A slight stuttering problem

[sebtiger]

Hi all

Im kind of new on here and could really do with a little help even though I have been a bit slow in asking for it.

I have just finished my rebuild of my original cnc machine that was posted on here, quite a while back.

This is what roughly what it looks like at the moment.



If you look carefully you can see a small hole to the left of the gantry (i think that is the term for the top movey bit). The hole currently has another ballscrew and anti backlash nut in it along with its corresponding motor mounted at the very rear of the machine.

Looking at my machine so far you can probably tell it is pretty heavy, thats a result of my impatience in coming up with a good plan.

So as you might have already gathered it might have some movement issues.

Well it does and doesn't.

It doesn't in that the x and z axis are fine. They move like silk.

BUT

When it comes to moving the gantry backwards and forward (y I think) you can imagine that is quite a bit of weight to move. Especially from only one side of the gantry. When I move it backwards or forwards the other side lags behind or wobbles quite a bit. Making cutting cutting anything other then some horizontal lines next to impossible.

This is where I am really in need of your expertise.

I am guessing I really need a second screw set on the otherside to apply and equal force. For me though it only introduces more problems.

I guess to get the otherside powered I need either a pulley system of some sort or a second motor.

I am not sure how to go about getting the right pulley system or where to even start with that.

As for another motor, the board I have only outputs for 3 motors. So I wouldn't think that was possible without a big change.

Thanks for reading this far, and sorry for being such a newbie.

I hope you can help me out.

Thanks

Seb

[ger21]

Adding a second motor is the most common method used by most members here. If you use MAch3, it's very simple to slave the two in software.

As far as the 3 axis drive, you an always sell it on Ebay and buy a 4 axis.

[sebtiger]

Thank you for the quick reply,

So you reckon that the most viable option is just to upgrade the board from a 3 motor to 4 motor one.

I have looked them up the upgrade wouldnt be to expensive especially if I sold my other one on.

Still I guess its cost sort of pales into insignifcance when I am having to get a new ballscrew.

Thanks anyway for the reply.

[lumberjack_jeff]

there's also the option of rigging a set of cables under the machine to keep the gantry square.

If you search the forum for "cable pulley gantry alignment" you should find it.

if the design can accommodate it, it might be worth a try.

[packrat]

If this is the complete machine, what is tyeing the two gantry rails together? Just bolting them to the plywood won't do it, especially when the plywood is in two pieces.

What I'm saying I guess is, what is keeping the rails from racking? Unless there is more of a frame under neath the plywood, when the gantry tries to move the rails will also move causing binding.

cary

[sebtiger]

If this is the complete machine, what is tyeing the two gantry rails together? Just bolting them to the plywood won't do it, especially when the plywood is in two pieces.

What I'm saying I guess is, what is keeping the rails from racking? Unless there is more of a frame under neath the plywood, when the gantry tries to move the rails will also move causing binding.

cary

Hey,

Just want to say thanks to all of you, its been alot of help.

I am thinking I might try the pulley system first as it is a cheaper alternative to adding the extra motor system.

Also yep, joining the bottom rails together has been done, sorry the picture is a little old. I have managed to loose the SD card for my camera.

Are there any other cheap fixes to try?

Thanks again

Seb

[mlabruyere]

Just saw this post....I was going to recommend bracing between those rails as well. Glad to hear that Packrat's recommendation worked.

Most of us use this Cartesian coordinate designation: