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Author Topic: 2nd Build - Steel Tube, Gantry Style, Mill / Router  (Read 21838 times)

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2nd Build - Steel Tube, Gantry Style, Mill / Router
« on: April 20, 2010, 10:58:50 PM »
Several years ago I built my first cnc router. It started as a plasma machine and evolved into a plasma/router/light duty mill. It never really was built to mill metals.

So, I decided it was time to build a new machine. This one will be much heavier then the first one. Hopefully it will mill aluminium and steel without too many problems.

The drive system will be AC servos run through a 1856 Galil card and Mach3. As far as speed goes, the goal is 600+ IPM on rapids.

Pictured is the gantry. 6x8" steel tubing, 1/2" thick wall, 70" long. Weighs about 300# with the flat bars welded on. Add the z axis and a spindle and the "mass in motion" will be over 500#!!

more to come...
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #1 on: April 20, 2010, 11:37:24 PM »
Very interesting project.

I think the most challenging part will be choosing the right guides and transmission.
I have a router with casting aluminum gantry I reinforced both gantry sides by making them 1" thick and added two UPN profiles to each.
Still the problem is at the linear guides.
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #2 on: April 21, 2010, 04:49:22 PM »
elpablito, please elaborate.

I have Rexroth Star linear guides for this project. 25's for the y axis and 20's for the x axis. They should be large enough. The one thing I did not do that I will be doing with this build is having a machine shop surface all the areas the guides will be mounted to. One of the problems I have with my first build is the gantry binds because the linear rails are not perfectly aligned.



Some more specs:
travels: x 59", y 33", z about 15"
3/4" precision acme screw 2 turns per inch direct driven 1:1 by 1100w ac servos
Full flood coolant system
BT30 spindle rated 15000rpm (I know it will be grossly underpowered, but I want to try driving the spindle with a 1kw Automation direct servo through Machs spindle control)
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #3 on: April 21, 2010, 08:38:59 PM »
Some pics of the first router I built several years ago.

Gantry style with about 38" x 38" travels and 12" z travel. I should have made the x axis 48"+ so a sheet of material would fit into it. I used THK RSR 15 W rails brand new off ebay. They work very well. However, one problem with the rails on this machine is the y rails are too low and are always covered in swarf. it would have been better to raise them up to the level of the gantry. The other shortcovering of this machine is the spindle. I never had a proper spindle on the machine for metal work. These issues are addressed in the design of the new machine. After I get the new machine up and running I plan to use the rails, motors, leadscrews etc. from the old machine and make a cnc lathe :)
 
Rob
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #4 on: April 21, 2010, 08:54:06 PM »
My router has a gantry made from cast aluminum. On each side of the gantry, there are 20mm amt linear guides, with two blocks each, 300mm from block to block.
Check at the figure (by the way I took it from http://www.superiorbearing.com/images/amtbrochure.pdf, very useful doccument)



For what I know, the bigger the guides, the bigger the force they can sustain.
But also by sepparating the blocks along Y you reduce the gantry twist in the MY and MP direction but loose some Y travel.

If I had to mill steel I would think of making the gantry sides as rigid as possible and putting two guides on each side at different heights to reduce twist in the MR direction. And maybe the screw or rack between both guides
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #5 on: May 03, 2010, 09:37:57 PM »
Picture of the gantry sitting on top of the base. So far the machine weights about 1200lbs. Gantry is 8"x6"x1/2" thick wall steel with 1" x 3" flats welded to the face. Base is made of 3/8" plate and 1"x2.5" flat bar.
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #6 on: May 09, 2010, 07:16:06 PM »
Here's a pic of the drives and some other items i'll have in the enclosure.

Anyone have any pointers on laying out the electronics in a enclosure to keep it neat and help prevent emf noise?

Looks so neat without the wiring :)
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #7 on: May 09, 2010, 07:39:18 PM »
Danaher servo motors i'll be using. On the left is the nema 34, 990 watt for the z axis. On the right is the larger 1100 watt motor I'll use on the x and y axis. Should have enough torque to move that heavy gantry. Planning on running them direct drive hooked to 2 turn per inch acme screws. I'll drive the gantry (y axis) with a similar belt setup as the old router with dual screws. This time I'll use GT2 timing belts because the htd belts I have on the old machine introduce a small amount of backlash. The GT2 belts seem to lock into the pulley better and eliminate the backlash - and they are quieter.

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Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #8 on: May 09, 2010, 09:41:47 PM »
Quote
Anyone have any pointers on laying out the electronics in a enclosure to keep it neat and help prevent emf noise?
I've done a bit of wiring in my time, but haven't really had to be concerned with EMF. The box itself should do the trick, I would think, as long as it's grounded. Generally, when I wired up enclosures, we tried to maintain 20% free space for upgrades/additional components. Personally, If I were to do one for myself, I would leave even more than that.There's always something you will find a need for. Relays, PLC, more inputs, more outputs, switches, indicators.... the list goes on. Space becomes a premium real quick. It looks a bit cramped already, so you may find yourself with an additional box in the future, or rewiring the whole thing in a bigger box if you do many additions. Small zip ties can help keep bundles of wire tight and neat. It looks like your moving right along though. Keep posting pics as you go, and thanks for sharing.

Here's a pic of the last enclosure I done. With the type of terminal blocks we used, we were far from 20% free. As the project progressed, I had to cram in a Danfoss VFD, an electrical outlet, more relays, and TONS more wire that came in and went out to all the components. The box is about 5 feet tall. As you stated....
Quote
Looks so neat without the wiring.
How true indeed!!
 Remember, too much space is always better than to little.
« Last Edit: May 09, 2010, 09:47:46 PM by Sam »
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: 2nd Build - Steel Tube, Gantry Style, Mill / Router
« Reply #9 on: May 10, 2010, 11:42:32 AM »
Sam, do I spot a PLC there with 12 IO moules? What brand is it?