What will cause cuts like in the pictures below? I think it is motor tuning because there is no play in any of the drives. I installed new consumables before this cut just to rule that out. This is on a 5x10 home built table with a Precision Plasma HDIY gantry and CandCNC DTHCIV Ether cut electronics and a powermax 65. The motor tuning on x and y is at 60 acceleration and 500 on velocity I think but that may be backwards. These cuts are on 16 ga at the low speed fine cut settings and I think that is 78 volts 40 amps and 150 ipm and 85 lbs of air if I remember correctly. Thank you in advance for any help you can give.
It's either play somewhere, or flexibility somewhere. On my machine, it was the gantry extrusion twisting. I fixed it with a combination of welding on stiffeners to the gantry, changing my Z axis motor position, and reducing my acceleration settings. (the motor tuning made the largest/most noticeable difference immediately)
With no power on the motors how easy does the table move in the X and Y directions. It should move smoothly if you have the bearing to tight I have seen this type of cutting. It seems that you are getting a jerk when changing directions as the motor is getting started.
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT
with motors on and locked go to each axis and try to move them on both directions, Then grab the end of your torch and se howfar it deflects when you put moderate sidways and back and forth pressure. The bearings on the Z are adjustable and need to be tight enough to no have slop . The settings you have may be okay. It depends on if you have the belt reduction option or it is direct drive.
Acceleration of 60 is high normal (Accel is in IPS/sec so multiply by 60 to equal ipm.sec. 60 means you can go from 0 to 2600 IPM in one second or to the commanded feed rate in a fractional second.
You might try lowering the accel to 35 and see if it makes any difference. If it does it STILL indicates something is loose mechanically , Lowering the accel just makes the moves less aggressive.
Another good way is to lay your hand lightly on the Z as it cuts and "feel " the moves. Motor tuning won't cause problems like this. That is overshoot in one direction then in the opposite....oscillation. i would be willing to bet the torch is wobbling or the z bearings are loose. It almost impossible to make a gantry move back and forth that quickly if if you try!
Velocity is the max seep you can go and is in IPM. Acceleration is how fast you can go from 0 to full speed or full speed back to zero.
Assuming the artwork is clean and not all ragged (would show up in SheetCAM ) then it probably is not electronics or software in nature.
Thanks for the replies. I just went back out and checked for movement and nothing. But one thing I overlooked was the side guide bearings (I was checking drives) Mach got screwy the other day and I had to reload it when I did I loaded the motor tuning but forgot to slave the a axis so it spread the bearings apart a little. Hopefully this is my issue I will adjust them tomorrow and try again. Tom I appreciate the explanation on the acceleration and velocity that helps a lot. And it is with a belt reduction. The reason I raised the acceleration was because my squares had round corners but I will back it back down and try again. Thank you all for your help.
Rodney
You have the electronics so why don't you look into some cut rules for corners. They help by controlling the speed in corners.
watch this one http://arclightcnc.com/sheetcam-tutorial-6-path-rules/
I am not saying this will solve you problem but will help for better cutting later.
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT
You get a wiggle in the cut right after it changes direction and it is on the same side every time. This is obviously play in your gantry somewhere. Check all your belts/gears and make sure they are tight with zero play. Don't just take them for granted, it has been found several times on this forum by others that the belts/gears looked tight, but when further examined, they found that the shaft was actually turning a little bit inside of the gear. The other thing that can be causing this is slat wave. This is when your gantry changes direction abruptly and shakes the table, letting your slats wave back and forth for a second.
Hope this helps.
Once you take flight, your eyes will forever be turned to the sky." "Lack of appreciation is the worlds biggest crime."
Ok here is what I done. I tightened the side bearings that I over looked originally until Tom mentioned them possibly being too tight but they were too loose and I lowered the acceleration to 45 I believe. It cut much better, as far as I could tell it took all of the wave out of it. I thought about using the cut rules but I am already using the low speed fine cut specs so there is already a lot of dross on the back, I may try to use the regular speed with cut rules for curves now that this is fixed. Plus I am still learning about cut rules and how to set them. I know how to do them but as far as settings that is what I need to figure out. So far everything that I know about this stuff has came from Luke @ CandCNC, Ron @ Precision Plasma and from here. Thank you all for your help this site is worth way more than the $20 dollars that it cost.
With plasma cutting there are many variables (torch, plasma unit, table mechanics, table operations, and software settings). This site allows you to talk with those that may or may not have had the same problems and they want to help. Almost all the time the problem gets fixed and the main thing replying with that info so that others may benefit. Like you said $20 is a great price for all the info supplied by this site in all the different categories covered here.
Have fun
Tom
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT
What is the machine using to drive the axis?Belts,rack and pinion,or lead screw.. I would guess at belt..Reason being it looks like the belts are stretching under high accell rates..and when you lower the accell rates it gets better..if it is belt driven the belts are most likely undersized or not properly adjusted..
