[ewest]

You may remember from a few months ago, I was planning on building a big router. Well, time to ice down the ol' credit cards, parts are coming in next week!

Details are this:

2 x 3 x 1 meter work envelope

THK 30mm SHS rails all around
THK 50mm Diameter ball screws on all three axes, all with rotating ball nuts.
2 sealed, caged ball bearing blocks on each rail

Steel frame, bolted, not welded

4x6" rectangle tube, quarter inch wall
3x4" rectangle wall, 5/16 inch wall

Total mass looks to be in the 3000 lb range, minus servos and table top. Thanks to the people who gave me the advice of "Figure out the weight before you size your servos! They're heavier than you think!" I'm always building stuff, but this one really shocked me - almost 500 lbs for the gantry!

Here's MY big piece of advice to all of you who have a big, expensive project in mind..

CHECK DIFFERENT DISTRIBUTORS FOR YOUR LINEAR COMPONENTS!!!
Even if they all come from the same manufacturer, the cost differences can be HUGE!

Example, one place quoted me $1920 for a SINGLE 3 meter long, 30mm rail with one block, with 10 weeks shipped from Japan.

The next place quoted me $570 for the exact same rail, and $240 for TWO blocks.... ships from Ohio, IN A WEEK.

All told, going to a different distributor saved me over $4000 and NINE WEEKS. Thank you Kaman! (serving New York City)

Also, for anybody wanting to build a good, small machine, the http://www.tos-world.com/ website is pretty good, plus it illustrates a pretty good point... which surprised the hell out of me...Using a rotating ball nut is CHEAPER than using a fixed nut and rotating screw when you factor in the expense of using two proper bearing blocks at each end of the rotating screw PLUS your regular ball nut.

[Zumba]

Good work on the pricing. Good choice of components as well. What'd you pay for the ballscrews and nuts?

[NC_jimbo]

Would love to see the details of your design.

Such as dual drive or single on lthe 2m/3m axis's?
I assume servos instead of steppers?
Ballscrew/nuts P/Ns?
How do you handle thermal expansion on screws at their ends?
Drawings?

[ewest]

Prices of the parts are as follows:

50mm rotating ball nut - $682 Each
3 meter rolled ball screw - $1415 each (I bought two)
( I think a 4 meter screw was only about $1700 and change)
SHS30 - 30 mm rail prices as follows
1 Meter - Each $195
2 Meter - Each $390
3 Meter, - Each $575

Pre-loaded block, sealed, standard length caged ball for 30 mm rail, each $110
Pre-loaded block, sealed, long length caged ball for 30 mm rail, each $120

I'm using the long blocks on the X and Y, and the standard for the Z. Each rail has two blocks on it.

Andy

[NC_jimbo]

Man I sure hope you do a build log.

Are you paying someone to build it or doing it yourself?

[ewest]

I do plan on doing a build log, but right now, I'm just concerned with finalizing the cut list so I can get the 3000 lbs and 40' long sections of steel out of the courtyard at the shop.... and between working, life, and debugging the nixie clock my girlfriend is building... well time is just at a premium.

And for the second question, YES I AM building it myself. My good friend has a metal shop in the same building, so I'll be using him and his tools to do the steel fabrication, plus he's got the mill and the lathe and CNC plasma, and anything I need to have CNC milled I can get done as a favor at another place too. I have a background in industrial automation, so while this is a big daunting project, I do know that I can see it through.

I'll throw up a link as soon as I have something.

Andy

[epineh]

We will need pics of that beast

Did I read correctly that you want 1 metre of Z travel ?

Russell

[ewest]

You're correct, I do WANT 1 meter of Z, but I can't have it :-) My components are only that long! Ideally, I would have more ceiling space too. I'll tell you though, with a bolted setup, I can always drop another few thousand and hook up taller gantry sections and a longer Z. In an ideal world, I'd have enough Z to throw an entire block of GeoFoam on the machine. Right now, I think I'd have trouble even getting a block of it in my shop!

Andy

[walter]

Great thread!

[mugabe]

...Using a rotating ball nut is CHEAPER than using a fixed nut and rotating screw when you factor in the expense of using two proper bearing blocks at each end of the rotating screw PLUS your regular ball nut.

imho, very good point. It is especially important for long axis where screw is vibrating due to its weight and length.
And less inertia for the motor to handle .

Thanks.

[ewest]

Good news - an 18-wheeler just pulled up to my shop, and unloaded two long, skinny crates...FULL OF BALL SCREWS AND LINEAR RAILS!! WHOOO!!

Will send pictures! I'm also working on the build-log web site.

Will post a link soon as well.

Andy

[harryn]

I may need to re-think part of my project. Those rail / carrige prices are substantially cheaper than the probably lesser components I was planning to use.

[NC_jimbo]

Still wondering what method you emply to accomodate temp change length of screws.

Maybe one end fixed and the other that can expand/shrink axially into a keyed/spline?