vacuum forming lexan

[steve_haskins]

hi wonder if anyone can help
i have a formech 300, the moulds,and the lexan 0.75mm
but im finding it difficult to work with, is it best to heat slowly or quickly, if so how long,

any tips?

thanks in advance

[Nick]

Hi steve First you need to pre dry the lexan at around 120 degrees in a oven for a good 4 to 6 hours maybe longer! This is to remove the moisture from the material which will stop it bubbling when heating and let you heat the sheet for longer. Also as your machine is a single sided heater machine it may pay you to heat the sheet then flip it over and reheat on the other side! the slower you heat the material the better as the heat will soak through the sheet better.

Hope this helps

[steve_haskins]

cheers
didnt realise i had to pre heat the lexan
can i preheat a few sheets then store them? or does it have to be done just before,

[Nick]

Just before as Lexan is real hygroscopic so it starts taking on water from the air as soon as its out in it!

this link should help
http://distributionbizwiz.wordpress.com/2007/08/22/machining-forming-polycarbonate/

[terry.sc]

To find out the best way of heating and for how long for each machine can only be found out by experimenting, even different brands of polycarbonate of the same thickness will need heating at different rates. Even if you get the right combination for one pattern, it will not necessarily work with a different pattern.

When it warms you will see the sheet start to sag, and you will have to experiment to find how much sag before you pull will give you the results you want. A useful property of polycarbonate is that if you reheat a failed pull it will attempt to return back to a flat sheet so it gives you something you can use to try again.

As Nick pointed out, the biggest hassle with polycarbonate is drying the sheets out first. If you don't dry the polycarbonate then the forms will have small bubbles all over them.

[steve_haskins]

thanks guys
i thought it was going to be easy [ i now know why a shell costs 15 quid]
the standard hip material forms so easy and assumed wrongly that this material would be similar,

so dry for hours, then slowly heat material in the former turn over wait for it to sag then pull,

[Gordonm]

Try using petg, from 0.5mm to 0.9mm, it's easier to form and at a lower temp..It's also under 1/2 the price of lexan so you can afford to waste some!!, Best of luck!!

[Nick]

Beat me to it Gorden! or though it does not have the same strength of lexan.

[steve_haskins]

last question where do i buy pgte!

[Nick]

most sheet plastics places! Amari plastics stock it http://www.amariplastics.com/amariplastics/

[steve_haskins]

thanks guys

[mrspeedy]

As most above have said really......

From personal experience using my own vac former for the first time at the weekend ..... I only dried mine in the oven at 120 deg c for 1 hour and it pulled fine , no bubbles at all.

First try was for 40 secs and the lexan wasn't quite soft enough to form properly, second pull was for 50 secs and was perfect :thumbsup:

It'll also help from if you warm the mould up a bit first if you only doing a few ...

HTH