Setting Y-axis square to X-axis

[Gerald D]

Roney, John & Bob
Can I suggest that you discuss the squareness issue in this seperate topic?

Bob's system of stops on the x-rails is essential. In fact, we always switch on the motors while we hold the y-gantry against the stops. The gantry is relatively flexible, and it can be pushed about 2mm out of square if the motors are switched off.

We actually fitted adjustable stops at all four ends of the x-rails so that we could check for y squareness at both ends of the x travel. Our gantry is now tack-welded together as security against slipping bolts, and to give better grounding.

During the assembly of the y-gantry, squareness is only one of the (easier) issues to deal with. More important is to get the 2 y-rails perfectly equidistant. The V-rollers simply climb up the side of the rail tip if the distance is not constant (parallel).

Then you should also check if both y-rails are perfectly horizontal. i.e. that the gantry is not twisted. A twist in the gantry will produce different xy-squareness at different z-heights!

[windsor@muskoka.com]

I've just upgraded my control box and the improvment in speed is amazing !! I did notice that when I push the limits on the x speed one of the x motors looses steps and racks the gantry out of square . I installed limit switches on both x rails that also act as adjustable bump stops for squaring the gantry . would it be posible to wire the input of one rail into say input 1 , and the other rail into say input 2 ,---- then run a file that would move x until one input was triggered , the first triggered x switch would shut down that motor , and the other one would continue to move untill it triggered the second input , at which point both motors would be energized and the gantry would be known to be square . ---The squaring routine could be pasted into long part files at different intervals .

[Ted Hall, ShopBot Tools, Inc.]

Hi Mike,

Glad to hear you are getting more speed. Note that with steppers, there will always be a speed at which you go too fast and they lose steps. The faster a stepper goes, the less power it has (this is related to the inductive physics of charging and reversing the coils ... you get to a speed that does not allow sufficient time for the coil to charge).

Anyway, on the other issue of running the motors separately. Yes ... when we all switch to the new software, the motors can be individually driven (in the software) so that very fine adjustments to square can be made and then the motors can be locked back into sync. More to follow on this one ...

[b.munday@sasktel.net]

I'm needing near-perfect square for the bulkheads of my Didi26 sailboat (Dixdesign.com) at the worst a 0.25mm diagonal error when I cross triangulate a 2000mmx1200mm rectangle (use a 0.125" drill bit on my 'A' axis for these corners. I'm not geting beter than ~1.0mm. How does the 'new software' where I can individually drive the 2 'X' motors help? Bob Munday Saskatchewan.

[windsor@muskoka.com]

I have an older machine that isn't as rigid as the newer ones and squaring is more of an issue for me . I'm cutting boat frames at the moment and am getting pretty anal about squareness . I mounted two bolts into oak blocks mounted on the end of each X axis rail ( end grain running the direction of the rail so that expansion and contraction from moisture is minimal ). each one of the bolts acts as a stop and is adjustable with lock nuts to the known square position (from cutting rectangles and measuring the diagonals) . Each stop is wired as a limit switch . I run the x car until it hits one of the stops . Then type MO ( motors off ) and tweak the carriage to the known to be square stops , then type an X move away from the stops to energize the motors. I usually do this every time I start the machine . ----------It would be really slick if the inputs could be wired seperately to different inputs and a squaring routine used like the homing routine to individualy shunt the x motors until both stops are hit at once .---Haven't figured out how to do that one yet but I'd love to hear if anybody has .

[b.munday@sasktel.net]

Thanks Mike, I figured this procedure out from other Forum talk. Would like to thank ShopBot for its marvellous product and support. I'm typing this from an Oil Drilling Rig in Manitoba (for those South of 49th the Tundra) where we've got Satellite Internet access, and I'm using all the down-time whilst drilling to get my ShopBot working A1-OK, its mostly software and ShopBot's has got to be about as good as it gets, especially for the reasonable cost. They'll be selling me the fancy vacuum hold-down and spindle-router next, a few more revenue cheques from drilling wells! SB3 looks to be s fantsatic improvement, especially its 3D preview

[gerald_d]

Robert, we have cut a couple of Didi26 boats, and after watching the builders put them together, we wonder why they want better than 1mm accuracy. When they put the frames along the strongback, they all seem to have a little drift in the distances between the bulkheads, simply because the bulkheads are so flexible before the skin goes on.