Machsupport Forum
General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: DAlgie on May 13, 2006, 01:26:46 AM
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Thought I'd post a couple of pics of my lathe as it is, most of everything is done and working, just now need to machine all the turret toolchanger parts, the wiring and everything is ready for it to bolt on. This lathe uses a 400oz/in stepper driving the X axis through a 2:1 reduction belt, plenty of power there. The Z axis is a 1200oz/in direct drive, it's marginal in power but I still have some drag to deal with yet. Both ballscrews are 5 turns per inch. Uses Gecko 201 drives, 34 volt power supply from a 500VA torodial transformer, PDMX 50 volt AC/DC converter- power conditioner, Cambell breakout board, huge fan cooled gecko heatsinks. Stainless sliding half cover for coolant and chip control makes it really nice and cleanup easy. Computer/ worktable cart is an old Indy car shock dyno cart that was perfect for this use. I still can't believe how much equipment, gears, feedscrews, front apron, threading gearbox and assorted crap I had to ditch off that wasn't needed anymore, you'd think that the ballscrews, steppers and electronics would't be much more, if any, money to manufacture and add for a low cost commercial CNC lathe. And without all that mechanical stuff the thing runs so much quieter now! Been a really fun project but I need to get back on the aircraft stuff...
Dave.
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So funny seeing your lathe, it's obviously the same as my Warco1340 which is a taiwanese copy of an English Harrison M300. I've had mine years, no intention of converting it though, already got CNC lathes.
Conversion looks tidy though, Have you not converted to ballscrews? That would seriously help.
Wayne....
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Yes, both are ballscrews, this is a chinese lathe, still made and sold by different companies, this one was from MSC, actually quite a nice lathe as it was.
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Youve done well. Show us some pictures of stuff you have made with it.
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Make stuff? I need to get the spindle index sensor to read right yet, still running in the 4 or 5 hundred thousand rpm range, not at 500 as it should be, so the feed per revolution is a problem and I don't have the confidence with it like that, still need to pay you guys for all your work with the software too...
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Whats up with the speed sensor?
I've also had some issues with a speed sensor on my VMC, I chose to make my own, it works ok, but have found some issues with stepper drive noise screwing low speed readings. Like 40,000 ish when it should be in the 100's. I'll probably end up making my speed sensor work at 24v levels like the rest of the machine. TTL levels are so prone to noise issues it pays to do it the way the machine was designed.
You dont HAVE to use feed per rev. I often just use feed per min on my lathes.
Obviously it will have to work right for screwcutting.
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Yeah, it's starting to annoy me a bit, I ran a seperate shielded cable, grounded one end, even ran a shielded cable inside the controller box, and no luck. Wierd though, it sometime works for a short time, exactly right, then goes crazy again, wondered if it's not just noise. Like you say, maybe the best thing is to convert it up to a higher level, low level signal stuff gets noise so easily it seems. But I don't know how to do that.
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What are you using for a sensor?
To convert I've jut used opto couplers witht the correct current limiting resistor for 24v.. All my limits,homes, etc are 24v already.
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I used the PDMX spindle sensor at http://www.pmdx.com/SpindleSensors/index.html it uses 5 volts, and is an optical. Found out now, the problem seems to be coming from the sensor itself, no amount of grounded shielding changes it a bit, messed with the index debounce, still no change. If I pull the sensor off the lathe, it goes to zero, if I put anything in the sensor gap, it goes crazy, metallic, shiny, dull, it sends it through the roof, seems like it's got problems of it's own, there is a correct 5 volts to it, and a decent ground back to the parallel port board, and the signal line is shielded, as I said. I'll contact PDMX and find out more there i think.
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I'm also looking at using the PMDX optical spindle sensor. Did you get the problem resolved with the sensor or what did you choose to do. I appreciate your input.
Thanks Ron
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The guy from PDMX is at the show right now, he's testing one with a Campbell breakout board to see if there's any problems there, I'll let you know what I find out.
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We ran one of Steve's (PMDX) spindle sensors on the lathe at the workshop... It worked good but the steppers on the lathe were a little small... Steve is taking a CNC Mill home from the workshop so he will be a little bit getting back to you.
Good luck
Brian
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Got the spindle sensor working right. Steve Stallings of PDMX suggested using a 0.1uF capacitor between the 5V and the ground right at the sensor, this fixed it totally. I ran the crap out of it tonight, never got a problem, ran a threadcutting program, was great. Then went and tied all the cables up together, thought this might send it crazy again, no, was still fine, so i'm very pleased with it now. Time to work on the toolchanger now I guess.
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hi
that is a nice piece of machinery u have made a nice CNC conversion , Im keen on coverting a 1980's copy lathe that i have here at my workplace
im interested in using NEMA 34 HIGH TORQUE STEPPER MOTOR 1812 oz-in, ½” Single shaft with flat, 180
KL34H160-62-8A Specification are on http://www.kelinginc.net/SMotorstock.html
KL34H160-62-8B ½” Dual shaft with flat
I know its over kill in the size of the stepper motors but thats meI like big things
I want spindle speed contol , and arrange say four different tools on the cross slide to have say like a tool change but not a tool change if u know what i mean., the software will select the required tool for the rquired maching process , seen this setup on a small desktop cnc-lathe, niffty idea.
cheers
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Should work out good, you will be able to use that large stepper direct drive for the saddle, Z axis. Note that I only needed a 400oz/in for the X axis, so don't overdo that one, but that motor will be the one that limits the voltage you can max out on. Make sure you get a .200" per turn ballscrew for the Z axis and you will be able to get .0001" resolution with a 10X microstepping drive, I used Gecko 201's, very nice drive. I increased my voltage a couple of days ago to 42 volts DC, it was 28 volt and I could only get 38"/ min rapid, with the higher voltage I now get 60"/ min. rapids and am about 20"/ min away from stalling speed. X axis is very fast at 80"/ min. for a small 7" travel with this voltage. Note that the steppers don't even get warm at this. You will need to remove the apron from under the saddle, these usually bolt on. Then need to make a stepper mount and should 2:1 reduce the X axis ballscrew so you can get .0001" per diameter. This lets you place the stepper under the saddle using a belt reduction drive and makes a tidy package. I sealed the entire belt drive enclosure from coolant leakage, which is a must, at you need at least chip protection if you won't be using a flood coolant system. Make sure you add a cover above the Z axis ballscrew to stop the chips from dropping into it. Will be a fun project.
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Just for reference, I think a good rule of thumb is that the Z axis on a lathe should have three times the power that the X axis has. Mills often get away with similar motors on at least the X and Y axis, but a lathe has a lot more weight to move around with the whole saddle than it does with just the cross slide. Also, you have a long, heavy ballscrew on the Z axis that you have to accelerate up, but the X axis has a small, short one typically.