3D Durability: Thermal Defense Solutions’ Suppressors
By Oleg Volk
Some would describe sound suppressors as “reverse heat engines” acting to slow gas expansion and cool the gases by disturbing flow and absorbing heat. Unlike muzzle brakes that redirect recoil forces, suppressors dampen recoil by containing expanding gases. A good sound suppressor cuts peak recoil by 25% to 40% by slowing the gas enough to make a perceptible difference in shooting comfort. The problem with conversion of these forces is that it eventually can accumulate to the point of failure of structural integrity of the suppressor itself. Suppressor makers using titanium and stainless steel found that even those materials can come short of required performance for high-volume shooting. Inconel 718, an alloy of nickel with a little chromium, iron and traces of a dozen other metals, appears to be the perfect suppressor material. Resistant to heat, erosion and corrosion, with less thermal expansion than stainless steel, it would have been perfect but for the cost of machining it. Since Inconel dulls cutters rapidly, it is often used with water jets and welding, but most manufacturers reserve its use for blast baffles only. Thermal Defense Solutions (TDS) makes the entire suppressor from Inconel!
The advantages of making the entire suppressor from a single material are clear: even thermal expansion, excellent resistance to erosion and solvents throughout. Compared to stainless, Inconel has slightly lower specific heat capacity and, once hot, radiates it away a little slower, but makes up for it by remaining strong up to 760°C (1400°F). By that point, stainless steel would have the consistency of butter. This makes all-Inconel suppressors superior for guns with high volumes of fire, such as machine guns. Future products are planned with Haynes 282 alloy, permitting operating temperature up to 980°C.
TDS is co-located with Volunteer Aerospace, a company that makes internals for space-going rocket engines and other things which must be strong, light and durable. Their main manufacturing method could be described as 3D laser printing. The printer, an $800,000 device the make of which they prefer to keep confidential, deposits Inconel dust in thin layers to be welded together in spots by selective laser melting. Once the layer is fused, the next layer of dust is added, all the way to the full height of the object being printed. The machine runs unattended, freeing up personnel for more research, development and design tasks. Generally, the slightly rough external finished is cleaned up after the printing, while internal features are usually left rough for better heat transfer and increased gas turbulence. Cross-sections of products like turbine blades show weight-reducing features like 3D mesh filling the interior of previously solid parts. That permits a considerable reduction of the turbine blade momentum as well as a weight savings that are always welcome in aerospace applications. 3D printing is about the only practical way of making a total Inconel can.
The two main advantages of the 3D printing approach are: (1) the entire suppressor comes out as a single unit, with no possibility of parts misaligning or welds failing and the internal geometry possible with the sequential build-up beats any subtractive machining method for efficiency and (2) the ability to create complex internal geometry. Some of TDS suppressors, for example, have convoluted gas by-pass channels near the outer surface for reducing muzzle flash. The theory is that gas jets converging on the main front aperture starve the environment of oxygen, reducing the exit aperture flame to a minimum. The manufacturer states that high-speed video confirmed the theory. Making such features by conventional milling would approach impossible. Some of the computer simulation is done in-house, and some is outsourced to Oak Ridge National Laboratories. Quality control is literally built into every product run, with bars for tensile strength testing produced with every batch of sound suppressors. If a bar fails any of the strength tests, the entire batch gets scrapped; if it passes, as is customary, individual silencers are checked further.
TDS produces four 5.56mm designs. “Bantam,” the size of a large flash hider, offers a manufacturer claimed 20db of attenuation but adds only 6.5 ounces to the gun. “Badger” is standard size, 11 ounces and drops noise by 30db. “Vulcan,” 11.5 ounces, is the same size and only offers 26db but sustains it during automatic fire. “Specter” is a thicker, shorter 14-ounce suppressor with a reflex chamber for reduced blowback with autoloaders and reduces noise by 28db. The reduction numbers are typical relative to competing models, but the other features—low flash, great resistance to erosion and solvents, reduced blowback—are all TDS specials. “Strix” is a .30 caliber suppressor similar to Vulcan. In actual use at the Middle Florida Big 3 East range demonstration, the five suppressors performed as expected. Interestingly, though some of them were fired extensively enough to produce very hot silencers, the Cerakote finish stayed put. Predictably, the thick reflex model worked the best on the AR-15, with no appreciable blowback to this author’s testing. The main measure of these designs’ success is that they match or exceed the heat endurance of host firearms and cease to be the limiting factor in the user’s combat capability.
Thermal Design Solutions is a fairly young company, but their technical expertise puts them in the forefront of the industry. With $999 to $1099 MSRP, TDS sound suppressors are not cheap—fortunately, they are the epitome of “durable goods” and should last almost indefinitely in normal use. Their other, non-public projects clearly illustrate the possibilities offered by unconventional 3D printed parts made from Inconel or various plastics. The trouble with writing about companies making such designs is the obligation to keep certain data private. If you’ve read cyberpunk science fiction about the year 2040, you will find much of their current R&D represented by writers as future magic. For now, visit thermaldefenseinc.com for such details as may be made public.
This article first appeared in Small Arms Review V22N8 (October 2018) |
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