Hello Guest it is September 27, 2020, 01:33:16 PM

Author Topic: Threading problem, strange motion, Please help!  (Read 1605 times)

0 Members and 1 Guest are viewing this topic.

Threading problem, strange motion, Please help!
« on: June 09, 2018, 01:32:50 PM »
Hello,
I have built a lathe and I'm having trouble with threading.
My system is very basic. XP Mach3 .062, CNC4PC C10 BOB, C3 Index board and optical sensor, C6 spindle Control board. My disc has a slot that is 1-1/2" wide.  I have tried different widths from 1/2" up to 1-1/2" with no real improvement. I use NEMA 34 stepper motors with Leadshine Drives.
The RPM is steady to +/- 1 rpm. I have a 3/4 Hp motor driven by a VFD.
The Index signal is working as far as I can see with the diagnostics LEDs. I've tried active Hi and Low.  It's on Pin 15.
I have slowed down the motion to 50 IPM with 12 acceleration. I'm not loosing steps. I usually thread at 400 RPM or there about.
I use the simple thread wizard for the code. I have been trying to make a 3/8-16 thread.
I have tried Index Debounce settings from 0-1000.
When I select Use Spindle Feedback in Sync Mode, it makes random motions prior to each pass. Strange ZigZag motions. I'll try to attach a screenshot.
When I do not select Use Spindle Feedback in Sync Mode, the strange ZigZag motions go away, but it makes a bad thread because it's not starting from the same startpoint.
What I don't understand it why is Mach sending the ZigZag commands.

Thank you for your help!
Mike
Re: Threading problem, strange motion, Please help!
« Reply #1 on: June 09, 2018, 02:50:47 PM »
hi
what are you using to get the signal for threading ?
change the pin you are using from 15 to another pin it could be a bad pin on the parrallel port ?
i had the same problem as you about 18 months ago & it took 12 months to sort & it was a silly problem that could have been sorted very easily , i was using mach 3 062 version on a windows xp system  & all i did was to buy a windows 7 32 bit system and loaded all my old xml files , tool files and all other files needed & it started working  as it had done before
this is the type file i use for threading for 1/8" bsp external thread

G95 G64
M6 T0505   (externnal threading tool 55 deg)
M3 S500
G0 X9.75 Z15.00
G76 X8.55 Z-10.00 Q1 P0.090 J0.090 L45 H0.080 I27 C0.350
G93
G0 X40.00 Z40.00
Re: Threading problem, strange motion, Please help!
« Reply #2 on: June 09, 2018, 04:38:53 PM »
Hi ministeam,
I use a C3 board and optical sensor from CNC4PC. With that I use a disc about the same size as a DVD, with a 1-1/2" slot.
I'll try another pin and see if that changes anything.

Mike
Re: Threading problem, strange motion, Please help!
« Reply #3 on: June 09, 2018, 05:57:55 PM »
I tried a different pin, 13.  No change.
I removed the C3 and optical sensor from the system, and installed a Hall effect sensor and magnet. I tried many different Debounce settings.  No joy.
I tried ECP mode on the PP.  No change. Set it back to EPP.
The RPM reading was a bit more stable using the Hall effect sensor.
When I run the program while the diagnostics page is up, I can see the wait for trigger flash with each weird motion.
I also tried version 066.  It was the same.
Re: Threading problem, strange motion, Please help!
« Reply #4 on: June 10, 2018, 01:50:13 AM »
hi
something i forgot to mention last night was i used the c3 boards at one time but found them very unreliable , i have 4 off on my bench that will not work . i have been using a round proximity switch  from cnc4you for the last 12 months & it has worked very well , the only problem is it will not work using a plate with a slot i had to use a piece of ali about 3 /4" wide x 1 1/4"long to cover the slot & overhang the edge of the plate , i will look at my xml to see what settings i had
all the best
robert
Threading problem, strange motion, Please help!
« Reply #5 on: June 10, 2018, 02:05:26 PM »
Hi,
I tried something new. I use a switching power supply for my steppers.  I thought maybe that was causing electrical noise and interfering with the index signal. I disconnected the power supply to eliminate any noise from the power supply or stepper drives. It still has erratic movements.  They are not as bad as before.
It seems to be a noise issue. I'm just not sure how to isolate the cause or eliminate it.

Do I need to ground the BOB?


Mike

Sent from my SM-G892A using Tapatalk
Threading problem, strange motion, Please help!
« Reply #6 on: June 10, 2018, 08:41:47 PM »
In a effort to simplify the troubleshooting, I disconnected the C3 index board and the C6 spindle control. So the only active component is the C10 breakout board. The spindle was turned on at the VFD and held a rock steady 400 rpm. No stepper drives or power supply was active either.  Even with it as bare bones as this, Mach was still making strange moves.
The C10 BOB is new.  Could it be bad? It seems to function just fine with the expecption of threading.

I'm about the throw in the towel and switch to the Centroid Acorn.

Thanks for any help.

Mike

Sent from my Acer Chromebook R11 (CB5-132T / C738T) using Tapatalk

Offline RICH

*
  • *
  •  7,412 7,412
    • View Profile
Re: Threading problem, strange motion, Please help!
« Reply #7 on: June 11, 2018, 08:50:15 AM »
Fusion,

Quote
- different widths from 1/2" up to 1-1/2" with no real improvement
The turn manual provides for calculating the slotwidth. The slot width can be wider than necessary.
If too narrow the RPM may not show.  Since you changed over to a Hall effect mute point on the
width of the slot. Just manualy turn the spindle by hand and you should see the index led turn on and off
in diagnostics. I cover testing of the index in Threading on the Lathe writeup.

Quote
- I have tried Index Debounce settings from 0-1000
Index debounce is simply how many times Mach must see the index before it accepts the input.
I personaly use a value of 100,  others can get away with 10. If a high index value is used  you may
have a long waite time before the index signal is accepted and the threading begins ( changes to G95).

Quote
- motion to 50 IPM with 12 acceleration

I also use the Simple Threading Wizard . You should always click the "calc number of passes"
and it will inform you if the accel / feedrate  is not adequate based on you motor tuning for the
inputed Spindle rpm.

Quote
- I also tried version 066
Use version 062 and don't use 066 as it is problematic.

Quote
- It seems to be a noise issue
VFD's can cause noise problems. Not sure noise is your problem.....

- You have backlash enabled and thus there is motion which takes place to implement the backlash.
Suggest you turn backlash  off and see if the strange motion goes away. As far a using backlash relative to
to threading................GET RID / minimize BACKLASH if you want accurate threading.  PERIOD!

Quote
- In a effort to simplify the troubleshooting, I disconnected the C3 index board and the C6 spindle
control. So the only active component is the C10 breakout board. The spindle was turned on at the
VFD and held a rock steady 400 rpm. No stepper drives or power supply was active either.  
Even with it as bare bones as this, Mach was still making strange moves.
The C10 BOB is new.  Could it be bad? It seems to function just fine with the expecption of threading.
HMM........ the signal for RPM to Mach for RPM readout is coming from the break out board with the
VFD as the source of the signal. There can only be one signal for rpm readout when threading.
I thought that you changed from using the C3 index board to a Hall affect? So the hall affect should be
used as the single source and you also click the spindle button on to get the RPM readout.

Manualy turn on and manualy set rpm of the  VFD.

You don't want two signals fighting each other for the basis of the RPM used in threading!

Just some thoughts,
RICH  
Re: Threading problem, strange motion, Please help!
« Reply #8 on: June 11, 2018, 09:52:47 AM »
- You have backlash enabled and thus there is motion which takes place to implement the backlash.
Suggest you turn backlash  off and see if the strange motion goes away. As far a using backlash relative to
to threading................GET RID / minimize BACKLASH if you want accurate threading.  PERIOD!


I've done all I can to eliminate backlash. The problem I am seeing is there with backlash enabled or disabled.


HMM........ the signal for RPM to Mach for RPM readout is coming from the break out board with the
VFD as the source of the signal. There can only be one signal for rpm readout when threading.
I thought that you changed from using the C3 index board to a Hall affect? So the hall affect should be
used as the single source and you also click the spindle button on to get the RPM readout.

Manualy turn on and manualy set rpm of the  VFD.
I did this too. I had the spindle manually controlled at the VFD set to 400 RPM. The stepper drives and PS were disconnected. The C3 board was disconnected. The C6 board was disconnected.

You don't want two signals fighting each other for the basis of the RPM used in threading!

Just some thoughts,
RICH  

I do wonder if I may have a bad BOB. I hate to keep throwing money down a hole.
I uploaded a video to you-tube. This run is fairly clean, but there are some strange motions being sent by Mach3.
https://youtu.be/RAAVSQNnDMk
The attached image shows some really strange motions.
Re: Threading problem, strange motion, Please help!
« Reply #9 on: June 11, 2018, 11:16:47 AM »
hi mike
does the bob you are using do threading , in the past i have seen bob that are only designed for milling  
all the best
robert