Metal Fire Rings Fire Pits Basics

October 14, 2018 Ahmed Nassar

Introduction.

The purpose of this article is to review the challenges that you may face in developing your own product lines for local or regional distribution. In concept, these considerations apply to many products. For the purposes of this article, we will use the production of fire rings for a kit or retail sale as an example.
Fire rings fire pits are a simple product that can provide a profitable revenue stream for a fabricator if designed executed properly to meet local demand and demographics. Many municipalities encourage or require some form of containment for “open” fires during the safe “burn season”. In the Pacific NW, this season generally starts once the rain returns and the local Fire Marshal decides that the risk of fire migration via ember or spark is low enough to permit “open” fires. Given the recent run of devastating fires across the West Coast, it is likely that both restrictions regarding equipment and opportunity will be restricted sometime in the future. This market should, therefore, be approached with caution and an eye on enhancing safety and reliability of open fires more than just the aesthetic a fire ring provides before the substantial investment is made. Partnering with local fire departments in terms of design criteria is strategically valuable. Key design elements to review include optimizing diameter, height, cross ventilation, upper edge treatment, the maximum size of un-screened cutouts or openings in the artistic elements, and whether a lid, screen, or other closure/safety device is required. Simply put, it is wiser to address these elements up front than to litigate them later. Particularly, if some deficiency in its design is later alleged. To be clear, the burden for safe use lies with the consumer however in our present litigious society it is far better to have addressed these issues in advance than to respond to them after the fact.
The fabricator should begin by deciding whether every ring sold is their “product” or simply a “part” or set of parts made to the customers’ order and specification. While the two cases may result in similar looking outcomes the difference between the two cases may be “distinguishable” in legal terms. You nevertheless likely will encounter customers that solicit your advice. It would be wise to have a conversation with a good attorney before this day comes. Assuming that product liability insurance is a non-issue (too expensive) for the average fabricator, every ring sold (should) include an appropriate Warning and Disclaimer. Ideally, these should be provided in both printed and physical form. Physical form can range from a clearly designed label to laser/plasma engraving in the product itself. Warning language varies with locale but should identify what the product is designed for (wood, charcoal, etc; or what it is not) and include a statement describing safe operation – such as “never leave a fire unattended”, “Ring may be HOT” and/or language taken from sources such as the National Park Service, Forestry Service, and National Fire Prevention (NFPA) and similar sources or associations. (think about what Smokey Bear would say, for example). Once the regulatory and legal considerations having been addressed you can then turn your attention to design and production.

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Definitions.

Beginning with the basics, let us define a fire ring. A fire ring is a containment device for an open fire – regardless of nature. Many serve a purely aesthetic function as an accent or element of a larger design
as in (propane/NG) installations designed to help define backyard entertainment space. Fire rings also provide some measure of indirect lighting, smoke management, and heat reflection depending on the design. For the purpose of this article we consider the term Fire Ring to include all forms of devices fit for recreational fire service so long as they are noncombustible, have an open top, are at least 6” in height with an aspect ratio of a ring or polygon creating effective containment of fire and fire byproducts, or, provide separation of hot elements from secondary containment designs such as stone, brick, or other materials in the proximate environment. A fire ring is not a burn barrel, tub, bin, drum or other more vertically developed shapes. The shape of the ring is left to discretion but may be described as either “formed” or “segmented”. Formed shapes are bent or rolled to develop their shape. Segmented rings are comprised of any number of flat surfaces in any arrangement; whether permanently affixed or capable of disassembly. In either case, the number of pieces or parts is irrelevant and driven by material costs, shipping constraints, aesthetics, and the end use intended. With these terms in mind let’s review some of the basics: design, material selection, thickness, production methods, problems, and shipping/installation.

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Design.

Product design ranges from concept to re-engineering as successes and failures are noted through the prototyping phase of development. It does not matter what the product is really – the steps are the same. Some just require more thought due to their complexity but no matter what the product it is important to take an iterative approach. Wherever you start there should be another version pending based on what you learn in the processes that follow. You must ultimately settle on a design to build and sell. Even then the feedback from your customers can and should drive what the next run or model looks like. To fail to do so is to potentially build in obsolescence; possibly market failure. Think of what your car or cell phone looked like 10 years ago and you get the point. Very few products are truly “timeless”. May you be fortunate enough to invent the next one. Even timeless designs do not always succeed. Not for the original designer, anyway. In the military you learn that “No plan survives initial enemy contact unchanged” and so it goes in the battle for resources that business owners face. It is impossible to get every design off a napkin or CAD program without some growing pains. Try to remove yourself from “your” design and remain open to input, advice, and market feedback. Your “perfect” design may only be “perfect” for you. The market is everyone but you though – so let the best design win whether it is precisely your invention or not.

Remember that it is a big market out there made of people of all circumstances and backgrounds. What sells to a weekend camper will be different from what a butcher, baker, or candlestick maker will want. For example, a permanent ring vs a packable segmented design. In any design however it is wise to choose a flexible and tolerant design. Flexible designs permit the customer some range of options up front and the ability to add and/or replace parts in the future. For example, a design that permits the user to stack or telescope rings according to fire size and height is one example; as are sliding vents, “doors” for ventilation and ash removal, rain covers, cooking surfaces, spits, and hardware.
Tolerant designs permit a range of material selection based on preference or perhaps availability. Tolerant designs are also “scalable” both in shape and material thickness (within reason). Tolerant designs also factor issues of alignment, edge characteristics, finish, and distortion as a by-product of the cutting, machining, or assembly process. This includes the draft angle created by the cutting arc, weld bevels, fasteners, and clearances required to construct, repair, or finish/paint the design. Whatever the design, the smaller the diameter the higher the probability that the ring will come in contact with fire and hot coals. The exception are propane/NG (Natural Gase) installations wherein the flame should not contact the primary containment vessel. All rings tend to collect radiant heat however and red/yellow hot spots can manifest when a fire is poorly tended. Think about how your design will be affected by heat stress as a result of the cutting operation, welding, customer negligence, or the fire itself. Mild steel moves a lot when heated. Across the perimeter of a 48-inch diameter ring it all adds up and has to go somewhere. Heat will distort and stress weak joints, warp panel sections, and bind any moving parts not designed with enough clearance.

Whatever your product or design, it should be tested thoroughly before developing tooling, making fixtures, and cutting large production runs. There is more to consider – a lot more – to the design and evaluation process. From market studies to destructive testing. At a minimum, your design and process should be reviewed by someone that has had nothing to do with its development. If possible, this step should include someone from the production side of your operation instructed to look for design weaknesses, potential errors, and to check practical clearances for all tools and processes required to make the product. Another person (or firm) should be consulted to independently evaluate the product for its intended use and abuse. Whenever possible this evaluation should be performed in the environment it is intended to be used. Some effort should be expended to predict or observe the effects that time and aging will have. Whether the material holds up as expected; if any moving parts tend to seize or jam once heat, dirt, and ash enter the equation, etc.

If funds allow, also experiment with finish and appearance. Things like color and surface finish often drive market acceptance/resistance. Once your costs are reasonably known then experiment with determining the price that the market will accept. Swap meets, flea markets, and trade shows are good places to get feedback. You can even incentivize this research with “discount” coupons and give away items such as may yield more accurate information than casual surveys of attendees. The objective is to evaluate as much about your product as possible for a reasonable level of expense and effort. Including, the relationship between appearance and your price point.

Sometimes referred to as “fit and finish” the same design in basic black may only command a basic price. Treating the same design with a bronzing or copper aging formula may turn the same design into something perceived as much more valuable. Intricate and well-executed cut-outs invoking scenes people can identify with are another example of cost, effort, and aesthetics that may or may not appeal to a wide enough customer base as to be worth producing as inventory in hope of finding a customer. In general, “less is more” in terms of the size, detail, and frequency with which a given pattern (can) and/or “should” be repeated in a given fire ring. Too much detail and it becomes difficult to distinguish overall. Cutouts may also reduce the strength of the material which may affect the uniformity that the ring bends. A border of undisturbed material should be left along the long axis of the ring or piece being bent: top, bottom, and ends. An inch to inch and a half is usually enough depending on radius bent. Designs may have to be biased towards the upper edge of the ring to avoid being obscured by mud,
ashes, and soil. Cutouts also affect such qualities as smoke migration, coal containment, and the shadows the cutouts cast. The latter being something to pay attention to and “stage” or demonstrate at shows and in sales literature. Our experience has been that a few distinct shapes that are well placed and sharply executed are better received than long strings of scenery or other details. A lone elk should look lonely and will invoke emotions that a jumbled herd does not – no matter how big the antlers are on the herd. The same is true with deer, birds, team logos, and the like. The exception may be in custom lettering, slogans, and personalized names. Lettering needs to be distinguishable in a font that is easily read and punctuated properly as needed. Thin lined letters in expressive fonts are difficult to read and do not cast shadows as well as fonts like Times Roman and similar common styles. If the flourishing script is essential to the customer then consider shadow lighting it with a reflective material like stainless steel fastened or welded about a quarter of an inch behind it (inside the ring). Ideally, the light of the fire will illuminate the lettering both by day and firelight. Alternately, a close-knit screen of punched or expanded metal may be used which has the added benefit of mitigating spark and embers from being blown out of the ring.
The design possibilities are endless however the ultimate question remains whether the difference is worth pursuing or not as a regular matter of production or as an option. Regardless, the comparison between two or more options can be used either to reinforce the value of the basic model or that of the more exclusive options. Patriotic, team and brand logos are all options worth evaluating/offering if only to add depth to your product line. Some customers know what they want before seeing it. The far majority need to have options to select from – to make the effort to offer it and either has samples cut for all to see and a very good quality brochure or page printed that they can take with them.

From there your product needs to be advertised and distributed. In today's media environment you may be able to market your product directly. Opening bid is a well designed, easy to use, interactive website that will run on anything and load quickly no matter what is selected by the viewer. If you have the ability to do this yourself then fine – but it needs to be professional looking and not crash. If you are not technically inclined, there are many, many such services available cheaply to choose from.
Your goal in using the web and social media is to attract and convert hits into sales. Sites like E-bay, Craig’s List, Etsy, and others are all possible venues for your products; as are local opportunities like fairs, seasonal shows, and events that sell booth space. It can be profitable but the work of marketing is every bit as much work and effort as making it. One effort should support and remain contemporaneous to the other. Nobody trusts pages that are outdated or simply never change. It takes time from your day and e- queries demand response at least as quickly as telephone or text messages do. If you do not have that kind of time (I don’t) you can hire a marketing and distribution firm to handle this part of the business for you. It can be effective but it comes at a price. Anywhere from 5 to 40% of the selling price depending on the volume involved. But the best-designed product in the world is effectively useless unless people come to know about it and to want it bad enough lay their money/plastic down to get it.
Trying to compete without giving at least some attention to the modern media trends is not a strategy for success or the future. But the choice is yours. There is also a robust business being done by people that do nothing but buy excess inventory and lots of goods that cannot otherwise be sold. With all sincerity, I would spare you the cost and pain of joining those unfortunately failed endeavors. Evaluate your designs and intentions thoroughly. It is worth every penny of effort and expense.

In the end, your design needs to fit both the market and your production costs; reasonable profits, overhead, taxes, and all expenses considered. Too many fabricators have failed for the sake of failing to understand the larger aspects of business they presume to compete in. Being cheaper than other products and fabricators in the area is not an effective business strategy by itself. Quite often the customer has no appreciation of what the fair prevailing labor rates, for example, even being in a given field. Being some or even a lot cheaper than the local alternatives is, therefore, an ineffective strategy long-term - even when it is effectively advertised. Consider national ads for collision repair. There are always cheaper venues to get your car fixed at. Small shops can be found pretty much anywhere the same way there are lots of guys with a portable stick welder bolted to truck with a magnetic “welding” sign on the side. Their company is defined by what’s in that truck or body shop and not much more. And that is fine- for them. Successful companies that run effective ads tend not to emphasize the cost of the repair so much as the service offered and the integrity of the work done. They encourage durable and dependable relationships over infrequent and discount services.

Stated more plainly, fire rings are somewhat discretionary purchases. Quality and aesthetics matter in such purchases and quite often the uniqueness of the design reinforces the identity of the customer because it is distinguishable from the inventory available online and through large retailers. Price often is not the driving factor in their purchase. In this our industry has a niche market of sorts in so much as relatively small programming changes indeed render very individualized – personalized – results at modest costs to change and produce. People want to know they purchased a good product at a fair price. One that they can feel confident about and trust was made well – especially if their input was ostensibly incorporated. In general, it is better to price your products at a fair price that stands on its own within your operation and cost structure- sometimes called a “revenue model”. If you want to add value to the product in terms of your customer service, personal time spent with the customer, or even upgrades offered at a discounted price – these are better strategies than simply trying to compete on the basis of price alone. Learning to make more efficient use of your scrap, streamline your production process, and minimizing re-work are investments in your future and long-term success. Being cheaper than other fabricators in the area is not.

Intelligent product design must consider all of these factors – including the technology you choose to produce the product with. It is important to be realistic in the designs you aspire to produce. Trying to produce laser-like precision in a design with a plasma table that can cut structural iron as well as a fire ring may not be realistic. Consider carefully the finer details of your pattern. The minimum radius specified as opposed to what your table will actually cut. Look at the profile of your flame cut edge; its draft angle, the degree of straightness and “linearity”. Does your table/program cut diagonals cleanly or as a series of stepped edges? Then compare these to your design. Stepped edge diagonals may be quite acceptable in a design detailing a skyline of trees. Maybe not so much in lettering. Whether it is worth upgrading or even just maintaining your table vs spending the time and money on post cutting clean-up is a matter of personal opinion. Chances are the money will yield long-term benefits if spent on the table;
post-finishing operations are sunk costs. In either case, the only point being made here is to pick a design you know your machines and people can actually produce at a minimum of expense. Then look at ways to improve the results and efficiency of your process to further reduce your costs and waste. As always, try not to get talked into work that you must struggle to produce to the specs required. Such work is tempting but at best results in less profit than anticipated; at worst a disappointed client that may advertise against you without you ever knowing it. In a former life, I was a rancher. Every morning a group of us would meet for breakfast and discuss the business. This was how we “networked” and helped each other when we needed it. When one of us had a “story” to tell about a given repair or vendor – you can bet the others listened. Take from that what you want but the point is that your work is being discussed far more than you imagine: good and bad. Especially when it is about a product or repair that a person could make themselves if they wanted to – but are just too busy with (calves) to make the time for. Fire rings are like that.
So be realistic about your capabilities “in camera” (today); not the way it “was” or what your machines and people “should” be able to do. A realistic baseline is more important than a memory of what you or they “can” or even “usually” do. People come to you for your reputation or availability. They bring with them their expectations; whether in search of a personalized product or in desperation. It is your job to manage all three: reputation, expectations, and profitability. Often only one or two are possible within reason.

In the case where your production results are lagging you have two choices. You can change the people, or change the people. This goes for technology as well. Either approach costs time and money. My experience is that you have to do both: change the people and stay current with technology. You must first be brutally honest with yourself though as to whether your shop, its equipment, and your expectations are realistic and well suited to the task. Too many owners expect the same results from a 20 yr old machine that it could produce new. For example in a welder: If you are not monitoring the basics like the condition of liners, the frequency of tip changes, prep before striking an arc, use of splatter spray, and consumables you are missing valuable data about your people and costs. The frequency that even simple things like a band saw blades need changing speaks volumes to either the condition of the saw and/or the diligence of the people using it. Do your people set the saw and drop the blade so they can check text messages while it cuts (or tears the teeth of the blade)? Or do they set the saw down carefully and monitor the cut for drift, stalling, heat and the size/color of the chips it is cutting?

In any case, choose your work, technology, and people carefully. If your business is industrial stairs and heavy iron - fire rings may not be the best fit for your shop. Also, consider what your backup plan will be if the cutting table goes down, your programmer gets sick, or a key person leaves in the middle of a job… All of which only happens when you least need it to. You need to have a plan and the means to adopt another approach or technology when needed to meet a deadline. Marketing and merchandisers operate on tight schedules for about 6 months in advance of a selling season. Miss a ship date and you may kill a deal. If the production of a side product like fire rings collides with your busy season (like summer in the PNW) your attempt to add revenue and stabilize cash flow in offseasons may be at odds with your goals. Evaluate whether you can/should stress an already busy shop, finance the material and carry production
costs through your slow season. It can be done but at the risk that your perception of what will sell some months or a year later is still relevant and marketable.

In an ideal situation, your equipment works perfectly and cuts perfect designs from the drop of other projects… that you can run as fill-in work between other more profitable projects or on a swing shift. Ideally, your crew can fabricate parts perfectly every time and you have more demand for your rings - just in your local market than you have time for - without even commercially advertising them. If this describes any product in your operation then you are more blessed than you may ever realize and I am happy for you. For the rest of us, there is more to this than people realize and/or may be willing to pay for.

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Material Selection.

As to material selection, our clear preference is hot rolled mild steel. You can make rings in other steels, including stainless but there are tradeoffs to doing so. For example, the ability to form, bend, or weld the material varies with formula and surface treatment. Nonferrous materials like copper and brass make attractive rings but they are not recommended for open wood fires as they do not tolerate extreme heats and weather very well. Copper and brass make excellent accents to a steel primary ring though – especially in properly designed propane/NG installations – but it is not a good choice for primary containment. Galvanized steel and Aluminum should never be used. Rings may also be constructed from repurposed materials with some success.
Within the category of hot rolled mild steel, you have to two basic options: plate or flat stock.

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Plate steel.

The plate is typically cheaper per sq/ft or pound than formed shapes and offers greater flexibility in design at the expense of space and weight. The potential savings, however, requires trucking and the ability to offload the truck in a reasonable amount of time. If you have a forklift or some means of slinging and lifting the load from curbside: great. If not, then you are looking at about 10.2 # per sq/ft per ¼ inch of whatever you ordered. In a 4 x 8 section of a ¼ inch you need to clear, lower and move over 300# without scratching or bending it. It can be done with a few strong people, an excavator, or a lifting frame. Think of the classic “H” or square entrance to a farm or ranch and you get the idea. In days past “f.o.b.” meant the entrance to the property and lifting frames like those were used to shift goods from wagon to wagon; truck to truck… Now we have hydraulics and loading docks – which means you (may) be able to move a good size plate with little more than a hydraulic floor jack, wood or pipe rollers, dolly wheels, etc… But then what? Outside storage will affect the surface patina. Inside storage is fine in a rack built for it. But it all comes at the expense of time, labor and greater risk of injury. People have been killed by plates stored vertically falling on them. Horizontal storage is safer but your rack needs to be able to handle huge loads with a safety margin built in. Freestanding racks are fine but racks on wheels their own risk. No matter your system, by the time you off-load, move, store, cut, and clean up plate stock you will have money invested in the process whether your design, part, or product works - or not. Don’t misunderstand– we buy a plate every week. But we have two forklifts and a cutting table big enough to lay out a 4 x 8 sheet out with clearance to spare. If you are working off a 2 x 2 or 4 x 4 cutting table you may find that there are alternatives to the plate that are ultimately cheaper to process overall.

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Flat stock.

If your design can be made from sections or runs that are 12” in width or less then flat stock may be worth considering. Flat stock comes in all thicknesses by the 1/16th or 1/8th and widths on the ¼ or a half inch. The finish in (HR) is mill scale blue or gray though we had a load of orange come through recently (?). Rolling marks, some crazing, and striations may be visible in the surface but generally are insignificant. RMS of the surface varies with the run from smooth to a hard sandblasted sort of look. Flat stock is fairly uniform across its width but may arrive with a hook or bend across its length. Bends and damage in transport are not uncommon. If precision is required ask for the order to be banded, stretch wrapped and/or wrapped onto a length of wood (batten) or pallet. The ends are typically sheared and distorted but the edges are typically a uniform rounded or blunt shape. Widths can vary lot to lot and supplier to supplier – but not typically enough to matter in a fire ring.
The advantages of flat steel are many. First, the typical length shipped is 20’ so only one seam is needed in an average fire ring. It moves easily on a section of rollers and cuts easily in a band, disc, or metal saw. Density across the section varies a little as sections get thicker but not enough to matter in a fire ring. It is also easy to bevel and cut diagonals and compound miters through. All of which can be done with a hand-held plasma cutter or on the plasma table too. Cutting (anything) on the plasma table comes with the risk of heat stress, slag or dross, variations in the edge profile as the flame wavers, and changes in the patina in the heat affected zone and where water and slag rebound on the underside of the material. In almost every case, flat stock is cheaper and easier to process than sheet materials regardless of the price difference compared to the plate. The exception is wherever a uniform patina is required. Finishing flat stock to match the unblemished appearance of mill scale plate is an art in itself and may be addressed in a separate article. It is work to uniformly remove the mill scale from any material and variations in stock surfaces can compound this effort. If your design requires homogeneity then test this before you order large quantities.

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Repurposed Materials.

Fire rings may also be constructed from repurposed materials. For example, large truck tire rims, sections of old cylindrical or oval steel tanks, cable, chain, car parts and virtually anything else you have the imagination to fabricate into a ring or geometric shape fit for the purpose. The costs of repurposed materials range from free to scrap value plus transportation. The risk of using repurposed materials centers on at least two aspects. 1) the hazard of whatever the item used to contain as a pollutant or hazmat, and 2) the risk of fire or explosion on cutting the material up for repurposing. Tanks are obvious hazards but every year people are injured by welding and cutting on shapes that explode
or catch fire in the process. The only way to mitigate this risk is to clean and empty the item until the risk of contamination, pollution, and personal injury are eliminated. Taking shortcuts in this process is not a strategy for success. Repurposing material can be very rewarding and produce some very attractive products. In general, these are one-off pieces however and therefore defacto intended for regional sales or sale through the web (Etsy, E-bay, etc). Profit margins are more difficult to estimate in such products and typically require more labor to produce than similar purpose products made from the virgin or remnant material. Shipping costs may likewise be inflated by the reinforcement that (some) artistic interpretations require due to their fragility, finish, or other characteristics.

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Thickness.

Thickness is directly related to cost and the longevity of the product. There are ring-like products marketed by some very well known brands that are essentially made from sheet metal. I encourage you to study these products carefully though I suggest that you will not likely be able to compete with them and probably should not try to do so. Rings made from sheet metal should be avoided unless the attraction of portability and compact design are your marketing vector. Even in such a case 18 ga is about as light as we would suggest considering. Our experience is that lightweight rings do not last very long in any environment and are unsuitable for permanent installations. Lightweight rings may also have sharp edges and are easily bent or damaged in use/transport. There is a market niche for such products but suspect you will find more interest in a more robust “quality” ring that permits individual customization in terms of weight, height, and design/cutouts, etc..
1/8th in the material is the thinnest we prefer to use and have made rings as thick as ½ inch plate. Shapes made from 3/8” hot rolled mild steel are not uncommon in permanent installations. Three-sixteenths (3/16) to quarter inch (1/4) material strikes the optimum combination of weight, strength, ductility, longevity, and production-ability in my opinion. Quarter inch material averages 10.2# to the sq/ft and are the most tolerant and compatible with (our) production practices. Obviously, the thicker and wider the material the more difficult it will be to form, handle, weld, and ship/deliver.
In designing your product remember that thickness does not describe everything about strength, utility, and/or the processes required to fabricate the design. For example, ¼” mild steel can be rolled efficiently. The same diameter in stainless will require more effort and be harder on your equipment.

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Production ability.

By far the single most important factor in launching a successful fire ring product line centers on the efficiency and reliability of the manufacturing process. Small details often make the difference between profit and loss with labor (time on task) being the most expensive variable of all. Care should be taken to evaluate each design and the special requests of the client before any metal is cut. Wherever there are doubt patterns should be made from scrap or plywood. Take care to make your patterns from a
dimensionally stable material of similar thickness to your design. Paper and cardboard patterns are useful approximations of a design and fine for prototyping and fit-up where some weld clearance is required anyway. The standard in pattern material though is medium density fiberboard (MDF) and only surpassed by high-density fiberboard (HDF) – both of which are essentially uniform stacks of paper glued and pressed together. MDF cuts and routers well and is generally fairly flat across the sheet. It is only mildly moisture resistant though so patterns should be painted and sealed if they are expected to survive years in an ambient air environment. The material is not cheap but cheaper than plywood suitable for patterns (many plies; no voids; sanded, etc.). There are no voids in MDF and if you keep blades sharp little more than a fine paper but will have to be removed with a brush of a glove or sanding block.
For shapes that must be deformed (like a fire ring) then a good pattern material is a plastic shower liner, Formica, and sheet metal. Shower liner (FRP or GRP sheets sold at lumber centers) comes to both smooth and pebbled finish and in at least two thicknesses. If your shape is large, consider the glass reinforced variety but understand that you will have to deal with the fiberglass dust as you cut and work with it (no pun). Sheet metal must be thin enough to deform uniformly but not so thin as to crease easily or be difficult to trace. 18 ga is a good compromise overall.
Thermoform plastics may be bent with heat; thermoset panels less so. An electric heat gun of 12-1800 Watts is perfect. A propane torch can be used if a diffuser tip is installed – but the hot air heat guns are far less likely to damage the material than an open flame is. If your design/pattern requires tapping, bending or breaking then consider the thermoform species of plastics like acrylic (plexiglass) or polyethylene (HDPE and MDPE) for your pattern. It is not cheap or even cheaper than MDF but more versatile and stable than HDF, MDF, or plywood but the ability to see through an acrylic pattern can be priceless. If the economy is essential then look for a plastic supplier that also does custom cutting and some fabrication. Such places always have drop or rem sections that can be purchased cheaper than virgin material. Both HDPE and Acrylic may be bent, drilled, tapped, and cut or shaped with a router but blade speed and direction of travel is important. Especially with products like Lucite, Lexan, Plexiglass, styrene, and similar. Use a dull blade or bit, the wrong speed, direction or technique and you will be left with a melted or chipped edge to repair or discard. Painting acrylic can be a challenge (persistent fish eyes), but it can be easily glued with the proper solvent (MEK, etc). Where strength is required to avoid simple flush fitting joints –especially when making tee sections and 90-degree corners. You will get a stronger joint if you 1) abrade the joint surface to 100 grit or so, and 2) rabbet a shallow slot or groove into the plate being joined. Likewise, consider a stepped joint at corners whenever possible. 45-degree bevels are more difficult to get right. Stepped joints are more tolerant of subtle variation in your prep and/or the material. Either approach may be easily cut with a table saw or with a router. HDPE welds quite well as do many other thermoform plastics like PVC and ABS. This attribute makes rapid prototyping strong, simple and cost-effective. Plastic welding is a skill however and about on par with the skill TIG welding requires. Good equipment is worth its cost. Avoid the tempting discount hot air guns. Trust me on that one…
For one-off or limited use patterns Silicone caulking, construction adhesives, or a hot glue gun can be useful in making fixtures and the prototyping process. Tube-based caulking should be of the fast setting type. For ultimate strength consider the moisture cured urethane adhesives on the market. 3M’s 5200 Fast Cure is particularly effective. Though more expensive than even the best 100% silicone caulking out there, 3M 5200 is both an adhesive as well as a gap-filling caulking. Cure times can be accelerated by spraying a fine mist of water on the joint – making overnight shop-to-service jigs possible. Whatever material used, be sure to consider the space that weld fillets need and either add to exterior dimensions or remove from internal clearances accordingly.
Designs that require substantial post-production (welding) clean up and grinding cost more to produce than those that do not. While some ingenious designs may be assembled via interlocking tabs, with fasteners, etc. Choice of the welding process is another consideration. Errors in fit up and heat distortion can cost more to correct than the steel is worth. Customers can also be very critical of heat affected zones, gobby looking welds, and distortion - but these are nevertheless the very details that customers look for and expect in a quality product. Wire feed welders have become the standard but by no means the silver bullet of processes. Where a classic look or certain aesthetic is required I suggest you consider alternatives like rivets and custom fasteners on the finish side of the ring – maybe backed up by discrete welds on the less visible surfaces and concealed edges.
Production ability can be improved by the intelligent use of fixtures. A fixture is a device that aides the assembly and fabrication process. Whether as simple as a saw stop set for repeated cuts or an elaborate design that holds any number of parts for welding. What matters is that the fixture is accurate and robust. They need to be strong and designed to last however many cycles you expect or hope to run. Season after season – without use and abuse being able to introduce enough error or distortion as to affect the reliability of the process it supports. This includes cutting table fixtures which are useful for material that is prone to distortion. All steel has a grain and internal stresses. Heat – as from the plasma arc – tends to exaggerate these stresses which can twist and curl thin sections as you progressively use the sheet – especially in thinner material and in thin cross sections between cut shapes. Fixtures and clamps can minimize the chance that a section will distort enough to catch on your cutting head or beam – which in turn may drag or turn the part mid-program. Not good; and expensive. It is better to cut off the remnants of previous shapes and concentrate your mass than to have the remains of a previous job ruin your resent part. Using strategically placed magnets to help hold the sheet down can be helpful as of course can clamps or scraps of a heavy plate positioned in areas the cutting head will not approach. If your table uses water/bladder system then, of course, these aides can be bagged, painted, or otherwise protected to assure their longevity and cleanliness.
No matter how your material is cut, bent or formed your jig or fixture must support the weight of the material as well as whatever force is required to shape or bring edges into alignment. Add the weight of the person working on the part leaning or standing on the assembly – if just to steady a weld procedure – hammer blows, transport, storage, and forklift abuse and forces compound quickly. Fixtures may be free-standing or mounted to a table… preferably an all steel welding table of sufficient weight and thickness to remain flat and allow you to exert force and leverage on the part however needed.
Rolling machines sometimes put a slight twist in the steel band being bent. This can be removed in the fit up the process but makes the process of hitting a precise diameter cleanly a much more challenging process. Rings are essentially giant springs anyway so some thought should be put into how you intend to join the ends of the material safely and according to the aesthetic characteristics of the design.
Lap joints are the strongest and lend themselves to several methods of fastening. Lap joints also make use of the “flats” or tails left on either end of the bending process typical to roller bending machines. Rather than simply cutting the flats off in order to approximate a perfect circle, consider using them to your aesthetic advantage.
If a perfect circle is required – for example where the ring is being used as a border on a sand or gravel propane/NG permanent installation – then the tails must be cut and married as seamlessly as possible. This joint in particular is an example of where a jig or fixture really proves its worth. Another simple fixture is a circle routed into a sheet of plywood or MDF the diameter of the ring intended. A nylon ratchet strap works well to pull the ring together so long as the ratchet is not near the seam. At a minimum, you should use a simple section of a ring of the same diameter as a clamping fixture to assure that the joint is made on the same radius or curve as the balance of the ring. This will require a section from a quarter to a third of the diameter intended. Once clamped the ring can be tacked or stitched enough to hold its shape before the fixture is swapped to the other side of the ring and reattached so that the other side of the ring can be similarly tacked and then welded. Failing to control the accuracy of the curve will result in a ring that looks quite amateurish and unsightly. Fit and finish the matter. If you can cut or shear a clean edge you may be able to weld only one side of the ring and let the edges neatly butt on the finish side. This seam can be left plain, painted, or accented with a contrasting material – like a strip of brass, copper or stainless. One effect we like is a rim or trim ring around the upper edge of the ring. This can be anything from a rolled edge or slit pipe bent to match the circle or shape – to a simple piece of ¼ by flat bar welded around the upper edge.
Carrying this idea further, additional strips or shapes can be added around the perimeter to mimic the cardinal and intercardinal points of the compass (N, NE, E, SE… etc). The fleur delis and diamond are common patterns used on a compass. Using this approach to camouflage seams and other details is both smart and good business. Frequently the drop or cut-outs from whatever design was cut into the ring – or from other projects - make perfect camouflage as accents. Especially if you keep your “lead in” angles shallow and distance short; or repair these tracks … Using external accents lends depth to the design. Many people associate the complexity and depth of a design with quality – so using your cutout circles, diamonds, trees, elk, logos… anything really – is like turning lemons into lemonade. So keep an eye on how your production challenges can be turned into an opportunity to embellish or otherwise upsell the product to everyone’s benefit. This approach is especially valuable when the original patina and finish of the factory must be maintained. Keeping a perfect mill scale finish is harder to do than it sounds like everything from splatter to normal oxidation makes keeping the mill finish intact a decreasing probability over time.
Another approach to joining the bent section is to cut a long diagonal or stepped diagonal “scarf” joint in the ring. This is a more challenging joint than a simple butt joint but can be worth the effort for the sake of its appearance and manner in which it preserves the shape of the ring better than a butt seam does. For rings of thinner material, you may need a backing plate to bridge the seam and add some support several inches either side of the weld. If your design permits an exposed welded seam, and/or the finish that post welding grinding and sanding leave you with; great. For thicker material, you should leave a space between the plate ends and/or bevel the plates being welded to assure penetration. A copper strip is a good backing material to push against while welding any gap or hole – if you have it. I have experimented with using aluminum sprayed with non-stick welding spray instead and it works pretty well too. The objective of either is to temporarily support the weld pool until it freezes in order to minimize the amount of material and carbon deposited on the opposite side of the seam.
Accept that any welding process will affect the patina of the metal though – backed or not. Stainless is especially prone to distortion and discoloration when overheated though it can usually be restored with some effort. Special consideration, care, and equipment should be considered when welding stainless. For wire feed machines, using a bit higher shielding gas pressure/volume and limiting the effect of ambient drafts in the welding space goes a long way. The cleanliness of the material is critical as well – especially if TIG is your process of choice. Be sure to clean your material and your rod carefully. Acetone works well for us. Brush or grind your starts and stops to keep inclusions to a minimum. If TIG is your only recourse then I encourage you to learn about the various aftermarket gas lens and cups being sold by Furick and other vendors. Especially in stainless production, these additions can really up to your game and the appearance of your product in the process.
Once you know what the effects of heat, stress, and welding are, then fit up and welding will be your next biggest challenge. Mill scale must be removed to get an effective bond but comes at the expense of the final finish. I encourage you to post-finish parts rather than try to sell them in the “raw” mill finish post production. The exception is in “kit” form where the customer will paint the product themselves. If you are selling to an installer or contractor then a decent primer may be all that is required to preserve the ring without the expense of finish painting that the contractor needs to drill through, tack in place or otherwise alter in the installation process. Clearly “something” should be applied to the surface however as steel being steel will age as it is left out on the job site, scratched, abused or just stored over time. Powder coating, in this case, is not worth the effort or expense. A better alternative is cold bluing which is essentially a solvent-dye formulated to bond with the base material (think layout dye). It comes in brown, blue and black; the browning solution is especially easy and attractive. More complex colors and dyes exist that mimic copper, bronze, and other patinas. All can be applied by spray, dipping, a roller or a brush/rag. Spraying yields the best results as dyes will leave streaks if brushed or wiped on with a rag. If you can find a roller that will stand up to the solvent then a good foam or short nap roller may work. If you do spray keep in mind that the volatized solvent dye is not something you want to be breathing. Your parts will look “finished” at a minimum of effort though. Dye tends to stain anything it comes in contact with – including people. So a dedicated area and some containment/PPE is appropriate. Disposable plastic or cardboard is a good idea. OSB and plywood are good flooring choices but the sheet or corrugated metal is, of course, safer for the walls. The material is highly flammable (of course) so some fire preparedness is wise. Paint is cheaper than dye on the surface but requires more time to dry than a dye. Powder coating is probably a wasted effort in the case of a fire ring. Any paint will burn off eventually though the high heat versions used on engines and BBQ’s hold up a bit longer. This is an area to consider carefully as the cost of fit and finish is substantial and affects marketability – yet in the end, it is a perishable quality as the ring gets used.
One alternative is to use a different type of steel (different chemical composition) that ages somewhat uniformly – like Corten (sometimes Korten) or even stainless if your market will support it. In the case of stainless: grade has everything to do with durability. Many “stainless” products sold on BBQ’s and similar consumer goods rust over time. Opening bid is type 308 and there is a version formulated for high heat and sulfur exposure (in the 400’s) but it comes at a price that likely will be appreciated by few. All these materials have differing levels of productionability and welding requirements and respond to bending, punching, bending, etc. differently than 1018 mild steel.
Another approach worth considering is pre-aging the material yourself. This typically requires stripping the mill finish and using a range of oxidizers to essentially oxidize or rust the material. You can do the stripping mechanically or by electrolysis. The advantage of electrolysis is the ability to get places that grinders and wire wheels cannot. Plus you can do batches of rings at a time. But this is a topic in and of itself as everything from choice of solution to electrode placement affects efficiency. The striped appearance is a lot like sand or bead blasted steel – which is another alternative. There are lots of blasting places that can be contracted with if it just is not in your means. No matter how you strip the steel, post finished results of an oxidized surface is predictable and very typically rust colored. The steel can be colored instead though: from bronze to copper, etc - but not inexpensively. In the end, the product looks about as it might some years on exposed to the elements but heat and soot will nevertheless foil your best efforts eventually. The exception being primary containment rings/shapes installed in propane/NG installations that never really get hot.
Final packaging needs to be considered as well. This can cost more than the steel. Stacking finished rings someplace in the shop for later distribution will only result in dusty rings later. Shrink or stretch wrap is a cost effective approach. Boxing may be required if you use a distributor. Study the methods used by importers from ROC. They have brought this expense and effort to a new level of efficiency and “value engineering”. Local markets may permit a minimum of packaging but every ounce of protection you provide up front will pay off in loss reduction later. Remember that your packaging is also a reflection of your company and influences the perception of quality in the consumer. Since the advent of digital printing, this expense has been reduced but is still not insignificant. Warnings and product limitations of (liability) should always be shipped with each ring and permanently affixed or otherwise engraved/stamped into the product. Consult an attorney hen composing this message and keep the fonts legible and large enough to be distinguishable (12 -14 minimum). They may be placed on the inside of the ring for aesthetic purposes. A bright colored dot or shaped label may/should be placed adjacent to the notice to call attention to the message. This may double as a “QC” or inspection record. An ounce of prevention is worth many billable hours later…

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Summary.

Fire rings are a good project to experiment with your ability to launch a product line – at least regionally. Like any product or venture, the challenge is in managing the finer details and processes required from inception to delivery. Fire rings may provide a worthwhile revenue stream and potential installation revenue. A methodical and realistic approach is required to efficiently produce a marketable product. Seasonal cycles and demand must be considered against your core business trends. The availability of slack production time, drop or rem from other stable product lines, and space to produce and store finished product some months in advance of the selling season – all contribute to profitability and efficiency.

Vincent Cantwell,
Vincent Cantwell is a fabricator working at Mac Welding in McMinnville. Responsibilities include welder, machinist, fabricator, layout, and product development.

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