X-axis straightness

Anyone made a straight cut across their x-axis and s checked to see if the cut line is actually straight?

Mine isn’t, has a wave in it, curves in on one side and then back out on the other. I cut a rectangle, 24.5” x 47.5” and the irregularity is the same on the top and bottom of the piece. Otherwise, measuring across the corners, it’s square, just the wavy edge really sucks.

Here’s with a level across the concave part of the wave, it’s pretty bad.

My frame is also a hair out of square, so bringing the Gantry down to touch the stanchion plates, resulted in an out of square gantry. So I moved the gantry to halfway up the y-axis and shut the machine off. Using a square and some fireball tool squares, I had a friend then the lead screws by hand until the gantry was square. Turned the machine back on and moved the gantry until the closer carriage’s bearings were about 1/16” away from hitting and parked it. Cut some 1/4” flat bar and self tapper’d them to the y-axis tubes. This way if I ever crash the machine, I can simply bring it back to the stops, turn it off, manually turn the lead screws until it’s square again, then turn it back on and carry on with what I’m doing.

I’m really tempted to just buy a 4’ piece of linear rail, bolt it to the gantry tube and put the Z axis carriage on some linear bearing blocks. Then it’s as simple as making a new bracket to reach the lead screw. Then there’s no more roller bearings and relying on the straightness of the tubing.

My internet is terrible, but I’m slowly uploading a YouTube video of the long cut. I’ll update this post when it uploads.

I have noticed a slight irregularity to long straight cuts. I haven’t been sure if it is torch play, or height variation in material while cutting and the THC wasn’t fast enough.

I originally thought it was the torch moving, since the torch holder has a little bit of slop l/r, but that wasn’t it. There was a tiny bit of play in the Z carriage bearings, turned the eccentric’s and got that right, made another long cut, same thing.

Kind of sucked with the 10 large parts I cut this morning, one side of every one needed hit with a grinder so they would hit the backstop in my brake properly.

I also put a laser down the gantry tube and it appears to be straight as well.

You can see when I pan along the level, there’s a gap, then no gap, gap, no gap then a gap when I get to 0,0.

An old level doesnt really seem like an accurate way to measure a straight line. Try a string like fishing line or a framing square

Yep, I see the same thing on my table as well. Only see it on long straight cuts on the x axis.

Did squaring up your gantry fix this or is it the condition of the x axis tube that determines this? I had noticed that the bearing preload changes slightly across the tube also.

Maybe it’s the change in pressure on the torch when the machine moves. Like from the plasma wire. And it causes the plasma arc to move ever so slightly.

My table does the same exact thing. Did you ever figure out what the reason was to what would be causing the wave?

I’m reviving this one to see if anyone has replaced their x axis rail to remedy the issue. I’ve adjusted and re-adjusted and if there’s a sweet spot, I’m in it because the machine is great except for this one location, under these exact circumstances.

I’ve been running the table for two years now, and the only time I ever notice this is the rare occasion I have a part that needs a straight light over 33 inches.

I was making a piece for my laser bed and the wave threw it out of spec just enough to be annoying. I’m cutting it again but shortening it two inches so I can cut it on the y axis.

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