Novaturn with problems threading and Feed mm/rev - encoder ?

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JSKRABA
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Novaturn with problems threading and Feed mm/rev - encoder ?

Post by JSKRABA » Fri 18 Nov , 2011 21:15 pm

Hi
First post here. Help and advise needed.
I have a Novamill amd Novaturn both about 1998 with Smartstep /3 boards
Both have Rom V2.1/b6 upgrades. The Novamill is running VRmilling via serial port and its OK

The Novaturn is running VRturning V1.27 and the standard Novaturn Mint file (although I have run the BigMint file)
The lathe works fine on most commands except (here is the main problem) the G99 (Feed/Rev) and Threading.
After a helpful call to Denford TS I started looking at the Encoder.
The machine speed display (on the m/c control panel always reads 0000 at any set speed) I understand this is a direct feed from the encoder. I have checked all setting to ensure encoder is selected.
On measuring the voltage in the control box. The Red/green +5 /0V is OK but the Green(0V) - Blue(pulse) is always at 5V (4.89v) I understand it should go 0V-5V-0V etc. Checked with Avo and scope.
Does anyone know if I do have a duff encoder? OR
I have read in the forum that there is a problem with Threading and its not supported on this age of machine with newer firmware and mint files - could someone (from denford) confirm. If so then the G99 problem and the display of machine speed is still there.

If it is the encoder can they be replaced or repaired (any idea of cost), if it is fixed will G99 etc and threading work with all else unchanged?

Last question, I have a Denstep control board from a 2001 Novamill with V2.1 Rom installed, Is it worth and can I install this in the Novaturn box to replace the Smartstep/3 board. Will this help anything. All boards have red LED display. I assume the Mill Rom will not work with the Turn or can I use the rom from the Smartstep?

Help please before I do anything drastic.
Regards JCS

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Denford Admin » Mon 21 Nov , 2011 9:58 am

I have read in the forum that there is a problem with Threading and its not supported on this age of machine with newer firmware and mint files - could someone (from denford) confirm
The thing about threading and older machines relates to the newer CAM software Quickturn 2D - it produces a threading cycle using single move thread:G32
G32 is not supported on older control cards and would only work from Nextmove ST USB hardware with the latest firmware, BigMint2, e.stop feedback and spindle disconnect modifictations to the wiring.
We developed bigmint2 so that all new machines can use the same logic and all new machines have checks for emergency stop contacts that have welded, and must have a spindle disconnect relay which is also checked before it's allowed to be energised. To add all this to your current machine would involve a fair bit of work on top of buying a USB top board upgrade.
The control you have with the 2.1 EPROM and smartstep bottom board should support feed/rev, CSS and threading, but will not support G32 - just G76.
Saying that, Martin needs to confirm that the encoder Pulse input on the Smartstep has worked on other DOS>Windows upgrades as I can't remember having seen one working.

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Martin » Mon 21 Nov , 2011 11:54 am

Yes it does sound like a faulty encoder.

The only other thing is the pins in harting plug but as you reading a voltage on the signal then it must be the encoder.

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by JSKRABA » Mon 21 Nov , 2011 22:30 pm

Thank you for all this info.
I talked with a Very helpful man at British Encoder who confirmed that the Encoder was Old and faulty BUT with his advice and fiddely soldering we were able to test and redirect the encoder to use another channel which was working. So now I get the Pulse ok and the MC/Control does read the spindle speed Feed/rev works (G99) as does Threading to some degree.

The problem is that instead of starting the thread at the same place each pass it advances by a fixed amount eg about +1.1 rotation per pass intead of 1. Its like its cutting a 10 start thread but each pass is deeper than the last. I have done lots of tests at different sizes and pitches and its consistant. Its as though the software sees the index pulse but then counts too many pulses each time then this becomes the new start. Not sure if its software that can be corrected or something wrong with the Reset pulse in the encoder. I understand that this reset (Z Index) pulse, once per rev is only used for threading.

I will continue the search for the final solution, I am very please that I am now close and that I have learned much about Encoders from very helpful people. Further advice would be very helpful.

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by JSKRABA » Tue 22 Nov , 2011 15:09 pm

After a few more tries it looks like the Z Pulse is not working OR the software is not seeing it.
It looks like a replacement Encoder is needed to get threading. Denford uses this pulse as the start point on the work.
The 2000 pulses are used for speed monitoring (Not control - no feedback) Feed/Rev and Constant surface speed.

Just to make sure, does anyone out there use the Novaturn with encoder fitted, with Smartstep board , V2.1 Rom and V1.27 VRTurning software and does Threading work?

Thanks

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Martin » Tue 22 Nov , 2011 15:50 pm

Yes it should cut threads.
If it tries to cut the thread then the Z pulse should be fine. If the pulse is missing the threading cycle would stop & wait.

I have had to alter the software before on upgrades to get threading to work. I can't remember if I changed the parameters or the .mnt file. I should be in the office Wednesday afternoon & able to check.

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Denford Admin » Wed 23 Nov , 2011 9:43 am

If I remember correctly, the fixed threading cycle (like a bath tub shape) on v2.1 EPROM will start slightly further into the job in X each time - it was an attempt to keep the load on the front edge of the tool. However, it sounds as though your machine is starting much further out of sync ?

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Martin » Wed 23 Nov , 2011 14:56 pm

The fix we did before was due to the axis stalling during threading. We changed the acceleration in the .mnt file.


What top card\eprom do you have fitted?

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by JSKRABA » Sat 03 Dec , 2011 19:29 pm

Hi
I have solved the problem by replacing the encoder.
I can confirm that A Novaturn with Smartstep board with 2.1rom and V1.27 VRTurning will cut threads as long as the encoder works.
The Z Pulse (One 5V Pulse per rev ) is only used by software to determine the start point of the thread
The A Pulses (2000/rev, Denford counts 4000 pulses up to 5V and down to 0v) is used to track speed and control Feed/rev and Constant surface speed cutting.
If Z is dead then the threading cycle will proceed but will start in wrong place on each pass.

If the encoder looses the A Pulses you can use the B channel (Encoder supplied with A & B) with a little soldering.
You will then get the speed and feed working but if Z has gone you will not get threading.

I got a new encoder from the very helpful people at British Encoder with a connector (rather than trailing lead) this made it very easy to swap out. Threading is now working.

Now I have fixed this I have tested the machine and find that it does not do as the software says, with all offsets set if I ask it to move from Z0 to Z-15 it only goes to Z12. The same in X Move to X0 goes to X3!!!
No idea why, the software simulation is fine.
Any Ideas where I should look?

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by JSKRABA » Sun 04 Dec , 2011 17:59 pm

Another long day in front of the lathe.

Found the solution to my problem in an old post, the older Novaturns used different steppers than the new ones.
The Machine settings for Novaturn Steps/mm was set to 160 the older machines need 200 set on all Steps/mm settings
Now works fine and cuts what it says it will cut.

Thank you to all who looked at or responded to this post

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Re: Novaturn with problems threading and Feed mm/rev - encod

Post by Denford Admin » Mon 05 Dec , 2011 10:37 am

Thanks for posting your fixes and glad it's all working now.

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