Can't add negative number to Low Range Spindle Speed RatioRatio <milling machine as a lathe, resolved>

[msauto]

post a fresh report.zip so we can see your current setup. do you have photos of the machine in a photo album? so we can see what we are working with?

note: you can always pay for custom plc work as an option if you'd like us to work on your project.

Sorry Kieth, somehow i overlooked this post

But i honestly thought about paying you guys but wasnt sure it was an option.Who do i contact to get a price?

Updated report attached but hasnt change since the one i posted earlier(unless i fat figered something,i have to type with 1 hand and 1 finger.lol

I'll post some photos shortly.

[cnckeith]

no worries,
good deal on the latest report, just wanted to make sure we have latest.
i'll wait for photos before commenting on how to proceed.
you can always purchase one on one tech support time here.
https://shopcentroidcnc.com/centroid-fa ... l-support/

[msauto]

Heres a link to some quick pics, wasn't sure what would help most so shot 4 corners and top. Please disregard the mess shop is in the midle of a remodel and i'v been adding external e-stop,tool check etc.. buttons so theres a few unconected wires in the cabinet.

This link should get you to the pics
https://1drv.ms/a/s!AlEMVpXAQYPSn8xbJxc6rG3FDikXMg

[msauto]

Sorry , I forgot that i had disabled parm 412 and set inputs back when the backgear switch didnt work. Heres a report with everything set where i believe it should be reporting the proper rpm in low gear (not even trying to reverse it untill it reports speed based on parm 65 properly which it is not doing right now. It does however turn on "spin low" led when i switch backgear on.

[cnckeith]

yes, the 'canned' back gear logic is not going to work for lathe, it is designed for a Milling machine.
i was suggesting we could use a back gear switch with the Lathe software with some Custom PLC programming to look at it and decided which way to spin the spindle when a m3 is issued.

[msauto]

Spindle reversing via m3 and m4 works fine. what doesn't work is when backgear or low range is selected cnc12 is not looking at and acting on parm 65 and adjusting the spindle speed encoder output accordingly.

[tblough]

Spindle speed encoder output is supposed to be the actual spindle speed and does not get changed by the back gear ratio. As Keith pointed out earlier, if you have a Bridgeport style milling head and you attached the encoder to the top of the spindle, then you are not reading the actual spindle speed when in backgear.

See this post https://centroidcncforum.com/viewtopic.php?f=64&t=1944 to see what is involved in reading ACTUAL spindle speed in high or backgear on a Bridgeport.

[msauto]

Spindle speed encoder output is supposed to be the actual spindle speed and does not get changed by the back gear ratio. As Keith pointed out earlier, if you have a Bridgeport style milling head and you attached the encoder to the top of the spindle, then you are not reading the actual spindle speed when in backgear.

See this post https://centroidcncforum.com/viewtopic.php?f=64&t=1944 to see what is involved in reading ACTUAL spindle speed in high or backgear on a Bridgeport.

Then why does it change mine and many others to proper spindle output in cnc12 mill with a ratio of -.117 entered into parm 65 or aka wizard entry spindle low gear ratio and has for 3 years with my encoder mounted on top of the spindle. ... And i have a comercial grade hand held laser tachometer that says i am reading actual spindle rpm, bothe in high and low range from cnc12 mill,just not cnc12 lathe. The issue has been stated already and it is that i am using a mill as a lathe (which works fine as long as i do not try to thread & or have a low torque at low rpm spindle like me due to using a vfd.) and if threading in cnc12 lathe it needs to sync my z axis movement with spindle speed the same way a quick change gear box does on a manual lathe .. but my mill does not produce enough torqe at 580rpm in high range to cut threads(and cnc12 lathe doesnt support gear changes or backgear although its listed in the vcp.But cnc12 mill does) , when the tool engages the part then the spindle speed slows (equivelant to trying to cut a 3/8x24 thread with the QCGB set to 16 tpi on a manual lathe..lol itll cut threads,but not what you want) but the motor doesnt have enough torque at that rpm. So turn up the rpm abit, you say. Unfortunatly if i try and go above 580rpm then i get a z max exceeded error meaning that my z axis is being commanded to move faster than the max ipm set in wizard which in my case is 60 ipm. My motors are 13nm nema34 and have lots (to much really..made originaly to run 1" tooling in deep cuts) of torque. So i have to as Kieth said Roll my own plc or pay centroid to do so. I just wish i had known this before i spent 175 on lathe pro and honestly without trying it first ,theres no documentation that i could find that says "No backgear and no speed ratio support on cnc12 lathe" Any way .. life is nowledge & knowledge is power and i blame no one but myself. Everything else seems to work fine so i will set up my gange tooling and see whats possible untill centroid decides there are enough people doing mill turning to add the same functionality for gearing that cnc12 mill has into cnc12 lathe. Kieth said he put it on what i know is an ever growing list...lol

Thanks for taking the time to try and help.
I only wrote this extremly long message because i feel like some people do not quite understand what exactly i am trying to do based on replies.

Thanks again for trying to help and thanks espeicially to CNCSW for going to bat for me and trying his best to help.

[tblough]

Because that's exactly what it's designed to do. CNC12 changes the DAC output based on the gear ratio. The spindle encoder reads the SPINDLE speed and therefore should never need any gear ratio applied to it. It also does not, and SHOULD not, need to be "reversed" by a negative gear ratio. The spindle speed is what the spindle speed is, and the spindle direction is what the spindle direction is.

People get confused because they think CNC12 controls the spindle speed based on the measured encoder speed. IT DOES NOT. The spindle speed control is an open loop system based on a line fit of two speed points. One point is 0RPM = 0V, the second is the Max rpm you specify in setup = 10V. If you set up gear ratios, those are used to divide the commanded spindle rpm, by the ratio, to get the output rpm for the DAC.

For example if you have a 4000 max spindle speed then M3 S4000 will generate a 10V signal on the spindle output. If you command M3 S450 with a .117 gear ration in backgear, then the DAC outputs (450rpm/0.117 = 3846prm) 9.615V. In addition to the commanded speed, if the gear ration is negative, then CNC12 knows that backgear reverses the spindle so in addition to setting the DAC to 9.615V, it swaps M3 and M4 so the motor runs in reverse and the spindle rotates the correct direction.

There is a transmission in the head of the Bridgeport. You are reading the speed of the input shaft at the top, not the speed of the output shaft (the spindle at the bottom) with your encoder. That's why you may command 350RPM in back gear, and you can measure the spindle speed with your laser tachometer and it's 350RPM. But you can't thread because the encoder (and the CNC12 RPM display) are reading the 2991 rpm transmission input speed. In addition, in back gear, the input shaft where your encoder is connected is turning in the opposite direction of the output shaft (the actual spindle where the tool is). That's why you say the encoder is reading negative rpm while the spindle is rotating clockwise.

The reason why it "produces a very ugly thread" when you're trying to run it with lathe software is once again, the spindle encoder is not attached to the actual spindle. Threading uses the index pulse from the encoder to time the start of the thread. This index is supposed to happen only once and always in the exact same spot for every spindle revolution. Your index pulse is happening 8.547 times (1/0.117) every spindle revolution when in back gear so CNC12 has no clue where to start subsequent passes of the thread.

Please post some photos of your spindle encoder and how it's attached to your machine.

[msauto]

Thanks again for explaining and i understand all of that but my encoder mounted where it is thread mills fine, i just don't like spending 60 bucks a pop for thread mills ..lol

With that said if there were an issue with the encoder positioning in cnc12 lathe then there should be a problem in cnc12 mill and there IS NOT.

As Kieth said earlier CNC12 Lathe was not designed to do what i am doing because they never expected someone to use a mill as a lathe , though its pretty common now i have not found any info on people cutting threads this way. But according to Kieth cnc12 lathe will not do what i want without a custom plc.

Again i have no issues with reported rpm exept that when in low gear... the reported rpm is the same as high gear in lathe .

The division you mentioned IS NOT HAPPENING even though the software is being told to. In mill the division takes place and even sends m4 to reverse the spindle(i do not care about reversing the spindle right now, i can do it manually).

Here's the link to the pics i posted a few posts back if you want to have a look.
https://1drv.ms/a/s!AlEMVpXAQYPSn8xbJxc6rG3FDikXMg

Also i think you may be off a bit on your ratio math heres a quote from the manual

11.3.54 Parameters 65–67 – Spindle Gear Ratios

These parameters tell the control the gear ratio values for a multi-range spindle drive. Up to four speed ranges are
supported, with high range as the default. Parameters 65–67 specify the gear ratio for each lower range, relative to
high range. For example, if the machine is a mill with a dual-range spindle and the spindle in low range turns at 1/10 of
the speed it turns in high range, then Parameter 65 should be set to 0.1. Note that these values can be signed +/-. So,
if switching from high range to a lower range causes the spindle encoder to count in the opposite direction, then a
negative value can be used to compensate for this behavior.

So to simplify this and explain where i came up with .117
My max rpm in high range is 4200 and my max rpm in low range is 750 as measured with my hand held tach.

So... 750/4200=0.1785714285714286 or .177 to compensate for some fluctuation on the tach.

With this number in parm 65 in cnc12 mill the software does the math and spits out 740ish rpm at full speed in backgear forward or reverse.
It DOES NOT in cnc12 lathe.