Does anyone have any plans , advice on how to construct a heater unit to do line bending with acrylic sheet

davefromdarlo wrote:

Does anyone have any plans , advice on how to construct a heater unit to
do line bending with acrylic sheet

6", 6', 6?

On Thu, 17 Nov 2005 17:40:09 +0000, davefromdarlo
wrote:

Does anyone have any plans , advice on how to construct a heater unit to
do line bending with acrylic sheet

Ask Trylon - they probably sell kits, plans and components. There are a
few other specialist schools suppliers too (Techsupplies.co.uk ?)

First get an element. This can either be a woven tape element, sold for
making line-benders and already wired with a plug, or else you can be a
hooligan and use a length of bare nichrome wire. You need about 50W /
foot.

Get some heatproof cement board (Versapanel etc.) Cut four long strips,
two slightly narrower than half the width of the other. Assemble with
water-based No-more-stickum to make a thick strip with a central gap
about 3/4" wide. The thickness should be adequate to not wobble,
probably involving a plywood base panel. Width depends on its use -
about 6" wide will be easier to use, but you might want a narrow one to
work inside a narrow section.

If you're using nichrome then make two threaded pillars to support the
element. Insulate their bases and attach power feed. Use fibreglass
sleeving etc. as needed, don't rely on normal temperature-rated
insulation within 3" of the element. Don't solder things either, use
crimps. Don't even trust screwthreads, unless they have a shakeproof
washer - heat cycling makes things unscrew.

Attach your nichrome wire and a long spring to tension it. Tension needs
to be enough to hold it taut when hot and low enough not to break it
when cold, so this means a long spring. Attach a bypass wire to the
spring, because passing current through the spring itself will heat it
and may even draw the temper.

Make or scrounge a power supply. This will depend on the thickness of
nichrome you're using - thick nichrome needs a high-current PSU which is
a nuisance to sort out - I'd want at least 50V, so as to keep the
current reasonable. For setup, you'll need an adjustable output with
some pretence of regulation. An auto transformer is ideal but you
_must_ also have an isolating transformer. The wire doesn't need to have
a visible glow to make bends and you might want to adjust the vertical
positioning to control heating rate - thicker plastic needs a lower wire
to allow longer heating times, but this also give a wider less-precise
bends.

Do the usual safety stuff.

Tune for minimum smoke.

davefromdarlo wrote:

Does anyone have any plans , advice on how to construct a heater
unit todo line bending with acrylic sheet-- davefromdarlo

I needed to make just a few bends in acrylic sheet, so spending much
money wasn't an option.

I used a steel guitar string as the element, the base was made from two
left-over ceramic floor tiles arranged with a 4mm gap between them and
glued to a third one which holds them all together.

The element was located in a bead if fire cement and had terminals that
had been cut from plastic terminal strip and was wired to a 12v
low-voltage lighting transformer. To control the temperature, the
transformer was fed via a dimmer switch.

It's dead easy to set a suitable temperature and heat up the acrylic.

I made this gadget about 10 years ago for one project, but it's been
used loads of times since.

On Thu, 17 Nov 2005 17:40:09 +0000, davefromdarlo wrote:


Does anyone have any plans , advice on how to construct a heater unit to
do line bending with acrylic sheet

I use an old- style radiant bathroom heater, with the reflector removed, run through a variac to
control the temperature.