Giant 20' x 3' x 2' router build

**charlieuk** · 27-04-2014

Call me sad but really getting excited now! Just mocked the z axis up with some wood plates to try and figure a few things out and all looks like it should be relatively simple.

I have decided to go with all your suggestions and do the double ball screw and all so add the 3rd vertical rail to the Z axis. Its going to cost a lot more but it will actually probably be more simple and figured probably give me less headaches in the long run and wont kick myself wishing i had done it that way.

The X axis will have to stay rack and pinion as i cant see any other real way to do it other than belt which people have said is not such a good idea on that length.

I will order parts tomorrow then will need to get a few more plates made up to bolt it all up.

still no real idea on what motors im going to use but hopefully some one will be able to help me with that.

**charlieuk** · 05-05-2014

Got the two 1100mm y axis ball screws through in the post and mocked up some plates that i will need to get made, now need to add the 3rd z axis rail and figer how to fit it all in together so it nice and clean.

**JAZZCNC** · 05-05-2014

Sorry I some how missed the post from a week ago.!! . . . . I would definately join the screws together with a single motor and belts. Far more accurate and less hassle.

You really won't regret those 2 screws and extra rail on Z axis.

Looking good and keep it going, shame your so far away I'd gladly help.

**charlieuk** · 27-04-2014

could any one tell me if i was to run two ball screws for the y axis what is the best or most practised way of running them as a pair? im my mind i am thinking there are a few options, i have had a search but not found to much as im not to sure on the terms used for this. Is it better to run two motors one on each or put a motor on one and have a belt going across to the other or have a centrally mounted motor with a belt going to each?

Also After a few people have mentioned it i am wondering if i would be better go for a hybrid closed loop stepper system due to the length of the x? servos are defiantly way out of my budget but is closed loop worth considering? can you run it on just one out of the 3 axis then upgrade the rest later?

cheers charlie

**charlieuk** · 05-05-2014

cheers no worries i have been advised that its been better to drive the ball screws with separate motors but then wired together so id there is any interference on start up the same goes to booth so not to sure now. I liked the idea of just bolting the motors straight up to the ball screws without having all sorts of belts and pulleys but having just the one motor would make some things easier. Another job this week is figuring out the x axis drive and what ratio i need to gear the stepper to.

**JAZZCNC** · 05-05-2014

Well who ever told you that is wrong.!! Problem comes from Mid band resonance and how the drive works out compensation and correction. When you have 2 motors connected to one drive it doesn't know which motor to apply the compensation correction to so it can throw the other motor into resonance.

I can tell you from experience that screws connected with belts are by far the best option and most accurate with least hassle other than attaching pulleys.

**charlieuk** · 05-05-2014

ok cool i will try work that into the design. is there a standard method for doing the belts i couldn't find much when looking last week?

**JAZZCNC** · 05-05-2014

Originally Posted by charlieuk

ok cool i will try work that into the design. is there a standard method for doing the belts i couldn't find much when looking last week?

No real standard way regards laying out as it's often machine dependant but regards sizes etc then there is kind of standard in that most use in HTD 5mm pitch belts and either 15 or 25mm wide. Pulley sizes will depend on if your having a ratio but from experience between 18-20T for 1:1 ratio is best. If you go too small you risk excessive wear and jumping teeth due to fewer teeth being engaged. Equally don't go too large on pulley size as the extra inertia will have a negative affect.

Really this is something you should have worked out before ordering the ballscrews as you could have had the screws machined in such away that they suited pulleys and made life easier.

**charlieuk** · 06-05-2014

ok many thanks for that. is it best to drive one screw direct with the motor and then take a belt of that to the other side or have the motor central and run two belts to ether side or is there another way? i could do with keeping all the motors and belts down to the one end if posable.