Build your own table . . . . . . (continued)

[gerald_d]

This thread continued from here where the recent posts were:

Gerald_D Posted on Monday, July 11, 2005 - 2:51 am:

Where are our non-standard table-builders these days? Mike, after having used your table for two months, do you think that you would build your next table any differently? Heavier, lighter, etc.?
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Mike John Posted on Monday, July 11, 2005 - 5:44 am:

Gerald
I would keep the dimensions the same, but move the cross pieces (and legs) towards the x zero end of the x beams so that the centre of the middle cross piece is directly under the bit when the x and y carriages are exactly in the middle of there travel. The table then overlaps the end crossbeams equally at each end.
I would also like to find a way of getting rid of the lower y cross strut at the zero end, in order to have a trolley loaded with sheet material that can be slid under or pulled out from there when needed.
I like my heavy x beams and me heavy legs, but I don't know if they are in fact any more stable than lighter material.
I like the legs being welded under the x beams, rather than bolted and protruding into the work area.
There is a message elswhere today about the building of a wooden table.
Again, with no experience I can not offer any real opinion, but I do feel that a metal table has the edge over wood.

And next time it is going to be Barbie Pink!
...............Mike
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Gerald_D Posted on Monday, July 11, 2005 - 6:34 am:

Mike, if you screw the feet to the floor, you can take out those lower cross-members.

Positioning the table crosspieces depends whether you have a single or double z-slide, or whether the single slide is in the center of the y-car. (We have put our single z-slide as near to the y-motor as possible, to put minimum "racking" stress on the y-car.) But you can always add another crosspiece at the x=0 end - maybe box-section so that it is easier for a g-clamp? Anyway, my cross-piece spacing proposal was based on a 96" long table surface and is already slightly stretched from the standard SB table plans. I guess the message to prospective table builders is to check whether they are happy with the crosspiece positions.

After enough pink gins any colour will do.

BTW, our bundle of cables hangs off the center crosspiece, about 6-8" in from the end. That is why a center leg will not work for us - it will chafe the cables too much.
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John Hesp Posted on Monday, July 11, 2005 - 7:19 am:

I would change my design (see higher up this thread) in the following ways:

i)....Centralise the surface with the tool, not the table (as Mike pointed out). This has caused me occassional problems with the tool hitting the limit switch before the tool has reached the end of the surface.

ii)...Make the surface is bigger in all directions so that the dust extractor skirt is always over surface. At present when skirt gets to edge of surface it stops working properly. I can do these two things when I resurface.

iii)..My under table storage is useful, but if I had a larger workshop with a flat floor it would have been better to have all this shelving on a wheel out trolley.

iv)...I would put the legs at the end of the table, not set back a foot. Those protruding ends of the X rails are too easy to crack your head on.

v)....I might mount the control box away from the table, but again, this would depend on available space.

vi)...I spent an awful lot of time thinking that getting the X track straight would be difficult. I was worried that my channel sections wouldn't be straight - they were straighter than I expected, but I still had a game getting the tracks straightish. It might have been better to use the idea I did toy with of having them mounted on adjustable bolts.
It would be good if the SB came with a straight edge of suitable length and accuracy for setting up.

John
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Bill Palumbo Posted on Monday, July 11, 2005 - 12:06 pm:

I'm in the process of helping to assemble a VERY beefy wooden table out here in San Rafael, CA at the moment. Luckily the new owners of this Shopbot (PRT 48 by 120) have a very well equipped cabinet shop, and every piece has been thought through carefully before being added to the mix. Each piece is braced in multiple directions, and it's probably oversized, but as we all know, that's a good thing. I will have pix to post when i get back to my shop next week. Can't do them from here as I'm typing this out on a Mac, and their shop isn't connected to the internet yet..
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Mike John Posted on Monday, July 11, 2005 - 12:27 pm:

Bill
As I said in another post, I was looking at some laminated beams 2 days ago.
These could be well stable enough for a table.
Look forward to seeing the pics, also interested of the experiences of wooden table owners.
................Mike
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Jim Frost Posted on Tuesday, July 12, 2005 - 10:44 pm:

Mike,
I'm Coming up on the first aniversary of operating with wood table. I surfaced only a 1 square meter corner initially, since we would "Never do something big" then realised that demand was different than expectation. The full surface has been leveled once, about 6 months ago when the temperature outside was -20 F and the humidity near zero. Surfacing has held up well, although I expect it needs to be redone with the summer humidity, but I'll wait for the next big project unless I see issues with small things.

The table shook pretty badly with the early SW releases and I bought some 2x6 to stiffen. But later SW seems to work well without table changes, so I never installed the additional bracing. Next plans are to replace the 2x8 X rail supports with laminated beams as part of an upgrade to reposition the X axis and add a dovetail/boxjoint vertical table. When I get the time.

Initially I was amazed at what the tool could do that I couldn't. Now I find myself asking "How can I do it better" As I get more critical, the wood table may be an issue; not yet.

Jim
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Mike John Posted on Tuesday, July 12, 2005 - 11:51 pm:

Jim
I remember when considering a wood or metal table thinking how good a table I could make if I could use the ShopBot

Gerald, time for part 3 of this thread?
.................Mike
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Mike Enright Posted on Wednesday, July 13, 2005 - 7:19 am:

Mike
I built my wood table using the CNC at work. All laminated beams straightened and mortised on the CNC. It's only a month old but everything seems to be working beautifully.

Mike
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[grant]

Mike, I would really like to take a look at your table. Do you have any pictures you wouldn't mind sharing? You can send them to my email - grant@shopbottools.com, or give a ring if you would like to talk about it. (888) 680-4466

Thanks!

[mnrite]

Grant,
Of course I meant to take pictures during fabrication and didn't! But I will take some tonight and try and post them tommorow.

Mike

[billp]

These are some pictures of the wooden Alpha table we just assembled in San Rafael, CA. They won't paste well here with the size limitation so I added a page to my web site for these shots...The table worked out VERY well, but largely because they were able to machine very stable wood, with accurate tools. I probably wouldn't try this the way I built my first Shopbot table with a circular saw and some clamps...
http://www.baycraftdesigns.com/woodtable.html

[evan]

I went down to their shop to check it out in person, it's quite heavy and solid...I haven't seen it actually cutting but I'm guessing it'll absorb alot of vibration and be a smooth running machine. And from what they told me it was quite abit cheaper than a metal table.

[gerald_d]

Comparing costs of wood and metal tables is like comparing apples and oranges. I am sure that they found their DIY wood table to be cheaper than the ready-made metal table - but that is also largely dependent on their skills and facilities for working with wood. However, it is interesting to see that the shop trestles are of metal.


Fine job Bill! Just curious, why is the table longer than the x-rails?

(looking at this pic, if you want the y-direction gussets on the center legs to make a bigger contribution to the stiffness, then you would need to beef up the lower half of the leg in the y-direction as well. The leg plank is inherently stiff in x-direction only and there are no gussets in that direction)

[billp]

Gerald,
They have ordered a longer set of rails, as in their area (SF Bay) a lot of the rooms have 9-10'ceilings, and some of their work will be longer than the 8'table. They knew thay could index the pieces, but they also wanted to simplify things. SO we went through the process of straightening these rails for practice ( as the new rails weren't going to be there while I still was...), and now they know how to do the next set on their own...I only ran a few test cuts before I left, but as Evan points out above it's mass seems to help absorb any vibrations created, and it's still not done...There WILL be further bracing on the legs, but now those pieces will be cut by the 'Bot itself..

[phil_o]

Bill,
what was the origonal dimension of the engineered material? Th x W x L I'd like to know more about the material.

[billp]

Phil,
I believe it was 1.625" by 12" by 12 ft.stock which they kept ripping down for their purposes. The material looked like it was plywood laminated side by side with another layer. It was very strong in the orientation of the grain, and I was able to suspend a cross piece ( 3.5" deep by 1.625" wide by 5 feet long) and stand on it, with minimal deflection (OK so I'm NOT the best choice as a "wood deflector".........).
The material was primed, and had very few visible voids in the substrate layers as we kept cutting them down. I would think that laminated plywood could also be a very similar, and viable material for a table such as this, as long as the layers within the plywood were stable.
"Glue Lams" would be another choice to consider. For mass you could sandwich a Glue Lam beam between some decent plywood, and you'd have an extremely rigid, and stable wooden girder to hang a machine from.....

[andyb]

Ok Gentlemen, you've talked me into a steel table. My bot (PRTAlpha 96) will be here the second week of Sept. Was going to use a wood table to save a little money but after reading all the posts I'm going with steel. I have a co-worker that is going to weld me a table together for free. I just have to purchase the steel. He suggested I use 2x2x1/8 square steel tubing for the frame, suggested 6 legs using 2x3x3/16 steel tubing using 4 feet scrap pieces that he has. For the cross supports he suggested 2x2x1/8 angle iron. Will this work for me or should I use 3/16 or 1/4 all over for the frame? Big difference in cost on the thickness. Also the C6x8.2 table sides, can he weld them to the table or should they be bolted to the table?

Thanks in advance for the help. I've learned a lot from all the areas and reading the posting.

Andy B.