# Tube-O-Matic

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#### Hephaestus

##### Well-Known Member
so you convert the tube to flat to cut it with the tub-o-matic?......must have missed that one.
you did talk about converting axis to rotation....went right over my head.
In the cnc end - theres no difference between rotation and physical travel in that axis.

In terms of software making the cut, its easier to digitally unwrap it. The tube is still cut as a tube - but rhe software doesnt need to know that its rotating an axis rather than traveling down a table.

#### proppastie

##### Well-Known Member
Log Member
what is the width of that plate? should be 3.0316

#### FritzW

##### Well-Known Member
Log Member
what is the width of that plate? should be 3.0316
It's a 1" OD tube. If my feeble mental math is right it should be the tube diameter times pi minus the width of the slot = a smidge less than pi

The slot must have been about .007" wide. (this tube was just to demo the unfold settings, the slot could have been narrower)
EDIT: I measured both sides to make sure it wasn't tapered (ie. if you use a box instead of a wedge to cut the slot)

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#### Aerowerx

##### Well-Known Member
I calculate the slot as 0.0073265358979 inches, +/-Brownian Motion

#### proppastie

##### Well-Known Member
Log Member
It's a 1" OD tube. If my feeble mental math is right it should be the tube diameter times pi minus the width of the slot = a smidge less than pi

The slot must have been about .007" wide. (this tube was just to demo the unfold settings, the slot could have been narrower)
EDIT: I measured both sides to make sure it wasn't tapered (ie. if you use a box instead of a wedge to cut the slot)
View attachment 90134
Ok here is the skinny from an old "Die Designer" me.....the blank is calculated from the neutral bend line....in this case t/2.....one half the metal stretches one half compresses....I did not figure in a slot width so the blank should be even less. for .035 wall the Diameter of the neutral bend line is 1.000-.035=.965.

.965 x 3.14159 (PI)= 3.0316.....if your slot is .007 then...3.0246 should be the width of the blank

I am not sure what your software is doing but understanding it when trying to match hole tool is very important.

Edit: I do not understand why you have a slot when figuring for round tube....do you need it to unfold?

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#### FritzW

##### Well-Known Member
Log Member
...the blank is calculated from the neutral bend line...
In this case it's the outer surface of the tube.

I am not sure what your software is doing but understanding it when trying to match hole tool is very important.
Solidworks lets you handle just about every conceivable aspect of a bend. The location of the holes are made in the tube while it's still in the assembly with all the other tubes, gussets, skins, etc. (the software equivalent of match drilling everything while it's in the fixture). The tube is unfolded on it's outer surface because that's the surface the cutting tool will see but you could unfold it midplane or the inner surface. ...the software would it but the g code would have to be setup for it.

The machine will drill the holes in the right place, that's not an issue. What is an issue is manually bending the predrilled gussets. A little human error there and you'd have problems.

Edit: I do not understand why you have a slot when figuring for round tube....do you need it to unfold?
Yes, you just need it to unfold the tube. it can be as narrow as you want to make it (the smaller the better). If you start getting down around 0.00001 it gets to be a PITA to find the edge to unfold it.

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#### proppastie

##### Well-Known Member
Log Member
Well perhaps for the Tube-O-Matic it does make sense to use the outside of the tube.....not sure about the gussets from flat blanks though.....as i said the outside of the bend stretches the metal. I have seen un-folding software that asks for the location of the neutral bend line.....for smaller bend radius it is not strictly t/2 , In fact my basic die making text says for an inside radius R<2t, .33t for the location of the neutral bend line, R=2t to 4t , a .4t location , and R>4t a .5t location.

Certainly a gusset with a R= .5 (fitting around outside of a 1"tube) for any thin gusset will be greater than 4t so the location of the neutral bend line will be .5+.5t.

#### FritzW

##### Well-Known Member
Log Member
It probably is going to matter on the gussets because they actually get bent. If the SW defaults aren't *right, it's just a mouse click to change them.

*on an .020" thick gusset with a .5" radius bend it'd be hard to see if the holes were misaligned without a microscope (theory vs. reality)

##### Well-Known Member
Log Member
...it took me a minute to "smell what you were stepping in"

When you convert the tube to sheet metal you just need to set the tubes K factor to 1.
View attachment 90091

It'll give the tube 100% contact along the edge, like the bad drawing in post #74 (I hope the post numbers stay the same when you have some of the posts "ignored")
View attachment 90092

View attachment 90093

View attachment 90094

View attachment 90095

View attachment 90096

EDIT: here's a cutaway showing the tube cuts are 90 degrees to the face of the tube like they need to be and that there are no overlaps or gaps.
View attachment 90099
Thanks Fritz for this clarification. Currently on the skylite the tubes are a perfect match and do not have the corner edge touching as shown in your last pic. When the time comes to jump back into the Skylite fuselage, I will try your suggestions above and see if it fixes the issue and matches more of what you have there. Currently I am a bit busy with a new baby and a new work project at the same time.

#### FritzW

##### Well-Known Member
Log Member
A quick update.

Keep in mind...
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.

I drew up a new steady rest. It might look like a real Rube Goldberg affair but it's actually pretty simple. They're still 3D printed but now they have skateboard bearings and hangar bolts from a big box store. My original idea would have needed six or eight "inner rings" per tube size, this is a "one size fits all" from 1/2" to 2 1/2" tube.

It also has a "cribbage board" that's drilled for mounting the steady rests and the drive motor. It should be real easy to change things around for different tube layouts. I'm not sure yet how things will attach to the cribbage board, bolts?, camlocks?

Version 2 of the collet, new steady rests (SR's) and the cribbage board.

One of the SR's will stop the tube from moving along the X axis (details TBD).

They get used in pairs and the cuts are made between them (same as the V.1 SR's)

Looks like an overly complicated mess but it's just printed and off the shelf parts.

Thumb screws adjust the rollers for tube diameter down to 1/2"

Again, it looks more complicated than it really is. The "pork chop" looking things adjust the height of the top roller, one of the pins that hold the pork chop will be eccentric to take any slack out. If I wasn't worried about every tube size in the range they wouldn't have to be so big.

I might use centering pins on the bottom to mate with the cribbage board, ...I dunno yet

I know it looks like a lot of hassle just to cut some tubes but if you think about how it's made (printing and CNC, OTS hardware) it really is simple as mud. The cribbage board will store under the table and the rest of it will fit in a big shoe box.

EDIT: The thumbscrews sit in a ball and socket. It's all under compression (not clear from the renderings)

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##### Well-Known Member
Log Member
A quick update.

Keep in mind...

I drew up a new steady rest. It might look like a real Rube Goldberg affair but it's actually pretty simple. They're still 3D printed but now they have skateboard bearings and hangar bolts from a big box store. My original idea would have needed six or eight "inner rings" per tube size, this is a "one size fits all" from 1/2" to 2 1/2" tube.

It also has a "cribbage board" that's drilled for mounting the steady rests and the drive motor. It should be real easy to change things around for different tube layouts. I'm not sure yet how things will attach to the cribbage board, bolts?, camlocks?

Version 2 of the collet, new steady rests (SR's) and the cribbage board.
View attachment 90255

One of the SR's will stop the tube from moving along the X axis (details TBD).
View attachment 90256

They get used in pairs and the cuts are made between them (same as the V.1 SR's)
View attachment 90257

Looks like an overly complicated mess but it's just printed and off the shelf parts.
View attachment 90258

Thumb screws adjust the rollers for tube diameter down to 1/2"
View attachment 90259

Again, it looks more complicated than it really is. The "pork chop" looking things adjust the height of the top roller, one of the pins that hold the pork chop will be eccentric to take any slack out. If I wasn't worried about every tube size in the range they wouldn't have to be so big.
View attachment 90260

I might use centering pins on the bottom to mate with the cribbage board, ...I dunno yet
View attachment 90261

I know it looks like a lot of hassle just to cut some tubes but if you think about how it's made (printing and CNC, OTS hardware) it really is simple as mud. The cribbage board will store under the table and the rest of it will fit in a big shoe box.

EDIT: The thumbscrews sit in a ball and socket. It's all under compression (not clear from the renderings)
View attachment 90262
Hey Fritz very nice design. I did notice one thing, of you want to avoid the ball and socket galling over time with 3d printed parts, you might consider using a spherical bearing to do the same thing.

This is a manual goniometer plate I made to rotate a RED camera on axis of the lens. This is just one axis of an alignment gimbal. As the plate translates through the arc, the spherical bearing lets the shaft go wherever it needs to. Also the connection can rotate as well to keep everything concentric as it moves. The bearing is only a few dollars and the one shown fits a #10 screw pretty nicely. I use these things everywhere and I think it would work well in your application.

Marc

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#### FritzW

##### Well-Known Member
Log Member
That would work great but it might be overkill for what I'm doing. The loads are very light, the rollers just have to touch the tube (plus take up a little flex in the system).

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
I'm not sure yet how things will attach to the cribbage board, bolts?, camlocks?
Metal strap in the board and magnets on the bases of the steady rests? The pins on the bottom of the SRs would do most of the work.

#### proppastie

##### Well-Known Member
Log Member
very nice drawings....and to think just turn on the 3D printer and have a part in the morning.....would be very expensive to machine. Does the hot plastic smell...do you have to be careful about fumes?

#### FritzW

##### Well-Known Member
Log Member
Metal strap in the board and magnets on the bases of the steady rests? The pins on the bottom of the SRs would do most of the work.
Yep! That's the ticket! I never would have thought of magnets (too much saw dust in my brain).

#### FritzW

##### Well-Known Member
Log Member
Does the hot plastic smell...do you have to be careful about fumes?
I've used all of the common filaments and none of them smell.

The same public school systems that make kids wear safety glasses when they grow Lima beans in a milk carton typically have a dozen 3D printers running 24/7 without worrying about fumes. NASA uses 3D printers on the ISS, you can imagine the toxic fume study they did before they allowed that.

There are some chicken littles on the internet that say you'll die if you use a 3D printer without a respirator but all the legitimate sources disagree.

#### Hephaestus

##### Well-Known Member
There's a minor issue with nanoparticles. ABS releases some nasties (at least in California) but most people use pla or petg, abs is pretty crummy to print anyway.

The SLA theres a lot more concerns about. I wouldn't allow that media in my house... But people do it claiming its non toxic... Read some of the ohs reports and see what your dentist is required to do for safety - and you may rethink the 'non toxic' claims as well.

#### FritzW

##### Well-Known Member
Log Member
Let's put this in perspective: You'll breath more toxic fumes (a whole cocktail of them) sitting around a campfire for an evening than you will in a lifetime of 3D printing in a normally vented living space. ...even if your printing ABS (the stuff Lego's are made of).

It's the same "the sky is falling" stuff we heard about the dangers of wooden cutting boards and plastic yoga mats a few years ago. Everybody changed to plastic cutting boards and hemp yoga mats until they found out that plastic cutting boards were toxic and hemp yoga mats had pesticides. Now they're back to wooden cutting boards and plastic yoga mats.

Some people thrive on worrying about the next big thing that's going to kill them. ...if their cell phones don't give them a brain tumor first.

#### mcrae0104

##### Well-Known Member
HBA Supporter
Log Member
Let's put this in perspective: You'll breath more toxic fumes (a whole cocktail of them) sitting around a campfire for an evening than you will in a lifetime of 3D printing in a normally vented living space. ...
Forget airplane parts. I am holding out for a marshmallow extruder, which should be much healthier than the aforementioned campfire.

#### Hephaestus

##### Well-Known Member
Our hackerspace back in the day (10yrs+) had syringe printers for marshmallow and chocolate christmas treats lol. Never got the caramel working if i recall...

And a drinkbot