Ya nowadays the deals are harder and harder to find. Wish I snagged more ballscrews when I could have, especially the ones with the bearing blocks..
They can be packed to pre-load them to make them a bit stiffer to move but with zero slop (and absorbing vibration) so I designed my machine more like a "mill" than a router, I have tight leadnuts and tight linear sliders so it's built for high accuracy and slower speeds. I do traverses up to 165 IPM but generally cut under 35 IPM and mainly machine plastic.
I like the IGUS linear rails N series, and the new W series is also well worth the look. The plastic sliders actually are rated for much higher load forces than typical ball bearing linears, they don't have the point loading problem, or the resonance or the (temperature dependent) 0.0005" slop all typical in ball sliders.
I was hoping to use SHS blocks on all axes, but have difficulties lately finding matching blocks; and I have some HSR blocks as well... Also, I have a friend who is affiliated with a machine shop, turning my ballscrews for the bearing blocks I got from lmb2008.
The free end bearings look fine, but it looks as if the bearings on the fixed end were painted over, and the lock nut seems like it would rub against the bearing seal when tightened. As I have no previous experience with these bearing blocks, can anyone tell me if this is cause for concern? Or do I need a small washer between the bearing and locknut? I haven't yet, but I might take them apart and replace the bearings...
OK I broke down and got a Chinese spindle for this machine...Only time will tell how long it lasts. The funny thing is, the shipping for ths spindle was $44, and the VFD $100. The package deal was a little cheaper, but the shipping was $222!
So I made an offer for $100 off the BIN price. I get a counteroffer for $50 off. I emailed the guy explaning the discrepancy in shipping cost, and counteroffered for $85 off BIN. He accepted my offer!
I think I could have held out for a better deal, but I'm happy... the first thing is to take the spindle and see how "German" the bearings really are! Would it be difficult to replace the bearings?
It's amazing how a part time consulting/managing position has cut drastically into my shop time! I do have most of my parts finalized. My battery died, otherwise there'd be pics. Hopefully this weekend I'll get some up.
Anyway, here's what I got so far:
Kuroda 15-15 ground ballscrews on the x and y asis, 15-4 on the z
THK SHS25 rails on the x (gantry), HSR25 on the y (moving table), and low profile HRW32 for the z
Sanyo Denki Step-Syn steppers, 330 oz-in all three axes (I have another incase I add a 4th axis)
2.4:1 (36:15) Timing belt gear reduction on the x and y axis. With the ballscrew pitch I should have roughly 4 turns per inck, or about .0013" mechanical resolution (though if I can hold .003" I'd be happy)
Cheap China spindle (for now) 3kW
Hope to get started on this next week or so... The workshop is going to be a zoo!
it seems to me that for fell for the Chinese "trick" about bearings:
A bearing manufacturer in China registered it's company name as "German"....
so they are in fact "German" bearings.
This is in principle just like the "American Tool" company selling tools made in Korea or Japan (and maybe assembled in the US - if they are). That makes them "American Tools" - doesn't it?
BTW, most Bosch tools are made in China or Thailand - but they are sold as "German" tools in Europe and the US.... (they may even have "German" bearings - now that would be funny.....)
Good luck with your spindle.
Joe in Aus
Maybe I'll find some REAL German bearings to slap in there, though seems most high quality bearings nowadays are Japanese...
Hey Joe... (sounds like a song...)
I bought the spindle/VFD knowing full well that these bearings are probably not "German." Obviously they would have to say bearings "made in Germany." Even then, who's to believe that too?
Just like you can buy ABEC-9 bearings. It don't mean a thing, because you can make the races out of lead, or pot metal, and as long as you make it to ABEC-9 tolerances, it's an ABEC-9 bearing!
I believe a long while back there was some controversy concerning USA parts made in Japan. There's a town in Japan named Usa, if I remember the story correctly. Fortunately, international export laws state products must have the country of origin, not just the city.
But really, at $500 shipped it's almost disposable. I considered a Colombo spindle, but I don't have $2500 to fork over, and then I still need the VFD. At that point, I'd have bought an $8000 mini-mill, but I have no way of getting it into my basement short of totally disassembling it!
So until I build my dream workshed, I'll have to plug away in the basement....
Last edited by louieatienza; 05-09-2011 at 06:14 AM.
After many false starts, it seems I will be getting to this after all. Juggling some parts around as well, so the specs on this machine have changed a bit.
I am changing to a moving gantry on raised sides/rails. The reason being, I plan to use flood/mist coolant, and don't want to get them in the profile rails. Also I have some projects requires somewhat heavy items to be machined, and don't want the weight of the objects affecting machine performance.
That said, I will be using HSR30 rails for the x axis and use dual leadscrews to drive the gantry. This complicates the build somewhat, as I haven't decided whether to drive both leadscrews with one or two motors.
Also finally I've found a source for machining the ends on my ballscrews. I've checked local machine shops but get the runaround. This has been one holdup, but a fortuitous one, as I would have been committed to my previous idea.
I also will have a few spindle setups that I could hopefully easily swap out. A Sherline/Taig spindle for harder materials, and the chinese spindle for aluminum though this is not set in stone.
Other aspects of the machine will remain unchanged. 25 series rails for the Y, low profile HRW21 for the Z. I still pan to use 15-15 ballscrews on the x and y, and will be using 15-5 on the z. I have a plan for making the z as lightweight as possible but still sturdy. Not having the moving table will give me a larger work envelope for my rail size as well.
After re-thinking everything, I changed my specs again, this time for good!
After seeing the builds of hack and rodjava, I decided to follow suit and mount my profile rails upside-down under my table plate.
I have already purchased a plate of mic-6 about 24" x 38" x 3/4" that will be my table top. Since both sides are blanchard ground, I'll have an accurate surface to work off of.
The plate will be dropped shipped to a machine shop where a water jet will cut the plate to size and punch all the holes. It will then be put on a CNC router so that the holes can be counter-bored and two grooves milled for the HSR30 rails. This way I can assure the rails will be parallel.
The frame and gantry will be made from aluminum extrusion. I'm pricing different brands right now. I was going to use some phenolic I had on hand, but machining it is a nightmare (fiberglass cloth). So I'll use the phenolic as a table surface for my current machine. Also thinking of using aluminum plate for the bridge, but the cost of machining would be prohibitive. I decided to do a raised gantry as opposed to raised rails because I want to minimize the footprint as well as maximize the cutting area for the table surface. So the gantry bridge will extend past the table surface to allow 25" of travel. The moving gantry will give me about 6" more of travel, though it may not be as ridgid as the raised rail design. But this way, I can mount the ballscrew under the table, and with my rails only about 20" apart, I think one ballscrew for the x should be fine.
I'm still using the Gecko G540, and 380in-oz steppers, and the Kuroda 1515 ballscrews. Interestingly enough, I thought they were GE series which were C7 accuracy grade, because the packaging and instructions listed it as such. When I packaged them to send for machining I was surprised they were stamped GG, which is C5 accuracy!
When I got them back, they fit perfectly on the C5 bearing blocks I received from Marchant Dice. I had keyways machined into the drive journal for the pulleys I'll be using. It will be 15 teeth at the motor and 36 at the screw, for a 2.4:1 reduction. This actually works nicely for me, since the effective drive ratio will be 4.064 revolutions/inch, or with the Gecko 10x microstepping, 8192 steps/inch or 506 steps/16th inch. My goal is to eventually upgrade to servos, and use the Gecko in my current machine, but if this performs well enough I may just keep it this way.
As far as the motor pulleys, I just noticed that the shafts on my steppers are not 1/4", so now I have to order two new pulleys. The z axis will be direct driven.
As for the computer: I have a HP server mobo with dual Xeon 3.6 GHz processors, and onboard ATI graphics. I also sourced out a touchscreen panel form a kiosk, as well as a very cool stainless steel keyboard with built in trackball. I plan to use a 32GB SSD, and the procs have passive heatsinks. I'd like to make an enclosure that houses both the screen and CPU.
Anyways, have to send the final drawing to the machinist...
Sounds like a plan...I have exactly the same GG1515 ballscrews and they ARE excellent. I am driving directly but I have big 1600 in-oz steppers. The resulting microstep resolution is 0.0003" which is more than good enough for my purposes. I can get repeatable positioning to better than 1/1000" (as far as my cheap dial indicator can tell).
Your belt drive should compensate for the lower torque motors and give you higher resolution but I am not sure what the belts may sacrifice in backlash and stiffness of the drive train.