- March 6, 2017 at 11:01 pm #29018
I am really happy with how I am able to handle the MPCNC, but there are still 2 things, I would like to handle:
1. I hit the boundaries of the workingarea once. It was just by around 4mm, and all happend were some lost steps in the Y axis, bit I would like to handle that issue, before something bad happens.
Will the Merlin board stop the job, when it hits an endstop while working on it? I would than mount 4 triggers in the corners, so Merlin can stop as soon as it hits those buttons.
2. Setting Z to 0 stucks 😉 I am placing the “Home-Position” manually for every job. That way I am free in mounting the workpiece and can place the milled part on it freely too. For X and Y its not that bad just doing it visually even with the dust shoe attached. For Z its a lot harder. On hard wood I do it, but starting the router and going down in 0.1mm steps until I can feel in the vibration of the table, that I hit the wood. You can hear that too, if you listen carefully. With soft wood (like balsa) both don’t work. Here I try to get as near as possible by looking, than moving down 0.1, moving up 10 and look for the hole. Repeat that until its there.
Do you have better solutions for that? I have seen the video from Christian (Estlcam) where he used metal-foil to measure the workpiece. I could think of something like that. If that piece is 0.5mm thick, I could add a script, that moves the Z 0.5 down and than resets it to 0 or something.
Thanks for hints,
JensMarch 7, 2017 at 5:31 am #29033
I have a piece of sheet metal, no clue what the thickness is, pretty thin, was one of the expansion slot covers on a computer case, that I use for my z touch off. I don’t bother with the -Z after I set 0, it’s close enough for everything I do at the moment. I don’t have X and Y max endstops, just the min endstops. I’ve only run into the end once or twice, it is a bummer since it ruins whatever you were cutting. You just have to be careful about the size of your job. I know I have a cutting area of 1220 by 1200 millimeters on my mpcnc, so if I’m doing a big job I create a grid of that size to make sure it will fit. When I’m setting my zeros, I pull the dust shoe off, then raise the z up enough to put it back on once I’m done.March 7, 2017 at 5:48 am #29034
Yeah, the workingpiece is damaged, when you hint the boundaries either ways, but I am in fear of damaging the CNC Machine.
I should draw lines where the max working area is exactly, that would make positioning a lot easier.
When I have Z 0 in 0.2mm above the item, I wouldn’t mill through the complete part.March 7, 2017 at 9:08 am #29038
I don’t think you’ll damage anything. If your belts are tight enough it shouldn’t grind them, the stepper will magnetically skip, but that doesn’t hurt anything.March 7, 2017 at 4:17 pm #29060
We use a waste board, all cnc’s do for the most part. A through cut gets cut past your material, and the top surface is usually milled flat (surfacing) so setting z zero super precision is not a common thing.
Endstops are not common either, they are generally on large machines to prevent crashes.March 7, 2017 at 10:16 pm #29063
Yes, I have a 3mm wasteboard below my working material too. Currently I am cutting 4.1mm deep if material is 4mm to have some room in the Z-axis zero finding, but its still something I have to do. I am a very lazy person, if it comes to stuff, you have to do, that might be done easier 😉March 8, 2017 at 4:18 am #29069
@Jens For now I use a piece of notebook paper to set the Z height like you would if you were calibrating the Z on a 3d printer. Works great for me and I’m able to get reliable depth with multiple bits.March 8, 2017 at 4:31 am #29071
Why are you not using a Z touch plate ? It doesn’t get easier or more accurate than that.
Use the Z_Min_Endstop connection on your RAMPS. One wire to the plate. The other wire attaches to your bit. Then home the Z. Then set G92 Z?? to the thickness of the plate you are touching off of. Remove the plate and wires. G1 Z0 will now place the bit exactly at the surface of your material.
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