Squaring Y travel

[blackhawk]

I am setting up a used PRT Alpha that I just bought. I have everything running and decided to check the Y travel alignment. I took a V cutter and milled a line in the X direction about .030" deep into my spoil board. I then set a framing square on this line and lined the side of a bit right against the other leg of the square. I moved the Y axis along the edge and the bit moved away from the square almost 1/8" over 24 inches of travel. I have read several old posts about squaring the Y axis, but I still don't understand those methods fully. My plan is to loosen all the bolts holding the Y rails (steel angle) to the aluminum extrusions, but keep one bolt on each end just snug, and then shift the Y rails to move the carriage into square. I am relying on some slop in the bolt holes to allow some movement for squaring. I planned to do all this with the motors energized. Is this the correct way to do this or am I missing something?

[gpari]

While the bot is turned off, SLOWLY pull the carriage against the stop blocks on the X-rail racks. While holding pressure against the stops turn on the bot. Then check for square. If you need to adjust, just move the corresponding stop block by loosening the set screws and adjusting. Rinse and Repeat until you are satisfied with the squareness.

Then just pull against the stops every time you power up the bot.

That's the way I have always done it. Works great and is very consistent.

Gabe

[bleeth]

Brad: If you are off that much then you should get it much better with the bolts loose. First you need to make sure everything is turned off and then un plug your motors. loosen all four bolts. Clamp one side. get it square and then tighten the bolts. Check it out. Then plug the motors back in and check it out again. Repeat as necessary. As you get more used to your machine you can also do this by loosening the bolts and only having one x motor unplugged (on the clamped side) and move the other side with the keyboard slightly till it is right and then tighten up. You just need to pay very good attention to what you are doing. If you use that way make sure you have your moves set on relative and use very small numbers for your movements. Once you have it square turn it on and check it, turn it off and back on and check it a couple of times. If it stays square you have it. Then unplug all (while the bot is off) and slide down till you hit a stop block. Make sure the other stop block is equally touching. If not-adjust them so they are. Then you can use Gabe's method above.

Moving it while motors are engaged should only be done very slowly and very little. The motors act as dynamos when pushed by hand and send power into your board. That can blow a driver.
You also do noy want to be plugging and unplugging motors while the control box is on either.

[blackhawk]

Gabe - I understand your method and this follows the procedure in other threads, but mine is out so much that I think that I need to follow Dave's suggestion.

Dave - I follow you, but what four bolts are you talking about? I have a PRT alpha and there are about 6 bolts (going from memory on the number of bolts) holding each Y rail to the aluminum extrusion. I think that I need to loosen both sides (total of 12) to adjust the squarenss. I looked at loosening the corners of the frame, but the extusions are up tight against the steel edges and I don't think this would allow the carriage to rack at all. Basically, what I am thinking about is just rotating both Y rails about one end in order to square things up. Of course, I need to move both Y rails equally to keep the distance between them equal.

[bleeth]

Brad: You are right about the Alpha. I was thinking PRT (Whis is actually 8 bolts.
You should line up you're "lower" y rail with square and then do the "higher" one with a distance jig so it is dead parallel with the other.

[blackhawk]

Dave - Since you are with me now on the Alpha setup, do you still suggest making this alignment with everything off? I would think that you would want the X motors energized to hold the X carriage in its natural operating position, as this is how conditions will be when cutting parts.

[bleeth]

Much safer with control box off & motors unplugged. Since this machine is new to you I suggest you actually start with verifying alignment of x rails if you haven't already done so. It would be heck to get your y perfectly square at one point on the table only to find it wasn't when you were 5 feet up in x.

You would have a tough time moving it around with the motors on. (By off I mean control box off and motors unplugged at the Wago's, not unbolted.

[blackhawk]

I was finally able to get the Y-axis squared up. I machined the edge of my spoilboard down one side to give me a straight edge lined up to the X travel. I then placed a 4 foot sheet rock square using that edge to give me a reference. I then chucked a test dial indicator into the router collet. I adjusted the tip of the indicater against the square and jogged the bot in the Y to get a reading. I was only out by about .050" across 4 feet. I loosened one rail and pushed it in the direction that I wanted to go. I had to repeat this one other time and got things within .020" acroos 4 feet. I am happy with that. I then jogged in X to get close to my stop blocks. I was going to adjust them both right up to the pinions as most people suggest for squaring on a day to day basis. My prox wasn't aligned and I just barely bumped the end stops. I re-checked my squareness and it was off the map. Shoot, I am not going through that alignment again. I fixed my prox and then clamped one side of the Y carriage to the X rail. I pushed on the opposite side with the power off and wow, I could move that thing about anywhere that I wanted. I disengaged the Y motor from the rack and pushed it across my square and got everything right back in line within a minute. I then clamped that side down and turned on the power. Removed the blocks and everything stayed square. I adjusted my stop blocks this time without crashing into them. I should be able to hold the Y carriage against the stop blocks and then turn power on and everything will be square. I didn't fully believe the other posts about this method, but it works great. I just wasted a couple of hours proving it to myself. Oh well, I did get one V roller lined up better and my Y tracks were a little out of parallel, so not all was lost. Live and learn.

[ljdm]

Seems like a pain in the rear, but it saves time, and wondering all the time if it is square, did it move, lose a step, etc.... only pain for me now, either I have to clamp it against the stops and turn power on, or hold the Y car with one hand and use a stick to reach the power button on the control box. Either way, I know it's square, and I don't have to use a lot of time checking it ten different ways to see if it's still square.

[bcammack]

Should this thread really be in the PRS Assembly area? It's a PRT under discussion, no? Discussing something not associated with the area's intended subject matter just worsens the signal-to-noise ratio for people who are looking for PRS information.

To be honest, I'm only mentioning this because I'm surprised that the moderators did not move this thread to a more appropriate section of the forum.

[gabepari]

I don't claim to have a PRS, but I did stay in a Holiday Inn last night


I would think this information pertains to any bot. Maybe the bolts are in a different place, but you still need to square it up, no?

Brad, glad you got it squared up. It's nice having a method that takes away the guess work.

Gabe