Table questions.

[dragginbutt]

With all the threads here regarding table warping etc. The question I have is if you had to do it all over again, would the Buddy still be your first choice versus a full sized shop bot with larger table. I have not used either, but I can't afford to choose the wrong machine either. THe buddy has many attributes I am looking for, BUT, consistancy in cut is very important to me. If a base is warping, this will affect cut, especially in 3D carving.
I do mainly 3D for mantles, and some 3D Corbels etc. So accuracy under these conditions is important to me. Which is a better choice as I only want to make it once.
Size is important too, but with an 8' stick, I am not gaining any work space. Just storage, and with a busy shop, I doubt that it will be put away.
Can this setup be stablized enough to perform as listed?

[cowboy1296]

my table has warped a little also. during maintenance a few months back i took the table off and ripped it and took about an inch off of each side. this did seem to help, maybe a temp help but it helped.

although i have never cut a mantel i keep telling people i can. obviously your z does not go up to 8-10 inches so how do you do it. by all mean post a picture.

[steve_g]

Gary

My response doesn't address your table question directly, but is my general thought on machine size...

No matter what size unit you buy, it will be too small... eventually. I bought a 48X48 PRT Alpha, Waaaay bigger than I needed for the project that prompted the purchase! Life changes... Now days most of my projects are done with Baltic Birch plywood which comes in 5' X 5' sheets. Buy the machine that gives you the most flexibility for your situation. A buddy using an 8' power stick requires more floor space while operating than a 48 X 96 machine does. I see they offer a buddy with a 12" Z, indispensable for projects like mantels...

SG

[Ajcoholic]

I have had my table with the down-pressure rollers now since early March. My table is DEAD FLAT. I mean, it is superb. It probably curls up slightly when the table extends off the rollers front or back, but when it is under the gantry (what really matters, as thats when the cutting takes place) it is dead flat. I have checked it a lot.

When I cut a half sheet of ply, I usually cut on top of a sheet of 1/4" MDF to avoid cutting into my table, and generally go 1mm past the thickness. The cuts are always uniform depth.

Go back to see how I did it in my thread (basically bought a sheet of 5' by 10' 3/4 MDF and cut it into 2, glued it together).

The down pressure rollers are awesome. Easy to do, also.

AJC

PS I have no regrets buying my Buddy (48" Alpha). I really couldnt justify a 4x8 machine, in terms of space or the extra cost. The main thing for me was a 4hp spindle and minimum 48 by 48" work surface. It has proven itself very good for my business and use. That being said, in the future if I really get more involved with the CNC stuff I can see a 5' by 8' machine with ATC.. :) But not anytime soon! All kidding aside, the Buddy really was an excellent choice. I dont think I will ever invest in the 8' stick. 4 by 4 seems to do what I need it to. I did buy the 6' stick new with my machine, as I knew 2 by 4 was going to be too small for me.

[dana_swift]

Gary- I regularly work with a BT-32 alpha (PC router) and a 96x48 alpha (HSD spindle). My BT-32 has the aluminum table (which is an extra cost item, but I believe still an option for you.)

Each machine has its advantages. Its so EASY to get things on and off the BT-32, but the 96x48 handles full sheets. The cutting quality I get on the BT-32 is noticeably better than I get on the 96x48.

The advantage of the BT-32 is it is mechanically more rigid. It uses exactly the same extrusions for the cross members and other parts, yet they are shorter, and the side members are mounted directly to the frame, not moving like the 96x48. The desktop has approximately 2x better cutting accuracy than my BT-32, probably for the same basic reason.

If I were to order a "stock" BT-XX today, I would consider making my base from optical breadboard with a 1" grid of 1/4x20 holes. That stuff is manufactured in quantity, so I suspect its less expensive than the 1/2" aluminum table on my BT-32. The 1/4x20 drilled-tapped grid pattern on the BT-32 is a tad odd, but that can be customized of course.

There is nothing to stop you from making your own aluminum table using the ShopBot to do the machining either. That requires a lot of precision, so I would not suggest it to a beginner, but its well within the capability of the machine to make a very good one. So later upgrading is a possibility.

If you wanted to drill/tap a 1" grid, consider an indexer, it can make drill/tap operations fully automated. Temporarily you would have to mount the indexer on your Z axis to tap the grid. But with my table of 24x36 there would be as many as 805 holes to drill and tap. Thats a ShopBot project any day. Then its a very special one-time setup, so if you are thinking the BT route, consider the optical breadboard where it's already done for you, or order the Aluminum table option from the factory.

In either case you would need a spoilboard on top of the rigid base. Possibly a vacuum hold down also.

On the other hand if you have the space and budget for a gantry router, its hard to go wrong. Whatever you end up choosing, you will customize it to meet your needs, whatever that is.

And- I like Andrews solution of side rollers. Another great contribution, and simple. My BT-32 just doesn't need it.

Best wishes, and try to avoid paralysis by analysis!

D

[dana_swift]

Here is an example of optical breadboard, already drilled and tapped-

http://www.ebay.com/itm/Optical-Table-Breadboard-18-X18-X1-4-Thick-Solid-Aluminum-1-4-20-6-32-Taped-/230799863177?pt=LH_DefaultDomain_0&hash=item35bcbe6d89

This is 1/4" thick and 18x18" (about half of what a buddy needs) but it gives an idea of what is out there and for what price. This particular breadboard is listed at $325. So figure about double that.. and you will have a very nice base for a BT table.

There are various composite versions, which may not hold up to years of CNC abuse, as optics almost never puts any stress on the table, look for the solid aluminum (or SS) sheets. The predrilled and tapped 1/4x20 is what makes them so great to use.

Thought I would pass along the link I found to spur the idea along..

D