bill z wrote:SteveM wrote:You can usually get a 2.2kw spindle, VFD to run the spindle and everything else you would need
The part 'and everything else you would need' is what I'm concerned about. Not the dollar, but, just what art those parts I would need?
Also, would the standard Shark controller run the speed or just on/off?
Again, I have not used a spindle or seen one used up close on any CNC much less a shark..
As I think about what surrounds my spindle, I see these things you'll need:
There will be a spindle mount plate to fit the new diameter. The higher torque and accuracy often mandates an aluminum one. Dixie Billets or something. I can make you one, but I'd charge you too much
There will be some time "tramming" the vertical alignment of that new spindle. Love them even as we do, the Shark spindle platforms sag in a load-dependent way. Which means when you get that bodacious spindle, the water inside it, the cables, the tubes, the wires and the massive mount plate loaded up, there's gonna be some droop. The way I've been able to tram out the vast majority of that sag was to loosen the clamp, and push the top of the spindle back towards the gantry to compensate, and then tighten. Or, loosen the bolts just a little, and use percussive maintenance to gently force it backwards, to compensate for the sag. Trust me, the closer you get the spindle to vertical, the fewer problems you'll have long term with strange problems with lines on bottoms and side walls.
There will be routing of the water-cooling tubes to and from whatever tank/pump combination you get. Lots of choices here, both for the tubes and tank, but also how you route those tubes. For me, I use a 3-Gallon boat gas tank filled with 100% anti-freeze and a boat lavatory pump. Nearly everything goes "up" and is suspended from rubber shock-cords to offset the weight
**You** can expect maybe $20 here, and cheaper is probably possible. And, use water...antifreeze is for freaks like me who put their coolant tank in an actual freezer, to no discernible benefit since the spindle bearings want to be "warm" and not "ice-cold-beer cold"
.
If you're interested in knowing the spindle's temperature without having to touch it in operation, get a couple of those stick-on beer home-brew thermometers. They work using LCD chemicals, so no electricity, and they go right on the (clean and oil-free!) spindle case. And, they're typically quite inexpensive; a couple bucks each, IIRC. One thing to keep in mind: if there is temp differences along the spindle-case, there might be strange effects on the thermometer, since each numbered entry corresponds to a different location on the spindle. Get a second one for the coolant water tank, and a third one because the next time you take the spindle out, it will ruin the first thermometer
. You want it "warm", but NOT "hot", and avoid running hard when it's "cold". Those are the technical specifications as I understand them. It's really more about the bearing grease being mobile enough to prevent wear and thus increased runout. Geeks!
There will be the mounting of the VFD module. If you get one where you can mount the power part a bit remote, I recommend it, so that would usually call for getting an Ethernet cable of a few meters. Mount the control where you do your bit-changes, so you will always check it's stopped before inserting soon-to-be-missing fingers.
There will be the heavy-duty, high-current (think 16Ga or larger), high-flexibility, armored and shielded cable that goes from the VFD to the spindle. Well, if you can find it there will be. I have some, but I'm not finding "Belden Style 2464" that anywhere resembles it. IIRC, it's 16Ga 4Cond + Shield and Drain Wire. Motor takes three wires, case ground is four. Connect shield to ground at VFD, but not at motor-end. The spindle should come with the connector, but you might need to buy and then solder that cable. Do NOT scrimp on that cable, and if at all possible, get a SHIELDED cable. This is not 60Hz AC being sent up that cable. The right wire is NOT cheap, and I'm pretty sure is NOT at the local hardware store. Yes, I've seen "people" using extension cords, but please don't. Unless you're not me and don't WANT a 986-foot spool of really expensive wire becoming another legacy item
. There should be a real ground in that cable. Get some really thick extension cord wire by-the-foot from the hardware store, or even yes a really large-gauge but flexible extension cord. Just remember: a wiring short or motor failure could put something like 100+ Volts at 600Hz onto that case. Protect first, die another day!
IMPORTANT: VFDs do NOT like being plugged in all the time, but at the currents they pull, a standard light switch ain't gonna cut it. The solution? A 3-terminal "contactor". Just get it; they're cheap, you don't want a fried VFD because your vacuum started and threw a spike at your turned-off system. They're available new and used, for example:
https://www.ebay.com/itm/BACO-172000-IE ... SwlptaFJ8i
There will be 220VAC service needed near your CNC, and you'll need to purchase, prep and install the "pigtail" from the 220VAC outlet to the contactor. If it's a standard household dryer plug, just pick one up at the local hardware store, cheap and powerful, and they even limit the length to keep you honest
.
There will be time spent reading the translated-from-Chinese operating manual. Look for the accel/decel ratings and extend them OUT to allow more even spin-up. Why? Because we're all lazy and nobody wants to warm their spindle up with 20minutes at 2000 RPM, that's why
If you want really FAST spindle braking, you'll need to invest in (typically) a 1 Ohm @ 700W vitreous-enameled, wire-wound resistors. They cost about $600 each...and you need TWO of them. But hey, you can get indexed positioning....you know you want it!
And if you're a GOD AMONG MEN, you'll also dig in and find the maximum Hz setting, and up that from 400Hz to 600Hz. Don't tell mom, but that moves you from 24K RPM max to 36K RPM max. Yeah, now you CAN spin a 1/32" endmill in aluminum and get proper cutting parameters!
You might want to branch out and try using some high-speed steel cutters. They're awesome in acrylic because they are "sharper" than even brand new, "solid" carbide bits, and they can be spun slower, leading to lower heat being put into the cut, making the cuts even cleaner. To do that, you'll likely need to find and change the minimum-frequency setting, and turn that down to like 10, which will let you get down to about 600 RPM. If you do that, be sure to increase the "low-RPM current boost" setting so you don't lose out on all that yummy torque. Don't max it out, as this seems to be able to freeze the motor in position when set too high (don't ask...). But, increasing the value by, say 25% is a good starting place. Remember, it's not so much the stall-torque, but rather the slowing of the motor under load that will mess up your cuts. So, give it enough boost current to handle the reasonable max you expect (relative to total motor torque available at that lower RPM), but don't overdo it.
There may (will?) be a need to become much more precise in how you calculate your cutting parameters, since you now actually CAN tell how fast the spindle is spinning.
Okay, so now you've got the spindle mounted and running, and we believe aligned.
Next up you're going to want to standardize on some bit-holding method. I use a Muscle Chuck, which means I then went out and got 2 units of each collet insert I expect to use. If you go with a more-traditional set of ER-20 collet inserts (or whatever your spindle has), those will be precise (proportional to $$$ inserted into online vendor), and let you hold the random drill bit as well. The downside? As a user of standard-sized bits, you'll probably never use 90% of them. But, they ARE pretty!
A note about collet inserts. If perchance you break bits, small or large, (it does happen) very...no, VERY carefully inspect the inside surfaces of the collet insert that was in place when it happened. If the bit breaks inside the neck of the collet, there will almost always be a gash in the inside of that insert. If you then take a NEW bit and clamp it in that insert, it will almost surely pinch the shank, and cause a weak spot in that new bit, making it even more likely to break under deflection. Which, absolutely SUX, because if you bought an el-cheapo brand set of inserts and you can't buy them individually, then you're going to buy ANOTHER set. So, when choosing your inserts, it might make sense to get a set of high-enough grade that later you CAN buy extra ones. And, I'd even recommend up-front buying an extra copy of the 1/8, 3/16 (don't laugh...3/16" EMs in aluminum are the bees' knees), 1/4, 3/8 and 1/2" inserts. Thing is, clamps will ALWAYS rearrange themselves in such a way as to hit your bit. And small bits break. They do. So, be prepared for when they do, because otherwise, you'll be down and whiny for days.
If you expect to use a wiggler-style edge finder, or an electronic one, you'll want to make sure you have that bit-holding situation in-hand. That is, don't choose a permanent collet/chuck solution that will prevent you from using other kinds of standard tools. You never know: as you learn more, you'll want to branch out and try new things. These machines can take you a long way if you want to go there, but in many cases, a copious application of bucks is needed. But, that's going to be true anywhere. The big boys have to slap down $500 for a (new Kurt D688) machining vise just like you and me.
That's the main points. The better a spindle-mount plate you get, the happier you'll be. And that other stuff too
.
As always, hope that helps.
Regards,
Thom