Sheet metal folder

[Roger]

I was kindly offered the use of Reg's (Greensands) folder, but you know me, I like to do my own thing. So I've done a bit of research and concluded that none of the designs I've seen really work the way I think they should, not even commercial ones.

If you sketch out a variety of thicknesses of sheet material, with a range of bend radii, it's clear that you can't have the hinge point where those designs all seem to be, ie at or very close to the base of the folder. Obviously if you stick to thin material and sharp bends then that's not a problem, but if you want something a little more versatile then it is.

To my mind, you ought to be able to fold any thickness material to any radius within the capacity of the folder, so that's what I've aimed at achieving with this design.

I've borrowed a few ideas from YouTube and added my own to come up with this. The idea is to allow the hinge point to be raised to suit the thickness of the material and the radius of the bend. Obviously that means that the folding arm needs to be able to remain level with the clamping table so that has to be adjustable too. I know this is sometimes adjustable on commercial machines, presumably to allow for slightly thicker materials to be used. That's a bit of a bodge though because the pivot point won't be right for the bend.

Here's the setup for very thin material with a tight bend, with the centre of the pivot being almost on the top of the sheet.

Thin sheet position by Roger Froud, on Flickr

.... and here the setup for a 10mm radius curve, with just the start of the bend being supported.

The idea is to have different clamping bars to suit the inside radius that's required. Just a rod will do for those, and they will be held down on the edge as necessary. This has been designed to be long enough to fold all of the cab parts and form the more gentle curves of the side tanks. I've never seen a folder that does these things, but I did find one that uses large rollers for both the clamping and forming arm for creating large radius bends without the use of rollers.

I haven't shown all the adjusting details, or any handles. The idea is you put this in the vice and then stow it away when it's not it use.

10mm radius position by Roger Froud, on Flickr


The base is made from some 40mm x 80mm RHS with a 4mm wall thickness that I used for the crane support. That fits firmly in the vice and keeps the weight down.

[Donald G]

Hi Roger
Many years ago, I bought a variable thickness and adjustable bend radii at a club auction of stuff from a deceased member. I think I got it for less than a tenner, but I have used it many time. It will bend a short length of 3mm, but for thin sheet for cabs etc, using 1mm or 1.5mm it will bend up to about 600mm. The top clamp is on slots and you can set the work to allow for a bigger radius.

Donald

[Roger]

Hi Donald,
That sounds like a really useful piece of kit. I don't know why these more versatile machines aren't the norm. I'd be interested to see a picture of that.

[KennLindeman]

While you busy why not make it a three in one and add a guillotine and a roller. But then it most likely wont fit into a vice and you may have to mount it on its own table. Anyway just a idea.

[Roger]

Hi Ken,
I could use all of those things really, but I don't have room for one big machine. I was tempted with that three in one machine that Warco and others do, but I concluded that not only was it too big, it didn't do two of the jobs I know I need to do. Those are the side tank curves and the small parts I'm making at the moment. Those Press Brake type on folders look good on the demos, but they're no good for some types of work.
Fortunately my mate has a nice pair of rollers, so that's one thing I won't need to make. I'd love a guillotine, but in reality I can machine most of what I need after sawing the rough blank from sheet. Not having a folder is a bit of a show stopper though, hence sorting that out now.

[fang]

Edwards box and pan folders do all these things. And they have separate pieces you can bolt on to the fingers for different bend radius's. I find a press brake type folder far better for precision sheet metal work, just use different diameter round bars press into the sheet to get different bend radiuses. If you go with your design you'll need fingers to clamp the sheet down rather than a single long bar, and if you could incorporate fingers into the bending beam as well it would be even more useful. At work I use both a box and pan folder and a press brake, and I find I need both as there are some things you can do on one but not on the other

Or how about one of these!!!!

link

[jem]

If you have a saw bench in your workshop, get an Evolution Rage circular saw blade 185 mm dia, it will cut steel sheet up to 3 mm with no problem, also al wood etc,I have had one for a while now and they are brilliant.

best wishes

Jem

[Roger]

May 9, 2016 16:32:14 GMT fang said:

Edwards box and pan folders do all these things. And they have separate pieces you can bolt on to the fingers for different bend radius's. I find a press brake type folder far better for precision sheet metal work, just use different diameter round bars press into the sheet to get different bend radiuses. If you go with your design you'll need fingers to clamp the sheet down rather than a single long bar, and if you could incorporate fingers into the bending beam as well it would be even more useful. At work I use both a box and pan folder and a press brake, and I find I need both as there are some things you can do on one but not on the other

Or how about one of these!!!!

link

Hi Fang,
I've never seen a folder that has a variable height for the pivot point, is that how the Edwards one works? Most folders seem to have the pivot at an arbitrary height above the base as a compromise, but it's not ideal. I don't know how you would accurately control the radius just by lowering the folding bar, but I have a feeling that's how they form larger radii. I just fancied making something that put the centre of the pivot at the true centre I'm trying to form the bend to.

I anticipate adding tapped holes to the bed to clamp fingers down to as necessary. It's not a production machine, so as long as it's possible to fold things with a little ingenuity then that's fine. The main thing is to provide a way to hold down any part and to forcefully persuade it to follow the curve I'm after. All interesting stuff and good fun to design.

I know what you mean about the press brake, but they aren't any good for fiddly bits like the little boomerang shaped brackets I've made for the drain cocks. I don't think that style would work for the fold on the edge of the main bracket either because it wouldn't stop the part from bending where it's weakest rather than where I want it to bend. For larger sheets or simple folds, I can see that the press brake is superior, but it won't do all the things I need it to do. In an ideal world I'd have both, but since I don't have room, I thought it would be better to have a design that does everything. The good thing about a simple folder is that it holds the work right at the start of the bend.

That's a clever idea with the magnetic clamp. I'm surprised that works with aluminium and Stainless Steel though. Presumably there's enough magnetic force transmitted through the material to the clamping bar. They still need many different lengths of fingers though.

[Roger]

May 9, 2016 17:00:30 GMT jem said:

If you have a saw bench in your workshop, get an Evolution Rage circular saw blade 185 mm dia, it will cut steel sheet up to 3 mm with no problem, also al wood etc,I have had one for a while now and they are brilliant.

best wishes

Jem

Hi Jem,
I'm afraid I don't have a saw bench. I've used them in our factory though, and boy, they make a lot of noise. I'm not sure I'd be very popular with the neighbours.

[Roger]

This is the base plate for the folder, the front corners need a clearance for the pivot. I can't do these in one setup because the table travel isn't enough to go round the ends of the work. This way I can make the corners square.


20160510_095210 by Roger Froud, on Flickr

This is the same part, it's held down to the base RHS with countersunk 6mm hex drive bolts.

20160511_204959 by Roger Froud, on Flickr

I'm using the same program to set out the holes in the RHS. These have been tapped M6 using a spiral point tap held rigidly in a collet.
It's fine doing something like that when the holes aren't deep and they aren't blind. I just single stepped the program and then typed M4 to reverse the spindle when it was deep enough. Very quick and easy.

20160511_214558 by Roger Froud, on Flickr

Hopefully the material I ordered will arrive tomorrow so I can crack on with it and get it finished.

[d304]

Hi all

This is my first post.

On my loco, (Australian designed, 5” Meares “Anne” 0-6-0, with everything above the footplate changed, influenced by the Scottish locomotive builders of Springburn), I wanted the side tanks to have the top edge, rolled to a 8mm radius. The tanks are just over 400mm.

I thought about clamping and other holding devices all of which get in the way or slip. In a previous life as an apprentice, the large car panel dies had locating pins for keeping panels in exact positions for pressing.

After playing with different ideas I came up with a length of angle, two location supports and the top die comprising a 16mm piece of round bar. To stop the 16 gauge brass sheet from moving while pressing, 2 1/16 holes are drilled in the middle of the radius 250mm apart. These must be square to your sides and base. The matching holes on the top die have 1/16 silver steel pins that locate and stop the brass from shifting while pressing. I used a 10 ton press and the brass was not annealed. I found the inside of the angle and the spring of the brass did not quite form 90 degrees so I used another strip of angle inside the angle to increase the angle. With the location pins, things are repeatable and the angle returned and fine-tuned to be the exactly angle required. Squareness will go back to how exact the original cutting has been. The two holes are filled in when soldering or brazing.

The images will show better than my words. The die is available to use, just down the road from 70036 Boadicea.

David

Sorry pix don't seem to have uploaded.

[Roger]

Hi David and welcome to the Forum and sharing what you've found.

It sounds like you've recreated a Press Brake that's specific to the radius you wanted to create. It's a highly satisfactory way of producing the sort of bend you needed and it would appear that you've made a good job of it. Spring back is always going to happen, so bending beyond 90 degrees and at a slightly smaller radius is needed to get the precise bend you need. Obviously the exact radius wasn't that important for what you're making and it's close enough.

Stopping things from moving is not as easy on that sort of folder, that's another reason I opted for a more traditional one which doesn't have that problem.

You can't upload files to the site, there isn't enough space for that on the server. If you take a look at the sticky threads on the front page of the site, you'll see how to go about getting pictures onto the site once they've been uploaded to a third party site such as Flickr.

Please do start your own build thread like Jim has done, I'm sure it will interest a lot of Forum members.

[Roger]

More progress today, this is almost finished, there's a slot that I've forgotten to put in the back to lock the sliding end blocks in place. I'll do that later.


20160513_211406 by Roger Froud, on Flickr

This is the first of the end plates made from 10mm thick BMS, held by a 0.3mm wafer. It's broken through in a couple of places, so that's probably not quite enough.
You can see how rough the finish is, and the enormous burrs the ripper is throwing up. That's because it's absolutely knackered, but I'll use it until it breaks since they're expensive.

20160513_201247 by Roger Froud, on Flickr

This is just starting the third and final pass on the finishing cut, removing 0.3mm to bring it to size. The burrs have all gone and it's not a bad finish considering the cutter is fairly worn. The holes were all drilled and reamed at the start. Two are for 8mm dowels and the large one is for the 12mm Silver Steel pivot pin.

20160513_212717 by Roger Froud, on Flickr

[springcrocus]

Looking good, Roger, but have you considered the force neccessary to create a bend in your chosen material? I suspect it will be much greater than you think especially when you allow for the fact that the applied force is (I think) a function of the square of the length of the material. I hope your vice is man enough for the job!

I recently made the tank sides for Britannia's tender which have a ninety degree bend at the bottom and a sixty (approx) degree bend at the top, both on a half-inch radius. I was contemplating making a bender similar to Geoff of Carlisle (Clan build) but realised that I wouldn't be able to apply the required muscle-power to the job and I eventually made them using panel-beating techniques. A quick and dirty test to see if I could bend 22" of 16swg brass sheet proved that you would need the assistance of someone like Geoff Capes.

I am sure that you will make your bender/folder work as you intend but I would plan to secure it other than in your vice. Welded to the floor would be good...

Steve

Edit. I went to bed thinking about my above highlighted statement and realised that I've got that wrong - it has to be a linear function, twice the length requires twice the effort. Since nobody else had posted here, I've left the original quote and added this edit.

However, what is not generally appreciated is the amount of effort that has to go into bending sheet metal and how those forces are acting on the folding tool. It can be quite considerable.

Steve

[ivattlms]

Hi Roger look forward to seeing the finished job as i am interested in the same idea for accurate bending side panels on my Dock tank
Robert

[Roger]

Hi Steve,
I have to be honest and say that I don't really think it will be a strong enough design as drawn to fold say 1mm sheet over the full length to a tight radius. The primary aim was to make something that would handle all the smaller parts and allow me to do the more gentle folds on the side tanks.

Looking at all the large commercial designs, they are truly massive, and I can see why. I have it in mind to beef up the stiffness of the long pieces using the triangulation idea they use on those machines if necessary. In that design, they have a bar with a shallow bend in the middle attached to the ends of the long piece. An adjusting screw that allows force to be applied from that bar You can see the sort of thing I'm describing sticking out of the bottom of the folder in this picture.

Having said all that, this is a small commercial hobby machine which is probably much the same strength as mine.  I ought to mention that it has a capacity of only 430mm so it's not particularly large.

I'll just have to give it a go and see what works and what doesn't. Thankfully I now have the TIG welder which might just have to come to the rescue!

[Roger]

May 14, 2016 7:51:33 GMT ivattlms said:

Hi Roger look forward to seeing the finished job as i am interested in the same idea for accurate bending side panels on my Dock tank
Robert

Hi Robert,
Hopefully it will be robust enough to do what I want, only time will tell. I'll certainly share my findings though, so you won't have to make the same mistakes!

[Roger]

Here are the finished side plates and the pins which will be used to adjust the height of them. The sliding end blocks will have a 12mm cross hole front to back to take the pins which will have an M6 thread across them to take the adjusting rod. I'll add those holes later.



20160514_124216 by Roger Froud, on Flickr

[Roger]

More munching of metal to try to get the bulk of this done quickly. This is my 50mm face mill that comes in handy for this sort of job.
This is one of the adjusting blocks that sit inside the RHS base tube.


20160514_190249 by Roger Froud, on Flickr

This is the folding bar getting the cutouts for the hinge arrangement.

20160514_210713 by Roger Froud, on Flickr

And this is the angle that's going to be holding down the work. Again it's a clearance for the hinge.

20160514_215033 by Roger Froud, on Flickr

Just a holes and slots to add.

20160514_215226 by Roger Froud, on Flickr

[Roger]

These are the hinges that hold the folding angle bar on the front. I machined them this way so I didn't have to make a fixture. Logically, you'd think they would be done on their sides, but it's not easy to hold them that way and it would probably have needed doing in more than one operation anyway.

Now I'm more confident with 3D milling, this was the obvious way to hold the stock and create half of the curve in one operation.


20160515_104815 by Roger Froud, on Flickr

It took a while to rough out, so I sawed the second one out roughly while this was being machined so I could go straight to the finishing operations on that one.


20160515_142752 by Roger Froud, on Flickr

I quickly copied the profile and created an inverted model with a containment area to make sure it only machined the curved part. This is a key thing you need to grasp when creating 3D tool paths.

The axis reference is the flat end on the right, the centre of the bar front to back and the top surface. That way it's easy to register the operations on this side to the ones on the top.

20160515_163422 by Roger Froud, on Flickr

It's not quite right for some reason, but it's not important because it's a clearance. That arc should blend more accurately with the top surface.

20160515_172722 by Roger Froud, on Flickr

Almost done, just the 12mm reamed holes to go in and the M4 holes on the end for the adjusters.

20160515_212122 by Roger Froud, on Flickr