One problem fixed, yet another problem..

[Greasetattoo]

Hey Guys,

Well, I got my machine back up and running.
Got new brushes, tried to install them, but broke the plate they sit on.
Ended up getting a brand new spindle motor.
Sherline has a new motor now, that you can change the brushes without dismantling the whole motor.
Evidently, a lot of people were having problems with the brush plate breaking.
Anyways, now I have a new problem.

Could you look at the attached picture and tell me what you think?
I took apart my whole Y axis and reassembled, and still the problem.
I believe it is my Y axis that is giving me the problem.
Looks like it is happening in the same spots, every time.

Could this be my backlash?
Even though I have the Kirk leadscrews? (auto backlash comp.)
http://www.haydonkerk.com/Products/Lead ... fault.aspx

I did not change any of my machine settings either.
I noticed the DeskCNC has a Backlash compensation, which I don't use, seeing I have the Kirk leadscrews?

Also, the bigger box is off measurements too!
Same as the smaller box.

Maybe, my bearings?
I am very confused here..

Any ideas.
Thanks for any help..
Grease

[metalworkz]

Hi Grease,

I had a minor problem with my SX3 mill cutting flats when interpolating a circle and it ended up being the coupler that connects the stepper motor to the ballscrew shaft being lose just enough to allow the coupler to move when changing directions(at 90º - 4plcs on circle) Have you checked the couplers? Maybe just the one on the Y axis since the X axis dimensions look good on the part you cut?

[gravirozo]

hi

Grease, please check the rollers on the Y axis.. if it would be backlash it might don't makecircle... but it shows the motor-routerbit moving out of position...

the imservice what sell they have special ballbearings with v groove in the outer ring...
they are in pair also... one carriage has four... two of them has fix shaft, and two ballbearing has excentershaft.... to set zero... check all of them and without nut, (loose up the three bolt) set the carriage as it stiff, but not thight...

i have same rollers on my small router and my first to do was when i bought, i made stronger shaft with my mini lathe..

of course check nuts too...
also the kerk motion don't sell directly in all 50 state... i'm in georgia, and i had to buy from carolina fluid...


thanks
viktor

[dr_when]

It actually could be a backlash problem as you can see the problem is right when you come over the circle where your axis would change direction. I am not sure about the Kerk anti backlash nuts or if they are adjustable. I have used backlash compensation in Deskcnc but ideally you want to get rid of it mechanically. I would make sure your motor's connection to the lead screw is secure (coupler). If you had low backlash at some point in time you should be able to get back to that point. I would try to quantify the amount using a dial gauge so that you can tell when things are getting better or worse.

[Greasetattoo]

Thanks guys..

Do you think it is the X axis and not the Y axis.

I am going to take apart the machine tomorrow morning and double check everything.

I did take apart the whole Y axis, this morning and low and behold it did the same thing.

Also, I kinda noticed the bearings in the Y axis were kind not real smooth.
I will check them to the X axis.

I will keep everyone posted.

Any other suggestions are welcome.

Fix one thing, then another pops up.
Oh well, I guess it is, part of the hobby!

[wcarrothers]

You need to use this problem to leverage the need for getting your self a larger machine.. we are all waiting for that day to see what you are capiable of with a larger machine.....

On all my machines I have ball screws with single ball nuts (no extra ball screw to help back lash. And don't see results this far off ever. think alot of that is due to being servo based vs stepper perhaps? I choose servos so my machine would be more quiet and comments from my step dad (who owned a machine shop back in the day) about how his old stepper machine from 1978 time frame would "lie" to him over time)..hehe But having never had a stepper based macine I can't say for sure.

b.

[jhop]

Properly tuned steppers are very accurate.

Jim

[larrybadgett]

Grease
Just a thought, you might want to check the way the material is clamped in place.

[Greasetattoo]

Hey Everyone,

Well, I think I may have it all fixed..
My gibs were tight. (loosened and oiled.)

Also, I noticed a wear mark on my Y base, right where the Kirk screw holder is.
I noticed when I tighten my Kirk screw holder down, the Y axis did not go smoothly.
Got tighter as I tightened down the screw holder.
So, I sanded some of the plastic off the bottom of the Kirk screw holder. (which was rubbing on the Y base)
And did not really tighten the holder down.
It is tight, but not as tight as it binds.

Did the same cut test and seems everything is working now.
Everything measures out good, and circles are circles.
Mind you, this is about the 3rd time I took everything apart on the Y axis.
(before, I did not notice the leadscrew holder was rubbing on the base)

I think the oil and gib loosing up help too!


Hopefully, everything should be fine now.

Thanks for the help, and suggestions.

Greg