1) If I import a file that has spindle speed of 18k and a feed rate of 240 ipm but my spindle (which has RPM control through my Acorn CNC controller) can only do a max of 3k RPM, will acorn give me a warning to tell me there is a difference between the requested RPM and the actual RPM of the spindle? Also, is the RPM displayed on the screen when a program is running? Would be nice to confirm it's what is expected...I looked while a job was running but didn't see it.
2) Are there any good charts for calculating spindle speed and feed rates? My motor has a max RPM of 3k and I would like to practice cutting soft material like wood before I try aluminum. I tried Azek and wood today but the Azek was gumming up and the wood was getting burned despite setting my spindle to it's max RPM and slowing the feed rate. Figured I would be safe running it slower but made me nervous to increase the feed rate.
3) My vertical Z-axis doesn't have a cover for the linear screw and in my limited experience running projects it's clear that a lot of material will end up on the screw and this will become a problem over time. I tried contacting THK looking for a cover for the slide with no luck. Are there suppliers of covers or is there a way I can make something myself?
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brightnight wrote: ↑Tue Feb 21, 2023 12:52 am
1) If I import a file that has spindle speed of 18k and a feed rate of 240 ipm but my spindle (which has RPM control through my Acorn CNC controller) can only do a max of 3k RPM, will acorn give me a warning to tell me there is a difference between the requested RPM and the actual RPM of the spindle? < No. M3 S18000 command with max RPM set to 3000 will result in 3000 RPM > Also, is the RPM displayed on the screen when a program is running? < yes, you have several choices for RPM display, Actual RPM measured from and encoder on the spindle, or measured from a hall effect sensor, or if the machine has no RPM sensor, Display programmed S command rate with the override % taken into account. you can even set it up so it displays both. > Would be nice to confirm it's what is expected...I looked while a job was running but didn't see it.
2) Are there any good charts for calculating spindle speed and feed rates? My motor has a max RPM of 3k and I would like to practice cutting soft material like wood before I try aluminum. I tried Azek and wood today but the Azek was gumming up and the wood was getting burned despite setting my spindle to it's max RPM and slowing the feed rate. < plastics are tricky but you can find the right cutter, speeds and feeds to cut them, trick is to cut it fast enough that you are not just heating it up and therefore melting it and gumming it to the tool. > Figured I would be safe running it slower but made me nervous to increase the feed rate. <plenty of info on line about speeds and feeds, this can take years to fully master. AL likes high rpm with the right cutters and high feedrates with lots of coolant. some users report that they like the free speeds and feeds calculator from cnc cookbook. https://www.cnccookbook.com/cnc-feed-rate-calculator/ >
Thanks for the reply and the link! I would love to pick up a high RPM spindle for wood and plastics. Really like idea of the spindle you linked has the same ER20 collet as my motor. Guessing I'd also need a VFD to get the 220V from a 120V outlet. Hard to know what's good and what will last with so few reviews, that link only has one review and three ratings. Are there any preferred brands for high RPM motors or has the one you linked worked well for people? I had heard HUANYANG was decent and something like this but hoping to use others experiences as a guide: https://www.amazon.com/gp/product/B07BB ... uage=en_US
If I can find something that runs off the 48V supply I have setup now or something simple to power that would be ideal. The ultimate goal of my build was to cut aluminum parts (I will probably do wood and plastics too though) so I thought buying a lower RPM motor for aluminum would be a good choice. Initially I thought my motor could also do very high RPM up to ~10k but I must've misread the website as looking back it only does 0-3000 RPM. My plan was to start with soft materials which will be more forgiving and work my way up to aluminum.
My motor is the 600W version: https://www.robotdigg.com/product/1751/ ... and+drill
Specs:
Size 60 NEMA24 BLDC spindle motor RD60ZK-4830
Power supply: 48V DC
Rated current: 12A
Wattage: up to 600W
Torque: 1.3N.m
Speed: 0-3000rpm
Runout accuracy: 0.03mm
Chunk: ER20
Net weight: 3Kgs
Wiring diagram for the 600W BLDC Spindle
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I machine only aluminum and HDPE on my CNC router and you’ll never be able to machine aluminum with that spindle. As Keith stated that’s not really a spindle but a drive motor converted to act like a spindle. That motor is suited for exactly what they sell it as, a motor for drilling pcb’s. Nothing more.
The O flute bits I use to machine aluminum and HDPE need to be spun at 18,000 rpm. You will also never machine aluminum at 240 ipm. As Keith also stated if you don’t get the feeds and speeds correct stuff melts and bits break. It’s a delicate dance with feeds and speeds. Look at buying Amana “O” flute bits. They are not cheap but they are amazing router bits. They will give you a speed and feed chart for every bit they sell as a great starting point. Not all machines are created equal and not all machines can cut the same material at the same feeds and speeds with the same bit. To cut aluminum cleanly and get a near mirror finish you need a rigid machine with the right sized motors. I’m not a fan of extruded frames but they do work to a point.
Look at buying a 2.2kw or higher air cooled spindle. There are “kits” all over the internet that bundle the spindle and VFD together for reasonable prices. I have a 4.5kw air cooled spindle and it’s muscles through aluminum with ease. I can cut 1/8” aluminum sheets in a single pass with a 1/8” bit. I cut all aluminum dry with no coolant.
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