Sheet Roll bending machine

[Peter Fairbrother]

Found a few surplus bits of 20mm round linear rail and thought I'd have
a go at building a sheet roll-bending machine. It's for light ally.

Had a look, and there seems to be several roll placement and gearing
systems. Hope this next bit isn't too confusing to read, it wasn't easy
to write.

Given one powered roller:

On one system there are two rollers vertically above each other, which
are tightened together until the sheet fits snugly between them. These
are geared together with two gears on one end of each shaft. There is a
third unpowered roller whose axis is is movable and which does the
bending. The sheet curls round the top geared roller.

On another system there are two rollers horizontally next to each other
with a larger fixed space in between. These are geared together with a
3-gear chain, so they each have a gear on the end and there is a third
gear which is driven by one roller and drives the other. There is a
third unpowered roller whose axis comes down between the powered
rollers. The sheet curls round the third unpowered roller.

The two geared rollers turn in the same direction in this second system,
unlike the first system where they turn in opposite directions.

A third type has no gearing.



Questions, are there any more systems?

Which system is best?

Is there any system which doesn't leave unbent edges?

How does the gearing in the first two-gear system work, if the
separation is variable? Do they use special gears?

I though a couple of standard 10-tooth mod 2 gears might work, pressure
circle is 20mm same as the rollers, outer diameter is ~23mm, and if they
were separated by a mm or so more than nominal to allow for the
thickness of the ally sheet they would still mesh. If I used a smaller
mod the possible separation range would be less. Opinions?


Thanks

Peter Fairbrother

[Mark Rand]

Post by Peter Fairbrother
Found a few surplus bits of 20mm round linear rail and thought I'd have
a go at building a sheet roll-bending machine. It's for light ally.
Had a look, and there seems to be several roll placement and gearing
systems. Hope this next bit isn't too confusing to read, it wasn't easy
to write.
On one system there are two rollers vertically above each other, which
are tightened together until the sheet fits snugly between them. These
are geared together with two gears on one end of each shaft. There is a
third unpowered roller whose axis is is movable and which does the
bending. The sheet curls round the top geared roller.
On another system there are two rollers horizontally next to each other
with a larger fixed space in between. These are geared together with a
3-gear chain, so they each have a gear on the end and there is a third
gear which is driven by one roller and drives the other. There is a
third unpowered roller whose axis comes down between the powered
rollers. The sheet curls round the third unpowered roller.
The two geared rollers turn in the same direction in this second system,
unlike the first system where they turn in opposite directions.
A third type has no gearing.
Questions, are there any more systems?
Which system is best?
Is there any system which doesn't leave unbent edges?
How does the gearing in the first two-gear system work, if the
separation is variable? Do they use special gears?
I though a couple of standard 10-tooth mod 2 gears might work, pressure
circle is 20mm same as the rollers, outer diameter is ~23mm, and if they
were separated by a mm or so more than nominal to allow for the
thickness of the ally sheet they would still mesh. If I used a smaller
mod the possible separation range would be less. Opinions?
Thanks
Peter Fairbrother

It is thought that the ones with the two rollers pinching and driving the work
and a third (and fourth, on the other side of the driving ones for big sets)
do a better job of avoiding flats at the end of the workpiece.

There is a further tweak on the vertically geared setup, produced by
G.H.Thomas, that is to use four gears to link the two rollers together, with
two idlers in series mounted on links to keep the gears' spacing constant. The
advantage of this is that as the pinch roller is moved closer and farther from
its other half, the gear meshing is kept constant instead of varying to the
point where it's hard to mesh the gears. In ASCII art (fixed width font) form
it's like so:-

O-O
|
O-O

Picture is here:-
http://hemingwaykits.co.uk/acatalog/copy_of_Bending_Rolls.html

Regards
Mark Rand