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Why do cnc mills have so many tool slots?

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awaqa909

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#1
I've seen cnc machines with either 20+ to 30+ slots for tools. Some of the machines I've gotten to push buttons on, have had 5~ tools which some are half way full, but never used. I don't think I've seen more then 7 tools used for one operation. The machines that are kept somewhat empty then have tools on the outside on shelves and even the populated machines have tools in shelves around them....

I just don't get why we have so many tools around here, when it seems like so few get used.


The button pusher,
Awaqa909
 

dlane

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#2
I guess it depends what there making, or what they could make .?
 

macd55

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#3
I've seen CNC machines with upwards of 100 tool pots. They are production machines that run a variety of parts that are left setup for long periods of time. The ones I've seen are used mainly on aircraft parts and mainly on aluminum. There may be as many as 10 to 20 different part numbers setup on the machine at one time. They just have to call up a different pallet and program to change what they run. search matsura on google to see some of the up to date production machines.
I worked in aircraft machine shops for 40 years and have watch the evolution from manual machining to CNC. Things have changed tremendously through the years.

macd55
 

darkzero

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#4
In production, often tooling gets purchased for a specific job. Then when that run is done, some of that tooling may not be needed anymore for the next job. That run would have paid for the tooling. Some tooling can be specialities, used for one specific op & may never be used again. But you just don't go and dispose of it cause who knows what may come up in the future.

I can relate somewhat, I have automotive tools that I've only used once & haven't touched again in over 10 yrs. I really should sell but I don't like to sell any of my tools.
 

Tony Wells

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#5
In a large scale manufacturing environment, there can be advantages of multiples of the same tools. For example, there may be 6 identical 1/2" end mills. All preset with any tool offsets already assigned to that tool number. After years of running a part number, perhaps even in the millions, experience (or these days with semi AI) tells the programmer when the tool should be discarded in favor of a new, sharp one. The concept of "lights out" machining has given rise to different approaches including defining tool life and making a change to a redundant tool at a given point, or with some controls, when the load factor indicates that the tool has dulled and reached the end of life.

Or on the other hand, some parts are simply that complex and the machines are capable of carrying out many different operations using multiple spindles and at times this can require more tools than you might think.
 

cvairwerks

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#6
In our instrument shop, we would keep about 25 standard tools in the changer. All the programs were set to know those tools if they were needed. The last 10-20 locations in the changer were for job specific tools. The guy that ran our mill most of the time, would do an offset check every other week on the standard stuff. Made it real easy to switch jobs most of the time.

We did have a few jobs that took as many as 40 tools to run.
 

coolidge

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#7
To drill and tap 1 hole...spot drill bit, drill bit, chamfer bit, tap/bottom tap. You use up tool slots quick there are never enough!
 

T Bredehoft

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#8
To drill and tap 1 hole...spot drill bit, drill bit, chamfer bit, tap/bottom tap. You use up tool slots quick there are never enough
So if you have 6 different tapped holes in a project, how many tool holders do you need, just for that? BTDT, and differing milling tools for differing parts. The machine this was on was a vertical, with a table about 40 by 60 inches. (too long ago, don't remember who made it.) It didn't have enough holders, we left 10 open for additional tools.
 

coolidge

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#9
So if you have 6 different tapped holes in a project, how many tool holders do you need, just for that? BTDT, and differing milling tools for differing parts. The machine this was on was a vertical, with a table about 40 by 60 inches. (too long ago, don't remember who made it.) It didn't have enough holders, we left 10 open for additional tools.
6 taps, 6 drill bits, 1 spot drill/1 chamfer bit (typically you can use 1 bit for both) = 13. For milling you frequently have 1 roughing bit and 1 finishing bit, roughing bit to HOG most of the material out of the way as fast as possible, then you come in with your finishing bit to clean up. Extends the life of the finishing bit. And you may have 1-3 sizes of these.

I'm talking a production machine here where reduced cycle times are important. You try to keep tool changes to a minimum because tool change time over 5,000 parts adds up. Shops spend silly amounts of time talking to tooling venders about the latest new wave end mills of crazy geometry and coatings designed to reduce cycle times x% lol.

ALL the above ties way back to the design of your part and tool paths in your CAD/CAM software, to minimize as much as possible the number of tools and tool changes. For your tool paths you consider the order in which machining operations occur, so that you can line up your tools in the machine's tool holder in the proper order, e.g. so when the machine needs to change tools the next tool the program needs is in the adjacent tool slot not 15 tool slots away, again to reduce the time it takes to change tools.
 

TakeDeadAim

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#10
I can think of many machines with 30 or more tools that stay in the machine/get replaced when dull because of frequency of use. It's easy for programming if they are in inventory and ready to run. It tends to promote the right tool for the job.

With as fast as they change now tool change time is not much of an issue. Then you have multi spindle machines......


Sent from my iPhone using Tapatalk
 

RJSakowski

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#11
With a CNC mill with reproducible tool offsets, it makes sense to dedicate a tool holder and tool position to a particular tool, used for multiple jobs. You only load the tool in the tool holder and enter the offset once rather than doing it for each job.

It is the same principle as setting up multiple QCTP holders for a lathe. You can get by with the basic set that comes with the lathe but it is much more convenient to have multiples and dedicate a tool holder to a specific tool.

Especially in an industrial setting, where time is money, it doesn't take too long to pay back the cost of a tool holder.

As a hobbyist, we can get by without having a 40 position ATC but the cost is having to rewrite the tool table with each new tool requirement.

I have 26 assorted tool holders for my Tormach and six generic QCTP holders for the lathe and it isn't enough.
 

RJSakowski

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#12
I should add that having a large variety of tools in holders make the CAM part of programming easier and less prone to errors. The tools tables in the machine controller and the CAM tool table are synchronized so the right tool is in the right spot when the program is run.
 

Rustrp

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#14
I just don't get why we have so many tools around here, when it seems like so few get used.
Maybe the shop doesn't really need a CNC machine, or maybe this is indicative of the experience level of the programmer. In larger shops, especially production shops, time is money and it pays to have the stations full, even if some of the stations are duplicates. The programming capabilities of the milling or lathe centers would make a difference too. In today's production environment an insert may have a 15 minute machining lifespan which seem short but at the same time how many parts were produced by the insert. A tool change out takes time and it's more effecient to change all the tools or a specific group of tools at the same time, so some may have a little more time in use and some a little less, but there's no point in running a 100 parts past the tool life only to have the parts rejected.

I think it would be appropriate to ask the owner of the machine in question **the why** and then step up and show them how production could be increased by using more stations.
 

Wreck™Wreck

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#16
To drill and tap 1 hole...spot drill bit, drill bit, chamfer bit, tap/bottom tap. You use up tool slots quick there are never enough!
In practice one would use a 90 Deg. spotting drill of sufficient diameter for the chamfer and save a tool change, many spiral point taps will thread nearly as deep as a bottom tap in a blind hole, also rigid tapping with 2 taps is likely to end in tears.

Set up a lathe job today, turn and face tool, drill, boring bar, internal groove tool (thread undercut), internal thread tool. Flip part turn and face, external groove tool (thread undercut) and an external threading tool, this is 7 tools for one simple lathe part, didn't part them off as they were 3" diameter blanks cut from bar.

1 or 2 more features such as a knurled section, dovetail O-Ring groove or face groove would have made for 10 tools on a lathe part. Mill parts will often have many more features aside from multiple thread sizes including different sized reamed holes, pockets with different sized radii at the bottom (requiring different ball end mills), different sized radii on outside corners and location tools. You can not have enough tools in the changer.
 

sanddan

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#17
In production, often tooling gets purchased for a specific job. Then when that run is done, some of that tooling may not be needed anymore for the next job. That run would have paid for the tooling. Some tooling can be specialities, used for one specific op & may never be used again. But you just don't go and dispose of it cause who knows what may come up in the future.

I can relate somewhat, I have automotive tools that I've only used once & haven't touched again in over 10 yrs. I really should sell but I don't like to sell any of my tools.
The day you sell that tool will be the day you need it for the second time. I'm the same way, never sell a tool unless you upgraded to a better one. And sometimes not then either. LOL
 

markso125

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#18
I have run dual spindle horizontal machining centers with multiple pallets and 300 tool changers and I have used every tool in the machine a minimum of once a week. This was large scale production aerospace facility making all of the flight control units for large commercial aircraft, think Boeing 737, Airbus A330.

When you are making 100's of parts a week that the company sells at thousands of dollars each the company wants as small of downtime as possible. Companies like it when all you have to do to switch from one part number to another is load a different program and push a button to load the right pallet in the machine and you are running in a matter of min versus having to pull tool holders out, possibly load tools into the tool holders, reload the tools, set the tool height ect ect.

In reality when you are using 50+ tools for one part number tool changeover can be an all day job, especially when you use shrink fit tool holders. This is pretty much causing a machine to be sitting idle for 8 to 10 hours every few days just to change over to a different part in a production facility.

We could put it into a more monetary aspect, that same machine I ran the company put a price tag of around $200 an hour that they would charge to the customer for the use of that machine. If the machine was down 1 shift a week (10 hours) to re-tool for a different job that would be a total of 520 hours of changeover time a year, so lets do some simple math 520 hours multiply by $200 an hour comes to $104000 a year the company is loosing just on that one machine sitting, (we had 6 of those Okumas). Of course that is not counting the fact that nothing is being produced during that time so the company doesn't have a final product to sell so more money is potentially being lost on top of the $104000 a year.
 
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jamby

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#19
Most of my time was in a proto type machine shop doing less the 5 parts in an order. But when work was slow we would take on production jobs to keep the spindles turning. When we loaded up the drums with 30+ plus tools to do a large run job some of the operators found that a easy way to get out of having to change tools. So when you called up a tool it would be dull errrr. But in the larger shops I worked in they had a tool setter who would set special tools to the sketches from the NC programmers and we would have several of the same tool waiting in a cart. They also had a "carbide man" who would design special tooling for both lathes and mills.
Dang wish I still had him available!

Jim

Oh yeah, went on a machine check-out when the company was buying a Excello 5-axis machine and those guys made some BIG machines. They had 60 taper tool holders and special design milling cutters with thru the head coolant. These would bore two sizes set the shoulder and cut the face in one operation that looked much like a car wreck...
 
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