[Gene0552]

Okay, we have a disagreement here as to what is considered "chip to chip" time in machining. I say its the time from when the cutter starts one cut to when it starts a second cut. Any thoughts?

[One of Many]

Okay, we have a disagreement here as to what is considered "chip to chip" time in machining. I say its the time from when the cutter starts one cut to when it starts a second cut. Any thoughts?

This is just terminology, based on someones definition. You can call it a material removal rate, hogging, roughing or chip per tooth feed rate. You give your definition, but not the other side of the disagreement. Unless you can't agree with yourself. I do that a lot! :boxing:

This sounds too much like a tomatoe, tamatoe kinda thing. As long as you can discuss the concept in equal terms, why should it matter if one persons jargon is written in stone. There are many names for specific operations to which most people can be flexible enough to figure out as long as it is communicated well.

Language barriers are the toughest situations to get by.

DC

[jderou]

I think he is talking about tool change time. What I have been told is it is the time from when the tool leaves the workpiece, to the time the new tool has been accelerated to max rpm and is at the workpiece.

[Dan B]

Yes, it is a tool change term. The lower the "chip to chip" time, the faster the tool change. When considering all factors in a machine purchase, "chip to chip" time is not one of the more important factors unless you are running production jobs with a lot of tool changes. For the average "one off" application, this is seldom a value worth worrying about.

Dan

[lakeside]

when the cutter returns to r-plane and goes into a G0 move until the next cutter goes into a G01 move Your tool time, rapid moves for both cutters this is your chip to chip time

[Dan B]

Looks like the disagreement continues!

[One of Many]

Looks like the disagreement continues!

Given a little more clarity on the terms. I'd think that from the last chip of tool 1 to the first chip of tool 2 would be chip to chip.

Anything in between is "time" no matter what other wasted motion happens to get there? I can just see marketing people claim a faster time if they start it from some other point. Like not including the retract at feed rate to the clearance plane before a rapid as "not part of the tool change time" Heheh!

It makes me very happy I don't have to worry about such minute details.


DC

[jderou]

Actually, what lakeside said was pretty much what I meant.
In my environment, we have about a 40 second cycle time for one part, with 2 to 4 tool changes each cycle. It runs 24 hours a day, 5 to 7 days a week. Our tool change time is about 2 seconds (chip to chip), and that adds up.

[miljnor]

I used to do some die cast parts that were run in like 10seconds machining and about 12 seconds tool changing! So chip to chip time is very crittical when your doing real High volume low cycle time parts.

But we were using HAAS and the chip to chip on most mid to low end machines is high like 3-4 seconds (probably a generous guess)

[JPMach]

The regular Haas machines have a chip to chip time of 3.6 sec and I believe the Super Speed Haas machines are at 2.2 sec (which is damn fast when you watch it) Of course these numbers are assuming you have a side mount tool changer with the next tool staged and ready to go. If you have an umbrella style it will be longer as you have to release the tool and then index to the next one, and if the tool you are changing to is not right next to the empty pocket then it takes even longer.
This is why in the new multitask machines you are seeing tools that can mill and turn and drill all in one tool as it skips tool changes (just a spindle orient, which you have to do in a regular tool change too)
I wouldn't mind having a new Mori seki multi tasker so I could use tools like that but the $250,000 plus price tag kinda scares ya

JP

[RICHARD ZASTROW]

CHIRON FZ08 W Tool change 0.8 sec. Chip to chip 2.2 seconds.
RZ

[jderou]

We have Kira (anyone ever heard of them?), we are looking at brother for the next round though. Both have around .7 - .8 tool to tool, 2 chip to chip (and 50000 to 60000 mm/min rapids).
We are drilling/tapping die cast.

[Gene0552]

I think lakeside has it nailed. At least thats what I'm going with. It most closely agrees with my belief and most of us here. Thanks guys.

[Dawson]

Something I've come to watch out for is ultra fast tool change times on new machines. Quite often they are sped up for trade shows and the like, but not feasible for the long run. It's quite easy for the mechanisms to get out of time as parts begin to wear slightly. This can cause catastrophic failures resulting in days waiting on repairs and new parts. Those fractions of a second become quite small. Your far better off using long tool holders to decrease the rapid distance in Z vs 1/8 of a second faster tool changes.

Back on topic, my understading of chip to chip is the time tool 1 stops making them and tool 2 resumes. How else can chip to chip be explained? If there are no chips it doesn't meet the criterea.

[lakeside]

[QUOTE=Dawson]Something . Those fractions of a second become quite small. Your far better off using long tool holders to decrease the rapid distance in Z vs 1/8 of a second faster tool changes.

]
when using long tool holder can lead to other issue less ridged means slower feed and increase load on spindle and more bearing load you should always use the smallest holder and keep the tool out no more than need

[gus]

In reality, the maker 'assumes' that the part being machined is as close to the tool change position as possible, so machines with fairly slow rapids show faast times, but aren't really. The robodrills and the like are the onley reeeeeallly fast toolchanges.

Truth is, running multiple parts on the table makes toolchange times almost unimportant[within reason]

[Geof]

.....Truth is, running multiple parts on the table makes toolchange times almost unimportant[within reason]

Yes; if you have 12 parts on the table and your chip to chip time is 3 seconds the time per part is 1/4 of a second. It is much better economics to buy a big low cost machine with a slow toolchanger and a lot of vises when doing production work than it is to go for something with a fast toolchange and an exorbitant price tag.

[miljnor]

Truth is, running multiple parts on the table makes toolchange times almost unimportant[within reason]

Oh contra!

That is so not true. It mainly depends on what type of parts you run.

If you run parts where the tool in the cut for several minutes then, your statement will hold true.

But lets say you doing something like die cast cleanup or something of that nature (quite common in the machining industry). On these kinds of parts you may be making 15-20 tool changes on 30 parts and the tool is only in the part as long as it take to drill a shallow hole (read seconds). Then you have to change your strategy and use combo tools (drill-taps or draps) otherwise the tool changer eats up your profits.

But Geof statement about a low cost slow tool changer can still work but your way of machining has to improve to take advantage of the latest and greatest combo tools, to improve your machining times.

[lakeside]

lets face some facts more part per tool change is less time newer machine with higher feeds and rpm spindle tool changes time faster cycle time but one chip wrapped around spindle and you have stop no time saved on either one chip to chip time who realy cares not me

[JPMach]

Also to consider is that when using fsater spindle speeds, it takes longer to get up to speed and to stop the spindle thus adding more time to the tool change.
No matter how fast the tool change time is it still comes down to how good the guy programming the machine is so that there is as little air cutting as possible. It is often times quite easy to shave a few seconds off a part just by changing a clearnce here and there or switch the order of holes around.

JP