[Over Engineered]

Not with a screw drive. Some use planetary gearboxes with rack and pinion drive, but good, low backlash planetary gearboxes cost $500-$1000 each.

Belts are far easier to use, and shouldn't have any of the issues you're worried about.

Hmmm yeah that's about 300-800 reasons per ballscrew why to use belts instead! I'll be triple checking everything before each use anyway so it shouldn't be too bad. I should have the gantry design/whole design finished tonight minus ballscrews so I can start figuring out all the math and what it needs to run as well as possible.

How many hours are people roughly getting out of belts? Also, is it best to run an idler/tension bearing with them rather than moving the motor?

Cheers for the info!

[bhurts]

Belts should last year's not hours. Most people just move the motor.

Ben

[ger21]

I'd expect at least 10 years of belt life, provided there are no alignment issues that cause premature wear. No idler, just move the motor to adjust tension.

There are belts on our $150K router at work, and I think we're at 7-8 years of 30-40 hours per week with no issues. This is with big servos, moving 1000lbs at 1500ipm.

[Over Engineered]

Makes sense! I used hours as most machine service go by hours. If they last that long well they are perfect for the job!

Well I have all the steel for the stand etc ready to tack up and weld tomorrow morning...

Couldn't find any suitable castors locally so have to order some online instead... Can anyone recommend some good ones to get? Preferably from Australia if possible.

I still haven't finished the design yet but I'll post up what I have as I have a few questions regarding incorporating the ballscrews and servos into it. It would be better to get it sorted before going any further with the Z axis if I need to change anything that won't work or needs to be done different.

It's 2 linear rails for each axis bar the 4th with 12 trucks total, 2 ballscrews for the X axis, 1 for the Y and 1 for the Z.

Main questions are what would be the best ballscrews I should use for the Y and Z as that will determine placement and if I'll need to reconfigure the gantry to make it work. I would like the largest possible to ensure rigidty throughout. I also need to know if my placement for the X axis linear rails would be the best for rigidty as well or if I should change and move them to be on top of the sides the. Run the ballscrews where the rails are now.

You'll see what I mean when I post the drawings. I think it should work as is but there may be a better option out there. I'm going for the most rigid aluminium design possible rather than the cheapest but as long as it works.

Cheers for all the help and info!

Steve

[Over Engineered]

This is where I'm up to...





I'm thinking of putting the X axis ballscrews on top of the 80x40 T-slot with the 16mm plate on top of the T-slot frames on the inside of the gantry. I'm not sure on the angled brace sections at the ends of each x axis, I'm going to house the motors there somehow so that will probably change... Thinking about it, it might be better to move the x axis rails down to the bottom of the sides but leaving 10mm for clearance, then have the ballscrews just above so they are out of the way of swarf whilst keeping rigidity. Or is there a better way? The HRW35CAM bearings leave 35mm gap from the gantry risers to the sides of the frames. I'm not sure if I will have enough room for ballscrews in between? It would depend on the type but they will be 1868mm long for the x axis.

I'm thinking of running the ballscrew for the Y axis on top of the gantry where the plate for the z axis extends up past 80mm and mount the Y axis stepper on top 1 side of the gantry's risers? The bearings I have draw for there are HRW27CAMs (the HRW CA's have the best side load capabilities so in this case for vertical load from what I have read.) which only leave 27mm in between the gantry and the 25mm plate for the Z axis so there isn't much room to run a ballscrew in behind it. I could also mount the ballscrew for the Y axis on the back of the gantry as it is. Or should I move the 3 x 80x40 stacked T-slot that's housed in 16mm aluminium back and use bigger linear bearings for the Y so I can run the ballscrew in between that and the Z axis plate?

The Z axis will be 2 rails that I'm not sure of yet but I want the strongest for that section as it will be 210mm of travel and want to run the ballscrew in the middle of them with the stepper on top.

Just in posting this, I realise a lot needs to change but it's a start of what it may look like and a rough idea of what I'm thinking for the design. The end plates will change to suit the motors, there just there for reference, pretty much like the rest of the design ha ha ha!

Please help with what will and won't work. The HRW CAMs can be larger but anything over 35mm and they're not stainless though. Once I've sorted it all out I'll break up the parts and add screw/bolt hole layouts so they can be cut out on another CNC for accuracy. It's just a sketch at the moment.

Cheers for the help!

Steve

[Over Engineered]

Is there going to be any problem with running the CO ball screws onto of the X axis 80x40 + 16mm frames? Also any problem with running the Y axis ballscrews on the back of the gantry?

Cheers for the help!

[Over Engineered]

Most of the stand is welded up, just need to do the draws and feet. It's on castors and not a single rock in the frame, nice, square and flat.

What are people's thoughts on using FC floor sheeting as a top for the table/stand, seal it then self level epoxy on top? Shouldn't have any movement or is kitchen bench tops the best?

[Over Engineered]

Bump... Anyone??? Is FC flooring stable enough?

[lucky phil]

Hi Steve, it's been a while since your last post have you finished your build? Have you got any pictures of your machine, it sounds about the same size as I am building. which way did you end up going with drive motors.
Philip