Do I need speed above 60 IPM on a hobby mill

With the original Bosch drives, my 145v motors, etc, the mill was capable of 200 IPM rapids. Right now I have a 70v power supply with
30A8 drives and the top speed is 60-70 IPM.
My question is how much am I losing, in reality, but having faster top speed. My feeling is not much, but I want to know.
This is not an entirely idle question, as I could install drives that match motor voltage (30A20AC or 25A20AC or some such). They would use 120 VAC as power source.
So, would I see any improvement in anything valuable with higher top speed or no?
i
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Ignoramus11290 wrote:

I have artificially limited the speed of my machine to 72 IPM (60 IPM plus a little leeway) to avoid expensive oopses! The machine and servo drives will do 120 IPM, but I had a few accidents in the early days with it, and thought it might be best to "slow down and save lives" so to speak.

Probably not. All you'd do is reduce non-cutting time by a few seconds. Unless you are making long traverses across the machine's working cube, it just won't buy much. Increasing acceleration makes it possible to make sharper corners, that is an actual advantage. But, you are highly unlikely to ever cut anything above 60 IPM, so it could only make much difference in production runs.
Jon
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Jon, I think the same about it. A lot of safety is in my ability to stop the mill quickly enough.
i
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On Fri, 20 Aug 2010 17:31:29 -0500, Ignoramus11290

FWIW, I set mine at 75 ipm max. so it takes 20 seconds to move the table end to end.
Karl
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Iggy, you are not running tested production programs making large lots of parts.
Speaking as a guy that has put all too many wrecks (crashes, also known as 'bumps' by the green button pushers) I can say that going faster in rapid is counter productive considering your level of learning (not a slam) and your applications.
I'm not a big fan of blink of an eye crashes. We have engineers that have pushed machines to the edge but when it takes days or longer to get parts and then more time to repair the machine, how much did was really gained out if this? Seconds mean nothing in this context. Not to mention accelerated wear.
The pay dirt is reducing cutting time and tooling cost. There is where the real productivity increases lay.
JMHO,
Wes
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I guess it depends on what you are doing. I suspect probably not. That being said, if you are doing some really long programs ( I just did one that took almost 2 days) rapid speed can make a difference of several hours. If most of your jobs are only a few hours probably not at all. Not enough savings to risk crashes as others have said.
HOWEVER, if you are making fifty of something with a small cutter out of aluminum you might be cutting at that speed or higher... once you get your high speed spindle all figured out. I was just doing some speeds and feeds calculations today that were giving me (wishful thinking) suggested feed rates of over 100 IPM using a max spindle speed for the calculation of 21000 RPM.
Seriously though 60 IPM is pretty darn fast for most of us. I can get that speed on my Taig with the Gecko controller, but I backed it off to 52 (mathematical speed based on kernel speed that works really well with my PC) and cut at 30 or less and I am thrilled with the performance.
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wrote:

My OmniTurn lathes will cut at 300 ipm, but few materials allow that at 4000 rpm
Gunner
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    [ ... ]

    Hmm ... that works out to 0.075" per revolution. Perhaps cutting machinable wax -- if it won't blow up at 4000 RPM?
    Enjoy,         DoN.
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wrote:

Actually..Ive seen it done with cyrolac and delrin and I think...filled nylon.
The boys were using a nice .50 half round Microcentric carbide cutter.
Wierdest thing Ive ever seen. BANG and the part was done. They claimed that anything else..and tolerences went to shit because the parts tended to spring. They were cutting pullies for rescue gear.
I nodded politey and backed out of the door, with my hand over my wallet and the other one hovering above my backup......
Gunner
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    [ ... ]

    :-)
    I've made a pair of Delrin pullies -- black, because I made them to be used out exposed to the sun's UV full time -- but the tolerances were not that critical. I happened to have an insert cutter with round inserts on the lathe which worked out well. These were for the setup to allow me to lay down the pole for my weather station from the ground when I needed to change batteries (RF link to the station).
    Everything is either Delrin or PVC except for a few setscrews so there is not a path to make it attractive to lightning.
    In the past week we got a rather extreme amount of rain. Take a look at:
    <http://www.d-and-d.com/Weather/weather-report-classic.html
and scroll down to the bottom where the hourly rainfall shows up for the past seven days. Actually got about 5.45" of rain in the middle of the night (Perhaps around 3:00 AM or so -- maybe as late as 5:00 AM. Totally overflowed the "test tube" gauges up a ways. I had to spend some time playing with the scale factor before I could see how much rain actually arrived. :-)

    Perhaps they would like to use the backup for putting the hole through the pulleys? :-)
    Enjoy,         DoN.
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On Fri, 20 Aug 2010 17:08:52 -0500, Ignoramus11290

I'm in beginners learning mode, too, but I see the factors as being
1) What are you cutting? 2) What tool are you using? 3) What precision do you need? 4) What finish are you looking for? 5) What quantity of product do you need, and in what time frame? 6) What is your machine capable of?
For a hobby machine, I'd think that 60-70ipm is a great top speed. Some of the machines in the links folks have been posting are giving 20ipm cutting and 80ipm fast return rates.
-- We're all here because we're not all there.
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I am also learning, but I think that you are basically right. Those top speeds are for guys making production runs.
i
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wrote:

And for mills with faster spindles and much higher spindle motor HP. Download Bob Warfield's G-Wizard and check out how much HP is required for various cuts. That can be pretty illuminating.
Mike
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Mike, I downloaded it and it runs, however, it says that I am not authorized to use it.
I would really much prefer to write my own feeds and speeds calculator. Both as a perl module (for everyone to write their own programs) and a website calculator.
I have already started (yesterday or so) a metalworking section on algebra.com.
http://www.algebra.com/algebra/homework/Metalworking/Solvers.html
I want to do a real speeds and feeds calculator, however.
I have looked up various references and they seem to contradict each other.
i
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wrote:

G-Wizard was free while in Beta; maybe it's released now and no longer free. I think that there was also an email you had to answer (or click on a contained link) to "authorize" it. There's also ME Consultant Professional, which I use. The latter can have user entries for materials, feeds, and speeds but G-Wizard probably does as well. ME Pro is Windows only, though.
It's a complex project if you try to do it right and as you say, different sources have different data.
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It probably depends a lot on the type of job at hand, but for the stuff I do the difference is pretty insignificant. I ran a tyical job through the simulator on SprutCAM (my CAM program) which estimates run time and tried rapid speeds of 65 ipm (my mill) and 400 ipm. The difference in run time was less than 10%, AIR. If you have a sample design, I can run that through the simulator and give you ballpark data.
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wrote:

Most..not all..but most of the speed differences is in moving the tools around, not in the cutting. Now when you get up to high hp and decent rpms....thats where it starts making a difference.
Gunner
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Gunner Asch wrote:

Where it makes a difference is in peck drilling. Idiot.
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John R. Carroll

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There is a case I didn't consider. Watching our robodrills move in rapid always gives me the willys.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
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On Sat, 21 Aug 2010 20:04:52 -0700, "John R. Carroll"
SNIP

SNIP
Hey John,
According to the YASDA web site, they will be at
IMTS 2010 Date From 13 to 18 October 2010 Host country USA (Chicago) Place MCCORMICK PLACE Machine YMC 430, YBM Vi40 Contact us YASDA PRECISION TOOLS K.K Sales Division,Overseas Sales Division Tel:+81/865-64-2511 Fax:+81/865-64-4535
Try to get there for that. You'll be a hit with them for sure, but pretty lonely though, as everyone else will have gone home by then. If you do get to talk to them, maybe suggest they get an American translator to do the web and catalogue for at least the "English" versions.
Take care.
Brian Lawson, Bothwell, Ontario.
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