table not cutting square

[bigcreek]

Hi guys,
My table is not cutting square. On a 4' square piece the top of the 4' piece could be off by 3/8" or so. Its almost like when you take a square and slant it, that is the shapes I am getting. Cut quality is fine, is just not cutting square. What would you do to resolve the problem? I have a 5x10 Sampson table. I am planning on taking apart the whole table and putting it back together again to try to get it straightened back out. I am really kind of dreading it because it is going to eat up a big chunk of time but it needs to be done. Just wondering what you guys would do.
Thank you.

[WyoGreen]

Sounds like your X axis is not square with your Y axis. What I have done in the past was chuck up a pen in the torch holder and use the machine to draw two intersecting lines, one parallel to the X axis and one parallel to the Y axis. Check to see if they are right angles to each other. If not you'll need to adjust the axis. Sometimes it's a matter of loosening the bolts on the gantry and tweaking the gantry in the proper direction before re-tightening the bolts. Sometimes it's as simple as adjusting the reference switches on the end of the Y axis if it's a 2 motor slaved axis.
Of course you also could be losing steps on one of the drive motors, or have a loose gear on a motor shaft causing some slippage.

Hope this helps some, Steve

[Gamelord]

Could be in your software also. Check that your ratio settings for your motors are all correct.

[Francisco]

Sounds like the gantry might be cocked sideways, out of perpendicular. To confirm, place the gantry at the origin and check if the yellow tabs (the one with the gantry limit switch, at the near end, and a similar one at the gantry's far end) are contacting the leg uprights equally. If they aren't, release the roller tensioning spring underneath the gantry's near end yellow bracket, so that you can gently tilt the gantry to disengage that side's pinion from the rack; then you'll be able to move the gantry back or forward, so as to re-engage them where the gantry is correctly aligned. Reinstall the spring. Rinse and repeat (should actually work at the first try).

[Joe Jones]

Sounds like the gantry might be cocked sideways, out of perpendicular. To confirm, place the gantry at the origin and check if the yellow tabs (the one with the gantry limit switch, at the near end, and a similar one at the gantry's far end) are contacting the leg uprights equally. If they aren't, release the roller tensioning spring underneath the gantry's near end yellow bracket, so that you can gently tilt the gantry to disengage that side's pinion from the rack; then you'll be able to move the gantry back or forward, so as to re-engage them where the gantry is correctly aligned. Reinstall the spring. Rinse and repeat (should actually work at the first try).

I have a Samson 510 table and this is exactly what I believe the problem is. When the gantry initializes, BOTH ends of the gantry should be directly against the legs. If one is off, your cuts will be off.

[Francisco]

As my explanation is a bit of a word salad, I took some pictures in the hope that they may be of help:

Gantry - Far side tab.JPG

Gantry - Near side tab.JPG

[Binderman]

Sounds like the gantry might be cocked sideways, out of perpendicular. To confirm, place the gantry at the origin and check if the yellow tabs (the one with the gantry limit switch, at the near end, and a similar one at the gantry's far end) are contacting the leg uprights equally. If they aren't, release the roller tensioning spring underneath the gantry's near end yellow bracket, so that you can gently tilt the gantry to disengage that side's pinion from the rack; then you'll be able to move the gantry back or forward, so as to re-engage them where the gantry is correctly aligned. Reinstall the spring. Rinse and repeat (should actually work at the first try).

Our table won't initialize unless I cheat the switch in the pictures below with a piece of 1x1 tubing stood up in that corner. I haven't had time to throw a square on the frame to see if it was assembled out of square or has shifted since assembly but this too could be the issue.

What causes the gantry to cock sideways? Torch crashes maybe? Rails and racks need a good cleaning?

Our table is in our Ag department so it very well could be user error, crashes,etc.

Thanks for the heads up as I was about to start trying to square the table up.

[Francisco]

Our table gets moved around, requiring disassembly, a couple of times each year. The procedure described above is a routine check we do after each reassembly.

As for "cocked gantry syndrome" causes: I'm not aware of our gantry ever getting out of square on its own. A collision bad enough to get the gantry misaligned would probably result in more serious damage elsewhere. On the other hand, missing or weak bearing preload springs might , I think, allow one of the pinions to lose contact with its rack under hard acceleration.

[Dan-PlasmaCAM]

Our table gets moved around, requiring disassembly, a couple of times each year. The procedure described above is a routine check we do after each reassembly.

As for "cocked gantry syndrome" causes: I'm not aware of our gantry ever getting out of square on its own. A collision bad enough to get the gantry misaligned would probably result in more serious damage elsewhere. On the other hand, missing or weak bearing preload springs might , I think, allow one of the pinions to lose contact with its rack under hard acceleration.

Inside the Gantry tube is a shaft that runs between each set of rails on the racks inside the rails. It is very common for the tube to get off a tooth in these rails. Run the gantry to the end of table. If they are not hitting on both sides at the same time push down on the gantry to disengage it from the teeth of the rail and slide it back into proper position. Easy as that.

With a samson if your rails are not pushed together correctly at the rail mesh points your table will get off a tooth on the other end of the machine. Check this as well. You should be able to hear it clicking when you are running the table back and forth.

[PlasmaMac]

Also check to make sure that you don't have to replace any parts that may have been worn through the years. Check your
Shafts (with pinion gears), gear racks, and all rail gear racks, or even a worn pulley belt. Having these parts in good condition can be a huge factor if you are having issues. If you even hear any king of rattling, this usually a good indication that some of the parts could be worn. Give the tech team a call and they can definitely help.

Good luck Brother,

JAG

[Mreeerox]

is it safe to assume that when attempting to cut out a circle and an oval is cut out instead, that the table is not square? i have a torchmate and the cad program shows i am cutting a perfect circle but my results show otherwise. I also had a recent problem where my images were not being cut out completely, could this be from the same problem? thanks