How to bend perspex

[DoubleEnder]

The coloured lenses on my deck level nav lights are horribly crazed. They are very old, and I can't get replacement lenses. But I like the fittings a lot, so would like to make replacement lenses. I am trying to bend 5mm thick perspex around a former to achieve a curve with radius of about 30mm ( it is a wooden rolling pin that happens to be the right size). So far I have tried boiling water, but that isnt hot enough. I have tried the oven, but the temperature seems to rise too rapidly and the perspex goes straight from being stiff and unbendable to floppy and fizzy and filled with bubbles...

Anyone got experience in this? I'm about to go for the hot air gun, but thought I would ask first. If this doesnt work I will try casting new lenses in acrylic resin, but that's all a bit fussy and sticky.

(I am happy to have clear lenses with boatlamps.co.uk excellent coloured LEDs behind them)

thank you

 

[GregOddity]

The coloured lenses on my deck level nav lights are horribly crazed. They are very old, and I can't get replacement lenses. But I like the fittings a lot, so would like to make replacement lenses. I am trying to bend 5mm thick perspex around a former to achieve a curve with radius of about 30mm ( it is a wooden rolling pin that happens to be the right size). So far I have tried boiling water, but that isnt hot enough. I have tried the oven, but the temperature seems to rise too rapidly and the perspex goes straight from being stiff and unbendable to floppy and fizzy and filled with bubbles...

Anyone got experience in this? I'm about to go for the hot air gun, but thought I would ask first. If this doesnt work I will try casting new lenses in acrylic resin, but that's all a bit fussy and sticky.

(I am happy to have clear lenses with boatlamps.co.uk excellent coloured LEDs behind them)

thank you

I've bent Perspex for small applications, I used an electric heater suspended above the Perspex. I had the Perspex in a little frame with a much larger area then the shape required. when it started caving on the centre, the frame was lowered over the part and vacuum applied. It was small things so I made a wooden box with plenty of 3mm holes spaced 1cm apart all over connected to a vacuum cleaner. Worked like a charm, you can vary the distance of the heater until you get the heat required. On the oven all my tries were a disaster. Top of my head the temp must be around 160 something Celsius but you can google it.

I had two old ones laying around the garage. It did take a few tries.

 

[moomba]

Try using a heat gun, and gently heat the Perspex and mould it around an object that fits your shape.

 

[sailorman]

I've bent Perspex for small applications, I used an electric heater suspended above the Perspex. I had the Perspex in a little frame with a much larger area then the shape required. when it started caving on the centre, the frame was lowered over the part and vacuum applied. It was small things so I made a wooden box with plenty of 3mm holes spaced 1cm apart all over connected to a vacuum cleaner. Worked like a charm, you can vary the distance of the heater until you get the heat required. On the oven all my tries were a disaster. Top of my head the temp must be around 160 something Celsius but you can google it.

I had two old ones laying around the garage. It did take a few tries.

Formica type laminate is also "post formed" the same / similar way

 

[seaangler23]

Heat gun and a flat nozzle like this, https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/143087628087
Will allow you to hear it uniform, heat it slow and get it around the former then a bit more heat, make it big so you can clamp it then cut the shape out of the formed piece, I use to make boat windscreens and it’s a pain to get right

 

[vyv_cox]

Try using a heat gun, and gently heat the Perspex and mould it around an object that fits your shape.

That's what I do. I made perspex covers for some unattractive table fittings very similar in shape to the OP's requirements. Heat the perspex and drape it over a wooden former.

 

[reeac]

A chap who worked for me way back once made a replacement windscreen for a UFO Interceptor (remember those splendid childrens' programmes?) . As I recall he used a gas flame and a wooden former and applied some tension to the Perspex. My son was delighted.

 

[rszemeti]

Piece of cake ... place the perspex in an oven at about 90 degrees C for an hour, this bakes out any moisture that would otherwise cause bubbles to appear.

Raise the temerature to 140 degrees, when it is up to temp, take it out and lay it over a mold. I use felt to cover my molds. If it is a "tight" curve, you will need to use a matching outer mold to press it around the curve if it wont sag naturally. If it is just a small lens, then just pressign gently with a soft cloth or pad may be all that is needed.

Anyway, oven, 140 C ... job done.

 

[rszemeti]

https://www.youtube.com/watch?v=0TOW92869cg

 

[Mistroma]

Piece of cake ... place the perspex in an oven at about 90 degrees C for an hour, this bakes out any moisture that would otherwise cause bubbles to appear.

Raise the temerature to 140 degrees, when it is up to temp, take it out and lay it over a mold. I use felt to cover my molds. If it is a "tight" curve, you will need to use a matching outer mold to press it around the curve if it wont sag naturally. If it is just a small lens, then just pressign gently with a soft cloth or pad may be all that is needed.

Anyway, oven, 140 C ... job done.

I've been lucky and only needed to bend it. Just clamped between 4 pieces of ply and slowly warmed the gap with a heat gun (might have been a hair drier). Really easy, just a matter of controlling how far it bends. I needed to rotate and repeat this 4 times to get the shape I needed.

I'll remember the oven method if I need something with a more complicated shape. Only thing I need to watch is the temperature controls. I'm not certain about the accuracy of the oven control, 140°C is fine but >160°C would be a puddle (if I remember the melting point correctly).

 

[DownWest]

OK, I got landed with building parts of a staircase in perspex. Built an oven that could heat the 10mm thick sheets to 120°C, at which point it drapes over the mould. Absolute clean mould or you get tiny dinks from the bits of dust and they show in the finished product. These bits were were about 80 X 50 cm on a spiral twist.
The key bit for the OP is 120°C it is quite flexible at that.
A heat gun might bubble the surface before it gets the rest up to the temp to bend.

 

[rszemeti]

I'll remember the oven method if I need something with a more complicated shape. Only thing I need to watch is the temperature controls. I'm not certain about the accuracy of the oven control, 140°C is fine but >160°C would be a puddle (if I remember the melting point correctly).

I built a simple oven out of an old fan heater and a load of 50mm polyurethane insulation board, with the silver foil backing. A thermocouple and temperature controller takes care of the rest. next thing going in will be some windows for a Feeling 1090 ... in 12mm.

 

[Davy_S]

Instead of boiling water, you should use Glycol (antifreeze solution) many moons ago I worked in the industry, we had an order for hundreds of small curved perspex pieces, similar to a small curved printer lid. Glycol was heated in a tank, the perspex dipped in, then dropped into a wooden mould, so could probably use a saucepan or similar, with a bit of experimenting, it would work. otherwise the oven suggestion would also work.