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machine safety limits

fella

Plastic
Joined
Jul 29, 2004
Isn't their usually saftey limits set on CNC lathes to keep the turret from crashing into the chuck.Our new one just did.
 
Hi,

if you want to prevent your machine to make a second crash you might be interested in some features like:
- collision detection
- detection of overload conditions
- avoidance of overload iduced tool breakages
- reduction of secondary damage
- wear monitoring
Have a look at www.prometec.com. We can help you to control this manufacturing process.

Alex
 
Unless there are aftermarket or added options, the answer is no. The reason for this being as such. many CNC lathes have chucks, and also collett adaptors that can be changed off at the spindle. Most collett adaptors, from my experience, are a bit shorter than the chuck.

The situation with chucks is also this. There are chucks that are wider (deeper) than others, depending on manufacturer, though I believe there are now some standards in place. The next thing is chuck jaws themselves, which can range from 1/2 inch thick (soft jaws) to over three inches in thickness (borable soft jaws - steel or aluminum). Hard jaws also vary a bit on height for different manufacturers of chucks.

There is also the difference in tool mounting positions and type of tools, from boring bars to RH (to the spindle) tools, and left hand tools (away from the spindle).

There are also work shift setting coniderations, as there are some people who maybe have a workshift set off a tool, others set right to the "turrett face" of a drilling holder, such on and so forth.

As I recall, there are ways to "set limits" in the software, control setting (Cincinnatti has a control where you can st a tool change position and max travel to the chuck with just a quick tool positioning and a button push - seperate fom the program, an in some cases, over riding of he program, meaning hn you call the tool number, the machine automatically returns to your set position first, thus will NOT change in a bad position - provided you set this FIRST) and even programming on many machines. I can look this over at some point on both of my lathes, and get back.


Darned frustrating when machine "chucks up", been there, done that.
 
Don't know about the rest, but all Okuma lathes have had a chuck barrier function for the last 20 years. Simple thing to use, in that you just enter some x and z values in the neighborhood of the chuck, and a tool won't enter this region. obviously, you can put a longer bar in some position and not redo the offset, and the bar can still hit the chuck, so its not idiot-proof. The function can be turned off for setup work and then re-enabled when you're ready to run. On their 4-axis lathes, a similar system is there to prevent collision of the upper and lower turrets when doing 4 axis cutting in close proximity. In my experience, they're as crash-proof as a lathe can be unless someone does something stupid to defeat the system.
 
I second metalmuncher's Okuma experience.

Those machines (and probably all the other decent CNCs out there) have mechanical limit switches fixed onto the ways to stop further movement of turrets, slides, etc., should the software limits fail. You could move these, but it's not a very good solution, since the axis drives and machine control will be tripping out more often than you'd like. Furthermore, you would always have to be monkeying around with the soft limits everytime the workholding or tooling changed, as spope mentioned.
 








 
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