Mega Bot Underway

[dirk]

Hey guys
I've been welding up the new bot this week. It has a cutting area of 8' x 24'. Have a look, I've posted pics to my blog.
http://cncshare.blogspot.com/
Dirk

[Brady Watson]

Holy Stromboli!
Dude that thing is a monster!!! Thanks for sharing the pics. Let us know when it is running!

-B

[gerald_d]

Jee, I wish that was in my shop! Are my eyes deceiving me, or is your stock of alu up on the wall getting less?

[pfulghum@qwest.net]

holy cow batman

By the way the blog shots are great...
How can I start my blog?

-- pat

[mikejohn]

Gentlemen,
I found this (http://news.bbc.co.uk/2/hi/europe/3514061.stm) on the BBC web site.
Suspicious or what?
............Mike

[bill.young]

Hey Pat,

This thread (http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=6720&post=21582#POST21582) has some info on starting a blog. There are lots of other options as well but Blogger is free and makes the process pretty simple.

Bill

[dirk]

Gerald
I haven't made the first cut in the aluminum. There were a couple of 20' ladders stored on top so it looks like less. I'll be using a few pieces of the T-slot on the new machine to mount linear rails and for hold-downs. I may make a small section of the table solid T-slot for clamping. I still haven't decided on the gantry. The lightest steel tube I can find over 4" is 3/16 thick. I'm afraid I'll have a weight problem using a 4x8x3/16. I’m leaning towards welding two 11 gauge. 4” square tubes together. The only other option I've come up with is an 8x8x3/16 aluminum Tube, weight and strength look good on the deflection calculators but it's aluminum and expensive ($500 for 12'). Any suggestions?

Dirk

[gerald_d]

I'd also weld the 2 steel tubes together, with 1" long welds no less than a foot apart.

[johnm]

Dirk -

Boy, talk about the Mother of All ShopBots! I've gotta ask - an 8x24 table would hold 6 standard sheets of panel goods - what the heck are you building that you need that kind of capacity? Heck, I've worked in shops that were smaller than that... Are you boat-building?

Nice work and nice shop - we built an addition last year, but are already (gulp) running tight on space.

John Moorhead

[dirk]

John,

I’m a bit like Tim Allen (Home Improvement TV show) when it comes to machines, but I think there are some real advantages to building a large machine. My original thoughts in designing this machine where to eliminate tool changes. If I rout a house of cabinet doors, it usually takes about 5 sheets for 50 doors. On my current bot, that would be 5 tool changes per sheet times 5 sheets, which equals 25 tool changes. With the new bot I can hold 5 sheets and only have 5 total tool changes. This should eliminate a lot of watching and waiting.
I envision the large router to help expand my business and cut labor cost. I think it opens the door to a multitude of other options and high production such as:
Set up specialized work zones for vacuum holding and clamping
Reload parts in one area while the bots cutting in another.

[gerald_d]

Dirk, how are you going to manage your looonnnggg cables? Do you think that any current will reach the other end?
...and that those long antennae won't pick up interference?

[dirk]

Good question
Dust collection will be overhead. Any cables will be on trolley underneath the 4" square tube overhang on table. I'm planning on having electronics on board gantry. So the only lines will be power and a serial/parallel or usb cable depending on system used. I may even try to mount a laptop directly to gantry.

[bruce_clark]

How are you going to keep your 8 foot+ gantry from sagging?

Bruce

[dirk]

Hey Bruce
The short answer is I'll be using a rectangular tube with 8" vertical sides. There should be much less deflection on this than current production SBs. If you’re interested, this long thread
http://www.talkshopbot.com/forum/messages/28/9164.html
shows discussions and a learning experience on my part as to sizing and stiffening the gantry.
The long part of the answer is I am going to have a challenge keeping the weight down. I will have to cross that bridge when I get to it. I expect that a combination of larger motors and gearing will overcome any of the problems in weight.

[gerald_d]

Dirk, if your heavier gantry has the same friction as a shorter one then the motors should be able to cope provided that you lengthen the ramp times to accel/decel the extra mass. What bearings/rollers are you planning to use?

[dirk]

As far as the rails go I've posted some drawings on the blog.
http://cncshare.blogspot.com/
I'm tempted to go the welded option. I've already picked up the W4 wheels off of CNC Zone.
If that dosen't work I'll have to do some grinding. I may be better off with the cold rolled bar idea. Either way I can spend the bucks and revert to Hiwin rails
Dirk

[gerald_d]

Dirk, if you are happy to let the wheels work their own grooves into a rail, have you considered cold-rolled hexagon bar? The alu backing channel behind the square bar looks like it will work loose unless the you can pull the bolts up tight.

Can you mail me a dxf of your square bar idea - I may have another suggestion for you.

(I have made my own v-wheels - basically a tyre that has 2 ball bearings pressed in with Loctite. The tyre is vacuum hardened to retain its finish. You could make tyres for hex bar...)