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Armor : Sintra Shaping 101

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Sep Ho'ban

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: Sintra Shaping 101
« on: Jun 12, 2018, 02:46 PM »
Sintra Shaping 101
Lead Author: Sep Ho'ban
Edited by: MMCC Education Team

This guide is going to cover the basics of shaping Sintra into armor plates.  This guide will focus on a set of modern Jango/Boba style plates in the male style.  For an advanced guide on achieving female breast plates, please check out the Female Sintra Darts Tutorial.

There are safety tips and guidelines in each section of this guide.  But this guide is by no means a comprehensive safety guide for all of the tools and materials referenced.  It is a must that you wear the appropriate personal protective equipment necessary for each tool.  Dust masks or respirators must be worn at all times when sanding, painting, or heat shaping.  Once particulate gets into your lungs, it doesn't come out.  Eye protection must be worn when operating any power tools including rotary tools/Dremels, band saws, belt disc sanders, etc.  According to OSHA hearing protection is not required for anything under 90 dB.  Most shop tools do not reach that volume, but if you have uncommonly loud tools or are sensitive to noise, you may want to keep hearing protection handy.  Have a first aid kit on hand and where it is located. 

For materials and chemical adhesives/cleaners/etc. you may use, please:
Read the material safety data sheet (MSDS) on any material or product you are unfamiliar with. These can almost always be found online.

As you read, please pay special attention to the safety sections.  If you exercise reasonable care, caution, and focus while using the tools and materials in this guide, you should be able to cut and shape your armor efficiently, and without injury.

3mm vs 6mm vs MORE

The most common thicknesses of Sintra used in the club are 3mm (roughly 1/8th inch) and 6mm (roughly 1/4th inch).  Some kits also add layered detail on top also known as "trauma plating."

In general, 6mm is harder to shape and to cut than 3mm,  but the difference is easy to compensate for if you adjust your technique.  The sections below will include advice where there are specific differences for working with 3mm vs 6 mm. 12mm (roughly 1/2 inch) starts to become a real challenge to cut and shape, and will not be covered in this guide.  If you would like to achieve 12mm thickness using these techniques, doubling up on 6mm after cutting and shaping separately is recommended. 

Safety: For whatever cutting method you choose, please use the appropriate safety gear associated with that method.  Eye protection is always recommended.  Gloves are a good idea for some of the options below, and not recommended for others.  As always, please follow the manufacturer's safety recommendations, protect your eyes, and keep your fingers attached to your hands! If one hand is cutting and another is moving material or supporting material in the way of the blade, a glove for the "victim" hand is highly recommended, but  it is not a bulletproof vest.  Dremels, and other blades can and will eat gloves and keep going.  It just buys you an extra second or turns a laceration into a nick.
Please NEVER cut Sintra or other PVC based products with a laser cutter. The C in PVC is Chloride, and cutting with a laser cutter produces Chlorine Gas. Chlorine gas is very bad for you.

Xacto/Utility/Razor knife:
3mm can be cut fairly easily with these types of knives.  It is highly recommended that you not try to make the entire cut depth in one pass, but instead make a scoring pass to establish a line and then make 1 or 2 additional passes to finish cutting through the material.
6mm can also be cut following the same method, but will take more passes, and more pressure to be successful. More pressure with a sharp object is almost always less safe than lighter pressure. 

Rotary Tool/Dremel:

The next step up from one of the knives above is a Rotary Tool (commonly sold under the brand name Dremel).  These tools use abrasive discs rotating at high speed to cut the material, and are also useful for sanding and detailing your sintra.


Scroll saws use a reciprocating (up and down) motion to move a blade and cut the material.  Scroll saw work involves getting your hands relatively close to the blade, but in with reasonable care, it is easy to stay safe while cutting fine detailed work with a scrollsaw.  When cutting sintra, particularly 3mm, you will need to hold the material firm to the table so that it doesn't bounce up and down.  Scrollsaws are capable of cutting tight curves that are as accurate as you are capable, so can decrease sanding and finishing time.  Practice on some scrap first.


Safety: This is the only cutting tool that gets its own specific safety section, and that's with good reason.  Bandsaws were originally designed for use by butchers, to cut large, thick cow bones, ribs, steaks, etc.   Most bandsaws, like most tablesaws, will not notice or otherwise care if it is your thumb, wrist, forearm they are cutting instead of the intended material.   Keep non-sintra things at least a couple of inches away from the blade at all times so you don't casually bump into the blade when you become either too focused on the cut, or distracted by something else.  If a piece of sintra gets stuck in between the blade and the table, wait for the blade to come to a COMPLETE stop before you remove that chip.

Bandsaws use a looped band blade that rotates between rollers constantly to cut the material. They provide a consistent downforce against the material so you don't need to hold it firm to the table as with a scrollsaw.  They don't cut curves as well, and the larger your bandsaw is, the less well it will cut curves.  You may need to sneak up on curves, cutting triangles of material out. 

Heating Methods

Sintra becomes pliable when it's heated. The great thing about Sintra, is that unlike some other thermoplastics, it has a nearly infinite "reset," meaning that if you screw it up, you can just heat it up and bend it back, or make small tweaks or large tweaks multiple times.

There are 3 typical methods of heating up Sintra. Each has associated advantages and disadvantages.
General Safety:  Sintra doesn't have to be heated to 500 degrees to be pliable.  If you're heating Sintra gently, you may not even need gloves to form it.  However, never grip it firmly when you first remove it from the heat.   Touch it gently where you can easily pull away.  If it's hot enough you're concerned about burns, please wear gloves.    Sintra produces SOME fumes when heated -- please do any of these methods in a well ventilated area, or outside. Wearing something like a surgical mask to prevent breathing in the fumes is also a good idea.


Safety: A heatgun looks a lot like a a hair dryer, but gets MUCH hotter than.  Never point the heat gun at a person (unless they are wearing appropriate protection -- t-shirts are not appropriate protection).  The end of the heatgun remains hot for several minutes after you turn it off, so do not touch yourself or anyone else with the end of the gun when you put it down. It is absolutely hot enough to burn you even though the Sintra you've just warmed up may not be.  Also don't let the end rest on any scorchable/meltable/flammable surfaces.  Many heatguns are made so that you can rest them vertically on the butt of the gun.

Heatguns can be purchased at discount hardware stores for around $12, and online for around $20 - they're relatively inexpensive, and they're extremely useful and versatile.   It's the only one of these three methods where you can apply heat with the armor on a person, without damaging the person.  (If you're doing this, it's highly recommended you use the low setting, and only for minor tweaks very specific to their body shape).   

To heat the Sintra, swing the gun slowly back and forth in the area you want to bend.   Flip, and do the same on the other side of the Sintra for even heating (especially important with 6 mm, less of a concern with 3mm). 

Boiling Water:
Safety: Boiling water is hot enough to scald you - please wear gloves for this method and be careful not to splash water on exposed skin. Never expose the person you are shaping them for to boiling water.

For this method you'll need a pot large enough to submerge the sections of Sintra you'd like to bend, a heat source capable of boiling that quantity of water, and water (tap water will be fine).  The major limitation with this method is that you can't shape a part of the plate that won't fit in the pot.

Fill the pot with water, bring the water to a rolling boil, then turn the heat down so that you're just getting random bubbles instead of a steady froth.  Submerge the Sintra, checking it every 10-15 seconds to see if it's pliable enough to bend until you have a good idea of the timing for your conditions.   

Sintra floats--use tongs to hold it under the water.

Safety: What is coming out of the oven will be hot enough to burn you - please wear heat resistant gloves. If you're using a person as the anvil to shape the armor, have them wear a hoody or jeans - something thicker than t-shirt material or leggings. 

You can use a toaster oven, or the oven in your kitchen. This method is great for getting even heating over a large area. (Highly recommended for Backplates or anywhere with complex shapes).   Preheat the oven to 200 degrees and put your Sintra on an upside down aluminum sheetpan (grill marks look amazing on steak, they're not nearly as appetizing on armor).  If you're heating up 3mm, check on it after 2 minutes, then about every 30 seconds. It won't take long to get to "floppy" stage.  If you're heating up 6mm  - 6 minutes to start, then check on it every 2, depending on whether you want pliable or floppy.

6mm Sintra ready to go in the oven

Shaping basics
Your Sintra is cut, and now it's hot.  Time for the actual shaping!

Pliable vs. Floppy:
There are two basic states of heated sintra. Pliable bends with some degree of pressure.  If you're REALLY forcing it, it's cool Sintra, and it will likely snap.  Floppy means that when you pick up the piece it droops or conforms to the shape of whatever is supporting it. Pliable is ideal for tweaks and a lot of rough shaping.  Floppy is the only way to achieve some more complex shapes without cutting darts.  In its pliable state it may pick up finger prints, but if you carefully apply pressure it usually won't; in its floppy state it picks them up very easily.  You should already be wearing gloves if you've got floppy Sintra, so try to use the palms of your hands to apply most of the pressure, and make your fingers "mitten style" - all together, not spread apart or pinching.

Everything is an anvil:
Most of us think of an anvil as something a blacksmith uses to beat metal into a shape or that a farrier uses to bend horse shoes.  For our purposes, an anvil is ANY object that is sturdy enough to bend Sintra around, that can take the heat, and that has the shape, or part of the shape, you're trying to achieve. 

Off cuts of various diameter PVC pipe are really helpful for things like shoulders, shins, knees, shnees, gauntlets etc.

Edges of countertops, tables, workbenches are ideal for achieving sharp corners. 

The person you're shaping the armor for is also made of anvils.  Just be sure to protect them from heat accordingly).

This is often the best way to achieve those final tweaks and get it laying perfectly on the body.

Single Axis Curves vs Compound Curves:

Bending a plate along a single axis is simple.  Orient the plate on your anvil of choice.  Apply pressure on opposing sides of the bend line until you're happy with the shape.  Hold in place until the Sintra cools enough to stay put (won't take more than a few seconds).

Shoulder plate with a single axis curve

Compound curves (curves that bend around more than one axis, like a sphere), are a lot harder to achieve with Sintra.  There are a few ways around that. Heating to the floppy stage, laying it on your anvil, and applying pressure across the entire shape, will help you achieve compound curves that are of a relatively conservative nature; cutting darts (removing triangles of extra material to allow the Sintra to curve) will let you achieve more extreme compound curves; and cutting, and gluing together multiple segments that have been bent along a single axis.   This limitation of the material is why we have entire other tutorials dedicated to female chest plates.

Shoulder plate with a compound curve

Typical Modern Kit Bend Diagrams
Green lines indicate a gentle bend across the entire surface.  Red lines indicate a sharper bend or crease.  Not all of these bends will be necessary for all people.  Some people will need different bends. These diagrams represent a starting point.



Chest Plate:




It's worth noting that backplates are typically a TEAM sport.  It's pretty hard to shape your own backplate to fit you perfectly.  You're also not required to use this backplate design unless you're doing a canon build, and this backplate is one of the harder backplates to get shaped to lay down against you well.  It is also, however, one of the most widely used back plate designs in the MMCC.

Always maintain good safety practices when cutting, heating, and shaping.  If you've posted paper templates taped to you for feedback on sizing and placement, and you've read this guide, you're now ready to start cuting and shaping your plates.  Do be aware that your flak vest and flight suit will alter how the pieces fit to your body, so it's best to wait for final shaping until you can do it while wearing those pieces.

--MMCC Education Team--

« Last Edit: Jul 23, 2019, 09:38 AM by Raestin Ke'Varek » Logged

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