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How close do you rapid?

At the last shop I worked at I believe we would rapid in to .05 on Z on most jobs. Usually not any closer. Some of the CNC machines supposedly had enough inertia to overshoot when they came to a stop

Our Cincinnati horizontal mills we would give about 1/2 an inch or more. Sometimes it took a second for the hydraulics on those to slow it down after it tripped the dogs on the side of the table. Scary when one of those cutters slams into the part and explodes - better have your safety glasses on there!
 
For most of our work, I let the Mazatrol default determine the clearance planes on our Quick Turn lathes---which is 2mm (.080" is how I remember it) in X and Z.
The most common one to change is for a boring bar, often you don't have .080" to back up down inside a hole!

ToolCat
 
On lathes I rapid to within .1" on X and .05 on Z.
On mills, I rapid Z down to within .250" with a jump height of 2" to clear clamps and whatnot.
You can crash a lathe all day long, but crashing a mill will cost you big $$$

last time I crashed the lathe it cost a $20k subspindle... dont underestimate me! lol!

Im seeing some patterns here, awesome feedback!
 
For most of our work, I let the Mazatrol default determine the clearance planes on our Quick Turn lathes---which is 2mm (.080" is how I remember it) in X and Z.
The most common one to change is for a boring bar, often you don't have .080" to back up down inside a hole!

ToolCat
Yeah, that got us on the qtn250 the first time I was boring a teeny tiny hole. Shortly after had my center drill shatter and stuffed my sandvik boring bar right into oblivion before I could hit the estop.
 
It's actually the opposite from what I have seen in different shops. Lathe crashes are a lot more costly than mill crashes. They can be catastrophic.
Yeah. Working in a Haas shop, it’s like this. Run an end mill into a vise and smash it to pieces, you’re probably ok. Might have an extra tenth of runout, what’s that matter on top of the already atrocious Haas runout spec.

Run a boring bar into a part with no hole, or index a turning tool into the part at 5% rapid, and you’re looking at $4000 to realign the turret/ways.
 
Yeah. Working in a Haas shop, it’s like this. Run an end mill into a vise and smash it to pieces, you’re probably ok. Might have an extra tenth of runout, what’s that matter on top of the already atrocious Haas runout spec.

Run a boring bar into a part with no hole, or index a turning tool into the part at 5% rapid, and you’re looking at $4000 to realign the turret/ways.

Yes, if you side crash on a mill you're most likely fine, you just shear the end mill off at the holder. But if you crash in Z, chances are you're replacing the spindle if it was full rapid.

Lathes are far more robust. We had a small Mazak, the guy crashed it every god damn day for months, the machine never came out of alignment. We have Mori's and Okumas that have been crashed a few times each, some minor in-house alignment and we're off and running. We did have one HUGE crash on a smaller Okuma lathe though that cost us quite a bit of money.
 
I like to see .1 on all my feed/return planes. It's a good round number. I can see it matches my position with a glance. I don't need to get my calculator out to see if distance to go is a crash. .15 with a feed plane of .1, is pretty easy to understand. .125 with a feed plane of .05, takes a second to interpret mentally. But I'm basically retarded, sooo?

R
 
I use .060-.100" for clearance values, including raptor fixtures, custom fixtures, vises, and other work holding such as palletized pieces on machine pallets, or from Schunk and System 3R because I know exactly what and where they are in my machines and in model space in NX.

I am fortunate to be able to program machines capable of linear positioning so I can keep the tool down when and where I want. Typically it is .060-.100" but if a situation requires tighter amounts, I have used .025-.030" clearance. And that is deep down in 3D part geometry.

As long as I set the right options, verify my results, and the operator and tool crib persons do their jobs correctly, I am 100% confident in zero collisions.

Programmers do need to be mindful of lesser performing machines' capabilities, especially some lower end machines that have relatively high rapids speeds. Servo lag can be severe and the .030-.060 that's fine for one machine may leave the tool clipping the part on a lesser machine, in which case .100 or more may be your friend. If people quibble over that amount is too much for their runs then they really should look at higher performing machines.
 
Not just lesser machines....on one of my BBT30 machines with an 0imF control and fanuc Alpha pack with 60 metre rapids, it caught me out rapiding while down inside an enclosure.
Just kissed (couple of thou) a lug at 25%, took a bite at 50% and made a hell of a twang at 100%.
No fanuc parameter available to tweak following error or anything - it is what it is....the only solution was to rapid up clear to day light and then continue....
Yes! We also need to be careful of machines that appear to position in a linear fashion but really don't. I believe Fanuc controls with HPCC, and other similar configurations, rapid in varying arc moves in an attempt to be smoother and/or faster and obviously this poses issues for programmers. Some control revert to true linear positioning with their high accuracy modes turned off, which is great because we can easily modify a post to turn off those modes for positioning. There are some exceptions such as some older high performance controls that revert to "hockey stick" moves when their high performance option is turned off, such as old Makino Pro controls and turning off SGI.
 
wtf what? A mill spindle will cost you $30k easy and the machine will only be down for a couple of days if you're lucky.
You pay $2k to have them come in and realign the turret. Which one do you choose?
I've seen some really bad mill crashes and most the time things line back up. Lathe crashes, if it's a small crash a turret might get bumped but a big crash can put someone in the hospital not to mention completely scrap the machine. What comes to mind as big crash is big parts coming un-chucked at high speed wedging between the spindle and turret. If it's a box way machine hopefully only the easy stuff moved and nobody got hurt but if it's a linear guide machine you can bet every rail is completely bent.
 
On lathes I rapid to within .1" on X and .05 on Z.
On mills, I rapid Z down to within .250" with a jump height of 2" to clear clamps and whatnot.
You can crash a lathe all day long, but crashing a mill will cost you big $$$
I agree with your parameters. I use the same to a "Tee".
But I disagree on your crash outlook 500%!
 








 
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