shoptask turnado lathe to acorn

[KevinTaylor]

October 25, 2019

Kevin

Will do on Monday when I'm back in the shop.

Did you look at Marty's post above? Your report is suggesting that you have your x and z-axis swapped?


Britt

I saw his post, I didnt know that he was trying to tell me that my z and x was swapped. Hmm... I set my lathe up like in the attached picture. Is this wrong?

[tblough]

That's how I have my lathes set up.

[martyscncgarage]

Your picture is correct. I am questioning the accuracy of your turns per inch on X and Z

[KevinTaylor]

Ok so after all the posts I recieved tonight, I went out to the shop to check some things.

My z axis is indeed belt drive with 2 gears, and it does in fact seem to be 1:1 ratio

My x axis is direct drive with coupler

So I think Marty is correct with the diameter mode and why my x axis revs per inch are double. To clarify, when I do a g0 x1 command, that should move the x axis .5" and not 1" correct?

Would this also explain why my x axis seems to move twice as fast as my z axis even though the speeds are the same in the wizard?

[martyscncgarage]

Ok so after all the posts I recieved tonight, I went out to the shop to check some things.

My z axis is indeed belt drive with 2 gears, and it does in fact seem to be 1:1 ratio
zaxis-beltdrive.jpg

My x axis is direct drive with coupler
coupler.jpg

So I think Marty is correct with the diameter mode and why my x axis revs per inch are double. To clarify, when I do a g0 x1 command, that should move the x axis .5" and not 1" correct?

Would this also explain why my x axis seems to move twice as fast as my z axis even though the speeds are the same in the wizard?

I think you have your turns ratio wrong on X. Test it like I said. Turn the screw, count how many turns it takes to move the axis 1". Enter that value for X to start with.

Yes. Tell the control you want to remove 1" of material, X only moves .5". Lathe defaults to diameter mode.

[brittfussel]

October 25, 2019

Kevin

I made the assumption that your z-axis was the same as mine: belted with a 2:1 ratio. I see that your machine is 1:1 on the z-axis. I've been pondering that modification to mine.

If you calibrated your x-axis in diameter mode, and if you were expecting the table to move one inch when you commanded it to move one inch, your turns per inch would result in a number 10.16 plus. Change it to radius mode and command it to move one inch. It should move two inches. I don't think this is your problem though. I believe you should still test it with something of a known dimension such as a gage block or 1-2-3 block.


Britt

[martyscncgarage]

Here is what I do.
I put a dial indicator, on the slide of the X axis, parallel with the X axis. I put a right angle plate down perpendicular to the X axis. I jack it up on 1-2-3 blocks if needed. I move the indicator to the angle plate to take up backlash, I jog the indicator tip into the angle plate until it reads 0.
I set a part zero on X.

I go into MDI.
I do a G98 so I can move without the spindle turning (my machines have encoders)
I command a G01X-1.0F5 move. I watch and count the rotations of the indicator and see where it lands.
Let's say it moved .499"
BUT I commanded a 1" move, which is actually .5" (diameter mode)
So I take .5" and divide it by the actual moved distance of .499", which equals 1.00200401. I then go into the Wizard and then multiply that number by the turns ratio currently in the Wizard, enter the new value in the Wizard and retest.

For Z, I chuck my 2" indicator (gently in the jaws), and set the angle plate ON the X cross slide perpendicular to the axis. I jog the cross slide in the Z- direction to take up backlash and zero my indicator, set my Z part Zero, command a G01 Z-1.0 F5. This time I use the commanded distance to travel, 1" and divide it by the actual distance travelled, then multiply it by the turns ratio in the Wizard, replace the number in the turns ratio with the new value.

When I am done calibrating the axis. I repeat, the above, but this time I command a move back to the original 0 position, the difference between 0 and where it landed is my backlash. I enter that into the backlash table. Retest. That usually takes care of everything. Probably other ways to do a lathe, but that's how I do it.

I hope that makes some sense. I just finished setting up 3 benchtop lathes for a customer that way.

Marty

[KevinTaylor]

I reset my x axis revs per inch and it is correct now. The new number for my x axis is 5.110149884.

I also checked my machines DRO against the 2" plunger DTI and they seem to be fairly accurate with each other.

My machines DRO says 2.009

My DTI says the same thing

So while I haven't completely ruled out that my machines DRO is off, it seems its not my problem with my x axis.

The further I go in x+ the more off it becomes. At just 2" it is already off by 9thou. And that number keeps increasing the further out I go in x+.

Again just to make sure in case what I have done is already buried in my thread, I have adjusted the x axis gib. I have tightened the x axis thrust bearing. I have taken out the ball screw and ball screw mount -> reinstalled and made sure all bolts are tight. I have upgraded my limit switches to metrol (which are supposed to be good I hear), and I have replaced the direct drive coupling.

Could it be a bad stepper motor? I have no clue as how to proceed at this point. Any suggestions?

[martyscncgarage]

Did you supply the stepper motors or were they on the machine?
What drives are being used?
What voltage power supply is being used?
Sorry, I can't spend the time to wade through 6 pages of posts.
Are you GAINING or LOSING?
X+ is AWAY from the spindle center line. That how you have the machine setup correct?
Carriage AWAY from the headstock is Z+

[KevinTaylor]

Did you supply the stepper motors or were they on the machine?
What drives are being used?
What voltage power supply is being used?
Sorry, I can't spend the time to wade through 6 pages of posts.
Are you GAINING or LOSING?
X+ is AWAY from the spindle center line. That how you have the machine setup correct?
Carriage AWAY from the headstock is Z+

The stepper motors were supplied with the machine.
It is using a gecko g540.
48v power supply I believe.
I am gaining.
My machine is set up exactly like in the attached picture.