Vacaero

Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services.

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Backstreaming

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In simplest terms, backstreaming is the movement of pumping fluid back into the vacuum furnace chamber, that is, oil vapor molecules attempt to reverse course and move up and back toward the vacuum vessel, opposite to the direction of the desired gas flow. Backstreaming is not limited to the pumps themselves, but encompass the entire pumping system (e.g. plumbing, valves, baffles, and traps). The oil type and characteristics play a role as well. In all cases, the result of backstreaming, namely the contamination of the work chamber or workload, is totally unacceptable and often catastrophic.

Backstreaming is often due to; incorrect start-up or shutdown procedures – the far most common operator mistake as far as the writer is concerned, exceeding maximum pump throughput capacity for long periods of time and exceeding the critical discharge pressure in the foreline. Users of vacuum furnaces should be sure that the vacuum system is equipped with all the appropriate interlocks to prohibit vacuum valve cycling above specified pressures that can cause these effects to occur, which will help protect your system, especially whenever it is left unattended.

Saving Money by Maximizing Furnace Uptime Productivity

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“It was only a tiny drop of water, now and then,” lamented the homeowner. “How was I to know that all those little drops would add up to a huge water bill?” The same can be said of a heat treat furnace that is always down for this reason or that. Avoiding the hidden costs associated with equipment downtime is the key to saving money. Maximizing furnace productivity requires a proactive approach, which must continue throughout a unit’s operational lifetime. This requires careful planning and anticipation of problems. The process should begin even before the purchase of a piece of equipment by matching equipment and supplier capabilities with production and process needs. Buying good, well-built, high-quality equipment and operating and maintaining it properly will avoid most hidden costs.

For example, suppose a work center is scheduled to run for a 435-minute shift. However, the work center experiences 30 minutes of unscheduled downtime. The available time equals 435 minutes (scheduled time) minus 30 minutes (downtime), or 405 minutes. The availability is 405 minutes divided by 435 minutes or 93%. Not bad, or so you think. Now, let’s look at performance. Performance represents the speed at which the work center runs as a percentage of its designed speed. In other words, parts produced times ideal cycle time divided by available time. Continuing our example, if the available time is 405 minutes and the standard rate for the part being produced is 40 units per hour (or 1.5 minutes per unit), then the work center produces 242 total units during the shift. If the time to produce the parts (242 units times 1.5 minutes per unit) is 363 minutes, then the performance is 363 minutes divided by 405 minutes or 90%. Again, not bad, or so you think.

Hot Zone Design for Vacuum Furnaces

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The hot zone is perhaps the most critical feature of a vacuum furnace in terms of its effect on furnace performance and operating cost. There are a variety of hot zone designs and the choice of a design should be based on a careful analysis of specific processing applications. Most vacuum-furnace hot zones consist of four major components: the heating elements and the details on which they are mounted; the insulation package (or heat shields); a surrounding structure that supports the heating elements and insulation package; and a hearth that supports the load during processing.

Most vacuum-furnace hot zones consist of four major components: the heating elements and the details on which they are mounted; the insulation package (or heat shields); a surrounding structure that supports the heating elements and insulation package; and a hearth that supports the load during processing. A hot zone can be constructed in either rectangular or cylindrical form, with the latter being far more prominent in vacuum furnaces today. All hot zones are constructed in modular form for ease of installation into and removal from the vacuum chamber. BY JEFF PRITCHARD

Important Considerations for Establishing a New Vacuum Heat Treating Capability

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Many companies that outsource vacuum heat treating must eventually decide if they would be better served by setting up this capability in-house. Establishing a new heat treating capability requires a significant capital investment in furnace equipment.· However, there are other costs and issues that should be considered when assessing the business case for such a project.· VAC AERO has prepared a few brief guidelines to assist customers who are not well-experienced in heat treating but are assessing the need to establish a heat treating capability. (Download PDF of this article)

Furnace Selection – There are a number of factors that should be considered in selecting the best furnace equipment for a new heat treating operation.

 Size – Vacuum furnaces are available in a wide variety of sizes.  The initial capital outlay and operating costs are in proportion to size.  The furnace chamber must be physically large enough to handle the largest workpiece or load being heat treated, plus an allowance for tooling or fixtures.  To achieve proper heating and cooling in a vacuum furnace, individual workpieces within a load must be evenly distributed.  As a result, the furnace work zone may need to be slightly larger than what might be expected by someone unfamiliar with vacuum heat treating.  The furnace manufacturer can review the customer’s heat treating requirements and advise on the most appropriate size and orientation (horizontal, front-loading or vertical, bottom-loading).  When selecting a furnace size, some thought should also be given to future processing requirements.  It is usually impractical (and sometimes impossible) to enlarge a vacuum furnace if larger heat treating applications develop. 

 Budget: The basic equipment price for most popular smaller and medium sizes of vacuum furnaces will range from $300,000 to $500,000.  Additional costs will likely be incurred for site preparation and installation, auxiliary systems, tooling, staffing, and others.  These additional costs can be in the range of $50,000 to $100,000. 

 Throughput: The amount of work that can be processed in a single furnace load is proportional to the size of the furnace.  Typical vacuum heat treating or brazing cycles range in duration from a minimum of about five hours to much longer cycles, many in excess of twelve hours.  With allowances for loading and unloading time, only two to three complete heat treating cycles are typically completed in a 24 hour period.

 

Using Vacuum Furnaces to Achieve Lean, Green and Agile Manufacturing

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The long-standing practice by furnace manufacturers of offering only “stand-alone” pieces of equipment is changing. Today, some manufacturers, especially those who manufacture vacuum furnaces are capable of building completely integrated systems, which can be placed directly into the manufacturing flow. Of the choices technology available, only vacuum furnaces offer a true lean, green and agile solution. Let’s explore why.

To begin, we need an understanding of what being lean, green and agile is all about. Lean manufacturing (lean enterprise, lean production) is a production practice that considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination. Working from the perspective of the customer who consumes a product or service, “value” is defined as any action or process that a customer would be willing to pay for.

Energy Optimization in the Heat-Treat Department

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Savings can be achieved by improving energy efficiency, which reduces the amount of electricity consumed. Savings can also be easily achieved by making slight changes to the timing of this consumption, thereby reducing the peak electricity demand.

Large heat-treating facilities are substantial electricity consumers. Specializing in vacuum heat treating and brazing for aerospace and other high-technology industries, VAC AERO International’s Oakville, Ontario, plant operates more than 24 vacuum, air and controlled-atmosphere furnaces. Included are three very large vacuum oil-quench furnaces, all of which result in substantial electricity consumption. Indeed, the company’s electricity costs have increased by more than 30% in recent years, thereby driving an effort to find lower-cost solutions. by Mark Passalent

Welding of High Strength Steel Landing Gear Components

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For many years, VAC AERO has been performing welding and heat treating operations on a landing gear component for a popular turboprop aircraft. Because of the part design, the welding operation, in particular, is complex and challenging and often involves substantial re-work.

In order to minimize the rate of re-work, VAC AERO undertook a comprehensive process review. The review determined that a minor design change could virtually eliminate re-work at welding. The assembly is a five-piece, tubular structure manufactured entirely from 4330V steel. It consists of a hollow tube approximately 1500mm long by 120mm in diameter, two fittings (upper and lower) that are TIG welded to each end of the tube and two backing rings that bridge the gaps between the fittings and the tube during the welding operation. BY JEFF PRITCHARD