Squaring Table...

[geneb]

Ok, I don't know if I'm losing my mind or what, but I've been fiddling with my new ShopBot table all day and I can't get it square.

I've got 136 1/16 across one diagonal and 136 1/8 across the other. Is 1/16 an acceptable error? I just can't seem to make it perfect.

What kind of error would 1/16" introduce into cut parts?

Thanks All!

g.

[myxpykalix]

There are others who are more knowledgable than me but from my experience I had a welder make my table and as they were taking it off the truck it bent some and by the time we were thru jerking on it, I was out of square by 1/8th inch. I called shopbot and they didn't seem to think it was a problem. The critical part is the relationship of the rails to the carriage. I measured from wheel to wheel on opposite sides, took that measurement to both ends when deciding where to drill my holes for the rails to the C channel.
The next thing you would have to do is set a bit in the router bring it down to the side of the plywood/mdf and clamp the board or drill it to secure that end. Then take the carriage to the opposite end (staying at the same location in your Y plane). Then take your plywood/mdf and slide it againt the side of the bit. Clamp/drill that end to secure. You should then be square to the carriage. After i did that and screwed my plywood down, then mdf I took a sharpie marker and chucked it up and drew a line on an edge of the mdf in the X plane to register jigs to and it seems to be fine.

[geneb]

I'm using a ShopBot supplied table and I haven't reached the point where I've even mounted my X rails yet. Attached is a picture of the table so far:


3266

The legs & parallel supports are positioned along the extruded track frame as per the CAD drawing included in the documentation. My concern is that if I don't get rid of that 1/16" error, it's going to cause me problems down the road. You may be right and it might be a negligable(sp) error, but I have to know for sure.


Thanks Jack!

g.

[fleinbach]

Gene,

Jack is correct. Even though the main table is not square by an eighth of an inch. You will be able to compensate in your final adjustments after everything is together. Your next step is to put on the x-rails, and they need only be parallel. The actual squaring to the table is done when everything is assembled. The x-carriage stop blocks are used to square the table to the X rails.

[geneb]

I'll take your word for it. You guys know far more about this machine than I do.
The error is only 1/16th though, not an 1/8th.

Wish me luck, I'm going to try to get the rest of it done today.


g.

[richards]

Gene,
Even after you get the X-axis rails perfectly aligned, you may run into the same problem that I have. My gantry is 3/32-inch out of square. Even after loosening all the bolts and 'adjusting' it to the limits of the bolt holes, it is not square. What I've done is to set two combination squares so that when each side of the gantry is butted up to the blade of the square, the gantry will be square. I do that each time before powering up the steppers. Once the steppers are powered up, they hold the gantry in place - and everything works properly. It's a minor problem that is easily worked around. Of course, when I'm cutting plaques, signs or decorative type work, where things don't have to be 'perfectly' square, I don't take the extra minute to line things up at the start of the day.

[fleinbach]

Mike,


There is an easier way. There are 2 stop blocks at the end of your X rails. The first step is to square your X car using your prefered method. Now loosen your stop blocks and move slowly until you contact one of them. Now push both stops against your gears and tighten them.

Now all you need to do is before hitting your reset pull the X car agenst both stops. You will feel it hit one, then pull a little harder and it will hit the other. While holding in this position hit your reset button. I hope it is mounted near enough to reach. I know some people mount there control box away from the table.

[mthomas]

I dont own a SB, and I'm not trying to stir up trouble or anything referring to their quality, but I just have to ask this...

When these things leave the factory are they square? I could understand a 64th or (maybe) a 32nd, but a 16th?

[myxpykalix]

Well they come unassembled, and in my case i didn't buy the table from shopbot, but had one made locally because i wanted to have a indexer to do big columns. I actually was surprised that when we got it in the shop it was as square as it was(the table). We had some minor banging and stretching we had to do but after calling shopbot we decided that that fraction was not bad enough to worry about. I used a square to measure my carriage/rail/table/router relationship and other things and mine all went together with a whole lot less problems than i anticipated.

[richards]

When I assembled the Shopbot supplied steel table, I attached nylon tie-down ratchetting staps diagonally on the x-axis to pull the table into exact alignment. When measurements were exactly the same on both directions, I tightened the bolts, checked the measurements again, took off the straps and checked measurements one last time.

Frank, thanks for the tip. As soon as it warms up enough to work in the shop, I'll move stops.

[geneb]

Michael, as Jack said the ShopBot table is completely unassembled. It bolts together using 1/2" bolts and is quite heavy. Because of this there can be a little trapezoid(sp) problem that can be adjusted out.

My question to the group now - can I safely use a pnumatic impact wrench to tighten up all of the 1/2" bolts? I know better than to use one on the 5/16 bolts that grab the t-nuts in the extruded sides..


tnx!

g.

[mthomas]

Ahh, ok thanks.