Ball Screws for Laser Y axis

Bearings/Motors/Belts/Gears/Etc.

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Mon May 14, 2012 7:54 pm

Hi, Im microsteppering.

Would this cause vectors that look like their effected by backlash?
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Re: Ball Screws for Laser Y axis

Postby canadianavenger » Mon May 14, 2012 7:59 pm

is it possible to re-configure your set-up for full-stepping for testing. You will, of course, lose resolution but at allows you to work forward from a more reliable base. Micro-stepping does not come without cost, and one of those is a loss of torque at the intermediate points.
canadianavenger
 
Posts: 153
Joined: Wed Nov 30, 2011 3:24 am

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Mon May 14, 2012 8:07 pm

Yeah, I don't see why not I think my drives have that option. I will give it a try and report back.
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Mon May 14, 2012 9:03 pm

fsdfsd.png
Square?
fsdfsd.png (1.25 KiB) Viewed 20874 times
Unfortunetly with the LightObject DSP the lowest I am able to go is 16 times micro stepping. The motors just make a high pitched whine and don't move when I set it less the 16. At 8 time micro stepping they move a bit.

If my missed steps was down to carriage momentum. Why are my missed steps always in the same direction? The image above is what i get when i engrave a square with y axis doing the rastering
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Re: Ball Screws for Laser Y axis

Postby macona » Tue May 15, 2012 5:08 am

gavztheouch wrote:
Another options is to use a higher lead screw. Something like 1/4" per turn or more. On the laser cutter I have not been building it uses a 1/2" per turn lead screw with a rotating nut.


Yes I have been looking at screw with a large amount of travel per rotation, my only concern was backlash distance might be increased? Not sure about that..

My leadscrew for the Y would be 1M is that long enough to cause whipping issues?

Here is a picture of my machine before I uprated the y axis shafts to 10mm stainless steel.

I think I am getting between 0.1 and 0.2mm backlash on the y axis, looking at my machine do you think it is possible to reduce this backlash.

Many thanks

Gavin


It all depends on the diameter of the screw. A small screw, like 1/4" diameter will whip. It all has to do with the flexibility of the screw. I have had a 1" feed shaft on a metal lathe with a 12' bed start whipping. Kind of scary.

You really should not have any backlash in a belt setup like that. You need to find where it is coming from.
macona
 
Posts: 363
Joined: Tue Aug 17, 2010 10:30 pm

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Tue May 15, 2012 10:47 am

pulleycarraige.png


I thought of a possibly explanation as to why I was seeing missed steps in one direction.

1.It presumes missed steps are down to carriage momentum.
2.The motor shaft is connected to pulley marked pulley in the picture.

If carriage is pulled in the +y direction and then stops, for the momentum to effect the carriage the force need to work its way round the opposite pulley and back again. However in the -y direction a sudden stop or change of direction will directly pull on the pulley connected to the motor?
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Re: Ball Screws for Laser Y axis

Postby bdring » Tue May 15, 2012 12:42 pm

The missed steps look the the same problems many people have had. My LightObject controller outputs a negative pulse. If your driver expects positive pulses it will still work, but a step is lost at each direction change.

What stepper driver are you using?
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Tue May 15, 2012 5:08 pm

Hi Bart,

These are the spec sheets for my drivers http://www.cnc4you.co.uk/resources/CW5045.pdf

From the spec sheets it does say it is looking for the positive edge of the pulse.

My missed steps are a lot more than one step off, I would say more like 25 steps out of whack (0.5mm in distance). Also I would expect the steps to be lost in both directions I am seeing steps lost only in one direction or it a least appears that way.
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Re: Ball Screws for Laser Y axis

Postby bdring » Tue May 15, 2012 5:54 pm

Those drivers can be wired for positive or negative pulses. Try attaching +5V to the PUL+ and your pulse line to PUL-.
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: Ball Screws for Laser Y axis

Postby gavztheouch » Tue May 15, 2012 6:04 pm

There is an option within the DSP software to change pulse direction to rising or falling edge?
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

PreviousNext

Return to Mechatronics

Who is online

Users browsing this forum: No registered users and 12 guests

cron