Messages

1

Show"N"Tell ( Your Machines) / Re: CNC Large Lathe Conversion pictures

« on: January 05, 2011, 10:55:11 AM »

Hello everyone!
Last night I did the first tests of the lathe using lazyturn and machturn. I gotto tell ya lazycam is much more functional than I expected.  The video was done at night, so its a little dark and grainy (sorry about that) but I couldn't wait till today to test it.   In the video, a 50mm radius bar stock has already been brought down to 47mm in one pass and the video starts at the next pass which is 3mm deep with a 15mm feed rate at 164 spindle rpm.  The tool is a 1" high speed steel blank I had laying around (I didn't want to test on $100.00 inserts  ).  I did a quick and dirty groover grind on it and slapped it on with a little angle to hide the face and cut with the leading corner as if it were the tip on a bit.  There was a little chatter, but I attribute it mostly to the small tool (we usually use 2x2 and 3x3 tooling)  and that my grinding was piss poor.  I haven't installed the coolant system yet so I just cooled down the work with a little 140w when the chips looked like they were coming out too hot. Even though the tooling wasn't even close to being the right one for that type of cut and had no coolant, I did 2 more passes and pulled it to see and it was still pretty sharp.  I was guessing it would last one or two passes at most.

<a href="http://www.youtube.com/v/D3JaiqHLLeE?fs=1&amp;amp;hl=en_US&amp;amp;rel=0" target="_blank" class="new_win">http://www.youtube.com/v/D3JaiqHLLeE?fs=1&amp;amp;hl=en_US&amp;amp;rel=0</a>

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Show"N"Tell ( Your Machines) / Re: CNC Large Lathe Conversion pictures

« on: December 30, 2010, 04:23:47 PM »

I'm working over-seas in Panama, however I'd be more than happy to have y'all over for a beer or two or three if you're ever in this neck of the woods.  Today, we've been putting the finishes on the machine: covers, closets, pans etc.  I think that by Tuesday I should be ready to turn some wheels after I do some test runs.  I'll be certain to post more pictures and some videos once I do.  Question:  Can I embed a youtube video on the forum?  If so, how?

Frank

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Show"N"Tell ( Your Machines) / Re: CNC Large Lathe Conversion pictures

« on: December 29, 2010, 09:04:52 PM »

Sam WD is good fufu, but it make a better mouth wash  

Tweaky -- You know, I 've been around this machine for over 15 years and I never thought about that!  But you are right, the tool post is on the "wrong" side DOH...wait, maybe its from the U.K.!  

Dan -- The original ACME screw on the X was also .75" and according to spec its within spec as its pulling from the axis inwards.  Remember that the heavy feed is actually being performed by the Z as the tool cuts heavy across the profile at the prescribed depth... shooting your tool into (as opposed to across) the profile 15mm at a time would make for a bad day to say the least.  Take a look at the Z screw again its at 2.5" diam its actually 3.33 times larger than the X  

4

General Mach Discussion / Re: Question about turning profiles and G-Code

« on: December 28, 2010, 03:40:02 PM »

Thanks Overloaded!
I tell you what, after everything I went through to find that large screw used I nearly pooped my britches when I saw how it had bent...just to think about how I was going to explain how I'd screwed it up.  I was floored when it sprung right back to shape like nothing had happened...man they ARE tough!

Decreasing the machining time is definitely a plus, however: One reason to digitize the cut is to limit the passes needed to reach the final shape and preferably be able to perform the cut in a single pass.  The wheel profile is somewhat L shaped with specific radii for the flange cut (keeps the wheel centered on the track).  The flange wears flat on its "in" side, so that the radius becomes flat and the treadwears mostly at the side adjacent to the flange. This means that in order to fit the new profile inside the worn profile you need to be able to fit the new flange radius inside the now narrower flange which causes you to have to cut the tread much deeper than if you were just to straighten out the tread and give it the correct angle.  Normally this is done on a pass-check-pass-check basis with a pantograph or with the eye-crometer-gauge .  Since the inserts wear about the same on a 1 inch cut than on a 2mm cut (provided sufficient coolant) its better to be able to get a single cut...cuz man I'll tell you those inserts get EXPENSIVE at $100 bucks a pop.  

Frank

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General Mach Discussion / Re: Question about turning profiles and G-Code

« on: December 28, 2010, 01:29:25 PM »

Thanks Rich, I checked out LazyTurn, but I think that Dolphin has everything we need and isn't outrageous in price.  The finished profile is in fact standard for solid wheels, however it is the uncut profile that changes with each used wheel.  This depending on wear time before removal, train speed, type of terrain, is it a freight car, was it on a 2 or three axle truck on a locomotive, was it flat spotted, etc.  Now, I just need to decide how I can quickly digitize the uncut profile of the used railway wheel and turn it into a spline in a DXF.

Frank

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Show"N"Tell ( Your Machines) / Re: CNC Large Lathe Conversion pictures

« on: December 28, 2010, 01:15:42 PM »

Thanks!
I believe the machine is from the early 1940's, it didn't have a motor when we recieved it, but I am pretty sure it was electric.  The machine came to us from a shipyard (the original owner) and was exclusively used for straightening prop shafts and had been replaced by another machine many years before.  Other than a little clean-up it was ready ready for use... its amazing how excellent old fabrication is.  

The servos are Panasonic 750W (1 H.P.) 3P 230V units with matching drivers.  I am using Parker 50:1 gear boxes on both axis.  Because most of the cuts on this machine are slow (20 R.P.M. low gear and about 164 on high gear) and deep (we regularly did 15mm cuts manually before the conversion), we decided to add the 50:1 gearboxes to increase the feed torque at the low feed rates required (approx. 15mm/min low gear and up to 40mm/min in high gear).  So far it looks like that was a good idea, the only draw back is that my max shuttle speed is roughly 25 cm/min on X and 50 cm/min on Z.  But even at that speeds its WORLDS better than the 5 minutes it would take to shuttle the saddle BY-HAND from one end to the other!  

The ballscrews are .75" diam/5mm pitch on X and 2.5" diam/10mm pitch on Y.

The timing belt and pulleys were a last minute thing, my father was concerned that having the X axis servo and gear box straight out from the saddle would risk it being ripped out by a careless forklift operator, falling part etc.

Hood, you are certainly right about the chatter being a pain, but its not from the saddle flexing, its from the play on the ways when the X axis out past the Z ways, the way guides need to be very well adjusted for play.  It doesn't happen very often, but when you start to see chatter (see pic) its almost always because the X or Z way guide needs to be tightened.  We also fabbed the tool post and holder ourselves because the original one wasn't sturdy enough for the wheels (another thing that caused chatter).  I'll post a pic of the original tool post in the afternoon.

Frank

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General Mach Discussion / Re: New PC's and parallel ports

« on: December 27, 2010, 10:01:22 PM »

I just bought a new PC for my lathe conversion (to replace an old one I was using to get started) and put 2 PCI parallel port cards in ($16 bucks a piece) and everything works peachy.

Frank

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General Mach Discussion / Re: Question about turning profiles and G-Code

« on: December 27, 2010, 09:58:55 PM »

Thanks!  I'll be sure to check it out!  Now that I know this, then what I need to do is find a way to quickly (video-probe?)  get the profile of the wheel and turn it into dxf spline that I can send to Dolphin.  I am a programmer by trade, I suspect it should be pretty simple to write something up that will do this.  By the way, I just posted some pictures of the lathe as its comming along.

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Show"N"Tell ( Your Machines) / CNC Large Lathe Conversion pictures

« on: December 27, 2010, 09:54:46 PM »

Hello everyone!
Here are some pictures of a lathe we use to turn railway wheels that I converted to CNC using Mach3.  So far, the servos, drive and control are installed and work very well.  I've done a few tests with Mach3 and everything has blown away my expectations.  I also found out the hard way why one should install the limit switches before you go playing and testing stuff... This week I am going to start putting the electronics in their proper enclosures and knocking out all the details necessary to get it working (ball screw covers etc.)

Specs---
Year:
Max turning diameter to ways: 60"
Max length between centers: 8 Feet
Spindle HP: 25
Spindle R.P.M.: Approx 20 (Low Gear) and 160 (High Gear)

I'd be happy to answer any questions about the setup.

Enjoy!

Frank















And this is what happens when you start playing with stuff before you install the limit switches.  Luckily, the ballscrew sprung right back to shape with 0 runout, I did have to re-do the mounts for the servo and gearbox. 

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General Mach Discussion / Question about turning profiles and G-Code

« on: December 27, 2010, 08:42:47 PM »

Hello everyone!
I am putting together a cnc setup on an old lathe we use to re-profile railway wheels (pictures comming soon).  I am using Panasonic 3P 220V drivers and servos with a parallel breakout and Mach 3.  I was able to wire all of the connectors and setup the servos and Mach 3 without too many problems and I am at the point where I can input single lines of G-code to manually perform cuts.  I am new to mach 3 and CNC machining so please forgive me if this is a stupid question:  Is there a software I can use, where I can input the current profile of the wheel to be turned, then input the the desired final profile to be turned and have a cutting path g-code output generated taking into acount the radius of the insert (its a 1"r round cone shaped insert) and the max cutting depth in order to achieve the final profile?

Thanks!
Frank