Steel Table Assembly

[ckurak]

I am preparing for the assembly of a PRT120-60. I want to have all of the tools ready before the unit arrives. Also, I am trying for a high degree of accuracy during the setup phase to avoid as many problems later on as possible.

The assembly manual for the steel table indicates that a 6' level would be invaluable for leveling the table sides. My largest level is only 4', so I will be buying a larger level. However, the distance between the sides on a 5x10 unit is more than 6'. Woodworker's Supply carries a "ComPac 8' Expandable Level" (110-495) that expands from 4' to 8.5'.

Does any one have any comments regarding an expandable level, or another way to accurately level my table?

[rgbrown@itexas.net]

How about just buying a piece of rectangular Aluminum tubing to bridge the table and level that? Aluminum extrusions are quite accurate and affordable. A machinist level is more accurate than wood-workers levels. Perhaps you know where you could borrow one.

Ron

[gerald_d]

I would not purchase a 6' level to build the table. A 6' level is no more accurate than a 3' level.

I would purchase a 12' length (as long as your x-rails) of extruded aluminium rectangular tubing to use as reference straight edge - for getting the x-rails dead straight and flat. (I don't think a string is good enough).

Putting a 3' level on top of the extruded alu will give you better than a 6' level.

[charles48]

Charles,

I am a carpenter and very familiar w/ levels. Levels vary quite a bit. W/O going into telling you a how to tell a good level or getting something level with a not so good level I would recommend you buy a small Stabil. I have gone to different stores and checked these levels out and they are consistently good. The best I have found on the market. Get what length you want, but I would not invest in a 6' or longer level just for this setup. Take Ron's advice about the aluminum extrusions.

Charlie

[Normand Blais]

I have use a 1/2 inch clear water hose

[jkforney]

Charles
Did you finally make the plunge and buy a unit? Your first product should be selling the extensive notes you've taken. Welcome to the club.

John

[ckurak]

John,

Yes.

I did take a "few" notes at the Camp. :-) But I couldn't sell them. They need to be coupled with an in-person Camp experience. Thanks again for hosting the MidWest Camp ShopBot. The Camp was a great place to meet other present and future Botters, see a PRT and a number of accessories in action, hear many honest opinions, and receive helpful information from multiple sources.

Also, thanks to all of the Camp attendees. (You know who you are.) The Camp would/could not have been a success without your valuable input.

Thank you for the welcome.

[davidallen]

this is where one of those rotating laser levels comes in handy. set it up so that it's about 2" above your rails then you can use a piece of scrap to adjust all of the surfaces to the same distance below the line.

prices range from around $80 to over $300 at HD. I'd suggest getting one that's 'self leveling' but the main issue is getting all of your surfaces in the same planes.

[gerald_d]

David, I don't think that a rotating laser is anywhere accurate enough for this job. We used the alu. straightedge on top of the rails, and against the side of the rails, and used a feeler gauge between them.

[rgbrown@itexas.net]

I don't think one can go too far in trying to setup a machine tool being level and square. I set my ShopBot up using an optical level that was accurate to a millimeter at 100 meters. I've never checked it since. I'd bet it was off what it had been set to. I'd be willing to make the same bet on folks who have their machines on concretre floors unless deep piers and solid beams were employeed in the foundation. Another bet I'll take and win is a 3/4 inch piece of plywood will flex and lay on surface far more out of "specification" - whatever that means, than a ShopBot operator will allow. And, a sign cut from said piece of plyeood and slightly crooked table will be hard to distinguish from one cut on a straight and perfectly level table.

I suggest you use good careful technique and start making sawdust. Unless you need to make "Mil-Spec" parts, I doubt you will know the difference.

Ron

[gerald_d]

My feeling is that there is too much emphasis on getting a ShopBot level. Even if the whole thing was tipped over by 4.38 degrees, it will still work okay. Here is the basic process that I would recommend, bearing in mind that the rails you get from ShopBot are very flexible.

1. Bolt down one x-rail to your table, making sure that it is firm, flat and straight. Use the supplied shims and test with a straightedge and feeler gauge. (2 hours)

2. This step optional at this point: Get this one x-rail level by packing shims under the appropriate leg of the table. (2 minutes)

3. Bolt down the second x-rail to the table, making sure that is firm, flat, straight and parallel to the first rail. In addition to the straightedge and feeler gauges, use a distance rod to check the parallel. (2.5 hours).

4. Level the whole table by shimming under the other legs - you may have to come back to the first leg that was shimmed. In fact, step 2 above can be left out until this point. (10 minutes)

Note: No concern about squareness so far.

5. Assemble the y-gantry across the table.

6. Get one y-rail firm, flat and straight.

7. Get second y-rail firm, flat, straight and parallel to first y-rail.

8. Get whole y-gantry square to x-rails.

9. Re-check y-rails parallel to each other.

10. Fix adjustable end-stops to the ends of each x-rail (4 places) making sure that the square gantry hits both stops simultaneously at each end of the x-rails.

Only at this stage are you finished setting up the x-rails.

11. Set the level of the y-gantry by adjusing the heights of the 4 v-rollers. ie. make sure the gantry is not twisted.

12. Surface the table (roughly)

13. Set router perpendicular to surfaced table.

14. Re-surface the table (final finish)

I particularly want to emphasise the issue of parallel rails. If the rails are not perfectly straight and perfectly parallel to each other, the v-rollers simply ride higher up on one flank and destroy all your efforts to get everything level. And it is not always the same V-roller that wants to climb up the rail, it is the one with the lightest load, meaning the one furthest from the router. So your y-gantry could be lifting either of its two ends . . . . . .

[ckurak]

Thanks to all who made the above suggestions. I purchased a 24' length of 1"x2" extruded aluminum from a local wholesaler. I cut it into 3 pieces, 12', 8', and 4'. The 12' section made the rail alignment a piece of cake. After careful spacer (washer) selection during the X-rails installation, I used the 12' section and a feeler gauge to check vertical gaps. I only needed two 0.005" shims. The 12' straight edge made this trivial. I used the 8' section to check level in the y-dimension with a level on top of the aluminum as suggested. Again, the job was trivial.

Also, I have seen some comments in the past about the use of bolts for the 4 feet. My shipment came with adjustable circular feet, each with a 3" diameter. They work well on my somewhat rough concrete shop floor.

The whole installation, including the table and the PRT, took a few days working by myself. The biggest issue I had is that the Emergency Stop Switch needed to be wired differently than the standard instructions suggested (I'm using the Windows version). One phone call to ShopBot, and I was quickly referred to a README file that I had overlooked. The appropriate instructions were easy to follow.

My Bot is up and running fine. :-)

Nice job, ShopBot.

[robtown (Unregistered Guest)]

Congrats!

Now, let the fun begin...

[gerald_d]

Charles, I am glad it all worked for you.



The only thing that surprises me a bit is the small number of shims that you needed. I wonder if your 2"x1" alu straightedge was not too flexible? Especially over 12' ? We used a 4"x.75" straightedge and held it in 2 positions for each rail:
- on top of the rail to check for "flatness", and
- against the side of the rail to check for "straightness".

[T.EARLE (Unregistered Guest)]

Where can I find 1 IN x 60 In X 120 IN MDF for a new Table Top. I just finished building the steel table. Any Help,,,,,Thanks Tom