I have about a 90% success rate in cutting a square with either a 1/8" end mill or a 1/4" end mill. Without going into detail about my very simple design, I draw (in Carbide Create) a single line square. I then choose either of the above tool bits to cut out the square (outside offset) to about a 8mm depth, i.e. the depth of my workpiece. However, every so often, I can hear the end mill chatter slightly, usually along the bottom x axis. It then fails to cut to the end of the line and turns northwards before it should, thus ruining the cutout. This chattering usually occurs at about 2 - 3 mm depth.
My thoughts (probably wrong…I’m just a beginner) are that either the end mill bits are blunt, or there is some sort of problem (wear?) with the horizontal drive. Can anyone throw any light on this? At the moment, I am scared to try and cut out my workpiece using the end mills. Instead, I have resorted to removing the whole workpiece and cutting out the relevant square using a bandsaw.
where possible avoid slotting and add geometry and cut as a pocket
and/or
and consider leaving a roughing clearance and taking a finishing pass.
When was the last time you did maintenance to your machine? Lubrication on moving parts is very important in keeping things running properly. I had a problem not quiet the same as yours and realized that I hadn’t lubed up my ball screws in a long time. This could be your troubles. Then again you could have issues with equipment as well.
It sounds like the machine is chattering and then losing steps in its location. That would explain why the tool is moving in another direction much sooner then it was programmed to do. Check you driver motors for looseness and lubricate your ball screw bearings if you have a ball screw machine. If you have drive belts, check your drive motors, and belt for proper tension. Lubricate all that needs lubricated. Many times we find out that some of our issues with our machines are do to lack of maintenance on them. I never really think about it on the big metal CNC machines at the machine shop. They have Way oil reservoirs that hold constant oil pressure to the Ways, and as they move, the pump pushes a little bit of oil along the Ways each time they move.
Good luck.
Thanks for the info. We (Carnoustie Men’s Shed) have a donated Shapeoko 3 CNC which has only recently been used by me after I realised it had been lying idle for some months. The previous user had since left our small community so I had to learn from basics. Your post led me to look at the drive belt set-up and I found one of the Delrin V wheels seemed to be binding. Apart from the fact that the wheel was not quite making contact with the carriage rail, it also seemed to have a very “iffy” bearing in it. Anyway I moved it closer to the rail using the acentric adjusting screw and lightly lubricated all the carriage rails of both X and Y axes. I will also lubricate the Z axis worm when I get some suitable grease. I was wondering whether Vaseline (liquid paraffin grease) would do.
I prefaced the above steps with a thorough vacuuming to get rid of all dust. This will represent, I think, its first “major” service. I will only know in the next few weeks whether my problem with stuttering has disappeared, but your post was a timely reminder of the necessity to keep on top of such things.
The aluminum V rails should need lubrication (the Delrin V wheels are self-lubricating) — just keep them clean.
For the Z-axis linear rails/blocks you will need Mobil Vactra No. 2 which would also be used for the ball-screw on an HDZ, but if you have a Z-Plus then the anti-backlash nut should be self-lubricating as well a concern about lubricant is it will attract dust.
See:
https://carbide3d.com/hub/docs/maintenance/
for the official statement.
The big thing for an SO3 is that a Maintenance Kit:
will let one rebuild a machine to like new.
If need be also get:
and:
for any other needed parts see:
and everything one needs to know should be at:
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