Table not level?

[NickB]

Well, actually it is level, just not in relation to the Z axis.
I just did my first real part and the Y=0 end of the table is about 3/64 lower than the middle of the table.
Is there a procedure for leveling the table with respect to the Z heights

I haven't checked the total run out across the whole table I guess that's next
and I really don't want to just flatten out a 3/32 tilt across the entire table.
I'd rather get the table almost perfect then remove a 64th or so to flatten.

[Simops]

I assume you surfaced the table?
Then checked that the spindle or router was plumb to the table?
If so, good to go, if not, then adjust and re-surface again?

Also worth checking is that the rollers are level with the powerstick.

Cheers

[bleeth]

Shaving your spoilboard a few 64ths to flatten your table is not something to be concerned about. Just go ahead and do it and start cutting some projects!

[NickB]

Okay after careful measurement last night I determined that the table has a .060" arch from center to both edges in the Y direction. and less than .002 in the X direction.
Do I need to fiddle with the rollers or just flatten the surface?

[jerry_stanek]

You should mill the table to get everything to coincide with one another.

[bobmoore]

Welcome Nick. What model machine did you buy and was it new or used? Generally speaking you need to level the bed x and y and square the z to the bed. You should have gotten a manual that will walk you through the process pretty easily.
Bob

[NickB]

I have a new (<2 months) Shopbot Buddy BT 48 PRS Alpha. Looking over the machine this morning I noticed that the secondary MDF spoil board is not tight to the Primary board in the center I may have shot My self in the foot when I installed the secondary board by not cleaning the primary sufficiently I'm going to redo that board and see if the issue goes away and then flatten the secondary board.

[bleeth]

Yep-That would be a boo-boo. Assuming your base is ply and your top is mdf it's very important to have them well secured to each other. A very normal lay-up (with vacuum) is to have a good quality plywood base, regular mdf for the next layer with your vacuum plenum cut into it and then well sealed (shellac works well here) and then your spoilboard of ultralite.
You can not only glue your second layer to the plywood (a good quantity of titebond well spread and then weighted down till completely dry) but also suppliment it with screws if you like. Then temporarily screw the spoilboard down and skin it, pull the screws and flip it, this time gluing down with more titebond (some use silicone) layed down on the channel tops, and again, weighing it down till good and dry. Toolboxes, sandbags, 5 gal buckets full of whatever, etc. Best to have your x and y zero limits on the bottom two trimmed as an indicator and then your spoilboard overlapping until dry, and then trimmed.

For no vacuum you don't need the center layer and don't need to skin the bottom of the spoilboard and can use standard mdf.

The Brady-vac system is somewhat different and he goes into detail on how to do it.

Before skinning boards it is good to ensure your rails are level. I like a digital level for this. hose levels work well also. By patiently adjusting legs and shimming rails I make sure the rails are level and flat in length and then go across with the level on top of the beam

[Simops]

Nick, I went through what is happening to you with my Buddy. The Buddy is somewhat different to the standard table/ gantry CNC. With the Budy the table moves and its the area directly below the spindle that is important. When I got my Buddy half way across the globe the deck that came with it (1 1/4" ext MDF) was cupped badly. So I removed it and used it as a template for a new one.
With the Deck off its good time to start from the bottom up. I checked my rollers to be co- planer with the powerstick.....found a few that were not and adjusted them.....foundation step.

Then I put on the new deck and gave it a thin surfacing 1/32" or so and then put on a 1/2" MDF spoilboard and nailed it down flat and secure to the deck.....I use nylon nails (shot from a nail gun) so that when surfacing the bits just cut through the nails without issue.

Then I surfaced the spoilboard and use the 'Fingernail test'. If running my finger nail across the spoilboard in both X and Y cause it to catch then I need the plumb my spindle (Z), either parallel to X or Y depending which way the ridges go. In my case along the X (your Y as I reversed the axii...but that is another story).......see this thread in relation to adjusting my spindle plumb with table:
http://www.talkshopbot.com/forum/showthread.php?t=16866&highlight=Plumbing+spindle

After adjusting the spindle (if required) re-surface again and now you should be good to go.

This was my experience, worked for me....hope it helps....

Cheers

[NickB]

Hi again,
And thanks for all the good advise.:D I remounted my spoil board, flat this time and did a flattening pass taking a 30 thou cut that flattened the board along the Y (long axis)And along the X-axis at y=0->10 and y=40->48. the two portions where the movement was in the X direction:)
However, I ended up with a series of ridges on the board that run along the Y-axis. My measurements of the depth range from .0005 to .012 probably due to bad measuring. There are no ridges where the cutter made movements in the X direction only in Y. :(
The arrangement and measurements indicate that the Zaxis is vertical in the Yaxis direction but is tilted in the Xaxis direction by .367 degrees with the top of the axis tilted away from the front (x=0) side of the machine. To correct this I calculate I'd have to move the top of the spindle body .0512 forward.
Judging by my past performance I will end up bouncing back and forth between too far forward and too far back and only get the right amount by luck or by getting frustrated and giving up.:rolleyes: I've checked the documentation and can't find a procedure for squaring up the Z-axis in this direction. Does anyone know if a written procedure for this.

[Brady Watson]

Check square between the table and spindle body. You *may* have to remove the spindle, and then the spindle mounting plate to get them parallel to each other, THEN put the spindle back on the Z & re-square.

The numbers you mention are well within the ballpark for woodworking & I would question your means of measurement. The only real way to get blueprinted/perfect adjustments is with a dial indicator. You don't need to take it that far. Start cutting and making mistakes...then worry about precision 6 months from now when you can appreciate it.

-B