My new 4mm single flute upcut bits arrived, thanks to @Brandon_Satterfield and +SMW3D ! So I started cutting again, much better this time with the addition of a bit of air from a 60W air pump and some lok line to clear the chips. However…
Seems like the board was not level or my cut went too deep since if you watch near the end of the video I managed to dive deep into the spoilboard which caused awful chatter and messed up the cut a bit.
Also noticed after getting the part out that the round holes which I though cut perfectly turned out not to be round at all, quite off in fact. I also measured the cut out part from the center and its out by 0.3mm in one axis. Not sure if this is just chatter/deflection or if my machines XY steps are out. Going to have to recalibrate that again I think
There was a lot of chatter but it is possible that your axis are not spot on really depends on the method you used to calibrate them. If you use a .005 dial indicator and a calibrated block that will increase accuracy. However if your z has not been trammed that could cause inaccuracies. If you have a lot of tool deflection it should be present in both axis. I have to ask where did you get your spindle mount it looks awesome.
The mount is the one @Brandon_Satterfield was producing on the early R7 builds, I think I had the 3rd or 4th unit. It really is very nice.
I just re-surfaced my spoilboard it came out perfect not a single mark with a 0.75" mortising bit 0.5mm into MDF, so I’m pretty happy with the squareness of the machine.
I’m sitting down now to re-calibrate my stepper motor settings with a dial indicator. I’m not sure how you use a calibrated block to do this? I have some 3 2 1 blocks I can use, but I’m not sure what to do with them! As it is I’ve setup my dial indicate to be as square as I can with the axis and am just moving back and forth a few mm and measuring the offset. Seems over 2mm of travel I am 0.1mm out thus far which is pretty large!
There are a couple videos on youtube on how to calibrate a cnc router using 123 blocks and a dial indicator. The blocks have to be stationary so they don’t move during the process. I can’t remember who it was I watched on Youtube but there are several
Ok after much fiddling with dial indicators I concluded that I was about 10% out, reducing my travel per revolution value from 8.016 to 7.8 seemed to make my dial indicator measurements about spot on (to within 0.0005"). So I stopped using the indicator and did some larger moves and found that it was now horribly innacurate, a 500mm move was moving 516mm. After tweaking the value again using the error on these larger moves I ended up with 8.0095, which really isn’t all that different than what I had before. Honestly not sure if I messed up usage of the dial indicator, or my dial indicator is rubbish or if its just that small moves always suck with stepper motors?
The dial indicator readings were very stable and repeatable so I’m not sure that there’s anything wrong with it.
There are a lot of factors involved with accuracy, speed of travel is one of them could be losing steps in small increments. When I calibrate my machines I calibrate the the full distance of each axis and I re-calibrate at least 7 times to check repeat ability at full length. Does your software have the ability for compensation adjustments
I’m using cambam for gcode generation and tinyg G2 firmware to drive the stepper with chilipeppr feeding it gcode. Probably don’t have compensation adjustment anywhere in there that I have seen. I did measure the full length travel moves a half dozen times or so with no variation so reasonably confident it’s not missed steps. I am only doing 8 microsteps so perhaps holding position for very small moves is just out.
I use CamBam for design work and G-Code and I use mach3 to run my IM483 drivers. I know mach3 has compensation capabilities. I don’t know much about Tinyg G2 firmware or chilipepper other than some of my friends have had similar issues as well as issues with arc movements and look ahead capability. If you calibrated the full length with good repeat ability in the full length it might be what you mentioned about small moves sorry I don’t have an answer for you
Just ran another job after levelling the bed, and all the tweaks above. I homed Z to zero at the bed surface and tried to cut the piece and once again it dived into the bed on the last arc through the piece. Everything else looked great, even got the triangle tabs working this time, but as soon as it bites into the MDF it all goes to hell.
Have you tried adding ramping in and out using Cambam?
Yup this is with a spiral ramp. I’m begininng to wonder if its the ramp causing it to be honest!
can you send me your file
You do have a spiral set but you don’t any angle of approach which could cause an issue
try adding a lead in and a lead out of 10 to 15
where is says spiral angle
I thought that but then I checked this http://www.cambam.info/doc/plus/cam/LeadMoves.htm and it appears a 0 spiral angle essentially spreads the lead in across the entire pass then does a final ‘levelling pass’ at the end to flatten the bottom.
You can email me if you like
Try adding a number instead and also reduce the depth of cut per pass by 25 percent
Guess I can try that tomorrow.
Though I have done similar cuts at further reduced DOC and had the same issue. I’m also not convinced its a DOC issue. The R7 I know handles cuts deeper than this, and the rest of the cut performs great.
This also only occurs at this last tab and at no other point, and it also doesn’t matter where the tab is just that its the last tab on the cut before the final arc. I guess potentially this is the inner part thats attached to the tab vibrating and causing an issue since this only happens right at the very end when the part is only supported by the tabs. I could try adding more tabs I suppose.
Anyway, that’s enough noise the garage for one day, will try again tomorrow. Thanks for helping me debug!
