Everything you want to know about forming & fabricating with Acrylic. ***STRIP HEATERS*** A...

Tenecor Aquariums

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The simplest method of forming acrylic sheet along a straight line is to use a strip heater. Strip heaters are typically used to for the rapid production of simple boxes, and frames. They are generally limited to straight line bends. The process is usually used for small parts where the length of the bend is relatively short. Longer bends over 24 inches tend to bow, what we call the banana effect.


BANANA EFFECT.jpg


Inexpensive strip heaters are readily available. They are wired for 110V line current and come in assorted lengths. Older styles are housed in sheet metal while newer designs utilize T slot aluminum profile. Some newer designs also have cooling channels through which water can be recirculated. Cooling channels confine the hot zone and are a nice addition in high production set ups.

STRIP HEATER.jpg


Strip heaters work well with thinner gauges, less than 1/8 inch. Thicker gauges up to 1/4 inch can also be bent when a V-groove the length of the bend is cut prior to forming.

VGROOVE CUT.jpg


After heating, the acrylic sheet should be bent quickly. The piece should be held in a fixture until cool. In production, a number of strip heaters and fixtures can be arranged so as to make several folds in one operation.

Acrylic sheet should be heated to temperatures from 290°F to 350°F. These are sheet temperatures. The formability of cell cast acrylic sheet changes little within these temperature ranges. However, the formability of extruded acrylic sheet changes greatly. Higher temperatures may reduce the tear resistance of extruded sheet and may impair its physical properties. This is the main reason why extruded sheet should not used in aquarium manufacture. However, is is perfectly fine for use in non pressure loading applications such as shelves, sumps and similar.
 
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The simplest method of forming acrylic sheet along a straight line is to use a strip heater. Strip heaters are typically used to for the rapid production of simple boxes, and frames. They are generally limited to straight line bends. The process is usually used for small parts where the length of the bend is relatively short. Longer bends over 24 inches tend to bow, what we call the banana effect.


BANANA EFFECT.jpg


Inexpensive strip heaters are readily available. They are wired for 110V line current and come in assorted lengths. Older styles are housed in sheet metal while newer designs utilize T slot aluminum profile. Some newer designs also have cooling channels through which water can be recirculated. Cooling channels confine the hot zone and are a nice addition in high production set ups.

STRIP HEATER.jpg


Strip heaters work well with thinner gauges, less than 1/8 inch. Thicker gauges up to 1/4 inch can also be bent when a V-groove the length of the bend is cut prior to forming.

VGROOVE CUT.jpg


After heating, the acrylic sheet should be bent quickly. The piece should be held in a fixture until cool. In production, a number of strip heaters and fixtures can be arranged so as to make several folds in one operation.

Acrylic sheet should be heated to temperatures from 290°F to 350°F. These are sheet temperatures. The formability of cell cast acrylic sheet changes little within these temperature ranges. However, the formability of extruded acrylic sheet changes greatly. Higher temperatures may reduce the tear resistance of extruded sheet and may impair its physical properties. This is the main reason why extruded sheet should not used in aquarium manufacture. However, is is perfectly fine for use in non pressure loading applications such as shelves, sumps and similar.
Hi I've been working with acrylic for 40 years and gave yet to come up with an idea to stop the banna effect on short return bends in a long piece of acrylic.
I found v grooving increases the effects as there is less material to fold .
Any other ideas?
Many thanks
Graham
 
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Hi I've been working with acrylic for 40 years and gave yet to come up with an idea to stop the banna effect on short return bends in a long piece of acrylic.
I found v grooving increases the effects as there is less material to fold .
Any other ideas?
Many thanks
Graham
We use very little strip heating on the aquarium side. Mostly for tiny frag racks, Skimmer stands, and similar so the banana effect is not a problem. But on our commercial displays side we strip heat and bend up to 72 inches. (Museum cases, etc) But not much thicker than 1/8 inch nominal. The way we keep the bends clean and straight is what is called "annealing". Bringing the workpiece temp up close to bend temp before bending. And then rapidly fixturing the bent piece. Annealing also prevents the buildup of stress points. One more thing to consider is the strip heater length. 48 inch strips don't really bend 48 inch workpieces very well. The heat zones don't extend the entire length of the strips. Better to oversize the strip heater by at least 12 inches. Six on each end. I will be posting another article on a step by step design /build of a diy overflow siphon. Those things are expensive! We can do a diy for about 1/4 the cost. It's on the list.
 
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We use very little strip heating on the aquarium side. Mostly for tiny frag racks, Skimmer stands, and similar so the banana effect is not a problem. But on our commercial displays side we strip heat and bend up to 72 inches. (Museum cases, etc) But not much thicker than 1/8 inch nominal. The way we keep the bends clean and straight is what is called "annealing". Bringing the workpiece temp up close to bend temp before bending. And then rapidly fixturing the bent piece. Annealing also prevents the buildup of stress points. One more thing to consider is the strip heater length. 48 inch strips don't really bend 48 inch workpieces very well. The heat zones don't extend the entire length of the strips. Better to oversize the strip heater by at least 12 inches. Six on each end. I will be posting another article on a step by step design /build of a diy overflow siphon. Those things are expensive! We can do a diy for about 1/4 the cost. It's on the list.
Here are a couple of DIY siphon overflows images of what we are working on. You can ignore the red lines and notes. They are for the design team's purposes
DF27D122-0FE7-4E5B-87E7-3B65A60EF9D2.png

7A2870D2-EC14-445D-9335-751BF4F70BB1.png
 

Graham 414

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We use very little strip heating on the aquarium side. Mostly for tiny frag racks, Skimmer stands, and similar so the banana effect is not a problem. But on our commercial displays side we strip heat and bend up to 72 inches. (Museum cases, etc) But not much thicker than 1/8 inch nominal. The way we keep the bends clean and straight is what is called "annealing". Bringing the workpiece temp up close to bend temp before bending. And then rapidly fixturing the bent piece. Annealing also prevents the buildup of stress points. One more thing to consider is the strip heater length. 48 inch strips don't really bend 48 inch workpieces very well. The heat zones don't extend the entire length of the strips. Better to oversize the strip heater by at least 12 inches. Six on each end. I will be posting another article on a step by step design /build of a diy overflow siphon. Those things are expensive! We can do a diy for about 1/4 the cost. It's on the list.
Thanks for the feedback, yes annealing works well especially on tubes ,and before glueing.
We also normalise a lot of material we use when fusion bonding .
Thanks for the reply
Graham
 

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Heating from both sides of the bend limits the banana bending for thicker materials than .236" materials. You still have to deal with "necking" by machining the top and bottom of the bend area after cooling the part. I successfully bent up to 3/4" materials this way.

You can achieve this heating of both sides by turning the part over half way through the heat cycle as well on a single strip heater set up.
 

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Hi I've been working with acrylic for 40 years and gave yet to come up with an idea to stop the banna effect on short return bends in a long piece of acrylic.
I found v grooving increases the effects as there is less material to fold .
Any other ideas?
Many thanks
Graham
Pretty easy if you clamp a aluminum or steel angle down both sides of the acrylic and leave like a 1” gap exposed for heating and bending.. the only way I bend my acrylic..
 

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