The machine pictured above relies on a mechanical cam
traverse which 'locks in' the traverse distance - meaning a new cam is
required for each change of traverse length.
It has long been a challenge, for me to design a *stepper motor
controlled traverser with computer control (CNC -no cams!).
Recent experiments (April, 2003) have brought this closer with some
insights and revised outcomes along the way.
* For readers unfamiliar with stepper motors, these are commonly used
in a range of computer controlled (CNC) equipment including printers,
plotters, robotics, etc. Web searching will prove informative elsewhere
- space prevents detailed info. here.
My early prototype traverser to test feasibility
Some time back I had built a stepper motor controller board, but
hesitated about executing the actual traverser design, and gaining the
associated computer skills needed to write a program for slaving the
whole set-up to a pc.
In the process of designing a geared cog and rack traversing unit, I
pondered further the issues of having to input data via a pc. for each
changed parameter involved in winding and/or associated adjustments.
I wondered,
'Wouldn't it be easier to offer direct 'hands-on' adjustments in real
time without
dependency on a pc. at all?'
While I admire the achievements of those who have taken the pathway to
pc-based programming, (and it remains an as-yet untapped option on my
winder), I chose the latter approach as my starting point - to offer
direct 'hands-on' adjustment on
a 'stand-alone' winding machine.
After much R&D and generous input by a knowledgeable friend, our
combined efforts provided the following features -
- Stepper driver using either onboard manual control for speed
and direction, or, - pc control via parallel port.
- 'Real-time/hands-on' traverse adjustment.
- Custom-built traverser slide assembly using 1/4"rails and nylon
guides.
- Disengageable motor and gearing for manual setting up of traverse
distance and 'start' positioning.
- Failsafe back-up switches - where the traverse is shut down
(preventing motor strain) if change of direction switch fails.
- LED indication for 'turnaround and traverse' helps with manually
setting traverse limits. Red = port, Green = starboard.
- Traverse switching via micro-switches to flip/flop circuit to
stepper driver. Power supplied by 9 volt dc. plug pack.
- Two power switch modes - a) w/o motor but LEDs operative for
set-up, b) for 'all systems go' (motor and LEDS).
- Set and forget tensioner based upon that used in the top-of-page
unit but
configured horizontally rather than vertically.
- Fine (or coarse) lateral adjustment of wire guide (see component
atop movable carriage).
- Hidden wiring channels to circuit boards located in base with
flexing allowance for adjustable cable travel.
- Traverse speeds of one inch in 4 seconds (approx.) to one inch in
14 seconds (approx.).
- Traverse distance can be set from 1/8" through to around 2 inches
('Tallbucker' coming? No! - just joking!).
So what does it look like . . .?
'The Designed2Wind Stepper-Powered Auto-Traverser'-
Component List :
1. Base, circuit boards inside
2. Retractable drive assembly
3. Wire guide (black, rod end eye)
4. Function switch
5. Speed control
6. Traverse distance adjust (left & right)
7. Feed arm angle adjust
8. Tensioner
9. Tension adjust knob
10. Right LED (left not numbered)
11. Carriage
12. Outfeed Wire guide
Note: Photos above and below show traverser
unit only - no coupled winder displayed.
The picture above depicts the view
as the traverser faces the operator. The winding machine
would be located on the farther side of the traverser, where
the traversing wire guide (component no. '12') would automatically
travel left and right on the moving carriage as wire is drawn to
the bobbin. In these pictures, for photographic convenience, no
power was connected - no LEDS illuminated. The light grey ('gray' for
U.S. readers) traverse adjust 'arms' are formed from laminated PVC
which allows for hidden internal wiring channels that carry wires to
the circuit boards in the base/box below. A custom fitting inside the
box
permits easy flexing of cables as traverse arms are adjusted.
In lower photo, lens barrel distortion falsely suggests misalignment of
components such as the nylon blocks which are,
in reality, 'in parallel' and not 'out-of-plumb'. The end-on
view (end section more clearly visible in 'prototype' photo nearer top
of page) of the carriage is an' inverted L-shape' so that the white
nylon blocks 'nest' within this upside-down angular section and are
bolted
and further braced to ensure stability.
Above: rear view of traverser shows LEDs, nylon
'glides', and outfeed wire guide on moveable carriage.
At far right :
In this photo, the carriage assembly has been removed to reveal the
FOUR micro-switches bolted to rebated and channeled pvc 'arms'.
Here, the gap between switches is clearly visible, and a 'bumper block'
on the carriage (not shown) would fit between the switch arms
allowing traversing, then switch activation - about 3 mm. (1/8")
at min. The
lower pair of switches is responsible for 'change of direction
switching'. The topmost two are 'failsafe' switches - in the event that
the 'CoD' switches fail, the fail-safe backups will shut-off power to
the traverser preventing damage to the gearing and mechanism. Fail-safe
switches were thought to be a useful innovation even though in practice
the change of direction switches have performed reliably.
Mounting is done with 2 mm.bolts.
The lower switch arm is 'hook-shaped', and under normal use will
activate on its own. Should it fail however, by flexing just a little
further, the upper switch arm is activated. Operation of this system
requires careful and accurate switch mounting. Some readers will
foresee, the fail-safe only stops the traverser. The winder will keep
drawing wire, even if to one side of the bobbin, but the traverser is
at least protected until the operator intervenes. An audible
'fail-safe' alarm could be fitted to monitor such malfunctions. To
date, as I mention above, the failsafe system has not been
called upon and the unit operates most reliably.
Look closely and you can see the wire channels in the laminated pvc.
arms. The indicator LEDS are just visible atop the motor
box. Each lights for one direction of traverse and indicates the
'turnaround point' (or switching point) when triggered.
This is particularly useful in manual set-up mode where the motor is
turned 'off' and disengaged, and the carriage (or appropriate arm) is
moved by hand until a LED triggers. This illumination reveals the
change of direction, or 'turnaround' point for set-up.
The overall traverser design presented various problem solving issues .
I refer to but two such issues by way of example -
eg.1. the sliding motor mount must offer a very firm and accurate
sliding motion. Any slack here will upset the smoothness of traverse
changing as the drive reversal copes with unwanted slack, 'play'
or 'backlash'. This was detected on an earlier 'model' where 'fit' was
on the slightly 'loose' side, and had to be promptly corrected!
eg.2. the manual speed control offers a very good (ample) range for the
intended purpose, however all steppers have their limitations and here
(on this unit), maximum motor speed is reached well within the pot's
(speed control's) operating range. This is only to say that on the
above unit, max. effective stepper speed is achieved short of the 'full
throttle' potentiometer position.
As with other projects on this site, this is not a conclusive nor
prescriptive model for others to duplicate/emulate. I only offer this
as a stimulus to the reader's thinking, and hope that it may generate
further exploration and enthusiasm for others.
Updated Information! The above traverser is now integrated into the
Model 8 auto-traversing Winder (see R & D Lab. Page)
*All text and photos above are copyright property of
spinner@designed2wind.alphalink.com.au - 2003, and may not be
redistributed, or otherwise copied/ published, or reproduced for
mass-circulation without written permission of the author.
