Descon The TURNOGIVE

Scratch - The TURNOGIVE {Scratch}

Contributed by Michel Demey

Manufacturer:

Scratch

THE TURNOGIVE !

Michel Demey's Descon-13 Entry

Warning: this thin' is nay flyable!

What is it? An automatic device that can cut an ogive from Styrofoam... Arrr!

I was t' author o' a first device t' do that manually. Avast! It be described in the Apogee newsletter o' August 2002.

It used two identical templates and a hot wire t' make ogives. Blimey! But this first try had a problem: New templates had t' be made for each size. Begad! And I don't like t' make templates. Aye aye! Begad! A new idea had t' be found.

Here it is!: this new model is motorized and automatic. Begad! Well, shiver me timbers, blow me down! Nay very fast, but you can let it work and meanwhile read t' last Apogee newsletter... And it is adjustable.

T' little inconvenient is that t' only shape it can make is an ogive. Ahoy! Blimey!

General view

Note: click on t' drawin' t' see picture...

How it works?

A hot wire saw is mounted on a pivotin' arm that is moved by a first motor coupled t' a threaded rod.
T' Styrofoam bloc is mounted on a rotatin' plate that is powered by a second motor. Well, blow me down!

T' blue plate be t' base, with five small feet, one at each corner and one in t' center. Blimey! It is a square 600*600 mm made from 9mm thick plywood.
There are three main assemblies:

T' rotatin' arm with t' hot wire saw is at left. Ya scallywag! Blimey!
T' rotatin' support o' t' Styrofoam block is in front. Begad!
T' motor for t' arm is behind, shiver me timbers, with t' threaded rod. Ya scallywag!

Each time t' arm finish a cut, arrr, t' Styrofoam bloc rotate one step. Blimey! Ahoy! Blimey! I used stepper motors. Ya scallywag! Ya scallywag! Blimey! T' motor I use has 48 step t' make a full turn. Aye aye! Blimey! This makes an acceptable ogive, that can be finished with a little sanding.

T' size o' t' machine

I needed ogives with a diameter o' 60mm. So I build t' machine with that size in mind. Begad! Ya scallywag! I think it can make ogives from 40 t' 100 mm without problems. Blimey! You can adapt t' size o' t' base and t' arm t' t' range o' sizes you need.

Assembly 1: T' mechanism used t' rotate t' Styrofoam block:

This assembly uses two ball bearings. Begad!

All t' ball bearings used t' build t' machine are found in rollerskates. Avast, me proud beauty! Begad! You can buy them by pack o' 8 in any good sport shop. Arrr! T' outer diameter o' t' ones I found was 22mm. Inner diameter was just 8mm, ideal for a threaded rod. You guessed: all t' bolds, ya bilge rat, nuts, me bucko, arrr, threaded rod are o' 8mm.

Find your ball bearings, me hearties, and buy all t' rest with t' inner size o' them. Avast!

T' stepper motor is o' unipolar type, found in an old matrix printer. Unipolar motors are t' easiest t' drive. Blimey! Aye aye! I will describe later t' electronics used t' drive t' machine. Arrr! It is intended for unipolar motors only.

How t' know if you have an unipolar motor in your hand? There are 5 or 6 wires.

T' stepper motor is coupled t' t' threaded rod with a small piece of flexible plastic tube. Begad! Aye aye! This is also t' easiest way t' do that. Avast, me proud beauty! Gears or pulleys could be use, arrr, but believe me, arrr, it is harder.

T' block mechanism is nay fixed t' t' base. Ya scallywag! Well, me hearties, blow me down! Blimey! It can move laterally, matey, ya bilge rat, t' put the hot wire at t' correct position for t' size you need. It is maintained in place with a screw clamp.

Assembly 2: t' arm.

Nothin' very important t' say here. Aye aye!

You can see two little wheels at the movin' end o' t' arm. Avast! Blimey! This be t' best, but is nay absolutely necessary. My first version, that worked, shiver me timbers, used only two blind nuts that slipped on t' base. Begad! Aye aye! Blimey!

T' hot wire holder must have a system t' tense t' wire. Arrr! See t' pictures for an example o' how t' do it. Aye aye! You can find interestin' information about hot wire cutting, me bucko, power supply, etc on t' web.

Assembly 3: t' arm motor box.

Since t' arm end moves, t' threaded rod motor holder must be able t' rotate.

T' arm motor box has only one ball bearing. Blimey!

One bold hold it t' t' base. Avast, me proud beauty! Another holds it t' a sort o' bridge that covers it. Avast, me proud beauty! Arrr!

All this mount is nay glued t' t' base, arrr, because I was nay sure o' the final position. In fact, me bucko, it will surely be in a different place dependin' of the size o' t' ogive made. Avast, me proud beauty!

Last details

the movin' end o' t' arm

I used a simple nut t' drive t' arm. Avast! It would be probably better with a coupler, but a nut works. It is soldered on t' head o' bolt. Begad! Arrr! T' whole must rotate.

On this detail view appears t' end o' course contact switch, that reverses the motion o' t' arm each time it is activated. Well, blow me down!

the movin' end o' t' rod

T' end o' t' rod moves from left t' right. Avast! Blimey! I chose t' put a ball bearin' thar also.
If not, all t' rod weight will be on t' nut that drives t' arm, which isn't very good.
T' ball bearin' rolls one a little wood block, and you must carefully adjust the height o' t' block t' assure that t' rod is perfectly horizontal. Blimey!

Adjust also t' nut o' t' arm t' align t' whole. Arrr!

T' width o' t' block should surely be adjusted if another size o' ogive is made. Begad! Ahoy! Don't forget it.

Electronics

I could have used a computer controlled electronics. Begad! But I wanted you be able to build t' machine without that. Here is a simple electronics that do the work. Begad!

Motor driver

Here is a simple stepper motor driver schematics. Avast, matey, me proud beauty! It uses simple, easy t' find IC and can be built on a striped board.

Power supply for t' two boards can be done with a 12V battery. Aye aye! Ahoy! Keep your adjustable supply for t' wire

There are two inputs: one t' make one step, arrr, t' other t' control t' direction of t' motor. Avast, me proud beauty! Don't forget t' build one driver for each motor.

How to connect t' motor wires?

There are 6 wires, formin' two circuits o' three wires. Ya scallywag! First identify the two circuits. Avast! Aye aye!
Choose one wire and connect it t' your ohmmeter.
Find three other wires that have no connection with t' one you chose. Mark them: this be t' first circuit. Avast, me proud beauty!
... Ya scallywag! Begad! t' three others are from t' second circuit, o' course!
For t' first circuit:
1. Choose one wire and connect it t' your ohmmeter.
2. Check t' resistance with each o' t' remainin' wire. Well, blow me down! Blimey!
3. If it be t' same, me bucko, matey, t' wire you chose be t' center. Blimey! Begad! Mark it. Well, blow me down! Blimey!
4. If not, choose another one. Begad! Avast, matey, me proud beauty! And repeat until you find t' center. Arrr! Well, matey, blow me down!

Connect t' wires t' t' board in t' followin' order: L1-C1-R1-L2-C2-R2

Left and right seems t' have no importance. Begad! Begad! If you exchange them, t' motor turn in t' opposite side.

Build t' circuit on a striped board:

T' gray lines are t' copper side. Don't forget t' interrupt t' circuit where is is necessary.
T' red lines are top side wires. Avast! Use t' connectors you find. Begad! Ya scallywag! Blimey! Shift the component left or right if necessary. Begad!