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DIY 4th axis on CNC mill doubling as CNC lathe

akb1212

Aluminum
Joined
Jun 26, 2009
Location
Norway, Vestfold
For a long time I have been looking for others making DIY 4th axis capable of doubling as a lathe.

After all there are loads of commercial machines combining mills and lathes. Having seen one myself on an exhibition I thought that must be the perfect concept for hobbyist with limited available space. Especially when one can have a fairly serious (but somewhat aged) VMC for a reasonable price these days.

So my idea was to get a reasonably sized VMC (in my case I got a 1991 Maho HM 600E with tool changer) and then make use of most of the already fitted CNC capabilities and add a 4th axis capable of lathe work. In my case I can either put this on the table of the mill, or remove the angle table and attach more or less a full lathe stripped of its base and apron. If I do this it won't differ much from a commercial combimill.

With this setup I can even attach a trunnion table between the 4th axis and tailstock and I won't even need my old angle table. Except if I need to do exceptionally heavy work for which the whole setup with trunnion table won’t be stiff enough maybe.

So in order to get ideas of how to do this I started searching this and other forums for others doing similar things. At first it seemed impossible because 99% of all indexers I found used worm gears with way to high ratio to be able to rotate it fast enough to do anything close to what is needed to do lathe work. Direct drive systems seemed like the only option. And that isn’t DIY friendly enough for me.

It wasn’t until recently I found a guy doing exactly what I wanted, although on a much smaller mill.

He's using Mach3, and obviously there are issues making this hard in Mach3. But it appears he has cracked it and is able to make it work. And there is a long and very good thread about this on the Mach forum. Success! Mini Machining Center under Mach3 control - Video link

I'm impressed with what he's able to do with his setup. And I'd like to think I'll be able to get something similar set up on my mill eventually. Also check out his videos where he uses it as a shaper to make shapes impossible to make with a rotating tool. I have some internal splines I need to make, and will also try that out.

Then there is the question of what to use. Take a working manual lathe and start chopping on it until it suits my need, or make something from the ground up like he has done. In my case I'd like to be able to flip it over so that the bottom is bolted on vertically to where my table attach on my mill. That means the ways of the lathe would be useless since they are no longer facing the correct way. It's not like they will be used much since the apron is removed. The only thing it will be used for is the tailstock.

So I thought about using a linear rail for that. I have 2 x 3.5 meter long 40mm round linear rails from an old wood CNC (a Morbidelli U26) I had to slaughter for parts (no room for it, and my wife made me choose between it or the Maho).

Today I also realized the main part of the ball nut carriage from this router would be possible to use as a test headstock. It has a 1.5 kW DC servomotor attached via a tooth belt with a reduction to a hollow spindle that turned the ball nut. This spindle has a 50 mm int. dia. axial and radial ball bearing at each end. The problem with this is that it's only 130 mm between the outer bearing edges. I think this is short for a headstock. And it has a bore of 41.5 mm, so it’s fairly thin walled too. But I can keep looking for a suitable lathe headstock while using this as a test. The best thing would be a compact headstock from a small production CNC late of some sorts. But I’m not sure where to find one at a price I would be willing to pay. Anyway, after all I have everything on it including the drive. I just need to convert my machine to EMC2 to do this. Mach3 won’t handle my tool changer so I was planning on converting it to EMC2 anyway.

So, anyone like to comment on the idea?

I’ll try to get some Solidworks drawings made of this to give a better idea of my thoughts.

BTW, before you ask. My intention with this is to build Stirling motors and coolers of a usable size. Not just hobby sized things to verify that the principle works unable to do useful work. So lathe work with indexed milling will be needed for pistons, crankshafts and the like. And the idea of having this all done in one machine is very tempting. And it would save space since it would be the only big machine I would need. Until I go in to mass production that is.....


Anders
 
I agree with Ox.

There is no way your hobby budget will allow you to make a true mill-turn like an Okuma Multus or the like. These machines have very sophisticated drive systems for the spindles/rotary axes. This involves brakes and servos with clutches and other exotic things.

The control is the other issue. That link shows just how many acrobatics he had to do to get Mach3 to run his machine. If you think Mach3 can successfully run a Deckel/Maho type machine you are in for some disappointment. Let alone adding an exotic setup like this.
 
Yeah, to run something like this Your going to need EMC2, Hahahahaaaa.

No I am pulling on your leg.

I have been down this road, and there are all kinds of stiffness issues, and problems. You are much better off trying to get the MAHO into a decent 4th axis setup, and doing the lathe work on a lathe.

If you proceed, try to keep things as simple as possible, put thee entire lathe on the bed of the mill, and see if you can turn material to your satisfaction with the head of the mill, tools in the spindle, or bolted to the head in some way. look at the Hitachi Seiki hicell and you will see what I mean, they turn with the milling spindle, but also have fixed tools bolted to the head, to do real turning.

Once you are satisfied with that, you could remove the bed of the lathe, and put the head and tail stock onto the mill table.

My guess the next step would be to integrate the 4th axis.

1. Put it behind the lathe head stock, now you have the torsional stiffness of the lathe spindle added to your machining.

2. Put it in front of the lathe head stock, now all your turning has to go through the 4th axis, I would put a large roller bearing in there somewhere. You will also need to have a way to lock the chuck to the face of the 4th axis.

3. Put it to the side, now you need to have a really good way of linking the two.

4. Put it in the lathe headstock, yup this is the way to do it, just not sure how you would.

Anyhoo, like I said, keep it reversible until you know it is going to work. I am retrofitting a GE2000 control to EMC2, but I don't plan on cutting any of the GE2000 wiring, so if it turns out to be a nightmare, I could go back to the old control easily.

Best of luck.
 
I was reading the OP when it occurred to me-

Should I need a mill/turn combo I'll bolt my South Bend 9x36 to my 9x42 Bridgeport.

Small work envelop, but I don't see why not...Because then I'd have to remount the motor/pulleys. Damn
 
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Dynamic stiffness.

A Cincinnati Milacron Centerless grinder has it at about a million lbs per inch, that's 100lbs to deflect it 0.0001"
I often ask machine tool builders what their dynamic stiffness is, most of them just go :eek:.

This is what your after. If you have it, things will turn out fine, if you don't, then you will have lousy finishes and make lots of horrible noise.

An Integrex is basically a lathe with a milling head on the compound. The spindle is in the main casting. With a lathe on mill bed design, your headstock is attached to two linear slides, then to the main casting with the tool attached to a third slide, and the slides have huge travels, much more than a lathe, and with that length you loose stiffness.
 
Doing it the other way is a lot more time-tested. Put your part in the spindle, and put turning tools coming off the table (in a vise or whatever). Spin the part up, and viola!

Doesn't work for big parts, though, and programming takes a little more thinking than usual.

If you're not in mass production, trying to save a setup or two isn't usually worth it. Spend the time making good fixtures instead.
 
My goal wasn't just to save space. Even though that is part of it. For some reason my wife want to have the car in the garage.......

And like at least 99% of all hobbyists I will not even consider farming out:crazy:. What is the fun in that? I’m not making this to make one single part. I’m making it to be able to make parts as I dream them up and as and when I need them. And there was no doubt I was a hobbyist and not a professional machinist seeking solution to one single problem was there?

One important thing is to have as few fastenings as possible. Not only because it's a lot of work, but the fact is that it's possible to have higher accuracy this way. That is in fact my biggest concern.

Anyway, the dynamic stiffness is my biggest concern. All other parts of this aren’t any concern at all. They have all been done by loads of hobbyists.
At one point I also contemplated sticking my small Toyo lathe to the bed of my Bridgeport clone. But after considering the resulting stiffness of the whole ting I abandoned it quite quickly.
After all a Bridgeport in itself is about as flimsy as one could get by with and still make somewhat decent cuts. At low forces that is, and you really have to watch your federate and climb.

Then I bought the Maho. This machine has a much more rigid construction. That is what got me thinking it should be doable now.

Especially when I saw Simpson36’ setup. He’s results showed me it should most definitely be possible to do it on my mill. I’m quite sure my mill is more rigid than his…..

I do realize the headstock is bolted rigidly to the frame on a lathe, and therefore the rigidity is higher.
Nevertheless nobody seems to get in trouble when adding a 4th axis to a mill like mine. And when you think about it there isn’t much difference whether you move a cutter rotated by the spindle of the mill in to the material attached to the 4th axis or move the material attached to the 4th axis in to the tool attached on the column of the mill.

You can compare drilling in a lathe and a mill. It's not that much difference in the forces applied and the dynamics whether you do it in a lathe by attaching the drill bit in your tailstock and rotating the work piece or put that same drill bit in your mill and rotate it and attach the work piece in your vice.
Ok, there are differences because of the differences in moving masses. But the main difference is in the way the construction between the two opposing forces is put together.

When you compare milling and turning in a 4th axis attached to a mill the differences are smaller. Everything is more or less the same since the only difference in this scenario is what part moves. And when you look at the dynamics in this there is even an advantage in rotating the work piece. If you do this there is a (more or less) constant force acting on the cutter since it is not going in and out of the cut like it would if it was sitting in a mill rotated by the mill's spindle. The only scenario this would possibly be worse in is if you get serious resonance and chatter.

My mill is more than capable of handling both 1 and 2 rotational axis put on the table. The manual shows a 5 axis setup that looks really attractive. And I don't se the big problem in changing the item moving from the tool to the work piece.

That is, I will need to make sure the construction is rigid enough to be able to do what I intend for it to do. And I need to put in a motor strong enough to have enough torque to be able to keep the position of the 4th axis since the toothed belt doesn’t have the same torsional rigidity as a worm gear.

Anders
 
Doing it the other way is a lot more time-tested. Put your part in the spindle, and put turning tools coming off the table (in a vise or whatever). Spin the part up, and viola!
Doesn't work for big parts, though. and programming takes a little more thinking than usual.

If you're not in mass production, trying to save a setup or two isn't usually worth it. Spend the time making good fixtures instead.

I can see where you are coming from. And I do to some extent agree. And as mentioned I'm also going to do turning the way you mention.

One scenario I have thought about in this scenario is to take away the vertical head on my mill and making a bolt on small lathe upside down to protrude out from the horizontal boom and attach the chuck to the spindle. Kind of hard to explain.....
There is a horizontal milling attachment resembling this available for the machine. Although this is made for horizontal milling with support at both ends. But having the possibility to have a tailstock would increase the usability somewhat. Depending on what you need to machine of curse.

What started me thinking was actually the fact that I dread doing a full conversion of my manual lathe (a Cazeneuve HBX360). First off it would be a lot of work. And it would not be able to do what I want it to without tons of work, indexed milling and tool changing.

And I do want a 4th axis to my mill, no doubt about that. And I prefer to make one myself due to the somewhat crazy prices of correctly sized good ones.

Then seeing what a full blown mill-turn can do, and then seeing what Simpson36 had actually accomplished I was convinced this was the way to go for me. I didn't se ONE single ting he did that I thought wouldn't be impossible to overcome. But I did se a lot of things possible to do that I deemed very attractive.
And I'll keep my manual mill for a while anyway. Until I know if I can do without it or not at least. But first I have to repair the leaking variator that seems to haunt almost all of these lathes.

Yeah, to run something like this Your going to need EMC2, Hahahahaaaa.
No I am pulling on your leg.

I'm not frightened by EMC2 if you worry about that. I'm an electronics engineer by trade, and the electrical part of this conversion is what is least worrying for me. And I do think I'll end up putting EMC2 on it at some point. So many things I'm missing on it now. A hand pendant amongst other things.

But in doing this conversion I'll be sure not to burn any bridges before it's working. Like you I'd like to be able to go back to the existing control if the conversion fails.
Right now I'm working on getting the old one working though. I have a parity output error. I have changed the I/O card, and no change. So now I'm trying to replace the control/teletext card. But this kind of fault searching is expensive, so if this doesn't work I'll ditch the whole 432 controller and put in EMC2 and removing all I can of the old control system.

And sorry, but I wasn't able to follow your steps in integrating my lathe in my mill. My table can take 400 Kg load, and my lathe is about 2000 Kg. I don't se how I can do what you are suggesting. My idea was to get the needed parts as I needed them, first a headstock as basis for the whole 4th axis.

And sorry, but I seem to be unable to write short posts.

Anders
 
I mentioned EMC2, because it is supposed to be better at things like tool changing than Mach3.

Mach3 won’t handle my tool changer so I was planning on converting it to EMC2 anyway.

Ah, sorry, that was after this paragraph, which scrambled my brain. :crazy:

Take a working manual lathe and start chopping on it until it suits my need, or make something from the ground up like he has done. In my case I'd like to be able to flip it over so that the bottom is bolted on vertically to where my table attach on my mill. That means the ways of the lathe would be useless since they are no longer facing the correct way. It's not like they will be used much since the apron is removed. The only thing it will be used for is the tailstock.
 
I mentioned EMC2, because it is supposed to be better at things like tool changing than Mach3.

Seems easy enough in Mach, I have a 6 position rear turret and a 6 position front turret on my lathe and both were easy enough to do.
Rear turret is the original one and its all hydraulic, only rotates one way and has to clamp each tool.
Front turret I got from a friend who was scrapping a Bullard which I used to replace the hydraulic 4 position toolpost which was originally on my lathe at the front.
Front turret was all hydraulic also but I fitted a servo and have bidirectional rotation and it doesnt have to clamp at each position like the rear turret.
Hood
 
I am a bit confused here.
If you are wanting to use the spindle of the mill, and run traditional milling tooling in it, then why would you need high speed revolution of your part?

I do this all the time, using a rotary table and a tailstock, and many times, I prefer it to using a lathe- I can do a lot of things that are not possible in a lathe, like indexing the work piece, making polygonal shapes, and it works much better on interrupted cuts than a lathe does.

And what do you gain by putting your lathe on the mill table if you are not using the mill spindle?

If you want to turn parts on a lathe, do that. Its easy enough to make a rolling cart for a lathe the size range you are talking about, and roll it out of the way of your wife's car.

I understand the allure of true 4 and 5 axis milling- but I fail to see what you gain by putting a real lathe on the table instead of a motorized rotary table or indexer.
 
This gets mentioned quite a bit so I have to ask:
Just what the heck is so complicated about changing tools on a mill?

Bob

Have the same thoughts as well, only thing I can think of that would be slightly different is orientation but why that make things hard to do I have no idea.
Hood
 
I think that this is a good idea, The cutter would be mounted upside down and programed in the x-y. Probably mounted to a qc toolpost instead of the spindle. the head of a lathe driven by a servo motor would work. Howeaver if no threading is to be done you could use the exsisting drive.(on the lathe head) The tailstock could also be mounted to the table. Some serious traming would have to be done. Threading would be possible but I dought the macros would be present. For indexing work you would need a 4th axis at least something with a brake. Howeaver in my opinion by the time you got all of this working you would have plenty of room in the garage and no more ambition to build sterling engines.
 
There is a huge difference between "it works" and "it always works in a real shop with real operators every day". Mach3 is a hobby control. No amount of wishful thinking will ever change that.

Issues with Mach3:

Mach3 has no realtime motion control. When you hit feed hold, it keeps right on moving until the "buffer" is empty. That alone is why I will NEVER use it again. This shows up all over. MPG is about unusable, rigid tapping will never happen, lathe threading is not great.

Mach3 has no built in ladder with dedicated I/O to control things like a tool changer. USB I/O emulators and keyboard type HMI devices and control through a parallel port are not robust. The other big issue with a lack of I/O is the lack of useful error messages to tell you what is going wrong.

The Mach GUI interface was clearly designed by a computer programmer. A mouse has NO PLACE in a shop. Neither does a touch screen. Fine on an Ipad, not in an industrial setting. Mach has no built in editor. There is too much emphasis on the tool path graphics. No dedicated rapid override. There is a reason CNC machines have all those real knobs and switches.

As far as I know Mach has no configuration for random or "floating" tool changers. There is no way to assign pot numbers or make tools dedicated to one pot for large tools.

No ability to use the encoder index pulse for homing the machine.

No lathe canned cycles for roughing or grooving. The whole lathe side of Mach is an afterthought.

Lack of other basic features like accelerating the spindle during rapid or restarting in the middle of a program with all the right modal codes applied.

EMC2 fixes many of these issues, but has it's own problems.

Sorry this is off topic, I needed to vent.
 
Lathe tool change

1. Extend turret.
2. Rotate turret.
3. Look for position pulse.
4. Stop turret.
5. Retract turret.
6. Give Ok command.

Mill tool change

1. Retract Z Axis
2. Turn off Spindle.
3. Orient Spindle.
4. Activate tool chain
5. Look for position pulse.
6. Stop tool chain.
7. Grab tool.
8. Extend tool change arm to remove tool from chain.
9. Move tool change arm to safe location.
10. Retract tool change arm.
11. Move tool change arm to spindle and grab tool in spindle.
12. Open drawbar.
13. Interchange tool in spindle with one in arm.
14. Close drawbar.
15 . Move tool change arm to safe location.
16. Activate tool chain
17. Look for position pulse.
18. Stop tool chain.
19. Extend tool change arm.
20. Move tool change arm to chain.
21. Retract tool change arm to put tool away.
22. Move tool change arm to safe position.
23. Give Ok command.

Umbrella style

1. Retract Z Axis
2. Turn off Spindle.
3. Orient Spindle.
4. Move tool umbrella in.
5. Open drawbar.
6. Retract Z axis.
7. Rotate tool change drum.
8. Look for position pulse.
9. Stop tool drum.
10. Lower Z axis
11. Close drawbar.
12 . Move tool umbrella out.
13. Give Ok command.

I am assuming the orient spindle doesn't need to be broken down into its components too.
 
Really shouldn’t be posting this here as it has nothing to do with the Op's questions but I felt it right to offer my opinions. Wont answer any more as its off topic and would be better suited to a thread of its own.



Mach3 has no realtime motion control. When you hit feed hold, it keeps right on moving until the "buffer" is empty. That alone is why I will NEVER use it again. This shows up all over.

As far as I am aware, when you Feed Hold Mach will calculate the stop, do it then clear the buffer and refill with updated data. I agree it can be slow and is not great but slow for me has never been more than .5 second from memory. Then again I tend to use the FRO more than I do feed hold.


MPG is about unusable

Not sure why you say that, works fine for me, have a rotary switch on the panel to change between axis, have another to change between constant motion mode and multistep modes of 0.01mm, 0.1mm and 1mm. In practice I have found constant and multistep @ 0.01mm to be the two I use most.

rigid tapping will never happen

I believe the DSPMC allows this, possibly the Galil and reportedly the Centipede. If you have a servo spindle then it is even possible with the parallel port. Also quite a few others being developed at the moment from what I hear.


lathe threading is not great.

Never been an issue for me and I do a lot of threading, there were a lot that did have issues but these tended to be hobbyists with underpowered spindles or people that used VFDs that would over compensate for the slow down. Work was done recently on the parallel port driver for threading and reports I have seen have been positive. I do not use the parallel port and have not done for a long time.

Mach3 has no built in ladder with dedicated I/O to control things like a tool changer.
Very true and I am in hopes that will be changed in the future. There are Brains which are similar but not as good as true ladder logic, then of course you have VB in the macropump.

USB I/O emulators and keyboard type HMI devices and control through a parallel port are not robust.

Personally don’t like keyboard emulators whether USB or PS2 or whatever but there are also USB devices that can accept real digital I/O (and analogue) but again it is not my preference as they are 5v.
Lots of controllers that work with Mach that have lots of I/O, Galil, DSPMC, Centipede. Then of course there are the Contec cards, mesa 5i20 cards and my personal favourite a PLC via Modbus.


The other big issue with a lack of I/O is the lack of useful error messages to tell you what is going wrong.

When you write your controlling macro for such things then the user can add messages. They can be written to pop up a window on screen detailing whats wrong or can be displayed in the Error window if that is your preference. For example if I press the cycle start button and my spindle is disabled (button on panel for safely working at chuck or headstock lever disengaged) I will get a message telling me I am a tit and I either have the spindle disabled or the headstock out of gear.

The Mach GUI interface was clearly designed by a computer programmer.
No doubts about that, the standard screenset is a jumble to try and keep everyone happy, and we all know that path never works ;)
There are screen designer utilities to make your own screenset up, you can have it as complicated or as simple as you like and are very easy to use in my opinion.

A mouse has NO PLACE in a shop.
Don’t like mice myself, much prefer the IP67 Stainless keyboard and trackball that I use on my machines.

Neither does a touch screen. Fine on an Ipad, not in an industrial setting.
I like my touchscreen for occasional use of non day to day functions. With regards to no place in an Industrial setting, well that’s a personal choice but seems to me a lot of automation uses them.


Mach has no built in editor.
Not really sure what you are meaning by that, if you press the Edit button your code will open in notepad to allow editing. It may be something different you are talking about however.


There is too much emphasis on the tool path graphics.
Make a screen up with no graphics if that is what you want. Or even just turn off the toolpath via the option in Mach.

No dedicated rapid override.There is a reason CNC machines have all those real knobs and switches.
OEM223 is the code for RRO DRO so not sure why you would say that.
I do agree that real buttons, rotary switches and pots are nice and that is why I have them on all machines. As mentioned previously I use rotary switches for MPG axis control. I also have pots for Feed Override and Spindle Override and quite a few buttons for things such as cycle start, feedhold, flood and mist coolant, spindle start etc etc.
I chose to have my feed and rapid override linked in Mach but if preferred unchecking the link option and fitting another pot would be no hardship, just one I personally would not have.

As far as I know Mach has no configuration for random or "floating" tool changers. There is no way to assign pot numbers or make tools dedicated to one pot for large tools.
Never done it or needed to as I don’t have changers on my mills however I don’t see too much difficulty in doing this when you write the toolchange macro as all it would require is you write to user DROs and read from them on next tool change to get the right pocket, could be wrong though ;)

No ability to use the encoder index pulse for homing the machine.
I use it, at the moment it is done in my servo drives as they can do it. Previously on my lathe the breakout board I used could do it and lastly it is planned to be a feature of the SmoothStepper and other devices as far as I am lead to believe.

No lathe canned cycles for roughing or grooving. The whole lathe side of Mach is an afterthought.
There are “wizards” for such things I believe, both ones included in standard Mach and also ones users have done and uploaded for others to use. I don’t use them much as normally I find it easier to use CAM or MDI for simple stuff. It would be good for more canned cycles though and I am in hopes of that changing.
You are quite right about Turn being an afterthought, one that works well for me however but it is definitely the part of Mach that gets the least attention. Lathe users are growing within Mach and the voice is getting louder and things are getting done slowly and I am in hopes the pace will increase.

Lack of other basic features like accelerating the spindle during rapid
Possibly you had a spin up delay set ?


or restarting in the middle of a program with all the right modal codes applied.
Often hear of people having issues with Run From Here but not had issues myself. There are a few things I would like to see changed such as the prep move box that pops up having an option to choose spindle direction, I believe this to be in the next big revision but not certain.



EMC2 fixes many of these issues, but has it's own problems.

Never used EMC2, have heard it works well but cant comment from a personal standpoint.

To me the biggest issues people have with Mach are because they tend to use DIY methods and hobby grade components to build their machines, I much prefer to use Industrial type components and Industrial type practices.

Hood
 
Lathe tool change

1. Extend turret.
2. Rotate turret.
3. Look for position pulse.
4. Stop turret.
5. Retract turret.
6. Give Ok command.

Mill tool change

1. Retract Z Axis
2. Turn off Spindle.
3. Orient Spindle.
4. Activate tool chain
5. Look for position pulse.
6. Stop tool chain.
7. Grab tool.
8. Extend tool change arm to remove tool from chain.
9. Move tool change arm to safe location.
10. Retract tool change arm.
11. Move tool change arm to spindle and grab tool in spindle.
12. Open drawbar.
13. Interchange tool in spindle with one in arm.
14. Close drawbar.
15 . Move tool change arm to safe location.
16. Activate tool chain
17. Look for position pulse.
18. Stop tool chain.
19. Extend tool change arm.
20. Move tool change arm to chain.
21. Retract tool change arm to put tool away.
22. Move tool change arm to safe position.
23. Give Ok command.

Umbrella style

1. Retract Z Axis
2. Turn off Spindle.
3. Orient Spindle.
4. Move tool umbrella in.
5. Open drawbar.
6. Retract Z axis.
7. Rotate tool change drum.
8. Look for position pulse.
9. Stop tool drum.
10. Lower Z axis
11. Close drawbar.
12 . Move tool umbrella out.
13. Give Ok command.

I am assuming the orient spindle doesn't need to be broken down into its components too.

So nothing realy more complicated as I see it, just probably more I/O required and a longer sequence to the ladder or macro.

Hood
 








 
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