SFA

We are in the middle of fabricating a job in a stone called Bronzite which appears very hard. Looks like there may be a significant amount of Iron in this stone.. My stubbing wheel has taken a beating already just trying to get the netting off in order to do a lamination.

I've read that I should slow the feedrates and rpms down when cutting harder stone.
The specs for the Ogees I will be using say I can run rpm 5000-6000 and 59"/min to 118"/min feedrates for diamond 1.

In slowing down a bit for hard stone would I simply choose the lowest rpm and feedrate in the spec sheet or should I be going even lower?

Also, any advice on how I should be running my fingerbit. I currently run at 5500 rpm and 12"/min in most other stone.. It is a 5 segment diamut bit.. Looks like some diamonds have already been knocked off after cutting just one radius..

Any help would be greatly appreciated!!!!

Thanks

N.

I will throw out there that you will probably drop your feedrates and rpm 20% for a rediculously hard stone like that. On other hard stone we would drop about 10% for both but if it is crazy hard than 20% may be the ticket.

At the same time your tools will still take a beating. Most likely need to use some carbide sticks to open the tools back up as you are running. Especially ogee. It is going to glaze like hell.

I can't speak for your machine, I don't know what you are running, but on our Intermac Master 43 I can slow things down on the fly. Its often on harder material I'll drop my speeds by 10-20% or even more on my milling tools (fingerbit and cali wheels) as much as 40-50%. I typically use the amp draw as an indicator and try to keep it in the "sweet spot", but that will be specific to your tools and your machine.

Train your ears, if it doesn't sound right chances are its not.

We are running a maxima brembana..
I can slow down the feed rate at the machine but the RPMs I have to set when programming..

Anyways thanks again for the replies!! After toasting 1 fingerbit, I have slowed the second one down by about 20 percent and it appears to have survived the first run just fine! Amps are way down too!

Thanks again!

Some materials I even resort to step cutting not to chance the piece moving.

On your Maxima, is the controller a Fanuc or an Osai controller?

If it's Fanuc then the knob next to the feed rate is the knob for the rpm's. You can drop it to 80% while its running.

I'm not sure about the Osai controller.

If you do drop your feed rate you have to drop your rpm's also or else you will glaze your bits really fast. The stone needs to pulverize and rub against the tooling to wear away the metal exposing more diamond. If you slow the feed rate down too much then basically the only thing hitting the stone will be just the diamonds which will wear them out and they will flat side i.e. glazing.

Dropping the rpm's keeps the core touching the stone so it can wear away also and keep you running.

Our machine has a fanuc controller,

However, there is only one other knob directly under the feedrate knob and it adjusts the rapid movement rate. It has no effect on the RPMs.. unless there is some setting in the controller to allow this knob to adjust the RPM instead of rapid movement speed..

below the jog key on the Fanuc's you will see 2 keys with a + and a - on them. These will drop your spindle speed while working.

I usually dress tools before each tool run and add an additional "step" on pos1 of about 2-4mm. As others state slowing down feed rates to keep amps in the sweet spot....about 25% or below on our bavellonis.

Thats wild. The second knob on our machine changes the rpm's of the spindle. Also the + and - keys change the radius of the tools you are running if they have a wear factor programmed into them, otherwise they do nothing on our machine.

Maybe a call into CMS will be in order then. Have you tried turning the other knob while the machine is running? Give it a shot. The machine should pause for a half a second, change rpm's, and then continue with its machining.

they took off the spindle speed knob after your vintage and before mine. Too many people destroyed tools with that knob. it can be dangerous. The function is still there, but it is kinda hidden in the Fanuc Keys that no one seems to ever use.

In the manual for my machine it shows that the knob you are talking about should control RPMs... I've got an email to CMS to clear that up.. In the meantime I will try the +/- keys on the screen.. I think they are the ones that look like tool cones?? I'll try to find it in the user manual..

Thanks again to all!!

Steve A wrote:I can't speak for your machine, I don't know what you are running, but on our Intermac Master 43 I can slow things down on the fly. Its often on harder material I'll drop my speeds by 10-20% or even more on my milling tools (fingerbit and cali wheels) as much as 40-50%. I typically use the amp draw as an indicator and try to keep it in the "sweet spot", but that will be specific to your tools and your machine.

Train your ears, if it doesn't sound right chances are its not.

Exactly what i did on the last Bronzite we machined. I think I ran 60% of normal. I also dressed the wheels for each work piece. that stuff is so hard it glazed the wheels really bad.
M