Making Windscreens

[vince]

Evenin` all. We have just aquired some polycarb sheet and would like to make a windscreen. I`ve been told that it needs "drying" first before its formed to get rid of bubbles? How critical is this, and does it need to be done? Thankyou for any expertise!

[Inde boy]

Originally Posted by vince

Evenin` all. We have just aquired some polycarb sheet and would like to make a windscreen. I`ve been told that it needs "drying" first before its formed to get rid of bubbles? How critical is this, and does it need to be done? Thankyou for any expertise!

Yes, correct it does,check out Arla website Sweden for correct temps and timing for Drying,(something like 1 hour per mm@100 degC) as it is hygroscopic, meaning it absorbs moisture. You would be better using PETG which is equally as good, approx 80% of PC strength, easier to work with as well, and does not require drying.
Try Barkston Plastics in Leeds 0113-2492222, Steve Rock
Hope this helps

Inde

[yoyo]

oooooooo.... Inde your so good

[vince]

Thanks Inde boy, this stuff i got is called Plazcarb, 6mm thick, so i take it the cooking time is 6hours @100c. If we didnt do this, will it affect the see-thru properties that much?

[Matt]

Unless the curves in the screen are gentle enough they can be done cold.
http://www.sheffieldplastics.com/web...EF_MAK_FAB.pdf

[vince]

Phew what a read! Thanks Madmat, we`ll just have to have a go with the scrap first. Will take pics to let you know how we get on.

[Inde boy]

Originally Posted by vince

Phew what a read! Thanks Madmat, we`ll just have to have a go with the scrap first. Will take pics to let you know how we get on.

I was involved in making some screens for lambretta scooters recently using acrylic, nice shapes, what is called press forming, we heat sheet under a sheet heater, and press with tooling, if you ever see a helicopter pilots screen cover ( black) on helmet we make them as well, as you probably guessed I work with plastics, vacforming,press forming any probs or help required contact me.

regards
Inde

[Inde boy]

Originally Posted by yoyo

oooooooo.... Inde your so good

Plasman at your service, hey what happened to the 20 mm HDPE sheet for transom modification??????



Inde

[Inde boy]

Originally Posted by vince

Thanks Inde boy, this stuff i got is called Plazcarb, 6mm thick, so i take it the cooking time is 6hours @100c. If we didnt do this, will it affect the see-thru properties that much?

drying is at @120deg, checked out info today, go for PETG

[vince]

All done! Managed to cold form in the end. Used button head allen key bolts and then finished off with motorbike trim. Am chuffed with the result! Thanks all for the pearls of wisdom, very helpful.

[Matt]

A bit of a follow up about polycarbonate. Found out you can low temp thermoform it to create tighter curves than the 100r cold forming rule.
To do this it doesn't require drying in advance since you're not getting the material into the melting zone where the boiling water vapour can damage the material. (I need to make a 10mm thick screen round a fairly tight curve)

[vince]

Tried with 6mm at first, but couldnt bend it, and we dont have an oven big enough, so went for 3mm in the end, it was easy, but its still very strong and doesnt move at all, very pleased.

Will a hot air gun do the trick for tight curves?

[Matt]

I suspect the problem with a hot air gun is getting it too hot and bubbling the material, but I'm sure it's possible.

Here's another link with details about low temp forming.

http://www.plexiglas.com/literature/pdf/94.pdf

[Inde boy]

Originally Posted by vince

All done! Managed to cold form in the end. Used button head allen key bolts and then finished off with motorbike trim. Am chuffed with the result! Thanks all for the pearls of wisdom, very helpful.

Well done! nice job I have been in plastics-thermoforming for years, I must try a cold form, never seen it done.

regards
Inde

[davis]

I need to make a windscreen too , any chance you could share the proceedure with us ?