Cutting out_of_round circles - loose V-rollers on Z-slide
 

HI All,

its seems funny - but - after the wonderful 3d carve - I decided that I will tidy the wiring going from the controller unit to the mahine - I got that plastic spiral - took all the wires in my hand and wound the spiral around the wires.

I has not put on the machine since then -

and today - when I had a part to cut a 20x20 area clearance - it screwed up pretty royally

and then i thought it was due to the high IPM (200) set on the machine - so reduced that to just 50 - and even then the same thing - the y car motor seemed to slip a heart beat.

this made me think of the changes I had done since carving that 3d and it was what I did with the wiring.

ok tomorrow is testing day -

anyways I had to deliver a custom audio amp facia and finished it on my smaller machine and was able to deliver.

will keep ya all posted - if it is a motor that is slipping or it was the wiring :)

RGDS
IRfan

Irfan
It really sounds like electrical noise and interference.
- did you use shielded/screened cables?
- if you did, are the screens attached to anything.
- do you have more than 1 ground point for the screens.
- etc. etc. etc.

Sean -

I have a little change from the normal

on the controller I have all the grounds converging to a common point - (mains earth)

since I could not connect all screens of the stepper power wires I have ground them individually to mains ground on the machine.

I have the shield wire on the Spindle power cable ground near the VFD earth - which is then connected to the controller ground common.

yes I know this is electrical and I have similar problem with my other machine

Being a Mechanical guy is so tough electrically :D

Irfan,
I would think you would want the screens tied to a common point in your electronics cabinet only. The other end should be floating. The machine should be grounded for safety but this should not be used for signal grounding. Try and keep all signal based gounds tied together in your control box only. :)

Hi All - there are no jerks on the cut - but the circle is no more a circle - its a oval by at least 3 to 4 mm

also look at the pocketing the entry and exit points have the tool going way off position

look at the circle - here also the entry and exit positon of the tool has it moving away from the regular.

now look a the star - over all looks good - but observe carefully and you can see it loosing positon while changing directions.

kindly help - I am lost

RGDS
IRfan

I would start by trying a couple of things. 1) slow the feed rate down and see if it has any effect and 2) slow the acceleration rates down in your Mach3 configuration.

I'm betting that you are losing steps in your X axis.

Doug - I tried everything - slowing down - both speeds and acceleration - even then we have the same issue

I will try re-routing the wire properly

Ok folks - tried the following things

1.Bought new ferrite cylinders and mounted them on the step dir lines for gecko - power lines for thesteppers - one near the gecko and one near the motor, then one at the start of the power line to the spindle near the VFD.

- after all this still no improvement on the auto estop happenning - only that it moved from the 6000th line to the 10000 series :)

I also changed all the connectors and wire lugs near all geckos and on wires near the motors. - now I am more confident.

OK to move on - the problems of bad cut and e-stop happenning on their own accord continued.

then I connected the )V of the 24V DC to the ground - some how I felt the machine smoothening a bit - but soon realised it was just my imagination.:D

OK

I felt it was not the spindle so then I notices a 220V connection to the spindle control board - overlapping the e-stop wire near the BoB

ah - there it is I felt - I changed the orientation of the board and voila there were no auto e stops :D HURRRAH! :cool:

OK the cut is still bad and now I seriously suspect the motor pulleys haveing 4mm grubs - I will retap them to M6 tomorrow and get some new grubs to solve teh problem permanently!

:)

having fun to do and I have a entire week off - withour pay off course :(

so lots of more work coming in :)

RGDS
IRfan

Set screws or what you call grub screws were the problems I was having also.

I hope that once you change them, you will see a cutting improvement.

Good luck.

Thank you Niils - yes i am going to try that out today.

RGDS
IRfan

well - posting a SOS
 

I am not able to figure out what is the problem!

I looked and cleared out all grounding and noise issues, put new grubs on the motor pulleys - had earlier taken care of all the other gearbox grubs - flats - indents on the shafts - interchanged gecko's - interchanged motors

hmm now I think I will recheck all the bolts of the machine

if any of u have any ideas kindly let me know!

RGDS
IRfan

more on this here -http://www.mechmate.com/forums/showthread.php?p=26010&postcount=200- thought there would be more visibility there.

Have you checked the hold down spring and bearing?
It sure looks like Mechanical slop or the tool bit is lifting off the material.

It is a pure mechanical problem. (not electrical, not software, not programming)

Something is loose, or flexing.

Induced by high load.

You can simulate high load without turning the router/spindle on. Hold collet, push, pull.

Otherwise, is the job held firmly to the table?

yes Sean - removed the gear box twice and remounted them - there is no slop on them - but I think what I will do is replace the shafts of the bigger pulley and have a keyway on them so that there is some positive traction - may be this is where it is slipping - but i have 2 M6 grubs holding em - and I doubt the shaft slipping too.

- tool bit lifting off the material how can that be?

RGDS
Irfan

Yes G' the job is firmly held down - I will try the push pull method tomorrow -

and also try cutting the same on a 1 inch thk mdf which does not even budge.

RGDS
IRfan

Irfan,

You ought to make a mark across the end of the motor and pully shafts using a magic marker or some paint and see if the marks are still aligned after cutting something. That might help you narrow things down.

An example of what could be causing that: A thin, long, blunt cutter, being pushed too fast, will experience high load and will flex to the side according to the cut direction. When the end of the cut meets the start of the cut, the sideways deflection is suddenly removed.

Dough, I did what you have suggested to the motors already - i will chk that for the pulleys today to find the exact reason

G' thats done with a brand new tool and the result is same at different speeds - I tried this at 5000mm/min @ 2000 Accln and also at 2000mm/min@600 Accln.

RGDS
Irfan

Can you cut two circles for comparison, clockwise and anti-clockwise?

ok - will do that today - I am going to the shop now will not return till late after noon - will try to figure out whats keeping me outta business for so long!

RGDS
IRfan

Irfan,

Are all of your wheels seated completely and firmly on the rails for the entire length of their travel on both the X and Y axes?

Ah G' you were right - I always tried to shake the spindle in the direction of the larger axis and there seemed to be no shake and now I tried the same in the direction of the gantry ans woooah - there was a definite shake

it turns out that one of the eccentrics was out - and the Z plate was free to move the distance which was showing up on the cuts - I did a few cuts now and no problems what so ever!

I can't imagine the things I have done to solve this -

but it was a good learning for me!

RGDS
Irfan