# Tube-O-Matic

Discussion in 'Workshop Tips and Secrets / Tools' started by FritzW, Oct 10, 2019 at 11:44 PM.

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1. Oct 10, 2019 at 11:44 PM

### FritzW

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A (mostly) 3D printed rotary 4th. axis with a pass-through collet that can handle 2 1/2" diameter tubes. >>The biggest cheap chinese ebay 4th. axis setups can only take (through the chuck) < 3/4" tubes.<<

It's not ready to print yet, still have some details to sort out, but all the heavy CAD work is done.

Here it is on a CNCRouterParts CPR4896 but it would work on any CNC machine (I used the CRP4896 because they let you download the model and it's the machine I have in the garage)

Just to be clear: these are the parts I'm talking about...

The stepper motor is mounted separate from the collet. If the "steady rests" don't provide enough tension on the cog belt (not shown) then I'll have to come up with some sort of tensioner, no biggy.

Everything that holds the tube is 3D printed. The printed parts will cost about 20 and take 2 or 3 days to print. The collet holder (off white) will fit all the collets (yellow) up to 2 1/2". The red handwheel is the collet nut. The red part in the steady rest has a surface for a hose clamp. I'll have to print different ones for different diameter tube but the mount (white) will fit all of them. Hopefully the V grove will remove any slop in the tube. Cutaway view. Yeah, yeah... I screwed up the threads on the collet, easy fix. I'm sure I'll have to adjust the fit inside the steady rest. But this is a NEMA 34 motor (big) turning at 4 or 5 RPM, I'm not too worried about it. The goal of this thing is to cope and drill thin wall tubing faster and more accurately than I could by hand. It's NOT for making mechanical heart valves for Humming Birds. proppastie and pictsidhe like this. 2. Oct 11, 2019 at 12:56 AM ### Victor Bravo ### Victor Bravo #### Well-Known Member Joined: Jul 30, 2014 Messages: 5,968 Likes Received: 4,786 Location: KWHP, Los Angeles CA, USA That's PFC (pretty dang cool) I'll bet that even using modest resolution printed parts that could drill holes repeatedly within .015" which means thatyou could do "matched hole" on something simple within welding range and within cleco range. I'm going to post a separate idea on another(separate) new thread that is relevant to this type of construction. See if you can design and print something to make this work... stay tuned... 3. Oct 11, 2019 at 3:12 AM ### ScaleBirdsScott ### ScaleBirdsScott #### Well-Known Member Joined: Feb 10, 2015 Messages: 995 Likes Received: 637 Location: Uncasville, CT I feel like one could build a more industrial-level version of this quite easily with mostly off-the-shelf parts. And still relatively cheaply. Some cheap bearing blocks, some 80/20, etc. Seems it could easily also be a good standalone device. 4. Oct 11, 2019 at 4:12 AM ### Hot Wings ### Hot Wings #### Well-Known MemberHBA Supporter Joined: Nov 14, 2009 Messages: 6,304 Likes Received: 2,247 Location: Rocky Mountains If Fritz modified his collet to also be the X axis hold - and automate the clamping with a second stepper or pneumatic cylinder swash plate style - the tube could be power fed as needed. Is there open source software for tube miter G-code? 5. Oct 11, 2019 at 4:18 AM ### FritzW ### FritzW #### Well-Known Member Joined: Jan 31, 2011 Messages: 3,529 Likes Received: 3,140 Location: Las Cruces, NM Actually, print resolution wouldn't have much affect on the accuracy and repeatability. A lot of other things would though. To keep from flexing the steady rests, copeing the end of an .049 wall tube might take 3 or 4 passes but it would probably be within just a few thousandths. A heck of lot more accurate and repeatable than a tape measure, Sharpie marker and a hacksaw and files. Drilling would be as accurate as the base machine would be without the 4th axis (IF everything was *aligned properly, ...but that would apply the same to10,000 4th. axis)

*a 1/10 of a degree misalignment between the machine axis and the tube, over the 8' length of the tube, could really screw things up (applies to any machine).

No doubt. This wouldn't be a full blown industrial production machine. But I think it would knock out a single airplane (or two or three) a whole lot faster and more accurately than it could be done by hand.

The real benefit/purpose/goal of this idea is that anyone who wants to build this airplane can download the files and print a major portion of the machine that will do all the tedious, PITA stuff for them.

For the purpose of building this (TBD) TnG airplane, it still needs the ability to cut out the gussets. But I think it could be the perfect add on to the MPCNC mentioned at the beginning of the other thread.

6. Oct 11, 2019 at 4:38 AM

### ScaleBirdsScott

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My only concern is being tabletop limits you to doing a few feet at a time. One could hypothetically make all the gussets and ribs on say a 2x2 foot shapeoko or similar unit. But if you want to do a full 10ft tube at once, you might want a separate unit. Meanwhile that narrow, long machine can easily fit out of the way 90% of the time.

7. Oct 11, 2019 at 4:52 AM

### FritzW

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Now there's an idea! I could put a V sholder on the collet and use something like the steady rest mount to hold it (or live a little and put some bearings in it). Then I could use much lower friction steady rests. ...and it would solve the issue of the belt tension flexing the tube.

You can do it right in SolidWorks. Just split the tube and "unroll" it (in SW). Use that as a flat pattern for your DXF. The CNC machine thinks it's cutting a flat pattern that's the width of the circumference of the tube. ...hard to explain, very easy to do.

Put another way: when a 1" diameter tube turns 1 revolution the machine just thinks that it moved 3.14159" along the Y axis.

8. Oct 11, 2019 at 9:43 AM

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Well I have darn near the same tube coping design for the skylite. I shelved it as I can design the tool but not the software to cut it. Fritz is there open source code out there already to cope tubing? If so I already have the Skylite fuselage in solidworks with all the tubes coped. I was going to give up and go with Vr3 but if the code existed I would give it a try. Hoping for good news on this... Oh and I just sent my resignation to my day job an hour ago to focus on a consulting gig, Once done, I will have more time to devote to airplane work semi full time starting in February...

9. Oct 11, 2019 at 12:54 PM

### Hot Wings

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"We" can do it in SW but what about those that don't have SW? With free EAA SW I suppose this really isn't a problem.

Edit: Since the new "Y" axis only thinks in degrees or rads we will still have to either shrink/expand the flat wrap along the Y axis in SW, pull the curve ordinates out of SW and run then through an Excel sheet, or come up with a macro for the G-code modification.

Shrinking/converting the Y axis to Pi width in SW is probably the easiest............

Laying awake this morning I was pondering how to keep the rotational index of the tube as it gets fed through the collet for the next cut. Anything clamped external to the tube, like a typical muffler shop tube bender, has the potential to snag on the various feed mechanism bits. Maybe a miniature internal ball mechanism like a slip/skid, or other switch that closes only at level, could be used with a software re-index for the second cut?

Last edited: Oct 11, 2019 at 1:03 PM
10. Oct 11, 2019 at 8:20 PM

### Victor Bravo

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Excellent, congratulations!

Take a deep breath, realize that you've got a unique skill and plenty of brain power, and push the throttle all the way forward. I'm already printing flyers that say "I knew him before he was a billionaire!"

11. Oct 11, 2019 at 8:39 PM

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Hello Fritz,

To keep the rotational axis, I planned to drill a small hole at each end on the machine prior to the CNC coping. However I could do it with just one hole and use that hole to fixture and clock the next coping operation. The hole has some benefits that it will let the tube breath during welding to avoid pops and splatters and once the fuselage is welded just weld the hole shut. For an aluminum tube and gusset version, it might make sense to add a thin pencil line down the tube and have a simple pointer on the side of the machine that you clock the tube to and set zero for each coping job on each end. If you want to get fancy you could use a sensor to find that line with a homing routine. Or clamp on a homing flag to the tube first and use a Omron through beam sensor as the homing sensor. However this is like using a chainsaw to cut bread. the analog version of a thin sharpie line and a pointer or a hole in the tube will get the job done.

As for flattening the cope profile, I have not tried that and unsure how to approach it. I have seen software that makes templates and rainbow aviation had a way to do it with their coping guides. Any thoughts on the process and getting it to Gcode.

12. Oct 11, 2019 at 8:55 PM

### Hot Wings

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It is a sheet metal tool. Slit the tube with a token width cut - like .02mm - down the full length. Then under the sheet metal tab pick 'flatten'.

13. Oct 11, 2019 at 9:25 PM

### Hephaestus

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https://www.thingiverse.com/thing:624625

3 jaw printed Chuck on both ends, if you run t-nut style bed your alignment will be pretty darn close... Simple spur gear direct to the A-axis stepper (beats another belt drive)

There's some great A-axis stuff out there to copy. Using lathe style Chuck's makes a lot more sense to me.

14. Oct 11, 2019 at 9:37 PM

### Hephaestus

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On the software side... I've got an old 720k 1.44 floppy here with a msdos program to do exactly this. It's out in storage, I'll see if I can find it and something to read the **** disk. Lol

You enter the specs for the 2 tubes, select orientation (centered or flush to edge), angle, and it kicks out gcode for the cut.

15. Oct 11, 2019 at 9:59 PM

### FritzW

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There are plenty of software packages out there that'll take a 3D file and generate 4th axis (round) GCode, unfortunately I don't know much about them except what I've seen on youtube. (tons of info on youtube and the CNC forums)

With the software I've got right now (SW, CamBam and Mach3) the easiest way I know to cope and drill a tube is to create a flat pattern like HW said in post #12 and connect the 4th.(A) axis to the Y axis terminals on the break out board.

...I'll go do a quick print screen

16. Oct 11, 2019 at 10:23 PM

### Hephaestus

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https://www.amazon.com/Sunwin-4th-Axis-Router-Rotational-Tailstock/dp/B00E3OM4LM

This is my A-axis. Use it for pretty useless stuff so far, like laser etching coffee mugs.

But I like the design, mounting it edge of table, and replacing the tailstock with another 3-jaw means you could effectively run full lengths of tubing through it fairly accurately and not be as restricted by the machine dimensions. As long as you kept it aligned vertically you could slide the length through for individual cuts or full length ('hold down tabs' to snip at the end might be a great idea to keep the integrity during the cut)

17. Oct 11, 2019 at 11:13 PM

### FritzW

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The reason behind the 3D printed one (besides being fun to mess with) is to have a pass through chuck that can take the size of tubes you'd need in a t/g airplane.

18. Oct 11, 2019 at 11:32 PM

### Hephaestus

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That's why I linked the 3d printed 3 jaw Chuck. Scale, find suitable bearing, add some herringbone gears... Pretty sure that ones original source is over on grabcad. Using external permanently fixed A axis will be easier than an internally fixed version wouldn't you agree? We could be even smarter and drive both ends of it with a nema17

I linked the one I own because it's a good example of how it's done on the high end Mills. There's less to go wrong with that arrangement than the layout you have. Wasn't criticism, just pointing you another way that may be mechanically better.

19. Oct 11, 2019 at 11:53 PM

### FritzW

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FWIW

This is how I do it, there are no doubt better ways...

Open the tube part

Find a line on the tube that misses any holes (it's not a problem if it does, just adds a few steps)
Draw wedge on a plane perpendicular to the tube. Using a wedge keeps the edges of the flat pattern 90 degrees to the surface.

Set the back of the wedge to something really small, like 0.0005"

Extrude cut the wedge down the whole tube.

Self explanatory, ...maybe

Hit the Flatten button to unroll the tube. You have to hit "Normal to" the surface you want or the next step will go wonky.

Save as A DXF. Showing hidden edges probably doesn't matter on something simple like a this but it's a good habit to get in to.

Bring the DXF up in your CAM software and good to go.

Last edited: Oct 12, 2019 at 2:48 AM
20. Oct 12, 2019 at 12:26 AM

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