Bending Plexliglass (ehi! without the proper tools!!)

[arma61]

Hi


how do u bend plexliglass ? I have a sheet 100x60 (cm), I need to shape it like this

╔══                  ══╗(side view)
╚══════════╝
(there is no interruption on the sides)

I thought I can warm an iron rod, they lean it on the surface and then bend the plexliglas, what do you think about this ?

Year ago I saw someone bending pg using a restistance ( a sort of spring) connected to 220volts, but I would like to avoid it! too dangerous 

what about a hair drier ?

any other idea pls ?

thx m8s
Armando

[tiges_ tendres]

If you could find an old toaster and some how safely disassemble it, and keep it working, that would be a good starting point.  Actually scratch that.  That is a little dangerous.

I seem to recall using a device which housed what appeared to be one electric bar from and electric bar heater.  The unit allowed you to place your acrylic over a gap and heat up the acrylic so you could bend it in a straight line, rather than having to revert to putting it in an oven and heating the whole thing.

[R.G.]

You want a strip heater. Plastics distributors sell these. There is around 1m of active length and an electrical cord. You put the strip down firmly in place on a flat surface, then use it to heat plexiglass until it is soft over the heater.

Another technique uses a wooden surface like plywwood with a 1/2"/12mm slot in it and covering of metal on the bottom of the wood. You then use heat lamps on the bottom to heat the plexiglass through the slot.

The idea is to heat ONLY the area which bends. You have to get it to 250F to 260F to bend it easily. You must also heat the bending area evenly and all the way through.

Once it is bent and cooled, you must anneal it in an oven up at a temperature of 165 F-180F for one hour for every quarter-inch of thickness, then cool to below 120F at a rate of no more than five degrees F per hour. Otherwise, the internal stresses left from bending will cause it to crack and craze with time.

[MikeH]

Once it is bent and cooled, you must anneal it in an oven up at a temperature of 165 F-180F for one hour for every quarter-inch of thickness, then cool to below 120F at a rate of no more than five degrees F per hour.

How do you know this stuff?!?! 

[arma61]

Once it is bent and cooled, you must anneal it in an oven up at a temperature of 165 F-180F for one hour for every quarter-inch of thickness, then cool to below 120F at a rate of no more than five degrees F per hour. Otherwise, the internal stresses left from bending will cause it to crack and craze with time.

are you kidding, or it's all true?!  it looks like it's more complex than I thought!! Ithought I could do this at home, but it looks like I need a factory to do this job 


thx m8s for suggestions, I think I'm going to cut in pieces and glue in shape with some sealing silicon!

Armando

[frank_p]

Once it is bent and cooled, you must anneal it in an oven up at a temperature of 165 F-180F for one hour for every quarter-inch of thickness, then cool to below 120F at a rate of no more than five degrees F per hour.

How do you know this stuff?!?! 

This is to be sure that there is no more residual intern stress that can make your work move with time and also, when the stress evens in the plastic, it's less prone to fissuring propagation (for acrylic it's important because it's a quite fragile material in the scientific meaning of the term) .  What you want is a stable "relaxed" object.  The molecules of polymers like this are long "spaghettis" that are all jammed together.  when you bent it fast, some spaghettis are more stretched than others.  When you anneal the way R.G. told, that permits to the spaghettis to slowly glide a bit on each other so every ones will have the same tension.  Thus you will have a more solid object because it is "relaxed".

A good industry example I know is:  A manufacturer produced a batch of fittings for pipes.  But they injected it too fast and cooled it too fast in the mold (as too have a faster production rate).  When the products went into home and winter came, They all cracked, and this is REALLY not good in a water system you have at home (imagine).  So the company had to do something with the stock that was left.  And that is exactly what they did (in a really big oven).  No cracking problems occurred after that.

[David]

Once it is bent and cooled, you must anneal it in an oven up at a temperature of 165 F-180F for one hour for every quarter-inch of thickness, then cool to below 120F at a rate of no more than five degrees F per hour.

How do you know this stuff?!?! 

He's probably done it...  or maybe Visual Sound does it.

[The Tone God]

thx m8s for suggestions, I think I'm going to cut in pieces and glue in shape with some sealing silicon!

There are glues made specifically for adhering and sealing acrylics (what true "Plexiglass" actually is made of) that provide decent strength and reduces the seems visual impact. If you make clean cuts the glues works quite well. Mind you I don't know how strong the glue is so if this is for an stomp application it might not take the beating.

Bending acrylic is a tough skill to begin with. You have to get it just before it hits the melt point. The gap between bend and melt is small. The thickness of the material comes into play and this is with proper equipment let alone an at home DIY method. If this is transparent acrylic then getting too hot means things like colour changes (yellow / brown) and optical deformation.

Andrew

[arma61]

This is to be sure that there is no more residual intern stress that can make your work move with time and also, when the stress evens in the plastic, it's less prone to fissuring propagation (for acrylic it's important because it's a quite fragile material in the scientific meaning of the term) .  What you want is a stable "relaxed" object.  The molecules of polymers like this are long "spaghettis" that are all jammed together.  when you bent it fast, some spaghettis are more stretched than others.  When you anneal the way R.G. told, that permits to the spaghettis to slowly glide a bit on each other so every ones will have the same tension.  Thus you will have a more solid object because it is "relaxed".

A good industry example I know is:  A manufacturer produced a batch of fittings for pipes.  But they injected it too fast and cooled it too fast in the mold (as too have a faster production rate).  When the products went into home and winter came, They all cracked, and this is REALLY not good in a water system you have at home (imagine).  So the company had to do something with the stock that was left.  And that is exactly what they did (in a really big oven).  No cracking problems occurred after that.

thx for explanation frank_p,  clear and "understandable" - BTW spaghetti is already plural so you don't need the "s"   

There are glues made specifically for adhering and sealing acrylics (what true "Plexiglass" actually is made of) that provide decent strength and reduces the seems visual impact. If you make clean cuts the glues works quite well. Mind you I don't know how strong the glue is so if this is for an stomp application it might not take the beating.
Bending acrylic is a tough skill to begin with. You have to get it just before it hits the melt point. The gap between bend and melt is small. The thickness of the material comes into play and this is with proper equipment let alone an at home DIY method. If this is transparent acrylic then getting too hot means things like colour changes (yellow / brown) and optical deformation.

Andrew

thx Andrew, got the point and I'll abandon the idea, my plan was to use transparent plexiglas to make this sort of "pocket" where I can insert my small pedalboard 60x40 cm.


BTW is there anything in this word this forum will not be able to answer? I don't think so, may be someone could even explain what's happening in Geneve about atomic fusion I'm sure 

great place, I love it.

Armando

[sean k]

I bent some 4.5mm once as small shelves in a display unit and knew nothing, or more likely cared nothing about annealing it. I used a heat gun and had it clamped in wood along the side of a bench and kept running the heat gun along the point I wanted to bend until it did and it took abit of force and coercion to finally get it to be where I wanted it to be which was 90 degrees. I only acheived about a 15mm radius in the end. The job fell through but I kept those "shelves" around for ages. slowly getting less interested in keeping them pristine. I eventually gave them away and they are most probably still floating around looking for a use.

Actually I may have annealed it somewhat by going back every quarter hour and heating up again but a little less each time but I can't remember but I do know I usually ask about thing s before I try them out.

The old glass casting technique of burying the cast glass in lime might work as the lime tends to hold the heat in. Cast glass definitely needs to be annealed otherwise it'll shatter under the internal stress build up so tricks from other trades are always good for the DIYer. Small job and a bag of garden lime and you should acheive 80% percent success.

[R.G.]

How do you know this stuff?!?!  ??

I'm addicted to reading. Once you get hooked, it's worse than heroin. Well, as hard to get rid of at least.  Kind of a positive addiction.

[tiges_ tendres]

I worked a lot with acrylic in high school (because I didnt have good woodworking skills!)

I don't remember enough about it or have the tools to work with it now.  But back in the day!  I made a number of "sculptures" that involved both heating to bend the acrylic and also gluing.

We used to use a glue that was under strict lock and key, 1 2 Dichloro... Something.  Anyway, gluing with that yielded pretty good results as long as you werent too rough with your pieces.  It would not stand up to being stepped on!

[frank_p]

I worked a lot with acrylic in high school (because I didnt have good woodworking skills!)
We used to use a glue that was under strict lock and key, 1 2 Dichloro... Something. 

Yes, Dichloromethane, chlorinated solvent: take good precautions.

[Paul Perry (Frostwave)]

I knew a guy who made a fortune back in the early 60s from a Government contract making acrylic covers for teletype machines.
the 'factory' consisted of a plywood shape, a large hot air blower that softened the acrylic so it draped over the mould..
and that was it!!

[frank_p]

I knew a guy who made a fortune back in the early 60s from a Government contract making acrylic covers for teletype machines.
the 'factory' consisted of a plywood shape, a large hot air blower that softened the acrylic so it draped over the mould..
and that was it!!

Yes for those interested in that process:

http://support.knowlton.ohio-state.edu/files/FormechVacuumGuide.pdf

You can even make yourself a simple machine that will do it.

[CodeMonk]

Back in my early years (about 30 years ago), I worked in a sign shop. Making signs for various stores, banks, etc.
Not sure what kind of plastic we used but I do know we used some Lexan.
What we used for a "glue" was a mixture of acetone and Methalyene (sp?) chloride.
I think it was like a 20/80 mixture.
It actually melted the plastic together. And held very strong.

[casey]

when i used to tour around with a christian band, we used to gig alot in churches. 
well, one particular church (in magnolia arkansas) had a plexiglass podium. 
as soon as we got there, the bass player and the drummer started acting silly running around
and playing like they were doing an interpretive dance routine.  well, they decided they would
run from opposite sides to the middle with these "capes" they found.  well, one of the capes
caught the plexi podium and down it went.  to their surprise the top had totally separated from
the base of the podium.  this all happened within 5 minutes of getting there.  the youth pastor that
was our guide in that town, was a little taken back by all of this....

Not Good.

well, i was the techie (and guitar player) of the band, and so i decided i would go looking
in my toolbox in the trailer for my DUCO glue.  we ended gluing it back!  i taped it, and the next morning
we were to play (sunday morning) and so i got there early and took the tape off that was acting like
clamps.

well, we played a pretty good gig, and then the pastor got up there all sad and stuff because a good
friend of his had died that morning.  there he was LEANING, SUPPORTING ALL OF HIS WEIGHT, on the glued top...weeping.

talk about stressful.  i looked over at the other band members and they were sweating it too.

well, needless to say, the duco cement held!!!  no kidding.  it was a relief.  i dont even know if you
can still find it in stores...i used to buy it at walmart.

[casey]

whoa, here it is...

http://www.drugstore.com/qxp81909_333181_sespider/duco_cement/multi_purpose_household_glue.htm   

[petemoore]

 Then there's drilling it without cracking it.
  Seems more brittle when it's cold.
   A regular drill bit will gouge and attempt to take a large chunk of ['unsupported'] material out as it exits a thick substrate [they always do that], at which point the stress is easily enough to produce a crack in the work.
  When I was trying to get drillbits through plexi-glass, I was heating the area at the drill hole, making extremely slow bit exits.
  Completing the drilling processes first means if you get a crack you can scrap the piece that doesn't have so much work-time in it.