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

[gerald_d]

This thread continued from here (http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=7&post=25993#POST25993) 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.?
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

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.
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

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..
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

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
__________________________________________________ _________________________________

[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 (mailto: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 (http://www.baycraftdesigns.com/11.jpg), 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.

[paco]

Hi Andy!

Good choice!

I would recommend 3/16" thick for the sides rails support and spoilboard supports (tubing or channel/angle), as much bracing needed (1/8" angle is enought) since this is what will make the table/frame stiff and the legs could be 1/8" thick too.

The sides/rails support can (and should if you ask me) be welded as long as they are intalled correctly (straight/square/leveled togheter).

I have welded mine with the suggest material by SB along with angle bracing and my setup is VERY stiff. I would'nt change anything else than maybe tubing for fancy/better look!

Have a look at the setup I choosed (http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=7&post=15724#POST15724)...

Still, look at how other Botters have done; many have quite interesting ideas...

[trevor_b]

to weld or not to weld
4 legs or six,

whats a poor boy to do..?

(Boy?..who am i kidding?)

i am getting a 120-60 - how will this affect my choice of table design? i need to order the material soonish, and not sure which direction ,of the many discussed here, to go in.

I hope you don't mind me dragging this all up again - if only i was around here 12 months ago! without ever having seen a bot yet, some of the finer detail is a little lost on me, but its having you lot here that has given me the confidence to buy one of these monkeys.

thanks in advance

UK Trev

[gerald_d]

Hi Trevor

I drove through your town about 3 weeks ago....why didn't you stop me?


If you can weld, that's the way to go....

[trevor_b]

Gerald

i was that close to the table guru?? i hope this doesn't sum up my luck for the coming adventure!

No, i can't weld, but i know a man who can. My first reaction is go with the two sides as welded sections, and then bolt the cross pieces, i can't imagine lifting the thing otherwise. also, i was planning to get it powder coated SB blue...

this may give you an indication of my "style over substance" approach!

Pop in next time.......

[gerald_d]

The last Brit in this thread wanted to go for a "camp" pink colour, and he managed okay.....

I think that guys who have followed this story, and built tables accordingly before their ShopBots arrived, would agree that the ideas here are "overkill" in comparison to the inherent stiffness of the actual machine that gets bolted on top. Heck, some folk even manage with wooden tables!

[trakwebster]

My ShopBot crate arrived yesterday, and awaits assembly. I had planned to build a wooden table, as I have a wood shop (being a guitar-builder), and then one of the fellows at ShopBot company mentioned that some botters had been able to get steel tables built for them for little more than the cost of wood.

Well, I know a couple of metal-workers, so I asked. Turns out that buying the steel for a PRT48, with sales tax, cost me $560. Not terrible, though surprisingly expensive.

My welder-buddy (Infinity Welding of Mount Shasta) wanted about the same amount to cut and drill and paint and assemble. However, he also wanted a website designed and built and I have those skills so we swapped the jobs. It's about the same amount of hours for each of us, and about the same amount of hours as building the wooden table would have taken me, so I'm happy with the solution.

So the steel table materials cost only slightly more than wood materials, and about the same time investment required.

I asked that it be painted a medium gray, and most likely it will arrive at my shop next week. Then the real fun begins!

[pfulghum]

Just finished the pre-build on my table before going to blast and power coat. I built it per plans on the website with a "couple of tweaks". I used 1/4" steel for gussets. I bought all the steel for $525 (All cut to length). Drill bits for $40. Hardware for $50. Got a qoute for sandblast and powercoat $200 today. That puts me into it for $700. Plus about 20 hours labor to drill holes. A couple secrets to drilling 1/4" steel... drill at 200rpm...and use a 1/4" starter hole before drilling the 5/8" hole.

I don't have my crate yet, but should be here next week.

I will post pics if anybody interested.

-- pat (in Idaho)

[trevor_b]

so, as far as i can make out, the tables discussed here so far have been for the 96, would Mike Johns approach work for the 120? to recap:

critical points

width between the side (x?)rails

width of top edge on the channel of x rails - issues with stock available in the uk

design of welded side assembly no. of legs, struts etc

length/hieght/direction of curve i am now on.

What else?

[hespj]

Trevor, you're welcome to come and see my table in Somerset.

(Is there a timber mechant in Midhurst selling FSC timber?)

[trevor_b]

thanks John,

i nearly made it to your weekend get together, and in hindsight ( why do i think that phrase will be used a lot in the coming months...?) i should have pulled out the stops to get there, esp. as Gerald was with you!

i have been notified that the thing is ready to ship 11th November ( very quick, money only sent Yesterday!), could i come during the week?




(There used to be a company called EC Timber in Milland, Hants, and i think they may well be nearer you now, Bristol possibly. I will check.

W L west & Sons are a great family run sawmill here, not sure if they are fsc, but certainly buy from local well run woodlands. Speak to Simon, 01798 861611, mention me)

[hespj]

Yes, by all means come in the week.

(Yes, Milland. Milland Fine Timber. A search reveals they still exist, but no website or email address.)

[gerald_d]

Hi John

This (http://72.14.203.104/search?q=cache:jVaSUgQqKQwJ:www.efi.fi/cis/english/creports/uk.php%2BMilland%2BFine%2BTimber%2Bmail&hl=en) cached (Nov 04) Google page may help you with sourcing FSC timber. Milland is mentioned in there as "withdrawn/no longer certified"

The current database can be searched here (http://www.fsc-info.org/english/dbcoce.asp)

[bakerkr]

Gerlad_D - Could you email me the pics of your table. Thanks,
Kevin

[gerald_d]

If I am Gerlad, them I am wondering where I offered to mail which pics?

[mikejohn]

Glader
Are you still grumpy after your great holiday?

[gerald_d]

Redgal had a great holiday? Here I am trying to figure the date and continent and wading through 350 photos.....

[bakerkr]

Gerald,

I sorry, I may have myself confused. I thought you had built a table everyone in the forum was impressed with. I also thought you had posted pics on a website, but had taken them down. I'll review the posts again.

Thanks,
Kevin

[mikejohn]

Dragel told me how to build a great table, but there are (and never have been) any great photos from Grelad.
He did have some pics on his web site of his new project, which he took down.
However Kevin, what are you looking for?
We will try to assist with pictures.
............Mike

[bakerkr]

Mike,

Here's my thoughts.
http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=7&post=28376#POST28376

[gerald_d]

Ladger's table is cocooned inside a dusty box. Good camera angles are impossible, and dust obscures the rest!

Kevin, are you and Trevor (Baker) related? Why would baker's suddenly want ShopBots?

[trevor_b]

we might be the same person, not sure though...
its all very confusing this shopbot business and we are only trying to build the table!

i do get called kevin ALL the time..

John hesp -any chance of seeing you on Tuesday late morning /Afternoon? and then i shall know all there is about tables. watch this space kevin.

on site , so use 07778 452164 to arrange if possible. many thanks

[bakerkr]

Sounds good, look forward to hearing more

[trevor_b]

Well , many thanks to John Hesp, i had a great couple of hours looking at my first 'bot - really impressed, both with the machine and johns' quiet understated knowledge of 3d design. His table wasn't bad either!

i am definately going for the welded side sections and then bolted cross supports - this helps me to powder coat and transport the pieces.

very busy in the workshop just now, so more details on the dimensions etc later.

Thanks again John - what a great place to work. ( need thick socks though.....)

[gerald_d]

The last 2 days were spent putting this 9'x6' table together. All one-piece, welded. From material lying around the shop. The main channels are 185mm x 70mm and the cross-bearers are 76x38. Turning the open side of the main channels inward gives clearance for wide boards, massive dust feet and hopefully looks better than with the open side out.


3282
Cross-bearers are 100mm to the right of center because the router/spindle axis is 100mm towards the y-motor side in the y-car.



3283
Damian spraying the etch-primer undercoat



3284

3285

3286
Welding kept to a minimum to reduce distortion of the x-channels



3287

3288
Half-painted table and unpainted gantry

Overall size of the blue wildebeest is 3400mm long by 2230mm wide.

[mikejohn]

Gerald
Have you gone from angle iron bracing pieces to tubular because that was what you had to hand?
And talking of what you had to hand, who has two pieces of 185mm x 70mm [ channel 3.4 metres long "From material lying around the shop"?

It does look good though.
(Would look nicer Barbie Pink
)
....................Mike

[gerald_d]

You may forget that my "real" career is metal.
link (http://www.mechlift.com/)
After Barbie lies in the local sun, she ends up the same colour as our primer paint!

These are the folk on the map so far:


Pete Meacham Santa Maria (CA)
Jim Umbaugh Hiram (OH)
Bob Standard Three Rivers (MI)
Luke Agens Denton (TX)
Paco Valcourt, Quebec (Canada)
Dan Dunn Stockbridge (GA)
Jerry Hicks Downers Grove (IL)
Ralph Hampton Cheltenham, England (United Kingdom)
rcnewcomb Hartford (SD)
SeanA Bothell (WA)
Donn Busby Portland (OR)
David Buchsbaum Atlanta (GA)
Mike Richards South Jordan (UT)
Steve Flanary Pasco (WA)
Paul Nielsen Cartersville (GA)
Robert Cheal Logan (UT)
Carl Vallance Evergreen (CO)
Evan Curtis Novato (CA)
Jay R Mack Aurora (NE)
Jerry Pendergrass Cedar Hill (TX)
Pat Fulghum Boise (ID)
David J. Morris Apopka (FL)
Tom Johnson Roseau (MN)
Don Ask Carmel Valley (CA)
Bob Lofthouse Blackburn, England (United Kingdom)
Dave Rosenbleeth Boca Raton (FL)
Bill Palumbo Toms River (NJ)
Wayne Locke Austin (TX)
Jim Dearborn Germantown (TN)
Bill thorpe Gorham (ME)
Stephan Voelkel Hutchinson (MN)
Lanny Nightingale Sandusky (OH)
Dirk Dunham Eagle (ID)
Mark Hill Victoria, British Columbia (Canada)
Bruce Clark Port Aransas (TX)
Boyd Godfrey Squamish, British Columbia (Canada)
Andy Brooks Oakwood (GA)
doug henry Greeley (CO)
Scott Worden Greenwood (WI)
Wayne McGhee Newcomb (TN)
Mike John Piatra Neamt, Neamt (Romania)
Wayne Walker Auburn (WA)
Holger Erendi Tallinn, Harju (Estonia)
Ryan Patterson Naples (FL)
John Haggerty Souderton (PA)
Gerald Kling Lewisburg (PA)
Phil O\'Rourke Pittsfield (MA)
George Chambers Bend (OR)
Dave Iannone Wilmington (DE)
Don Kerschner North Manchester (IN)
Norman Weller Evans (GA)
Lindy Hopper Canyon (TX)
Douglas Lawrence Coeur D Alene (ID)
Chip Marshall Point Pleasant Beach (NJ)
Randy Nelson Silver Bay (MN)
Jay Pengilly Moscow (ID)
Pierre Wessels Abbotsford, British Columbia (Canada)
Harold Weber Columbus (IN)
Ron Moorehead Olympia (WA)
Scott Smith Phoenix (AZ)
Gary Norman Paris (TX)
Terry Cheney Victoria (TX)
Charles OBriant Seattle (WA)
Ted Gus Gustafson Grand Rapids (MN)
Dennis Sapp Oklahoma City (OK)
Jim Tolley Black Hawk (SD)
Steven Patterson Ventura (CA)
Gerald Dorrington Cape Town, Western Cape (South Africa)

[gerald_d]

The above post suffered from editing the wrong post in a hurry
Sorry.

Anyway, to get back on track, Mike asked "Have you gone from angle iron bracing pieces to tubular because that was what you had to hand?" No, I also have lots of angle iron on hand.....

In the earlier threads I showed angle iron because that started out as a bolted design for a DIY person not experienced in welding. I always prefer tube as a structural member because it has torsional stiffness and gives a cleaner appearance (less internal dust collecting corners) - but it is no fun bolting tube. Welding round tube is tricky to get the ends to fit well, and easier if the points are partly flattened in a press, like you see above. Also, Damian needed a big welding project to get some confidence. on

[doglaw]

Does anyone have plans for a steel table that can accomodate a lathe? I recently purchased a PRT96 (still in crate) and am in need of building a table. I have the Shopbot supplied plans - but am really interested in somehow mounting a lathe in the table.

[billp]

Douglas,
Here is a link for pictures of Wayne Locke's table;
http://www.talkshopbot.com/forum/messages/27/8747.html#POST26556

[jay]

Bill, before I made my table I wish I had seen that posting.

If you want to have both a 48 x 96 cutting area and the indexer set up all the time a custom length Y should have been ordered. Hmm . . . come to think of it, there are lots of times when we, I, don't have to cut full sheets. . .

[billp]

Jay,
How about a "drop leaf" panel at the last foot or so of your "Y" Axis...Using pivoting cleats, or cantilevered supports you can just remove/ replace a section as needed. Then you could "drop"the last foot of your table supports to accomodate the indexer/workpiece...

[waynelocke]

Douglas,
I recently found the drawings that I made for my table. Let me know if you want them. I would do a few things differently, but it has basically worked out fine.

[jay]

Bill, Your drop leaf suggestion is exactly what I was thinking about as I typed my Hmm...

I want to make a new bed for the Bot when I get some time. I have been considering using some sort of rigid plastic. The huge swings in both temperature and humidity are a real pain in the butt with the plywood and MDF that I currently use.

Wayne, I would love to see your table plans and any ideas for improvement.

[Brady Watson]

Jay,
Not long ago I installed an indexer for someone right on the large steel support on the 96" end of the table. Picture it laying on it's side. The AL extrusions bolted thru the steel and there was plenty of room in all directions, however part lengths were limited to about 36" max. Just an idea for you...

-Brady

[jay]

Brady, thanks I have seriously considered mounting my indexer much the same way as The Marshall Brothers have mounted theirs. It is mounted on the steel side down the X axis. Since I have a 12 inch Z it would probably be ideal.

Maybe Chip or Gene could post a picture for Doug?

[paco]

Jay and Brady,

Is this setup have enought room for long tool bits?... I believe the Marshall Bros have got their Z installation up some more... but I do think it's a nice simple way to have it installed... just wondering about the use of some large stock with long tool bits... and what about getting it installed on the side channel (under a X rail) for more lenghty stock?

[gerald_d]

Some indexer mounts (http://www.mechmate.com/Forum/messages/8/60.html)

[doglaw]

Thanks to EVERYONE for the reply. The pictures are a great help and source of inspiration.

Wayne, right now I am leaning towards mounting the lathe on the end of the table - similar to the way Randy Newcomb mounted his indexer. However, I would really like to see your plans as well as to hear your thoughts on the matter. I purchased the standard PRT96 and am concerned about losing the ability to cut standard 4 x 8 sheets by mounting a lathe on the table. Also, from the pictures you posted on mechmate, it looks like you converted your lathe into an indexer. Is this correct and what size stepper did you use?

[rcnewcomb]

Since I just have a 48" it really didn't matter which way we mounted the indexer. The down side is that we are limited to 36" material in our indexer because the indexer head and tail piece have to fit between the rails. For our work that has been acceptable.

If I had a 96 then I'd definitely go with Wayne or Bob's mounting method.

[waynelocke]

Douglas,
I will email you the plans. One thing I would change on my table is to mount the legs differently so that they do not protrude on the inside. I mounted a Harbor freight lathe on the table and had the fabricator make a bed extension. I can mount the indexer motor to the end of the lathe shaft or move it back and use the lathe motor for sanding parts. I have a simple switch setup so that the lathe cannot be turned on with the stepper attached. I have given up on dust collection with the indexer. I use the stepper motor that SB sold for the PRT.

My PRT is a 5' X 8' confiquration, so I have a full 4X8 capacity and could cut 5' if I needed. I don't use the indexer a lot but it is avalued asset.

[gerald_d]

My first choice of mounting would be "Marshall Bros. (http://www.mechmate.com/Forum/messages/8/190.jpg)" style - unless you are planning to turn diameters that won't fit between the gantry and table top.

[hespj]

I was going to mount my indexer sideways on the X side of the table. In the end it was easier to just cut a shallow (1/16") groove the width of the indexer mounting track into the spoilboard and bolt the track to the spoilboard. But I have got a 12" Z, so this puts the CL of the indexer about midway of the Z travel. It's easy enough to unbolt the indexer when the full 96x48" is needed.

John

[mikejohn]

John,
Any truth in the rumour your table has contracted to 95"x47" because of the weather?


Happy New Year
.....................Mike

[trevor_b]

My hard drive has just died, so I have some time on my hands!

Here are some pictures of the table I arrived at after all the good advice I recieved . Its 10x5, and uses metric (UK) stock. The sides are welded, and the cross pieces bolt. I had it powder coated blue. Its got a 5hp spindle and I used the pvc vacuum kit from shopbot, and sourced my own pump in the UK from Becker. Its 10hp and sucks (in a good way)! I used the shopbot four zone file.

We run in metric and get some strange parameter error messages before every file execution, but apart from that its been great. ( we did have issues with the ZZero routine not working, but once the spindle cable was seperated from the brown zero plate cable, it has been fine.

One component we used to make by hand took 35 minutes - it now takes 6!.

thanks for all your help so far

Trevor.

[trevor_b]

Where are my pictures!!!!!!?????

Trevor

[gerald_d]

Yes, where are your pictures??????


Mail them to me and I'll post them for you if you want.

[gerald_d]

Trevor's pics:

3289

3290

3291

3292

3293

3294

3295

[zoltan]

Hi,

Can somebody post few pictures with the cable drive of old SHOPBOT? I am very curious how was that setup.

Thank you.

Zoltan - from Romania

[zoltan]

Nobody can help? I can not see such a setup as I am from Eastern Europe and I do not know somebody owns such a machine and I found nothing on net. I would like to use such a setup for my future diy "shopbot" machine and i have no idea how it can be made such a cable drive to not loosing accuracy and no backlash.

Thank you.

Regards,

Zoltan

[billp]

Zoltan,
I was an owner of one of the original cable drive machines. While it was a good machine to introduce me into the world of CNC it was NOT the most accurate machine on the planet. Yes it WAS accurate to .02" (I believe)and at the time I thought this was incredible ( I had never dealt in hundreths of an inch before...) BUT after we ran the machine for a few hours we had to run a "calibration routine" (UC?)which was built into the Shopbot software, as the cables would stretch and the machine's accuracy would suffer.
First we told the machine to go a specific distance (say 48") then we would run the tool and measure exactly how far it DID go. Then we would enter those values into the software and it would compensate for the cable stretch. And we also got used to moving our parts all over the table so we didn't wear out the cables in the same spot on the pulleys.As far as the "backlash" factor, I really don't remember that as being so important at the time. Most of us early 'Botters were SO thrilled that we could actually build our own machines, create files, and cut parts with it, that we probably didn't pay much attention to that factor.
Once Shopbot introduced the "PR" series, with the rack and pinion setup, our accuracy improved to something like .002", and many of us proceeded to upgrade our machines.
If you are really going to try and create a machine from the ground up, I'd encourage you to look into some sort of rack and pinion drive mechanism. There are a number of companies on the web which can supply the rack, gears, etc. (Bishop Wisecarver being one of them). It might save you the trouble of creating a second machine after finding the limitations of the first one.
Another site which might interest you is the one created by Bob Campbell (www.campbelldesigns.com (http://www.campbelldesigns.com)). He sells designs, and hardware for building your own machine, and it would be a VERY good place to start a project like this.
I'm sorry but I don't have any pictures from the old cable drive days as it was almost 8 years ago...
PS. You might want to try and contact Mike John ( who usually posts on this Forum a few times a day...) I believe he is in Romania, and maybe you could arrange to look at his current Shopbot...

[gerald_d]

Memory lane (http://www.talkshopbot.com/forum/messages/7/117.html)

Some believed that chains were better than cables (search for pcjet) and some believe that those were the good old days...

[zoltan]

Bill,

Thank you. I really appreciate your help. I learned about CNC from CNCzone since one year ago, and since then I have built some small hobby machines, from scrap MDF and salvage parts. Unfortunately they are so weak that can be used only for learning or just playing not for making real things. On other hand my income is so small (I am from Romania) that I can not buy real parts and I was thinking that I can build such a simple machine like old type shopbot with parts which I can find out here in Romania and I can afford the budget for. Unfortunately I am not too good at design either and from the few pictures of old models I could not figure out how it was built. This is the reason why any help to build my "shopbot" machine would be appreciated. I can not afford linear guides, ball screw, rack and gear, etc but a cable, few struts, roller bearings maybe.. Is Mike John Romanian?

Thank you.

Zoltan

[zoltan]

Hi,

Nobody could help with some pictures of old setup (cable drive)? or if it is not possible at least a drawing?

Thank you.

Regards,

Zoltan

[dhunt]

Everything here is double thickness 3/4 ply,
with the exception of those triangular braces on legs
3296
3297

[dhunt]

No flexing or vibration is expected on this table,
especially when the 4x8 baseboard is added and secured.
Ignore the bow,conveniently placed on the nearest flat surface: it doesn't go there!
3298
3299

[paul_z]

I did something similar for my table but I expected and got some flexing. I then pulled out "the secret weapon". I used Kevlar 200lb test string as diagonal tensioning device. Each diagonal is made from several strands of the 200 lb test string and tensioned by twisting. I used this on the bottom of the bed and on the legs.

The result is excellent vibration dampening from the wood and extreme rigidity from the Kevlar. (The stretch modulus of Kevlar is less than steel.)

I have a humidity controlled environment and would be reluctant to try this where humidity would vary a lot.

[mikejohn]

A follow up to the table I constructed, detailed in this, and the two previous threads.
I have just moved workshops.
I took the table to pieces, leaving the x-rails in place.
I marked everything carefully, to make sure it went back in the same place.
It went back together perfectly.
The x carriage rolled up and down perfectly.
And, rather spookely it was perfectly level in all directions!
I tried everything, turning the level around, going from end to end, then across the supports, then across the top of the rails, the bubble stayed plumb in the middle!
Reading in a recent thread of someone having loose wagos, and frying the board, I made certain they were well connected, tied with cable ties.
I plugged it in, tested the earthing (Zplate to router mount) then moved left and right, forward and back, up and down, then jogged everywhere.
No problems.
Then I aircut a file, with no problems.
I guess it's being English that brings this good fortune
.

..........Mike