Re: Need help brainstorming a solution for this mill turn spindle
Good thinking on the 45, 90 and 180 indexing and and 1:1 drive.
If I was going to cut gears with CNC I would use a conventional form gear cutter and just index the blank under CNC as usual.
In my opinion having idlers that pull in close to one another does mean you need to have a longer belt to give you a gap between the servo gear and the 4th axis gear...…..the idler diams also need to be big enough to not stress the belt due to a pointy back bending and if the belt slackens from stretch etc the adjustment also needs to allow the idler to get closer in.
I think that you only need to have more belt radial contact on the driver and driven pulleys if they are small like as in the EBAY 4th axis offerings at 1:6 reduction with a very small drive pulley and a large driven pulley...….that setup would benefit from a largish idler or two between the pulleys......you wouldn't want to attempt milling even aluminium with one of those......wood carving perhaps.
At the end of the day how much tightness is sufficient to just cater for indexing accuracy.....I don't think the belt will stretch in just turning the 4th spindle while indexing......the brake you favour will no doubt hold the spindle once in position against milling cutter forces...…...but when you mill on the move the brake won't be functional so the spindle can kick back.....probably not a problem on a finishing pass.
I considered the aspects of milling with a 4th axis for quite some time and decided on the resilient worm drive as it covers all aspects of both indexing and milling without having to add a braking force etc.
Ian.
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Re: Need help brainstorming a solution for this mill turn spindle
couple revisions later, its working pretty well. built a pneumatic disk brake for locking the spindle during index milling, very rigid now. it was pretty useless for index milling without it. A servo simply cant hold a rigid position when geared 1 to 1. Today is the first time running some parts continuous with the bar puller and m98 sub. still need to setup the multi channel coolant. With this setup ive turned aluminum, brass, 303 stainless, and titanium. Wont handle crazy removal rates without chatter, but plenty fast for the size of parts i work on. Think i was peeling off about 5 cubic inch per minute in aluminum. Faster than i can go with my milling spindle. Tolerance on diameters is pretty impressive. A mostly aluminum machine in a sealed insulated enclosure is very controllable thermally. When running continuous, the enclosure stabilizes at 82F, so thats where i keep it 24/7 with just the lights. Holding diameters at about 2 tenths continuously. Sorry for the crappy video quality. need to figure out how to lock the focus on my phone
https://www.youtube.com/watch?v=1SJS...AWUnfsmKtlYoto
https://www.cnczone.com/forums/attac...d=425260&stc=1
Re: Need help brainstorming a solution for this mill turn spindle
Well that's just fantastic. You've gotten that thing functional in a remarkably short amount of time considering all the features.
Care to share photos of the whole thing? I'm particularly interested in the brake and collet closer.
Re: Need help brainstorming a solution for this mill turn spindle
Looks like you did a great job. Quite a project. Would love to see a wider view of the whole machine.
Re: Need help brainstorming a solution for this mill turn spindle
Yeah I'll post some more pics in a minute here. Hard to show the inner workings of the spindle assembly so I'll post a couple cad pics too
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Re: Need help brainstorming a solution for this mill turn spindle
