TL bar feed design.

[DJPdesign]

Hello, I am hopefully getting a TL lathe in the next few weeks.
I am looking to see if it is possible to make automated parts on this machine (primarily low volume, mainly for the fun of trying to automate the process).
I have an air driven chuck that I could put on this lathe, that will function in a similar way to a hydraulic chuck, which I would be able to control from one of the relays.

I have seen bar pullers in the past, but have also read on CNCzone about “home made” bar feeds on TL lathes. I was wandering if anyone could help me out with the basics of the design and some direction to manufacturing my own.

Many thanks

Dan

[automizer]

could you add a little more to what you will be putting on the lathe. Are the parts small, large, long. If you part is say a 15min program you could have a stop in place of one of your tools, and the air chuck opens just before an M00 you more the bar to the stop manually then hit start the chuck closes and goes on its way. You say low volume, is the volume high enough to need a puller?

[DJPdesign]

Thanks for your comments. Part runs would be 50-100. Small short parts, (similar to pull studs but anvils for a impact tester in EN24). 200 off shear pins. I am more interested in getting the chuck going and seeing how difficult a bar feed would be to make.
Even though It may not be needed, I feel that it would be a good thing to try. Many thanks. Dan

[automizer]

ok so how long would your stock be? You may want to look at something that pushes that bar rather then pull it, with stock that small you might be able to use compressed air to push the bar to a stop in the machine.

[Geof]

It is possible you have seen mention in some of my posts about our shop-made barfeeds (shop-made sounds much more professional than home-made )

We have three units that are hydraulic powered; actually the working fluid is the coolant with one unit using compressed air over coolant and two using electric driven hydraulic pumps that are supplied from the machine coolant pump through a filter. The bar that is being fed acts as the hydraulic piston inside a long carrier tube that is the cylinder. Different bar sizes are accomodated by different sizes of liner bushings inside the carrier tube and the liner at the chuck end is just made a close fit on the bar and has an O-ring seal between it and the cylinder. The hydraulic pump has sufficient flow that the leakage between the bar and liner is overcome and pressure builds up to advance the bar when the chuck is opened; it is the cross section of the bar that the pressure is working on, there is not any piston head. For example a 1/4" dia bar has a cross section of about 0.05 in^2 and at a fluid pressure of 400 psi is advanced with a force of 20 lbs.

The carrier tube is about 7 feet long with chuck end screwed into a flange which mounts inside the chuck; most power chucks have a liner piece that fastens in the front of the chuck to stop chips getting into the works, we just made the carrier mounting flange to take its place. The opposite end of the carrier tube is mounted in a pillow block with a second pillow block close to the end of the spindle; actually it is close to the actuator for the hydraulic chuck and because this actuator moves in and out to open the chuck nothing can be attached to it. Hence the pillow blocks for the carrier tube. The pillow blocks are mounted on a large frame attached to the machine and are adjustable so the carrier tube can be kept concentric and parallel to the spindle within about 0.005" over its length. The 7 feet long accommodates a 6 feet long bar; most bar stock comes in 10 or 12 feet lengths so they are simply cut in half. A 12 feet long bar feed takes up too much floor space.

The fluid supply to the carrier/cylinder is through a rotating seal at the far end. On the air powered unit which feeds an air operated chuck a simple lip seal is used because the chuck has to be stopped and the barfeed is only under pressure when it is stationary. The other two units both feed hydraulic chucks which can be opened while running so they have face seals that can take several hundred psi while running at over 1000 rpm. All three barfeeds can run at a speed of 4000 rpm and the full hydraulic units feed at 1000 rpm.

I do not have much in the way of drawings for these units; they were built directly out of my head with a few rough sketches. I have attached a couple of photographs showing the end support where the rotating seal is. If you cannot build a good enough image in your mind from my description I can make a few sketches but I have the feeling this is serious overkill for what you want. Have you ever seen any pictures of what was used on manual machines for barfeeding? This could be more along thre line of what you need.

[DJPdesign]

Many thanks Geof, I think that it was your posts I had been reading. Your so right shop made sounds and looks much better than home made, (my shop is at my farm so they are synonymous). Geof, thanks for your input, I can now understand what you have been talking about in your threads. I am sure I will have more questions as I walk through the design. I may be too much for what I need, but I will build the rotating bar (to hold the stock) first, used with a puller and go from there.

Geof, I am not familiar with the manual machine bar feeds.

Thanks. Dan

[AMCTony]

Is it possible to hookup a standard commercial bar feeder to a TL lathe? I am interested in this as well.

[Geof]

Originally Posted by DJPdesign ....Geof, I am not familiar with the manual machine bar feeds. Thanks. Dan

The least complicated bar feed is carrier tube and a pusher that is driven by a heavy weight and a bit of cable.

The carrier tube is a plastic lined with a slot along the bottom and is mounted on a frame and lined up with the spindle. The end nearest the spindle slides on the frame so it can be moved sideways so a bar can be passed down the side of the machine and into the carrier. Inside the carrier tube is a sliding plug with a bracket that sticks out of the slot; the pusher is attached to this plug. Attached to the bracket is a cable that goes to the end near the machine and over a pulley where it has a weight attached. The weight is not directly attached but through a reverse block and tackle arrangement because the weight can only drop a distance of about 2-1/2 feet but the sliding plug has to move 6 or even 12 feet.

The carrier is moved to its side position, the sliding plug is moved all the way back and latched there and a length of bar inserted. The carrier is moved back in line with the spindle and the latch on the pusher released to push the bar into the spindle. A stop is in one of the tool positions and when the chuck is opened the pusher advances the bar to the stop. The pusher can only advance the bar until the sliding plug reaches the end of the carrier tube at which point it is pushed back and an extender rod placed between the pusher and the bar.

Normally this type of barfeed did not use liners inside the spindle or carrier tube for different bar diameters. The pusher had a cone shape and was mounted on a bearing on the sliding plug so it revolved with the bar and held it on center. Because the bar was only supported at each end and could whip if the speed was to high it was often the case that small diameter bars had to be run slower than larger bars.

[Geof]

Originally Posted by AMCTony Is it possible to hookup a standard commercial bar feeder to a TL lathe? I am interested in this as well.

The TL's have the user M relay controls. You have to pay a couple hundred bucks for the wiring harness and socket but then you can control any external equipment through a relay.