New 5 axis

[CNCAddict]

I think for the rotary axis you would be better off using very large timing belts. It would be very hard to get a geardrive to work with no backlash, and gears would need to be protected from the cuttings much more so than a belt.

[wisp]

Originally Posted by flinty Rob, just read this thread today, I am in the process of designing a new cnc machine to do 3 D carving my budget is up to $50K to get it right first time. But the question I have is why 5 axis surely 3 can do most if not all of the required jobs a 5 axis can do or am i seriuosly missing something. I believe that if I can interpolate all 3 axis similtaneously what advantage coud the other 2 axis add. I realise this may sound dumb to most of you but please indulge me chris

One simple thing is drilling a hole at an angle. With a 3 axis, you got one option, straight up and down. Another easy one is bevels. A five axis makes it quick and easy to tilt your tool at say 45 degreee, and cut a long bevel with a standard endmill, in one pass. You could 3D surface a bevel, but it would take many passes, and the finish would not be as smooth.

The real trick is generating 5-axis G-Code. Simple positioning of the A-B axis and then cutting is pretty easy, but simultaneous 5 axis movement is VERY difficult. I use EdgeCam at work every day, and even with $20k dollar software its diffucult.

Rob, have you thought of making the spindle tilt in one axis only, and adding a large rotary on the table face up. This would make designing the head much easier. Also make sure you have some locking bolts for the 4th/5th axis to get the more rigidity when doing 3-axis only milling.

Michael

[spoiledbrat]

I had no idea how much the software would cost to run these 5 axis. Building/machining them seems straight forward, I think helical gears would eliminate some backlash. Seems like I would do better to go with a 4 axis and leave room to upgrade later.

I am thinking once more about servos instead of steppers. Can anyone give me a reasonable estimate of what motors it would take, and the cost of these servos/controllers/and the power supplies? I think I can keep the gantry (with tooling) below 180 lbs. I want this thing to jog fast, and cut wood at whatever speed delivers an acceptable finish. Is 40 fpm a rediculous number? I saw a production machine do at least that.

[ger21]

Originally Posted by spoiledbrat Is 40 fpm a rediculous number? I saw a production machine do at least that.

Our router at work will cut 10 meters/minute, which is about 32 fpm. It won't move any faster. Some production routers can cut at 2000 ipm, but they are quite expensive (~$200,000). It is probably achievable, but it will be expensive. You'll need big servos, and high lead ballscrews (or rack and pinion).

[CNCAddict]

I think for very high speeds a chain or belt drive would be the least expensive. Ballscrews that large would be super $$$ and a rack and pinion is pretty costly too.

P.S. if anyone knows of a cheap source for rack gears...let me know

[Splint]

As far as 5 axis software goes, you don't really need to spend the big bucks to buy it, there are places around who can for a fee process the cad drawing of a part and generate the code to run the machine. Dig around a bit and see if you can find someone who can do this for you and see how much they charge, they don't even have to be local to you as the could be half way around the world and transfer the files over the net. Some of small shops do this if they dont have a person or software who is able to produce complex code for things like molds. There may even be somone here in this group willing to help you out who has access to 5 axis cam software at their work. It's worth looking into before canning the 5 axis project.
Cheers
Splint

[Khalid]

Soon plunge into making 5-axis machine.. The completion deadline will be 2 Months...