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barndog Newbie
Joined: 15 Apr 2012 Posts: 5 Location: eureka,ca
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Posted: Wed Jan 09, 2013 11:13 am Post subject: drying moisture out of lexan |
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hey guys ive been looking for the info on drying lexan im useing .040 to make r/c car prototypes and i was wondering how to bake it can you steer me in the right direction.i have been doing petg but they dont hold up for testing.thank you! |
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spektr Master
Joined: 07 Jan 2008 Posts: 425
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Posted: Thu Jan 10, 2013 11:44 am Post subject: |
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The secret here is the masking film. If the film is not hygroscopic, drying of 040 material is not necessary.
I've never had to dry any rolled material in those thicknesses. Individual sheet material might be different, but running 1 sheet should give you the answer. Be careful to understand that you can overtemp 040 easily and that decomposition bubbling can be mistaken for moisture damage. Decomp damage also turns the clear sheet white, somewhat like PETG does. Dust on the mold can also show up as a bubble on the inside of the part where it mated to a male mold. (assuming a male rc car mold).
If you actually have to dry the sheets, 180 f overnight in an oven was good enough for my 1/4 inch thick windshield blanks, so I'd do that since its simple to set up and walk away....... |
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barndog Newbie
Joined: 15 Apr 2012 Posts: 5 Location: eureka,ca
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Posted: Mon Jan 14, 2013 12:26 am Post subject: |
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great thank you i will look into that and order some up to try out i have heard of guys drying it in a plywood box is this a good method also. |
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glenn201 Newbie
Joined: 06 Apr 2013 Posts: 18 Location: Brazil IN
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Posted: Sun Apr 07, 2013 8:35 am Post subject: |
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spektr wrote: | The secret here is the masking film. If the film is not hygroscopic, drying of 040 material is not necessary.
I've never had to dry any rolled material in those thicknesses. Individual sheet material might be different, but running 1 sheet should give you the answer. Be careful to understand that you can overtemp 040 easily and that decomposition bubbling can be mistaken for moisture damage. Decomp damage also turns the clear sheet white, somewhat like PETG does. Dust on the mold can also show up as a bubble on the inside of the part where it mated to a male mold. (assuming a male rc car mold).
If you actually have to dry the sheets, 180 f overnight in an oven was good enough for my 1/4 inch thick windshield blanks, so I'd do that since its simple to set up and walk away....... |
I would like to see your oven Im making 1/5 scale rc car bodys out 1/8 inch
lexan I need to make something to dry it in |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Mon Apr 08, 2013 8:42 am Post subject: |
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I had to dry some ABS that had too high a moisture content. Not much to see but a plywood box with a door. I used "disc limit switches" that turn off at the desired temp but are cheap on Ebay, as in a few bucks a piece. Then some left over nichrome wire and hardibacker for the heat source but using a standard baseboard heater would've been easier.
Made the box big enough to keep the plastic 5-6" away from the heat source plus used a circulating fan inside the box. Spaced the plastic sheets so air would easily circulate between the sheets. After 4-6 hours the plastic molded perfectly instead of blowing up!
dn _________________ DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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glenn201 Newbie
Joined: 06 Apr 2013 Posts: 18 Location: Brazil IN
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Posted: Mon Apr 08, 2013 6:25 pm Post subject: |
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jdougn wrote: | I had to dry some ABS that had too high a moisture content. Not much to see but a plywood box with a door. I used "disc limit switches" that turn off at the desired temp but are cheap on Ebay, as in a few bucks a piece. Then some left over nichrome wire and hardibacker for the heat source but using a standard baseboard heater would've been easier.
Made the box big enough to keep the plastic 5-6" away from the heat source plus used a circulating fan inside the box. Spaced the plastic sheets so air would easily circulate between the sheets. After 4-6 hours the plastic molded perfectly instead of blowing up!
dn |
here is what im trying to make i got heat set up to run all the time how can i wire in a fan to come on at like 150 an go off at 140 would like any help you can give me
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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glenn201 Newbie
Joined: 06 Apr 2013 Posts: 18 Location: Brazil IN
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Posted: Tue Apr 09, 2013 4:31 pm Post subject: |
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thanks a lot i think that could do it |
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RobL Newbie
Joined: 19 Jun 2013 Posts: 24 Location: Indiana
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Posted: Fri Jun 21, 2013 12:07 pm Post subject: |
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Quote: | Be careful to understand that you can overtemp 040 easily and that decomposition bubbling can be mistaken for moisture damage. |
I think I experienced this with my couple of test runs, as I had long heat times.
Good info to have regarding the polycarb masking vs. hygroscopic issues. _________________ generalleerc.com
I love the internet....helping the ignorant and uneducated like myself get a little less dumb, one post at a time.... |
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RobL Newbie
Joined: 19 Jun 2013 Posts: 24 Location: Indiana
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Posted: Thu Jun 27, 2013 10:03 pm Post subject: Perhaps I was incorrect before.... |
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So, I re-cobbled my heater system, ( pics in my thread,) and in a 90 second heat cycle, I got these bubbles.
I did leave the protective mask on the top side of the lexan, as it's typically left on to help protect overspray during painting ( rc car body,) and it was easy to remove, didn't seem melted...which leads me to ignorantly believe that this is what moisture soaked lexan looks like?
I could see them forming when the lexan was heating, so they were there before they came in contact with the mold, to rule out dust, etc.
thank you,
Rob _________________ generalleerc.com
I love the internet....helping the ignorant and uneducated like myself get a little less dumb, one post at a time....
Last edited by RobL on Thu Jun 27, 2013 10:27 pm; edited 1 time in total |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Thu Jun 27, 2013 10:14 pm Post subject: |
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According to Spektr's post decomposition bubbles from overheating also turn the sheet white. What is your analysis on this?
dn _________________ DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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RobL Newbie
Joined: 19 Jun 2013 Posts: 24 Location: Indiana
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Posted: Sun Jun 30, 2013 9:31 pm Post subject: |
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I came across the video below which shows what the white discoloration looks like. At the 6:00 min mark, they've removed their lexan (?) and you can see bubbling and the discolored sections.
That's one hell of a heater they have!
http://www.youtube.com/watch?v=cseFvsFj2sk
So, at least for my pic, it's just moisture. Time to construct a drying apparatus. _________________ generalleerc.com
I love the internet....helping the ignorant and uneducated like myself get a little less dumb, one post at a time.... |
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spektr Master
Joined: 07 Jan 2008 Posts: 425
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Posted: Tue Jul 09, 2013 2:15 pm Post subject: |
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YOU DO NOT NEED TO DRY .040
YOU ARE LOOKING AT CLASSIC DECOMPOSITION BUBBLES.
REMEMBER THE HEAT TRIANGLE.... WATTS/DISTANCE/TIME.
ADJUST THE PARAMETERS AND YOU WILL GET THERE. |
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RobL Newbie
Joined: 19 Jun 2013 Posts: 24 Location: Indiana
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Posted: Tue Jul 09, 2013 5:44 pm Post subject: |
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Quote: | YOU DO NOT NEED TO DRY .040
YOU ARE LOOKING AT CLASSIC DECOMPOSITION BUBBLES.
REMEMBER THE HEAT TRIANGLE.... WATTS/DISTANCE/TIME.
ADJUST THE PARAMETERS AND YOU WILL GET THERE |
This is awful news, as I've nearly completed my "oven." Not much money has been spent, but the time...oh, the time.....lol.
Anyway, thanks spektr, I ignorantly thought I would see the "white" symptom when decomp was happening, good to hear that the bubbles are kinda' the first stage of improper heating.
Perhaps my heater distance is too large, so I end up cooking my material in order to get the right droop. So, I'll have to give it some thought, but my initial thought is to decrease the distance from the heaters.
Once again, thanks spektr, now off to figure it out.... _________________ generalleerc.com
I love the internet....helping the ignorant and uneducated like myself get a little less dumb, one post at a time.... |
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spektr Master
Joined: 07 Jan 2008 Posts: 425
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Posted: Wed Jul 10, 2013 12:06 pm Post subject: |
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I still can't seem to get people to get away from droop as a primary indicator of sheet temp... get yourself an infared heat gun and run it by the numbers.. additionally, i can almost gaurantee that you have sheet temps all over the map doing a part that large. pm me your phone number.. |
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