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  1. #21
    Mfg Engineer Scott_bob's Avatar
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    I honestly ask myself the question:

    Are our CNC machines capable of HSM?
    What defines High Speed in Steel or harder materials is not High Speed in Aluminum if you're talking about just speeds and feeds.

    Camminc, I don't know what data you'd get from your analysis that would discriminate between material that is Rc55, then I suppose you'd have to get a new reading when machining softer material say aluminum right?

    The dynamics would not be the same with different material right?

    Another thought, If I wait until I get chatter, or audible signs then when finishing with a .062 diameter ball end mill, my experience would suggest that the end mill is no longer any good. Quite often we are finishing with even smaller ball end mills say .032, what then?

    Just for clarity, Our data proves that it is the limitation of the CNC control that prevents us from HSM feeds even for steel materials.
    Accurate, smooth feeds above F30. inches per minute are not possible. No amount of speed / feed rate compensation can move us to the level of HSM performance. I'm not even talking about aluminum material where feed rates should be above F300. for true HSM.

    Sincerely,

    Scott_bob


  2. #22
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    Just to throw another wrinkle into the discussion, I noticed no one has mentioned the addition of high pressure coolant. I've seen some amazing displays drilling stainless steel with coolant thru drills on a Mori machining center. 70 - 7/16 holes to a 3" depth in under 3 minutes with the use of high pressure coolant.
    Normally when you try beefing up speeds and feeds your common flood coolant isn't enough to keep heat from being generated at the cutting edge. The heat contributes to premature breakdown of the coatings or material of the cutting tool. High pressure coolant breaks through the vapor barrier created at the contact point of the cutting tool and the material allowing the tool to stay cool. This allows you to acheive higher spindle speeds and feed rates and gives you the extended tool life to go with it. Lets face it, it doesn't make much sense to make a part faster if you have to keep stopping the machine to change tools. A good friend of mine owns a small job shop in the area and purchased a machine based on this demonstration. He has been extremely happy with its performance. Because he has the high speed machining capabilites he has been able to keep a step ahead of his competition and has stayed above water financially during the rough times most of the other shops have just gone through.

    Gunner

    Gunner


  3. #23
    Mfg Engineer Scott_bob's Avatar
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    So true...

    High pressure coolant is one of the other words that get watered down, a lot like HSM does...
    What I mean is this: Our Fadals have pressure in the neighborhood of 40 psi delivered by a pump running on 110 volts thru 3 nozzles.

    We are upgrading to a multistage 220 volt pump that puts out 150 psi and we have machined a new nozzle manifold with 6 high pressure coolant nozzles (that cannot be whiped out of their dirrection by stringy chips from drills). We have to redesign the Fadal circuitry to up the voltage to 220 from 110 volts.

    The point is this: Even with all this upgrading (3x the psi and gpm), this is NOT High Pressure Coolant. It's just good coolant pressure and directional control. I knew we would be breaking tools is we did not have good coolant delivery when we get our new HSM control next week. I can hardly wait...

    High Pressure Coolant is 1,000 psi and up...
    If you can get this kind of pressure thru the spindle, that is awesome. We use thru the spindle coolant at the low pressure level and get dramatic feed and tool life improvement...

    Thanks Gunner for bringing this up!

    Sincerely,

    Scott_bob


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    Scott_Bob
    If you ever get a chance to see a high pressure coolant demonstration, do it. It's very impressive. I believe they measure flow by gallons per minute not psi. My problem is I deal mainly in CNC Lathes. We have experimented with this technology on our Miyano's and although it did work it became expensive. The high pressure coolant would eventually infiltrate our main spindle bearings which caused some unexpected rebuilding. We run about 500 psi on our Emco 332 for our thru coolant blocks and tools. It helps but is not as effective as true high pressure.

    Gunner

    Gunner


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    Mfg Engineer Scott_bob's Avatar
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    Gunner,

    It is impressive. I have only seen video (Chip Blaster).
    Coolant Filtration is another significant factor that must not be ignored, espesially with the small end mill work for Mold machining...

    Here is an excelent source for nozzles:

    http://www.mcmaster.com
    then search for high pressure nozzle

    We machined a manifold, attached this to the spindle nose, and we have 6 of these...

    Awesome.

    Attached Thumbnails Attached Thumbnails What is high speed machining-high-pressure-nozzle-gif  
    Last edited by Scott_bob; 03-03-2004 at 07:18 PM.
    Scott_bob


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    Scott_Bob,
    I'm not involved in the milling portion of our business any more but as I recall we used magnetic rollers in the coolant tanks to remove fine and splintery chips. Our coolant was then filtered through a cloth bag with a micron rating. I can't recall what micron it was though. Most of our milling is with small endmills .125 or less at higher spindle speeds 20-40K in steel.
    Did you get a chance to check out Camminc's links? I looked through them the other day and it was interesting. I can think of a couple of times where an instrument such as his could have been useful. Most of our products have been run so many times now that they are dialed in for tool life and cycle time but years ago it would have been very useful. I'll have to suggest it to our mill supervisor.

    Gunner

    Gunner


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    Mfg Engineer Scott_bob's Avatar
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    Gunner,

    Yes I took a peek...

    But we have got to fix the CNC machines brain 1st.
    I have 2 competing controls on the floor starting next week, just back from vacation, a workload that is increasing and I just don't have the time right now to devote to another major project.

    Fadals new machine and control got delivered today...
    Interesting, they could not get their control to work with their own pallet changer. So, because they promised us a pallet machine, they had to purchase and integrate a Midaco pallet changer instead.

    The guys on the machine shop floor don't like the Midaco. Actually they hate it. (Bad experience on another Fadal)...
    Maybe "comfortable shoe syndrome", you know, that old pair of comfortable shoes get worn the most.

    At least the Midaco has a pallet system that clamps the pallets to the table... Fadals are not clamped to the table...

    Looking forward to next week,

    Scott_bob


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    Scott_Bob
    Resistance to change is common.... I usually find if the change is for the good of the boys on the floor it doesn't take long to catch on. Sometimes you have to enforce the issue a little... I'm not to familiar with pallet systems. We have some rotating tables on our Chirons and just got rid of our Kitamura which also had a pallet system. Sorry I can't give you any personal feedback on those. We do have a Fadal 4020. Been years since I programmed it but as I recall it wasn't a bad machine. I enjoyed writing programs that allowed the operator to answer a series of questions at the beginning of his run and the machine would go and do it. It wasn't fast though. We had planned on running production on it but it couldn't compete with any of our production mills so we ended up sentencing it to life in the tool room. Good Luck with your project!

    Gunner

    Gunner


  9. #29
    Mfg Engineer Scott_bob's Avatar
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    This is a good source for filtration:
    10 micron bags
    150 psi max.

    http://www.shelco.com/HTML/bag_housings.htm

    Reasonable price:
    Less than $450. total

    Anyone have another source?

    Attached Thumbnails Attached Thumbnails What is high speed machining-large_baghouising-jpg  
    Scott_bob


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    After reading my Machinist's Handbook (a Swedish one called "Karlebo handbok") I'll try to sum up what I understood were the most important benefits of HSM:

    * Lower cutting forces
    * Significantly lowered heating of the workpiece (since most of the heat is absorbed by the chips)

    ... and of course the decrease in machining time!


    Lower cutting forces and less heating means that it is easier to get a good surface quality (the book states that Ra < 2 um rarely is a problem). It also makes it possible to machine smaller parts with thin or otherwise tricky "features".

    The problems with HSM is that you need a machine capable of very high (accurate) feed rates, a very powerful high-speed spindle, and that special tooling is required that can take the high temperatures at the cutting point (problematic especially for steel, titanium).

    The book lists these intervals for HSM cutting speed (i.e. speeds where you'll get the benefits of HSM). (These values are read from a logarithmic diagram so might not be totally accurate):

    Aluminum: 1000-8000 m/min (3300-26000 SFPM)
    Steel: 400-1200 m/min (1300-4000 SFPM)
    Titanium: 100-1000 m/min (330-3300 SFPM)

    Cutting speed is NOT the same thing as feed rate! Cutting speed is the speed of the tool at the perifery (milling) or the speed of the work piece perifery (lathe).

    So, for aluminum HSM would be achieved from apprx 30000 RPM with a 10 mm dia tool.

    All this is from a book, so please feel free to correct me or give additional comments!

    Arvid



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    Mfg Engineer Scott_bob's Avatar
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    There ya go, finally someone who puts out there some real numbers for HSM.

    These numbers are more what I'd consider High Velocity Machining (HVM).
    This is a level of sophistication that only a select few machines / processes can achieve.

    Down a notch from this is what most people refer to as HSM.

    By the way, true HVM and HSM are well above the common CNC machine "controls" feed capabilities...

    Scott_bob


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    Scott_Bob,
    We've found on the CNC lathes that in some cases the insert technology has also surpassed our basic machine capabilities. A lot of the suggested speeds and feeds aren't realistically achievable because you have a 12 foot bar spinning out the back of the machine. Even if your machine has the available spindle speed your hampered by a barfeeds ability to dampen any barwhip. Once you slow your spindle to reduce the whip you change the characteristics the insert was designed to work at. Now the insert isn't as effective or may not be effective at all. Oh well, I'm thru rambling...been a long day with ISO audit and I needed to get my mind back into machining.

    Gunner


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    Gold Member Bloy2004's Avatar
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    I believe you could still achieve speed by rotating the insert around the bar instead of the bar rotating. The stationary bar stock would have to be fed from opposite end of machine? Oh well, what do I know....just a thought. It would require a completely different machine setup.
    ...key words- "basic machine capabilities"
    I hope this thread continues...it's been intriguing so far.

    Last edited by Bloy2004; 03-24-2004 at 05:33 PM.


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    That type of technology is available on rotary transfer machines. We are actually looking into a full blown cnc version from Hydromat. I haven't seen it yet though I will be involved in the project later this year.

    Gunner


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    To Hardmill

    Seeing is believing.

    Take a Âľ inch standard dished nose carbide end mill in aluminum and find out for yourself. Two flute, three flute or whatever. Flutes do make a difference, but this should do for now. Do a simple straight cut, full diameter. A small radius on the end will enable it to cut deeper on this test. Say .030

    Put it in a high-speed machine, the higher the better. Do not change the holder, do not change anything upon the cutter assembly during this test.

    Start at 1/10 range of the spindle max RPM - a good place to begin. Then go to a depth of cut at that RPM until it begins to chatter. Keep the same depth of cut and chip load through out the test at this point.

    Up the RPM’s by 1,000 and take the same cut with the same chip load and depth of cut, and document it. All the way to the top spindle speed.

    View the results. If you use a sound detection device that records in decibels during cut it might help later. What do you see? Is there a better RPM that this cutter run’s at? You can hear and see a better cut and go back to the documentation, then go deeper at those RPM’s to maximize. There will be several RPM’s with higher RPM’s. The Multiplyer.

    This is what it is all about, doing an impact test. You don’t need to do this test, it all shows up with a Stability Chart. A stability chart is simple to do, taking only a few minutes giving you the same results.

    Now, if you use the same cutter type, the same holder, the same gage length, the same stick out on the same machine, it will run the same 6 months later. That is where the database comes in, to document all this for tool crib, presetting and programming. Therefore, each machining operation is not different as far as the tool is concerned at it’s tool tip, it differs because programming does not have this information and they create programs which have incorrect parameters or the machine tool dynamics change. (Modal analysis)

    Have a nice day J



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    cammin, would you be able to explain how to do a stability test exactly? I would be interested in learing a little more about it.

    Industrial automation ????
    www.challengermechtech.ca


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    The method used to create a stability chart is simple. All that is required is the correct equipment and someone to perform the operation. The system I use is calle The MetalMax System. It takes only a few minutes and can be used on any of your machine tools with any tool. Once done, personnel assigned to perform this duty, inputs all pertaining information into a database for programmers, tool crib and presetting to use. Now programming, tool crib and presetting simply look at the tools in the database, all the information they need is there. A stability chart showing what RPM to use for highest depth of cut and to stay out of chatter, gage length, feed rates, cutter description, number of flutes along with much more information if wanted. If their looking for a ½ diameter - two flute ball end mill all they need to do is query the database for this style of cutter of the machine they are going to use and it will show all cutters in the database with those parameters. (The cutters in the database are called Stackup) The programmer simply chooses the Stackup assembly he wants to use and puts that Stackup assembly tool number on the setup sheet for presetting to assemble. He programs this Stackup to the known values, rpm, depth of cut, feed rate per material as the stability chart and database record information show.

    The method I use to collect a stability chart is: I have a portable computer on a cart with wheels. The dynamic process optimization equipment (MetalMax) I use is all attached to this computer so I simply roll it out to the machine I want to get a reading from. The cutter is in the machine, I attach the accelerometer to the tip of the tool with some wax, turn the computer on or it is already running from a batter backup, tap the tool with the impact hammer and get the reading. It’s done. I look at the stability chart, tell the operator what rpm to run, make sure the depth of cut is not over limit. I push my cart back to the tool crib, enter a few fields of information and that record is finished. I then go back out to the machine, make sure everything is running okay and if anything is changed or modified - I simply record that information into the Stackup record I just created for use later.

    Now many shops have already input cutter Stackup information into a spreadsheet. We can take this information and import it into our database. A database is much easier to use, better searches, more information, easy to view and creates detailed reports. My last customer had 1,953 Stackup’s in their spreadsheet, but they did not have any dynamic information – stability chart, machine information, etc. It was a mess to look at and search with no report functions. Once their information is in the database all they need to do is set up a picked Stackup and perform the dynamic process to get a stability chart and see if that Stackup is running at maximum. Odds are, it is not and can then be maximized further. The database automatically calculates spindle power, material, depth of cut to give proper parameters that will not exceed power limits, sfm, cutting stiffness, material specific power, etc.



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    Thanks for replying, sounds like a job for someone "in the know". We have outside companies doing our V.B. analysis,I think it would be intresting to do a stability test at our place, definetly room for improvement there. I think I'll leave it to the pro's..........

    Industrial automation ????
    www.challengermechtech.ca


  19. #39
    Mfg Engineer Scott_bob's Avatar
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    Our CNC control retrofit is now complete!

    It's very impressive to see an 8 year old DC Servo Drive CNC machine out perform a brand new Digital AC Servo Drive machine right next to it...

    I love the Rubicon (Numeryx) controls automatic feed rate motion algorithms that uses geometric look ahead, and jerk factoring to smooth out the motion.
    There is no point going fast if the control cannot maintain accurate positioning and smooth dynamic feed control, speeding up when it can, and slowing when it needs to, automatically. It's really incredible. We set "one" feedrate and the control does the rest. When geometry has sharp "inside corners", feed is reduced, or with small radii. When sharp "outside corners" are detected, feed is increased, as well as when cutting straight. I have simplifed the dynamics here, maybe someday there will be some video posted. Right now we gotta make some parts...

    By the way, the feed rate is constantly changing depending on the upcoming geometry, so there would be no point in determining a single feedrate that may represent an ideal "low chatter" frequency.

    Scott_bob


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    To trubleshtr:

    I understand what you are saying that vibration analysis "sounds like a job for someone "in the know".

    It sounds like a lot but it really isn't that difficult. You or anyone else can understand it and use it. I published an article from the beginning. June of 2004 at:

    http://www.moldmakingtechnology.com/

    Register yourself at that site to view articles. My article is not out yet, it will be out in June called " Chatter Myths".

    It should help you in HSM or Maximized Machining.

    Thanks, Randy



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What is high speed machining

What is high speed machining