Squaring the x & y on a prt standard

[signgie08]

IM not sure but the outcome has made me to believe that my x or y axis is off because I made a double sided sign and they dont line up. Now I made some adjustments to the gantry by cutting a very small line on the spoil board and running a tape measure 90 inches down to the other end of the table while and marking it.
1mark x 90 y 0 2mark x90 y 48
the difference between the marks after running the z to those points was off by 1/2 inch. My double sided sign was off by about a quarter inch. After adjusting the gantry shes still off on the sign by 1/8inch. Any suggestions would be greatly appreciated.

[Gary Campbell]

Keith...
I have an article on the ShopBot site that you should be able to get some help form. It was written for the PRS, but it should work on the PRT also. http://www.shopbottools.com/garysmusings.htm#Tuning_Up_the_PRS_Gantry
Gary

Try this link: http://www.shopbotblog.com/index.php/2008/12/tuning-up-the-prs-gantry/

[Buckeye Don]

You also want to check if your sign blank is the same if you mirror it in your CAD program. I have run into clipart for sign blanks that are not very close at all. Don

[jhicks]

Keith, sounds like youre definately out of square. Been there with my 60 x 120 PRT. The acid test is simple to verify square. Cut 2 squares or rectangles out of any stock. Lets say 12" square or 12" x 18".
After cutting, flip one over and lay it on top of the 1st one. If they match, you're square, if not, you are not.
Now, what to do about it.
Well there are many posts and techniques on that subject BUT once you are square the question becomes how do you verify it stays square?
If you have any stall, jam, or hiccup, you can pretty much be assured you are now out of square again 80+% of the time.
So what we have done is scribe a line on the x rails in a place we know it's dead square on both rails to match the Y car frame edge.
When we get out of square, we move the gantry to the scribe mark on the near side. Others use bolts to come back and rest against and that works too. ( I just dont like relying on a bolt head that can turn and then being uncertain its exactly where i left it) Power down the motors, and line up the Y car L frames to the known square scribe marks or at rest against the bolt heads on the near side.
If the other far side is off/out of square, I then simply clamp the car in place on the known scribe square near side with a block and clamp against the X rail to prevent the Y from moving when I adjust/nudge the other side, leaving the other far side free, power down the motors and reposition by releasing the springs or simply nudge the out of position side back into position to the scribe or bolt head, power back up the motors, and you're good to go until the next stall or problem.
I have taken to squaring/calibrating every day before running anything just to start with a known good. The 5 minutes is well worth the confidence and surely saves material.

I went to this procedure when I noticed that even turning off my PC at night and restarting in the AM that there was a bit of misallignment maybe 1/16" to 1/8" just by reseating the gears on startup from the day before.
Good luck with whatever method you choose but make it one thats easy and quick and check it daily and after any problems occur.

[jkaras2000]

Hi Guys: Great thoughts. I was thinking of running a bit to cut the X and Y AXIS EDGES. Essentially, this would be cutting a square edge with gantry and spindle making the edges true. After doing this, I thought I would attach a fence to nest work pieces into a corner of the table. I am going to check out Gary's link as well. :cool:

[Brady Watson]

I was thinking of running a bit to cut the X and Y AXIS EDGES.

Wait til you verify that it is square before you do that...no sense in shooting yourself in the foot. You can also scribe with a vbit right into the spoilboard .02 or .03" deep. If you make a 30X40" rectangle, the diagonals should be 50" (the old 3,4,5 routine) - But Gary has a great method all spelled out for you.

-B