[Cartierusm]

Ok I've asked a few of these questions before and never really got a good answer. So if some one could help I'd appreciate it.

First off will a ball mill for metal work fine for carving maple? I've used it and it works good but I'm just wondering if it cuts with the same sharpness or whatever, should I be looking out for anything?

Second can an end mill with carbide insert for metal work just as good as a regular wood router bit? I'm guessing it can as the replacement cutter heads for jointers use carbide inserts.

[ger21]

The geometry will probably be a bit different, and the metal bits probably won't cut as aggresively, but as long as the cuts are clean, go ahead and use them. And btw, you can get insert bits for wood too. Amana make a bunch of insert CNC tooling for wood. We have a few of them at work.

[Cartierusm]

Hmmm....how did I know Gerry was going to be the first one responding..HEE HEE. Thanks, Ger. That's what I thought but I'm really anal about things and I'm by no means an expert. I'll check out the Amana dish washer site...the only problem is they are super expensive but they do make dedicated CNC wood Tooling.

[Cartierusm]

Ger, what would you recommend out of the amana line of insert bits? The bits are anywhere from $80 - $115 and the inserts are $1.50 - $5.50. Do you thinks it's worth the extra money than a regular metal insert bit? How long do the amana bits last as opposed to the carbine insert metal ones?

[ger21]

I've never used any metal cutting bits, so can't compare them. How long they last depends on what your cutting. We cut a lot of plastic laminates on mdf and particle board, which can be pretty abrasive. The one I use the most is the RC-2154. The inserts can be used twice, so for $5.50 it's $2.75 per edge. I use it at around 125ipm at 17,000 rpm.

I don't feel real comfortable making recommendations, though. Different applications can require very different tools. What exactly are you looking to do with these tools?

[Cartierusm]

I build guitars, so lots of maple, rosewood, ebony and mahogany. I was using a 1/2" Whitesite bit today cutting the headstock .1875 depth per pass and it left buring marks. I was running it at 15ipm. It was plowing through solid wood and when I raised it to 20ipm it seemed too fast, this was only a guess. The router didn't seem labored or the bit but I'm afraid to run it faster for fear of hurting the machine or part. I mean what makes a machine be able to plow at 125ipm? What's a good test? I am using 425oz Keling motors with a 24v PS, the machine is pretty solid and all aluminum. I'm using a full size bosch router. I alway though that if the motors weren't strong enough I might lose steps without knowing? Any help on figuring out feed speeds for this size bit? All my other bits I have no problem calculating speeds.

[ger21]

IMO there's really no reason to cut slower than 100ipm. The limiting factor will probably be your router slowing down. But at higher speeds, you may need to watch for missed steps as well, if you don't have much high speed power. If the roputer slows down, decrease the depth of cut until it doesn't slow down. But 3/16" should be fine. I personally would prefer a spiral bit for cutting hardwoods. A chipbreaker is even better, but that are expensive. But they'll let you cut faster with less load on the router.

[Cartierusm]

Well I really can't go fast than 36ipm with my cnc anyway, so 100ipm is out. I also was chipping the wood THIS time, so I think I just have a dull bit.

[ger21]

Avoiding tearout (chipping) can be very tricky when routing hardwoods. You need to be very aware of grain direction and plan your cut direction accordingly. At work I have the ability to use left handed tools, which comes in handy at times when cutting hardwoods.

At 30 ipm, you should be using a 10-12,000 rpm spindle if you want to minimize burning.

[Cartierusm]

Hey Ger, I ran it faster at 36ipm, my fastest, and it seemed to do all right. The gantry was a little jerky from the weight moving around, but the cuts seemed to be the same. I was running it at the fastest RPMs which is 25,000 and the burning was a little less but still pretty bad. So at 36ipm I should run it at 12,000 rpm?

I was having some problems with some grinding sounds from one of my motors, loosing steps, I took the motors off and determined that my ball screws weren't working correctly, so I'm going to take them apart and clean them. Is the motor still good, how would I know if it's taken a toll on it?

[ger21]

You probably should work your way down slowly, checking along the way to make sure it's cutting OK. Start at around 18,000 and work down from there. What size bits are you using? small bits might need to spin faster than 12,000.

If your using steppers, you really can't damage them, unless you take them apart.

[Cartierusm]

Well I unclamped the ball nuts and checked them they spun OK, but some saw dust was covering them. I think it might have been the spring I use to separate the 2 ball nuts that might have bound them. They spun fine on their own. I didn't take them off as that's a huge PITA. When everything's together I can turn it by hand of course and it seems as though it's like it was when I first built it. The stepper definately doesnt' run as fast as when I first built it. I originally has it set at 48ipm, then over that past day or so I've lowered it to 38ipm until it stopped making the crunching sound. It is direct drive. I wonder if I should up my power?

Question: when I add more voltage does that increase the torque thorugh all rpm ranges? Right now I'm running it at 24V but can go as high as 80V with the drivers I'm using, All though I'm very gun shy as when I tried with my last set of drivers to up the voltage they all blew, NOT my fault I think the drivers were bad from the begining.

I've got all my other bits dialed in as far as IPM, I use bits as small as .0156". The particular bit I'm talking about is a 1/2" bit, so I'll start at 18,000 or so. Thanks Ger.

[Cartierusm]

Thanks Ger, slowing the bit down helped, I'm getting almost no burning now.

Question: when I add more voltage does that increase the torque thorugh all rpm ranges? Right now I'm running it at 24V but can go as high as 80V with the drivers I'm using, All though I'm very gun shy as when I tried with my last set of drivers to up the voltage they all blew, NOT my fault I think the drivers were bad from the begining.

[ger21]

Question: when I add more voltage does that increase the torque thorugh all rpm ranges? Right now I'm running it at 24V but can go as high as 80V with the drivers I'm using,

No. At zero rpm, torque will be the same. But the torque will fall off less as rpm's increase. A general rule of thumb, is that if you double the voltage, you'll double your top speed.

[Cartierusm]

So the torque stays the same but is spread out over a larger range. Instead of 425oz at 0-38ipm, it goes to 425oz at 0-76ipm using 48V 6.5Amp. Is that correct?

Another question if you don't mind as I want to get this modifided by tomorrow. I have keling 8078 drivers I have never been sure about the current setting. I have 3 keling 425oz steppers and I'll be adding a 48V 6.5 amp power supply, the motors are wire Bipolar Parallel. What should I set the current to on the drivers? Also can I keep the same wire; will it handle the load, I'm using 18AWG. Thanks again.

[ger21]

So the torque stays the same but is spread out over a larger range. Instead of 425oz at 0-38ipm, it goes to 425oz at 0-76ipm using 48V 6.5Amp. Is that correct?

No. It's only 425oz when it's not spinning at all. As soon as it starts spinning, the torque starts to decrease. The faster you go, the more it decreases, until you reach the rpm that the motor will start missing steps because the torque is too low. When you increase the voltage, the rate that the torque decreases is lower, so at any given rpm (up until you start losing steps), you'll have more torque with more voltage.

Another question if you don't mind as I want to get this modifided by tomorrow. I have keling 8078 drivers I have never been sure about the current setting. I have 3 keling 425oz steppers and I'll be adding a 48V 6.5 amp power supply, the motors are wire Bipolar Parallel. What should I set the current to on the drivers? Also can I keep the same wire; will it handle the load, I'm using 18AWG. Thanks again.

I don't now anything about those drives, but typically, you set the drive to the motors rated current, or slightly less.

The 18awg should be fine. You can probably go as small as 22awg.

[Cartierusm]

Ger, I knew what I meant but didn't express it correctly, but I understand. Thanks.

As for setting the current my motor specs say 4.17V 2.8A for Bipolar Parallel. So even though I'm increasing the voltage the Amps will stay the same? I've attached the motor document so you can see..Again I really appreciate all the help you've given me.

[ger21]

Yep, always 2.8amps

[Cartierusm]

I don't know if you read my posts on the problems I had with the keling 5057 drivers but everything worked fine with 24V then when I hooked up 48V some of the drives blew and others didn't.

Just for clarification changing out power supplies is just as simple as it seems, no other DIP switches on the driver, break out board or anything else? I know you don't know these drivers but there are only DIP switches for Current, Steps and standstill current. So I should be able to just wire it exactly the same and it should work?

[Cartierusm]

OH JOY!!! The Upgrade works....I was real nervous today because last time I tried to up the voltage to different drives they blew. But everything works YEE HAA.

Only one problem I tuned the motors and then reran one of my programs at the same speed I was using before but now after a minute or two it trips a limit switch even though it's no where near one. Is it just more electrical noise from the bigger power supply? What the solution, ground the power supply to the chassis of the CNC or control box?