you tried greasing your headstock bearings? Did your machine stnad idle for any significant amount of time. The reason I ask is a friend bought a toolchanger for his Orac and it refused to turn - on stripping we found that the grease had solidified!
Did your new computer not completely solve the problem?
I might be able to take some sound recordings of our one at work if that helps.
Cheers
Dave
Hi Dave, Yep I'm still having problems and I think it is due to the machine now. I thought I'd cured it when sorting the computer and after the refit I loaded a file that cuts a 5/8" bar to profile and it cuts that no problem at all apart from while cutting you can hear a faint note of the same sound that ends up as chatter. When I tried a similar program for 1" bar I get chatter all the time so much so that the cut bar ends up like the dog has chewed it. I tried adjusting speed and feed but makes no difference.
This is starting to be a pain in the arse as need the machine for my business and at the moment I am doing all the work by hand.
The only thing I haven't changed are the headstock bearings, i've regreased them and tightened them up to the point that i lost 200rpm off the top speed. It improved things slightly but the headstock was getting warm so I slacked off a bit.
Moving to this forum I am hoping that someone may have experienced worn head bearings and let me know whether I have this problem.
I've also heard that some of the Denford people who made the machines read this forum too.
I could also do with knowing the correct bearing numbers so I can get some.
I have a convention to go to next week so I am busy making stuff right now but after that I'm taking a week out and strip the bugger right down and try to solve the problem.
I'll post any results I find.
Thanks for answering my post
Kind Regards
John
This is starting to be a pain in the arse as need the machine for my business and at the moment I am doing all the work by hand.
The only thing I haven't changed are the headstock bearings, i've regreased them and tightened them up to the point that i lost 200rpm off the top speed. It improved things slightly but the headstock was getting warm so I slacked off a bit.
Moving to this forum I am hoping that someone may have experienced worn head bearings and let me know whether I have this problem.
I've also heard that some of the Denford people who made the machines read this forum too.
I could also do with knowing the correct bearing numbers so I can get some.
I have a convention to go to next week so I am busy making stuff right now but after that I'm taking a week out and strip the bugger right down and try to solve the problem.
I'll post any results I find.
Thanks for answering my post
Kind Regards
John
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davidimurray
- CNC Expert
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Denford admin beat me to it - I've got a copy of the same manual here - actually came from Denford about 4 years ago!
Don't worry about the headstock getting warm - we reckon it is the Yorkshire way of keeping your tea warm. Seriously ours gets very toasty - actually I would call it hot- can't keep your hand on it for long.
Cheers
Dave
Don't worry about the headstock getting warm - we reckon it is the Yorkshire way of keeping your tea warm. Seriously ours gets very toasty - actually I would call it hot- can't keep your hand on it for long.
Cheers
Dave
Hi, Thanks Admin, thats helpful. Cheers Dave, I was beginning to worry about the bearings being too tight. I can remember when I tightened up the nut as far as I could, there felt no stiffening if the spindle shaft when the nut was locked tight. I did the usual and slackened off one notch of the locking tab.
I know when i've tightened up taper bearings they will lock the shaft tight
but these didn't do that at all. Is there something amiss here or is that normal for these bearings?
Tightening up the nut takes up axial play but if the bearing seats are worn radially I suppose it wouldn't make much difference and could be the cause of the problem.
Regards
John
I know when i've tightened up taper bearings they will lock the shaft tight
but these didn't do that at all. Is there something amiss here or is that normal for these bearings?
Tightening up the nut takes up axial play but if the bearing seats are worn radially I suppose it wouldn't make much difference and could be the cause of the problem.
Regards
John
Hi, Duh, I've read the specs (after I posted the last) and the bearings are taper roller.
So when I tightened the shaft lock nut why didn't the shaft become stiffer to turn?
Also I've been reading the info on the SKF website and they recommend that a preload should be placed on the taper roller set.
If that is the case then my head bearings are slack as hell.
Could anyone inform me of the correct procedure for setting up the spindle head bearings?
Kind Regards
John
So when I tightened the shaft lock nut why didn't the shaft become stiffer to turn?
Also I've been reading the info on the SKF website and they recommend that a preload should be placed on the taper roller set.
If that is the case then my head bearings are slack as hell.
Could anyone inform me of the correct procedure for setting up the spindle head bearings?
Kind Regards
John
Hi, Just to end this post, Yes my spindle bearings were slack as hell. I was also suprised at the amount of force needed to tighten the spindle locknut to take up the slack.
Once adjusted to my satisfaction and an hour test run, temperature measurement by sticking my hand on top of the headstock and muttering "mmmm.. it's reasonably warm but not hot" a few times, I cut some stainless and after a few adjustments with tool height the lathe was performing well.
Many thanks for all help and advice received..
Cheers
Once adjusted to my satisfaction and an hour test run, temperature measurement by sticking my hand on top of the headstock and muttering "mmmm.. it's reasonably warm but not hot" a few times, I cut some stainless and after a few adjustments with tool height the lathe was performing well.
Many thanks for all help and advice received..
Cheers
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davidimurray
- CNC Expert
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- Joined: Thu 24 Aug , 2006 9:45 am
Hi John
Good to hear that you've got it sorted. Any ideas how your bearings got so slack?
Just got my Starturn working (apart from spindle control which is currently somewhere between here and australia) under Mach 3 and it's great! CV is lovely to watch. I'm in the process of testing it at the moment to identify its capabilities (how far can I push it!)
Cheers
Dave
Good to hear that you've got it sorted. Any ideas how your bearings got so slack?
Just got my Starturn working (apart from spindle control which is currently somewhere between here and australia) under Mach 3 and it's great! CV is lovely to watch. I'm in the process of testing it at the moment to identify its capabilities (how far can I push it!)
Cheers
Dave
Hi Dave, The machine was sold to me that way. I wouldn't know why it was as I couldn't even cut mild steel without some chatter. I do know
the VFD is a bit underpowered for the machine as it now struggles to provide the 2000rpm that the previous owner was proud to show me. I also found that the slides and the ballscrew mounts were loose.
The machine was set up with TurboCnc and the stepper motors were set to run at 60khz microstepping. Way to fast... I found after playing with it once i'd got it home that they would break step easily. I had to spend time fitting a coolant setup as I cut a lot of stainless and so a fair amount of time had passed since the purchase.
I must say though that the electrics are well sorted and were done by the previous owner (who is a respected name in TurboCnc circles) but as to the machine, I was sold a puppy. It's been a long haul from sorting the toolchanger as it need a spacer plate so the tools were level. In my search to track down the chatter problem I've virtually stripped most of the machine and checked clearances and rebuilt it.
It's now pretty much sorted to do real work and I had a good day yesterday cutting without any chatter problems. I'm getting just above 2m a minute rapids on the z axis so it's not slow. I now find that I'll have to rework some of my Gcode since I played with it a lot because of the chatter problem and need to speed up material removal.
Being reluctant to post a "look what i've done" on the Mach3 forum because of the previous owners contribution to the machine, I think now that I've done enough work on it to call it my own. It doesn't matter how fast the thing whizzes up and down, If it can't cut material to a good standard, it isn't a lathe.
My first plans for the next upgrade is to sort it so I can use G96 mode. The VFD speed control is powered from a DtoA converter on the parallel port.
Do you know whether I can get this working using the step and direction control or the PWM control for the spindle?
Next on the wish list will be using the spindle as an angular axis so I can use driven tools.
Good to hear you have the Starturn going, What spindle drive are you going to use with Mach3?
Kind Regards
John
the VFD is a bit underpowered for the machine as it now struggles to provide the 2000rpm that the previous owner was proud to show me. I also found that the slides and the ballscrew mounts were loose.
The machine was set up with TurboCnc and the stepper motors were set to run at 60khz microstepping. Way to fast... I found after playing with it once i'd got it home that they would break step easily. I had to spend time fitting a coolant setup as I cut a lot of stainless and so a fair amount of time had passed since the purchase.
I must say though that the electrics are well sorted and were done by the previous owner (who is a respected name in TurboCnc circles) but as to the machine, I was sold a puppy. It's been a long haul from sorting the toolchanger as it need a spacer plate so the tools were level. In my search to track down the chatter problem I've virtually stripped most of the machine and checked clearances and rebuilt it.
It's now pretty much sorted to do real work and I had a good day yesterday cutting without any chatter problems. I'm getting just above 2m a minute rapids on the z axis so it's not slow. I now find that I'll have to rework some of my Gcode since I played with it a lot because of the chatter problem and need to speed up material removal.
Being reluctant to post a "look what i've done" on the Mach3 forum because of the previous owners contribution to the machine, I think now that I've done enough work on it to call it my own. It doesn't matter how fast the thing whizzes up and down, If it can't cut material to a good standard, it isn't a lathe.
My first plans for the next upgrade is to sort it so I can use G96 mode. The VFD speed control is powered from a DtoA converter on the parallel port.
Do you know whether I can get this working using the step and direction control or the PWM control for the spindle?
Next on the wish list will be using the spindle as an angular axis so I can use driven tools.
Good to hear you have the Starturn going, What spindle drive are you going to use with Mach3?
Kind Regards
John
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davidimurray
- CNC Expert
- Posts: 194
- Joined: Thu 24 Aug , 2006 9:45 am
Hi John
Now you've got it going I can guarantee that you will love it - built like a tank comes to mind! Don't worry about the headstock getting warm - just remember to put yout tea on it
I think I may know of the lathe you have - I have a wiring diagram for a converted orac with AtoD and various bits.
If it is this lathe, then I can't see anyway you could easily hook up the spindle as it requires so many pins - 8 or 9 by my reckoning. It could be done - but I think it would require considerable work. What VFD is fitted to your lathe? Is a a Parajust Barry Wright ?
I plan to use a Digispeed XL, made by Peter Homann in Australia. Peter is absolutely brilliant. I've actually got 2 on the way, one for my own starturn and another for Alastair Clarke's Orac. More details can be found here - http://www.homanndesigns.com/DigiSpeedXL.html
You basically just hook the digispeed into where the speed control pot should be. Also has relays on board for forward/reverse and on/off.
Using the spindle as an angular axis would be a hell of a challenge. You would need someway to stop it (brake) and a high resolution encoder. Alternatively, you could hook a stepper motor up on a second belt. You use one motor for positioning and the main one for spindle drive.
Cheers
Dave
Now you've got it going I can guarantee that you will love it - built like a tank comes to mind! Don't worry about the headstock getting warm - just remember to put yout tea on it
I think I may know of the lathe you have - I have a wiring diagram for a converted orac with AtoD and various bits.
If it is this lathe, then I can't see anyway you could easily hook up the spindle as it requires so many pins - 8 or 9 by my reckoning. It could be done - but I think it would require considerable work. What VFD is fitted to your lathe? Is a a Parajust Barry Wright ?
I plan to use a Digispeed XL, made by Peter Homann in Australia. Peter is absolutely brilliant. I've actually got 2 on the way, one for my own starturn and another for Alastair Clarke's Orac. More details can be found here - http://www.homanndesigns.com/DigiSpeedXL.html
You basically just hook the digispeed into where the speed control pot should be. Also has relays on board for forward/reverse and on/off.
Using the spindle as an angular axis would be a hell of a challenge. You would need someway to stop it (brake) and a high resolution encoder. Alternatively, you could hook a stepper motor up on a second belt. You use one motor for positioning and the main one for spindle drive.
Cheers
Dave
Hi Dave, I'm going to fashion a magnetic cup holder just for the job.
My VFD is a Mitsibishi Freqol connected to a purpose made A to D converter which has 8 port pins. I had to write my own macro to control it.
Trouble is, I really need to use G96 and this setup wont work.
Thanks for the link to Digispeed. Wow, just the job that XL. I had a day off today and spent the whole day designing a PWM to 0-10V converter just to do the job. Trouble is these days I never find time to make PCB's and twiddle with the soldering iron. It's definately on my next shopping list.
Well, as for the angular spindle it is in the planning stage and I'll Post pics on Mach3 forum when finished.
Cheers
John
My VFD is a Mitsibishi Freqol connected to a purpose made A to D converter which has 8 port pins. I had to write my own macro to control it.
Trouble is, I really need to use G96 and this setup wont work.
Thanks for the link to Digispeed. Wow, just the job that XL. I had a day off today and spent the whole day designing a PWM to 0-10V converter just to do the job. Trouble is these days I never find time to make PCB's and twiddle with the soldering iron. It's definately on my next shopping list.
Well, as for the angular spindle it is in the planning stage and I'll Post pics on Mach3 forum when finished.
Cheers
John