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Author Topic: Chasing My Y  (Read 5222 times)

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Online fabr

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Chasing My Y
« on: August 22, 2011, 09:31:44 PM »
Been having issues with my Y axis on the machining center drifting around a couple thousandths for a while now. Nothing I was doing was very precision and so since I had a lot of other  things more pressing to do it went unsolved. Well, it bit me in the ass yesterday.  It drifted alright. about .070!  eyes So ,today i go on the hunt for the culprit. When rebuilding the machine I replaced ball screws and resolvers for best ,like new,performance.  Turns out to be that the resolver ("position sensor") has a bellows coupling. The end that i coupled to the ballscrew was tight. The end that came assembled to the resolver was not. eyes eyes Guess one should never assume others did their part huh. Anyway,4 hours work and tightening one little #6 socket headed cap screw and I have lost my ability to drift. rofl rofl rofl rofl
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
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Offline Carlriddle

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Re: Chasing My Y
« Reply #1 on: August 23, 2011, 06:13:32 AM »
I'm sure it was your fault.  No way, not theirs.

Like buying a bicycle, assembled from Wally World, has a tag on it to check all nuts and bolts.  WTF am I paying for assembly then.  bs1
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Offline Hammerworks

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Re: Chasing My Y
« Reply #2 on: August 23, 2011, 06:50:38 AM »
I had that same thing happen on the z on a Fadal.I was standing so the doors were to my right and could see the z out of the corner of my eye while I deburred some parts.Hmmm..why is the z going up so hi?....I dont remember that in the program....WHAM....rapid straight down into the table!
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Online fabr

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Re: Chasing My Y
« Reply #3 on: August 23, 2011, 07:02:05 AM »
Carl,you're soooooo right. In this case though the guys are very reputable and I will give them a pass. From now on though I check all the nuts and bolts like at Wally. LOL!!!

Hammer,you're right,Fadal is what I have and they have no limit switches on the axises. BANG!!!! if for any reason the resolver fails or malfunctions. I really dodged a bullet this time. 
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Bennyhanna

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Re: Chasing My Y
« Reply #4 on: August 23, 2011, 07:05:27 AM »
You are saying that a Fadal has no hard limit switches to stop the travels at their most extreme? it has to, or very bad things will happen.
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Re: Chasing My Y
« Reply #5 on: August 23, 2011, 07:16:18 AM »
I'm telling you that it's a 100% fact there are no limit switches on a Fadal.  Only the resolvers. Yes bad things can/do happen when the resolver fails or is out of position as happens with a loose coupler. The machine has no limit switches anywhere. No Fadal of any model has a limit switch on the axises. Zip,zero,zilch,nada,none. Yes a secondary limit switch would have been a cheap and much needed improvement on a Fadal.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Boostinjdm

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Re: Chasing My Y
« Reply #6 on: August 23, 2011, 03:57:08 PM »
Quote from: Carlriddle on August 23, 2011, 06:13:32 AM
I'm sure it was your fault.  No way, not theirs.

Like buying a bicycle, assembled from Wally World, has a tag on it to check all nuts and bolts.  WTF am I paying for assembly then.  bs1

Walmart doesn't charge for assembly.....
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This post has been edited due to content.

LiveWire

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Re: Chasing My Y
« Reply #7 on: August 24, 2011, 12:46:34 PM »
We had it happen on the Z a few years back. The shaft the the encoder was mounted to somehow broke loose. I guess it was just a press fit into the servo motors main shaft.

Does a Fadal have home switches? I retrofitted the machine we use from a Dynapath 10 controller to a one from AjaxCNC. The limit switches double as home switches to auto home the machine after startup.
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Re: Chasing My Y
« Reply #8 on: August 24, 2011, 01:03:37 PM »
Nope no home switches. The resolvers do it all. Well,supposed to anyway.  eyes Be nice if there was some kind of back up safety.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

LiveWire

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Re: Chasing My Y
« Reply #9 on: August 24, 2011, 01:23:55 PM »
I guess a resolvers must somehow be different than an encoder then. An encoder only knows it's position within one rotation. The controller keeps track of the number of rotations. When the controller is rebooted, it loses that. So it touches off the limit switch then backs up until it hits the zero degree position of the encoder. I forget what it is actually called. Since the limit switches are not consistent in the point they release, if that zero position is too close to where it hits the limit switch, sometimes the machine will be off one rotation which is .200 in our case. Rotating the encoders mount to get zero away from the limit switch fixes that.
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Bennyhanna

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Re: Chasing My Y
« Reply #10 on: August 24, 2011, 01:39:03 PM »
Livewire, on an okuma the encoders are absoute, therefor there is no zero returning or homing out.  you just turn them on and they are ready to run.  you can actually crank the ball screws with the machine off and it will know where it is when you fire it up.  maybe they are actually resolvers, but the service guys always call them encoders.  and they have hard limit switches only, no soft limits, the controller knows where it is at.
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Online fabr

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Re: Chasing My Y
« Reply #11 on: August 24, 2011, 02:38:02 PM »
Quote from: LiveWire on August 24, 2011, 01:23:55 PM
I guess a resolvers must somehow be different than an encoder then. An encoder only knows it's position within one rotation. The controller keeps track of the number of rotations. When the controller is rebooted, it loses that. So it touches off the limit switch then backs up until it hits the zero degree position of the encoder. I forget what it is actually called. Since the limit switches are not consistent in the point they release, if that zero position is too close to where it hits the limit switch, sometimes the machine will be off one rotation which is .200 in our case. Rotating the encoders mount to get zero away from the limit switch fixes that.
Yes resolvers measure rotation but in many segments. I forget ,off the top of my head,how many segments but it's a lot! LOL!!!
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

LiveWire

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Re: Chasing My Y
« Reply #12 on: August 24, 2011, 03:10:43 PM »
The encoders used with our retrofit read 8,000 segments per rotation. With 5 rotations per inch, that is 40,000 per inch.
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Offline BDKW1

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Re: Chasing My Y
« Reply #13 on: August 24, 2011, 07:20:57 PM »
I thought Fadals had limit switchs in the middle of the table, hence the reason they " home" to the center of the travels. Friken OCD machines always wanting to go home..........
 
BTW, spinning the jog handle to fast can result in a broken encoder coupling.............. Pis poor controllers........
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Online fabr

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Re: Chasing My Y
« Reply #14 on: August 24, 2011, 07:34:32 PM »
No limit switches anywhere. I rebuilt this machine from the bare casting up.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"
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