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Mechanic AH

Suggestions for easy ways to trim polycarbonate shells?

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Aside from the score + snap method, or using lexan scissors (curved and straight), or a circular cutter for wheel wells, are there other ways to easily (and cleanly) trim polycarbonate bodies especially thick and complex ones?

Has anyone tried a hot knife? Or a soldering iron with a blade? Any other suggestions? I came across an electric/vibrating cutter but don’t want to spend hundreds without seeing any results. Any successful tips? Thanks!

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I have tried a hot wire cutter in a soldering iron handle for polycarbonate and ABS, it does make short work of the polycarbonate but is definitely not a clean cut, the re-cast layer is problematic. Also the temperature variation, too cold and you get stutter marks from dragging the wire through the part, too hot and it burns/overmelts so I would not recommend the anything with heat approach... sharpest line I have had were with scissors and a ball ended dremel reamer for the small details.. I have had zero success get in the score and snap to work though most of the bodies I tried were quite curvy and intricate. 

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I have lost count of how many body shells I have done now and damage doing cut and score but ever since I got a dremil it makes the job a lot easier. You can even get cheap knock off that do a good job.

Get one and you will not look back.

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25 minutes ago, DayRider said:

I have lost count of how many body shells I have done now and damage doing cut and score but ever since I got a dremil it makes the job a lot easier. You can even get cheap knock off that do a good job.

Get one and you will not look back.

What cind of dremel do you use/recomend for this?.

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I don't think there's a magic bullet here - I find you need at minimum a curved pair of lexan scissors, a sharp scalpel blade and various grades of sandpaper.

A Dremel with various attachments can be useful but it's the most disastrous if it gets away from you.

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I've not yet managed a 'perfect' shell, but I get better with each one! I do use Tamiya PC Scissors to get as close to the cut line as I dare, and then a Dremel with sanding barrels and / or flap wheels to get the arches nice and even. I find the hardest part is actually long straight sill lines; sometimes I can get a metal ruler to line up and use a knife, others its just a case of doing the best you can with the scissors and tidying up as much as possible with the Dremel 

I know your original post said "apart from lexan scissors..." but I've had no trouble with them and can't imagine taking a shell on without them :)

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4 minutes ago, Howards said:

I don't think there's a magic bullet here - I find you need at minimum a curved pair of lexan scissors, a sharp scalpel blade and various grades of sandpaper.

A Dremel with various attachments can be useful but it's the most disastrous if it gets away from you.

That's true, but like with paint it pays to test first! I tend to trim as much of the lexan away with scissors and then keep the offcuts, draw lines on them and use them to practice with the Dremel on different speeds and different grips to get a good feel for it before I go anywhere near the shell itself

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5 minutes ago, Juhunio said:

I've not yet managed a 'perfect' shell, but I get better with each one! I do use Tamiya PC Scissors to get as close to the cut line as I dare, and then a Dremel with sanding barrels and / or flap wheels to get the arches nice and even. I find the hardest part is actually long straight sill lines; sometimes I can get a metal ruler to line up and use a knife, others its just a case of doing the best you can with the scissors and tidying up as much as possible with the Dremel 

I know your original post said "apart from lexan scissors..." but I've had no trouble with them and can't imagine taking a shell on without them :)

For long straight lines I've found scoring then snapping then sanding flat with sandpaper around a wooden block (for the straightness) is effective. It's hard to get a straight finish with a Dremel - with a sanding wheel it tends to bounce and is very sensitive to variances in pressure and resistance. 

Still the forward and rear edges of wings especially Tamiya period ReRe wings are absolute sods to get right.

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10 minutes ago, simalarion said:

What cind of dremel do you use/recomend for this?.

Any will do I imagine, as long as it has variable speeds so you can manage how 'hard' it goes at the lexan. The sanding drums and flap wheels work well for me

 

42259934.jpg

dremel.jpeg

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7 minutes ago, simalarion said:

What cind of dremel do you use/recomend for this?.

I use this one with the extension head and this cutting disc.

16056335650852769348686006921307.jpg

16056336045985563373105414850563.jpg

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( as a side point, you can get fixated on the quality of you cut job if you cut then paint. If you are brave and paint then cut you get a better feel for the level of quality required for a 'good enough' cut job. )

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59 minutes ago, DayRider said:

I use this one with the extension head and this cutting disc.

16056335650852769348686006921307.jpg

16056336045985563373105414850563.jpg

I use these too , I also use the smaller barrels for tighter curves - these are great . I do score and snap on a lot of plastic - especially lexan , but I also use the Dremel disc cutter on ABS to get chunks off

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I set the speed on mine really low and it cuts better the lighter you press on. mark on the out side the line you want to cut up to so you can see how far you have to go.

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1 hour ago, DayRider said:

I set the speed on mine really low and it cuts better the lighter you press on. mark on the out side the line you want to cut up to so you can see how far you have to go.

What do you do in those square corners?, for my 2 Lexan bodies so far both Top-Force (back spoiler) and Agrios (back end of the car) had square corners that i always seems to have problem with, turns out ok in the end after much hassel but never more than Ok. 

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31 minutes ago, simalarion said:

What do you do in those square corners?, for my 2 Lexan bodies so far both Top-Force (back spoiler) and Agrios (back end of the car) had square corners that i always seems to have problem with, turns out ok in the end after much hassel but never more than Ok. 

I have a cutting disc a bit like on a still saw for straight cuts but sometimes I still use sissies. What body are you doing?

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6 minutes ago, DayRider said:

I have a cutting disc a bit like on a still saw for straight cuts but sometimes I still use sissies. What body are you doing?

Having 1 curved Scissor :), ordered a straight one earlier today actually, for the next lexan body :). Also use fine sand paper after using scissor, i get the job done and it looks in overal Ok but execpt from those square corners  ... Then i saw here what other where using 

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10 minutes ago, DayRider said:

I have a cutting disc a bit like on a still saw for straight cuts but sometimes I still use sissies. What body are you doing?

Show us a pic of the widget!! 

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3 minutes ago, simalarion said:

Having 1 curved Scissor :), ordered a straight one earlier today actually, for the next lexan body :). Also use fine sand paper after using scissor, i get the job done and it looks in overal Ok but execpt from those square corners  ... Then i saw here what other where using 

Here you can see my first Lexan body work, as you can see on the back spoiler i strugle, i believe the tips i got here today would make the job easier ...

Hopefully the body i be doing tonight is my wife, but i ques we have to see about that as usual :)

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21 minutes ago, Juhunio said:

Show us a pic of the widget!! 

 

16056462315397895382651847835435.jpg

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I was hoping there was an easier way. It made me think about the topic question because when I worked on the TC-01, it took me more time than I expected, to the point where it wasn't as enjoyable (since I prefer building over body work). But knowing myself, I get a bit obsessed so that's the downfall. I have a CAT XLS on my to do list and the belt cover is very thick so I'm trying to decide on a new trimming strategy that's easy and enjoyable.

I do use straight and curved lexan scissors and a rotary tool, in my case a Proxxon. And then I still sand the edges with a block, sand paper, sand sticks, and the rotary tool's different sanding bits. I think with a thin polycarbonate shell I can do the score and snap method, but very challenging on thick and tricky lines, and that initial score is tricky especially when you have to freehand it. And the how to videos on Youtube, most of the shells they demo seem very thin and simple—making it look easy. I'd like to see someone do an intricate and thick shell with some decent results.

One tool I've been eyeing for a while is an ultrasonic cutter. It's basically a vibrating modeling knife (at 40,000 vibrations per second) and I think might be worth it for someone who works with a lot polycarbonate/lexan—that's if the knife even does a good job. It's about £300/$400 US but I haven't come across anyone using it and I'm hesitant to drop that amount to test it out. Has anyone tried this device? Or anyone willing to buy and test it :). I'd sacrifice buying a decent RC kit for the knife if it works.

Attaching pics (some of you may have seen) of the shell and completed project that made me rethink of an easier way on how to trim polycarbonate.

 

IMG_9811.jpg

MechanicAfterHours-1020150.jpg.12f07415d02d2b62573350d4cccbbcd1.jpg

MechanicAfterHours-1020119.jpg

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Sometimes it can be really joyful going through the hole proses of cutting and painting a body if you get it right, but one mistake and you just feel gutted. Sometimes if I had the choice I would like to get some that are done for you. Not everyone likes doing body shells.

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13 hours ago, Mechanic AH said:

trim polycarbonate bodies especially thick and complex ones?

I've done plenty of boat work and and trimming, and removing resin infested servo and motor mounts, transoms, stuffing tubes, hatch compartments ect... i had to get really good with a Dremel.

it's all in that adjustable speed control, too slow it, binds, too fast it melts so there is a medium, and depending how the cut particles meld balling up but not fusing back together and self sealing on itself again it's cut forward, then slightly back all the while to keep an edge that will have to be sanded, filed after the initial cut as to make room for any mistakes and keeping it from hopping and dinging any other part of the body.

Be it CF, FRP, ABS, Lexan, PVC aluminum, metal and even the dogs nails.

Dremel is my friend.

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10 hours ago, Mechanic AH said:

I was hoping there was an easier way.

IMG_9811.jpg

MechanicAfterHours-1020150.jpg.12f07415d02d2b62573350d4cccbbcd1.jpg

 

Wow, looks like you've done an awesome job on that! I'm not sure there is an 'easy' way for anything to turn out that well

There are many easy ways to do a bad job, and a good few even easier ways to totally screw up a great job! Those moments when your internal emoticon goes :):wub::(:angry::rolleyes:

But to do anything as well as that takes time, patience, a very steady hand and a fair amount of self-forgiveness. 

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17 hours ago, DayRider said:

Sometimes if I had the choice I would like to get some that are done for you

I cut and painted a set of shells for someone on here. Somewhat stressful...to say the least. Then you have to ship them...

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7 minutes ago, Howards said:

I cut and painted a set of shells for someone on here. Somewhat stressful...to say the least. Then you have to ship them...

 

"Sometimes if I had the choice I would like to get some that are done for you"

Well, not the painting that part i enjoy very much (specially removing the foil at the end)  and you can also correct issues with the right stuff ( like Tamiya body cleaner) which you can not if you do a bad cut in the Lexan, so the cutting part i could do without, it dont feel creative when just trying to cut it out and frankly i would prefer if i could get the bodies cutted from the factory. 

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