Recently I’ve been having quality issues with some of the cuts on my Crossfire. The problem only showed up on vertical or mostly vertical lines. I tried to make a Valentine for my Granddaughter and it came out so poorly I couldn’t give it to her
Here is an sample of that piece to show what I mean:
At first I thought it was a problem with the gantry mount and did discover that some of the Y bearings were loose (like two on one side of the square rod in more that one case). So I adjusted them but got no improvement in the quality. I’ve done quite a few enhancements to my system recently but couldn’t think how any of them would affect just vertical lines.
Yesterday I made some more cuts and had the same problem. So, trying to figure what I’ve been doing differently since my earlier cuts (which came out good) and messing around with the X axis arm, etc, I noticed something interesting. Whenever the gantry did a rapid move there were waves in the water caused by the rapid accel and decel of the gantry. I looked at the slats and realized that, with their 33" length, they would flex a bit from the waves. That flexing was in a direction consistent with the wobbly lines and with the sort of ripple look in the cut. I also realized that recently I’ve been cutting in the center of the table, rather than in the far left corner. The center of the table will have far more flex movement than the stationary corner.
Today, as an experiment, I placed a clamp bar across the slats with some foam to dampen and hold the slats from moving and made the same cut I ran yesterday. Voila! Nice straight lines and slotted hole which it the correct size!
In this photo the top piece was cut yesterday, the bottom, this morning.
Next stop, cut a crossbar to interlock with the slats in the middle. I’ll make the slot in the slats with a slight slope so I can push a wedge into each slot to hold the slats solid.
Finally, my issue is probably exacerbated by the fact that I have casters and they aren’t locked. This definitely allows the table to move more than it would with locked feet, but I would prefer to keep the casters as I’ll need to move my table to cut larger pieces.
Most people don’t experience those wavy vertical lines, even with the crappy casters and the slats just sitting in the tray. You may want to look for another problem. I have the XL and have ran my Hypertherm at 300ipm and haven’t experience those type of lines. You may want to look at the lead screws for whip. If you tightened down the set screws on the lead screw coupler or the bearing on the opposite end and the lead screw wasn’t perfectly straight/aligned, it may be causing vibration and/or whipping. Also look at the frame bolts of the crossfire to see if they’re allowing the frame to wobble. Bearing alignment on the Y gantry could cause it as well.
Your theory makes sense, but in almost a year on this forum and the FB groups, nobody has ever had a problem with cut quality because the slats aren’t anchored somehow to the water pan. If that really is your problem, I’m not sure why you’d be the only one. Seems to be something else going on.
Thanks for the feedback, but from the testing I’ve done and work arounds to fix the problem, I am pretty certain this is the issue. I’ve been using and building CNC equipment for years and have a pretty good sense of what could cause a problem based on results. That’s why this one had me perplexed, none of the types of things that you raised were a problem. It was only when I came up with the ‘wave ripple’ theory, that it started to make sense.
There is one piece of information that is likely to be important in my case: I mostly do small things with small scraps of metal. If I was working with large sheets, then I wouldn’t have the problem as the wave would be damped at more points. In my case (and as it was in this last round) my workpiece just straddled two slats and the problem occurred partly into the cut where a cut edge ‘welded’ to one of the slats and then, since it wasn’t being held down by anything other than gravity, it was free to move if that slat moved at all.
I agree that this probably isn’t a universal problem, but it sure seems like the ‘fix’ cured it. I’ll know more shortly as I tie down all the slats and I’ll report back one way or the other.
Tom
Pretty anecdotal. Almost all of us cut from small scraps of lightweight material. And the question stands: If it’s a design flaw, why is it only yours? I guess we’ll never know. Glad you fixed it easily at least.
Not really anecdotal, I can see the slat wobble with a wave. And I don’t think that cutting small pieces is the only factor, but if they’re cut in the center of a loose slat, I think the likelihood is increased. I also did not call it a ‘design flaw’, it’s a ‘behavior’ that I, at least, need to deal with. As to ‘knowing’, I’ve got my crossbar installed and will run some tests later this week (once I get more stock) and report back as I said.
I realized that I had enough scrap that I could cut just the letter portion of the Valentine so, after putting in the cross bar interlocked with the slats, I did this run.
As you can see it is significantly better than the previous run. In this cut the letter ‘L’ is approximately 1.5 inch tall.
I understand your table is shaking all over the place. You can see it, and you verified it by clamping it in place. I was suggesting you find the reason it’s shaking. It’s not normal behavior. In fact, if you’ve clamped the water tray to the frame and the behavior stopped, I’d guess the frame is loose somewhere. You could probably verify it’s not the positioning of the slots by orienting the clamps so they don’t make contact with the slats but still clamp the water tray to the frame. At least that would eliminate that variable.
And to be honest, that cut still isn’t very good for 1.5" lettering. You can still see imperfections all over the letters. Not nearly as bad as the original of course, but far from par.
I didn’t clamp the water table to the frame to make it stop - the water table is screwed to the frame so that isn’t even a consideration. I put a bar horizontally across the slats and clamped that to the frame/water table to keep the slats from flopping around. That did the trick as did the more permanent addition of the interlocking bar I show in the last photo.
I’ll admit the cutting still isn’t perfect, but, at least, it meets AQL for my granddaughter. The original cut did not. Now that I have some reasonable cutting going on, I can continue to fine tune my system.
I suspect that replacing the caste rs with solid feet and/or cross bracing the legs will reduce or eliminate the bulk of the shaking and, once again, improve quality.
@GunTruck1776, I believe the difference you’re seeing is simply with or without the water table.
Just thinking if the middle isnt supported it could definitely “sway” due to no triangulation.
You “installed triangulation” by clamping it so it cant move like a parrallagram
