The vertical pipes aren’t the root problem. As the gantry went in +Y (Y is on the wheels on my machine), it would move in the +X, because the carriages weren’t tracking straight. So as it would travel back and forth, it would slip and that was causing the steps.
I think because it was doing that and probably different underneath, I think that was causing the z pipes to end up crooked. They look straight now.
I also think it was consistent because I kept going back to the front of the table before each test, which was pulling the gantry to one side, then I would move it to the work area, and cut. Then it would move back to the other side.
I don’t think the parts were square in X/Y, but the smoking gun was that the steps were about the same size with 2.5mm depth and 1mm depth. If it was the z pipe angle, then they would be proportionally smaller.
If your z axis has that angle, and it was affecting the cut, I would think you’d see small steps, and one side of a pocket would be perpendicular, but the other side would be sloped. It would be tough to measure, unless you cut deep, and measured the width at the top and bottom of the pocket. It’s only what? 1/2" over 11"? That’s going to be 0.0125" over 7mm, so not very noticeable.
I have a 4th driver that I can make mirror one of the other drivers. Which axis would need it the most? I’m thinking the wheeled axis (my Y, designed as X). The Z would make sense because it’s carrying more load, with the weight of the gantry, but it has the screws for mechanical advantage… Ryan, I’m hoping you have some math that would help me.
The axis that is pulling the wheels. Now that we are wired in series, I can easily max out my steppers before the drivers. I don’t think this will gain you any advantage, but you never know till you try.
I should probably try wiring in series. It should take me all of ten minutes to do it since I have everything wired up with removable connectors. I’m really just looking for things to change. I’ll do this instead of the mirrored driver, because then I won’t have to take the pi out of it’s box.
The only skipped steps or stepper problems I’ve had in a long time are due to my connectors coming partially disconnected. It happened once with the Y motor and it happened yesterday with one of the X motors.
I upgraded the pi’s OS, and I updated to the latest CNC.js (1.9.7). I want to get a webcam timelapse recording of my gcode, but that will have to wait until I get a solid block of time to work on it.
Yesterday I started trying to push my lowrider, 2 hours of cutting and I was getting board. I found the belts stretching if I went to fast. I looked at thicker belt. It is way more expensive, and the pulleys and idlers are as well. The 6mm gt2 is dirt cheap from printers in mass production, the bigger setup is at least 3x’s as much if not more. As soon as I get the sand table part on the printer I am going to try and double up the belt, if that doesn’t work I am going to stack them face to face. Two 6mm belts should be stronger than a 8mm or at least as strong as a 10mm right? Two belts will also always be in slightly different tensions so that could be a good thing as well.
Seems like twice as many zip ties for folks to complain about. IDK. I thought these belts were supposed to be pretty tough to stretch. I’m guessing it works pretty much like a spring, so the deflection is proportional to the distance and the force. It will probably just change that stretch by 1/2 with twice the belt (if they are both configured the same). If the belts are really an issue, then 2x might not be enough of an improvement. Maybe there’s a better way to reinforce them? Are there belts with steel inside them, or made from a serpentine belt?
At some point, the answer is just, c’mon! It’s an 8 foot long machine! Is 1/8" going to kill you?
What do you set your accelerations to? I know they are detrimental to printing fast, and to lasers, but for CNC’ing, reducing them gives a perception of quality, and will reduce the force on the belts. I was just messing with mine, and the defaults for grbl are set to 10mm/sec^2. I set mine to 100mm/sec^2 for xy and 10 for z. I have no idea where I got them from, but I was hopefully smarter then.
The belts we use are reinforced, and one side of mine is worse than the other. It is the side we walk by, and it always gets hit and stretched and plucked like a guitar. I might have broken some of the fibers in it. Maybe I should just replace it and see if that helps. Lower accelerations would really help.
The ones I have are as fast as I am comfortable with that still give half decent 3D printing quality…for the MPCNC. So maybe I should lower them an make a separate Lowrider firmware again.