wow ... you only just found out that ALL metal stockists are scammers? thats amazing. I *know* I can get steel prices varying anything from "normal" to +100% around here ... you can tell all metal stockist are scammers because NONE (apart from shop4steel.com) will post prices ever. Not even in the shop.
Soon as you walk in the door, they are eyeing you up "wonder how much he'll pay" ... seriously they ALWAYS try and scam you for every penny ..ever been to s steel stockholder that has prices per-tonne quoted in plain sight? ha. course not .. they quote everyone different, depending on whether you look daft enough to pay their prices or not.
my local steel stockist (Underwoods of Worcester, UK) has tried to charge me over 850GBP/tonne for HR4 plate when the going rate is nearer
520. They must think I'm stupid.
For this reason NEVER think twice about screwing your steel stockist down to the last penny on price. shop around, be tight, demand free delivery, take several quotes and just order the cheapest lots from each one. Remember, do it to them before they do it to you. If you don't beat them down hard on price at every opportunity, they'll see you as a soft-touch.
In the case of your alloy salesmen moving 30% just on ringing 3 different guys in the same office .. that shows you the variation available without even trying .. if you cant beat it down to -50% off the top price by hard-dealing, I'll be suprised.
this message is a public service announcement for the benefit of all those stockholders who have ripped me off over the years.
Finally--FINALLY--got the gonads to delve into the, uh, bowels of my ash-resurrected Fadal, and fixed dat g-d ATC problem. Really quite simple, thanks to SVL's usual erudite and astute input and help. It was, as he said, simply an alignment problem due to the head having dropped during shipping (removed Z-axis motor due to height clearance problems). The ATC works like new! Interestingly, the problem got un-usably bad after the last move to my place, but also had gotten "sticky" after a previous move--but just PITA sticky. Surely the same issue.
So after the girst move, when the ATC just got sticky, local Fadal came up to fix dat $450 blown fuse on the 4th axis (thank you very much), I said, Yo, whazzup wit dis 4th axis, bea? The fadal guy said, Oh, gotta be a bent ATC spindle, bup bup bup bup buhhhh.... expensive to fix, bup bup bup bup buhhhh..... gotta order the part, bup bup bup bup buhhh..... I said, Yeah, a'ight...
'Ceptin how do you *bend* a gotdamm ATC spindle???? So we just opted to deal w/ the stickiness, hoping God would intervene or sumpn, and in the meantime, just avoided the particularly offending carousel positions--ie, no tools there.
D'ya think he woulda checked the fukn ALIGNMENT at the cold-starting position, fer chrissakes?? D'ya think they woulda had me check my fukn VOLTAGE, fer chrissakes????? Oh, sorry, old thread.... bad memories....
Anyway, moving along existentially, I'm looking at the ball screw I'm twisting, to realign Z0 for the ATC, and I am shocked--and AMAZED (Jessica Hahn, anyone?)--at how *coarse* the thread is on these screws! Man, one turn, and I believe you move about 1/8 to 3/16"!! Wow!! Ahm thinkin, Man, you could get a *whole lot* more accuracy and resolution by just finer-ing up dat thread a little--w/ likely no loss in strength, just probably slower max. feeds/rapids. Mebbe dats how Haas gets their humongo rapids, by making the ball screws a
1-pitch!!??
More existentially, I'm thinking that local dealers have to get a little more on the ball, bruhs, ie, demonstrate a little more "pro-active pre-emptive initiative", and watch our machine-owning backs a little better. Altho I cannot say local fadal has ever ripped me or the previous owner off, and indeed they certainly could have, I *do* get the impression that this whole machine-owning affair is a little like a spider's web, where we, le Bugs, are at times "allowed" to fall into a variety of traps. And then get mercilessly billed, clear up to our duodenums.
I must also say that it seems that a lot depends on *who* you actually talk to at a dealer. Some individuals are simply more pro-active/sympathetic than others. Fortunately, one guy showed great sympathy for my pathetic pyrotechniked ass, and really did me a solid, ito of a referral.
But it could have must as easily gone the other way.
(BTW, at my aluminum supply house, WHO you order from in the *same gotdamm office* can make a 30% difference in your bill. How do I know? Cuz I got pissed one day, and phoned in the EXACT SAME quote to 3 diff. guys in the office.... Nearly fell offa my chair when I compared....)
So anyway, another day in my miserable life, but fortunately w/ a better-working VMC. Greatly appreciate everyone's help here.
---------------------------- Mr. P.V.'d formerly Droll Troll
The ATC carousel is supported on a set of belleville springs....and it has a limit switch in order to process an estop and protect it in the case it does somehow get whacked hard.....
IOW.......whoever suggested it was bent was probly blowing smoke up PV's ass
Personally, I doubt I would allow that 'tech' to even enter upon the premises again.
You do have a point though......_dont fix it_ if it's_ not_ broken !!!
Those are metric screws. Fadal started using them when they went to AC servos. A whole lot fatter and stronger than their old 5 pitch screws. They also have Dowfrost from the spindle chiller runnig through them to keep them stable.
If you want more accuracy, you can program in mm. Four decimal places in mm is alot tighter than in inch.
That's doing pretty good for that coarse of screws then.....I would guess there is some acceleration parameters that make em a bit jerky on short, high speed movements--but thats only a guess ( that else the servos are oversized quite a bit )
Beautiful--downright gorgeous even, but dry as a bone....the driveway is all dusty like it usually is August or something--whenever a car pulls in it takes a minute or so to clear....we're gonna be in trubble because of the low ( read: none ) snowpack in the cascades.....someone really needs to raise the electric rates down south so them leeches aint sucking our cheap hydropower ( thanks a lot, Governor Gray )........
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Headlines in the local paper today went something like this :
"Belch confuses scientists"........luckily, no ash came this way...
Hopefully, that beast will settle down again, perhaps into an extended slumber..but in all truth, science really hasn't a clue as to what it might do next, or when.....
Im about 35 miles from the volcano as the crow flies, and so Im safe except for 'fallout'...you do realize that ( if the wind is just right ), you guys could get a whole bunch dumped on you almost as easily as us....
I'm betting that Mt Rainier pops soon. When I working out in the Seattle area a few years back people made fun of me when I braced the hell out of rails I hung from the ceiling. I told them I did it for seismic reasons, that area is very active with volcanoes around. Hah Hah hah, we don't get no stinkin earthquakes, they said. Well that one that jolted them a couple of years ago changed their tune. It toppled some pallet racks, and slid some damn big molding machines across the floor!
We can adjust the accel/decell parameters to suit the job on the machine. Sometimes you can get away with a lot. The motors are pretty big. When you undo that last screw you better be ready.
Yeah, That's why I'm glad I don't live in Yakima. Or east of Yellowstone. Hopefully we'll get some rain this summer to offset what we didn't get this winter. People who know me say it's my fault, but I claim no responsibility for anything other than a good guess.
Howja think dem superfast rapid numbers got inta all the 'chine-sellers brochure thingies? Y'all want big rapid rates? No prob. Ah'll jes get me some big, BIG muffuggin pitches on dem screws, an' tighten the strap on mah helmet. Slick as turkey shit, an' stinks jus as bad when the muffuggin bearings git blown right out thru da end o' da muffuggin table!
God, I hate it when people talk like that. I even hate it when I do it.
There was a time, ages ago, when almost every good quality machine tool had 5mm pitch screws. For the folks who wanted to stick with English numbers, there were .200 (5 pitch) models. And for the really big machines, like boring mills, maybe a 10mm pitch; but it was on a screw with a much bigger OD, so the helix angle, and the net mechanical load, were still something that sane engineers could live with.
Then, just when everything was running all nice and smooth, some clever clown in the sales department felt the need for speed. For a while, that was OK. Faster computer chips, faster servo drives, and faster feedback sytems, all added speed to your basic good quality machine tool. They just spun the motors faster, and life was good.
But speed is addictive; and once we got a taste of it, we just couldn't get enough. 10 meters per minute had been ok for a while. And
20 meters per minute had been exciting for about a month. But then we wanted REAL speed, like the kind that never actually happened because the accel/decel curves were longer than the whole machine.
So we maxed out the motors, and then needed more. And the only way to get it was with longer pitch screws. 10mm replaced 5. Then it was
15mm. And now, in the machines that travel at 60% of lightspeed, the pitches are so long that the mechanical advantage is actually upside down, and the thrust produced by a table or spindle is actually LESS than the torque from the motor. But we don't care, 'cause the machines are moving FAST.
And, as someone else mentioned, machinery builders could probably save money if they just didn't bother with the feed-hold or E-Stop buttons. Unless you're clairvoyant, and can see into the future, there's not a chance that either of those will ever do you any good.
And yes, you can and DO get a whole lot more accuracy and resolotion with finer pitch screws. That's why I use 2.5mm pitch screws on my grinders. And 24,000 pulse/rev encoders. In theory, with a calculator, I get a minimum motion increment of just four millionths (0.000004) of an inch. In reality, the machine's not that good. But even if the mechanical stuff screws things up by a whole order of magnitude, I can still split a single tenth into a couple nice equal pieces, and have change left over for my piggy bank.
But accuracy isn't the "hot thing" these days, except in a few specialized markets like mine. Folks want speed. And that's what they buy.
I know of some machining centers that will literally (seriously!) walk themselves across the floor, if they're not lagged down. The sudden, high-rate starting and stopping of surperfast tables and saddles (and whole columns, ferchrissakes!) is an awesome thing to see (as long as you're standing safely off to the side, of course). Other builders, who don't like replacing crushed thrust-bearings on a weekly basis, opt for long accel/decel strokes, to soften things up. The fact that max rapids can only be achieved after the machine has moved a distance aproximately equal to the whole shop, plus the parking lot, seems not to deter anyone who wants to play the speed game. If we can legally claim that it rapids at mach 9, then that's what we're gonna do, even if your stopwatch and your maintenance budget might want to argue.
And for those who are REAL speed addicts, there are linear motors. Nothing rotates. No pitches or screws at all. Just unwind the whole damned servo motor, lay it out flat on the floor, and turn on the power. The only actual speed limit for those babies is the speed of propogation of current through a wire - which really IS within just a few percent of light speed. Of course, since there's a load to carry, and maybe a milling cutter in the path of that load, we haven't actually seen relativistic velocities, just yet. But you can bet your toolbox that somewhere, in the back room of some machinery builder's R&D center, there's a prototype in progress, and some engineers wondering why their wristwatches all seem to run backwards, whenever the rapid over-ride switch is set to 100%
Hold onto yer hat. And hold on to that (relatively) tame screw you've been playing with. Someday, you'll remember it with a fond sense of nostalgia.
It went on, and on, and on, and then it went on some more. I didn't see it happening, but my boss told me the coolant on the floor was actually splashed off the ceiling before it hit the floor. The roads haven't been the same since.
You werent old enough, nor were you even around the area for the one happened in ~ 1964 or 1966 or somesuch...
I was in a schoolbus headed to school and the driver pulled off the road and started yelling at all us kids to stop "rocking the bus"....this was in Shelton, maybe 60 miles from Mt Rainer....might have been shocks from that big Alaska quake, not sure.
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Had an earthquake in Oregon in about 1992 ~1994, I was working graves shift at the ole lazy B with a girl named Theresa White...
(Nice gal, I wonder whatever became of her, and I wish her well if she ever reads this)...( Hi Theresa )....
Anyways....
We were busy changing pallets on the high speed machining centers when the
777 project was just getting underway--no robotic cell at that time, just a pair of twin pallet Mazak horizontals crammed in a corner of the 120 bldg........
She was operating the crane, and I was rigging the hook--the pallet / fixture tool weighed ~1500 lbs, and it was sitting on a wooden pallet, when all a sudden _everything_ took to _shaking_, and a low frequency audiable rumble started at the south end of the building, moving slowly to the north...metal roofing......
I got off of that wood pallet in a hurry, worried that the heavy tooling might upset on top of me...and she then noticed my alarmed state, and said "whats going on???"......
I said "earthquake".....and then she shot out of the building--inna heartbeat...left me standing there holding the hook, dumbfounded.....but by then it was all over...ten seconds tops........
No perceptable damage, a couple bridges along I-5 north of here have had kinduva "bump" since then is all I've really noticed.
It all has to do with your acceleration curves...top speed is meaningless on a one meter machine if it takes one meter to get it up to full speed...esp. if your workpiece (s) are 1/10th of that size....
IOW, lots of it is simply marketing hype....you can add bigger servos, yes..but at the disadvantage of ( much ) shortened leadscrew life when you go to higher pitches.....
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Kirk Gordon wrote in news:1110600760.32de174e1a17ce788f9e4d75698f1abd@teranews:
With the new digital drives, esp from Siemens, it is possible to really tailor the accel/decel curves a lot. It's not the old linear lopped-off triangle anymore. Parabolic curves are in use now, where you can get the mechanical slop and get everything tensioned before you do any serious acceleration or deceleration, then you ease it out at either the top or bottom of the curve. It saves tons of mechanical wear compared to linear systems, and takes the shock out of the system. It's the jerk that gets you.
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