mach3turn spindle sensing problem

[GDoc]

hello, I'm new to mach3. i have set up a cnc lathe, both the z and x axis are working fine , my problem is with the spindle speed sensing. i have a single slot disc with optical sensor. the motor speed is controlled by an external dc drive with a pot of setting the speed. with mach3turn running and motor running the DRO does not indicate the true speed, it seems to top out at 160rpm when the true speed is a lot more. the confusing thing is that if i close down mach3turn and start up mach3mill with the same settings, i get true spindle speed!

what i am i doing wrong?

[wlwoodall]

It is now July 2010, 2 years and 5 months later. I have the exact same problem. Has anyone come across a solution for this problem? I really, really need to have this solved.

Woody

[RICH]

The spindle speed here is spot on. I currently use a Hall sensor and in the past used a single slot in a disk and that worked also.

Gdoc and Woddy, what version of Mach are you using?
You may also want to post your xml fle.

If you look in the Manual there is a min slot disk width that you can calculate, did you do that?
Increasing the slot width can help as i remembered i had to almost double the calculated value to get top rpm readout.

RICH




 

[wlwoodall]

Hello Rich:

I am using version R3.042.040
I calculated the disk slot as follows:
Using the formula in section 4.8 of the Mach3Turn manual I calculated the disk width at 100 rpm (which is .006") and
calculated it at 2000 rpm (which is .126") and used an actual disk width of .250"
The disk is an aluminum disk 6 inches in diameter.

I don't have the sensor on the spindle yet, I am using a disk installed into a drill press and using the belt settings on the metal tag and the indicated rpm's to see if MACH3 display is even close. Here is what I have.
Drill press rpm       Mach3Turn       MACH3Mill
       208                  42                  230
       811                  51                  830

As you can see, MACH3Mill readings are very close to the drill press but Mach3Turn is way off.

I can't seem to attach my XML file.

Bill

[RICH]

Bill,

 Have a look at Section 7  "Mach3 Turn Configuration" in Threading on the Lathe - Mach3 Turn
and check your settings.

RICH

[wlwoodall]

Thanks for pointing me to the configuration guide. I would not have considered reading it unless I were doing threading (I'm still far far away from doing threading yet).
From reading this guide, I can see that you've done a lot of original research on the subject and your threading guide is impressive to say the least.
Thank you for your work in this area.

I've narrowed my problem down to the debounce interval/index debounce area. My current settings are debounce interval of 500 and index debounce of 100.
I hate to just randomly change the numbers to get my rotation correct. This situation currently has four variables which don't seem to correlate. #1 - actual rpm of the spindle (as measured by tachometer), 208 rpm & 811 rpm, #2 - displayed reading by MACH3Turn, 42 rpm & 51 rpm, #3 - debounce interval of 500 and #4 - index debounce of 100. What correlation exists between #3 and #4 that I can use to get #2 closer to #1?

On a side note, why did the default setting for spindle sensing in MACH3Mill immediately give the proper reading? It properly displayed the reading just after I opened it up for the first time. I need to investigate that.

Bill

[RICH]

Bill,
Post your xml for both the mill and the lathe that your are using.

Then we can try on our side to see if we can duplicate the problem or narrow down the possibilities.

I don't remember everything associated with improper rpm readings off the top of my head...... and i am still
using Mach 3.042.33. There were a few folks who had rpm reading problems in TURN after that rev and need to see exactly the problem and
solution ( it was PC related, but later revisons of Mach addressed the problem).
You realy need to get the rpm  reading by Mach right or you will never do threading on the lathe.

RICH

[wlwoodall]

Rich:

First of all I noticed how VERY similar MACH3Mill and MACH3Turn are in terms of settings. The RPM indications in Mill were dead on so I compared the XML files of the two (Mach3Turn.xml and Mach3Mill.xml).
The default settings in Mill that worked for debounce interval and index debounce were 0 and 0. I noticed that the defaults that came up in Turn were 150 and 100. I simply changed the debounce interval and index debounce
for Mach3Turn to 0 and 0 and POOF! the reads were correct.

As a summary for those researching this in the future, do the following:
First of all, enable a plugin which will help with spindle sensing called TURNDIAGS-TURN-DIAGS-1.00.1 as follows:In Mach3Turn, go to Config menu, Config PlugIn sebmenu and ENABLE  TURNDIAGS-TURN-DIAGS-1.00.1 then closeGo to PlugIn Control Menu and click on the TURN DIAGNOSTICS submenu
This will open a very helpful diagnostics screen.

RICH has  MODIFIED THIS reply striking thru some of the above text...see my reply.
Start your motor with the index sensor connected and use the diagnostics screen.
Make sure the debounce interval and index debounce in the CONFIG . . .GENERAL CONFIG screen reads 0 and 0 (extreme upper right of the screen)
Go to the diagnostics or manual screen and type M3 or M4 into the MDI line so that Mach3Turn will read the spindle sensor (Very important!)

Thanks for all your help Rich.

[RICH]

Bill,
DO NOT USE OR ENABLE THE TURN DIAGNOSTICS plug in or any other plug-ins like it since they were for testing purposes only.
The turn diagnostics 1.00.1 no longer functions properly. The rpm is read in real time where as before it was not.

The more closely the PC is to the kernal speed during the driver test the more solid your DRO rpm readout will be.

The index debounce can influence the rpm reading as you found out. The lower the better ( value of at least 1 and don't recommend 0 ) i use a value of  10. It's the number of times Mach will look at the index to determine the rpm in turn if i recall correctly. Since Mach will vary the feedrate based on displayed / read rpm,   it would seem that during threading Mach's varing of the feedrate due to spindle slow down would be more responsive. No Mach will not go above the called for feedrate during threading. When spindle speed averaging is checked in config, Mach will average the rpm in the adjustment of the feedrate. There is a lot going on in threading / turn.

Yes, you must turn the spindle on in lathe using M3 / M4. This was done to inform Mach to start reading the index pulse. It cured the problem of slow spindle speeds not being read.  

RICH