*Originally published January 21, 2003 by
Art Boyson, VP / Operations
Effortless cost reduction
If you are a box builder,or a board level assembly house the following concepts always apply to your operations
The concept of cost to build a product deals with two principal elements;
- Cost of Materials
- Cost of Labor and ancillary costs
In most assembly operations the cost of the materials amounts to 15% of the total, the balance 85% which we call The Big 85® includes a variety of labor costs some of which are subtle and all of which will be addressed here.
If you visit our website www.arnoldindustries.com, you will see many of the services we offer. One of these is a design review of the mechanical aspects of your product from the standpoint of simplified procurement and ease of assembly.
What would we look for?
Part rationalization – use the most common products! They are made and sold to a broad base of industry, they are made in high volume, quality issues do not exist, they are always available, and they cost less.
Sager Electronics offers their SynerSpec design tool which allows the designer to conduct a search by supplier part number or generic terms such as “thermal solutions”. You can actually build a BOM on-line, get samples, and check availability and cost from your desktop.
“Standardized theme of design” – use similar materials and finishes giving thought to the aesthetics but also attention to the build process in manufacturing including outsourced parts and sub assemblies.
We frequently see products where several types of materials, finishes, and fastening techniques are used, each of which requires special handling, installation tooling, and sourcing of new and unproven products. A common observation is to have a mixture of stainless steel and carbon steel plated, or painted parts used side by side.
The electronics industry in particular continues to use captive nuts pressed into sheet metal enclosures and chassis when they could use punch extruded holes and Taptite 2000® high performance thread rolling screws. (Described on www.reminc.net) Another obvious area is the use of inserts molded into plastic that add significant cost to the product because of the “insert molding technique” or the “ultrasonic secondary installation”. In most cases Plastite® screws can eliminate this insert or “second part”.
What we emphasize is what has been called “In place cost“. For instance, the captive nut pressed into the sheet metal chassis only costs $0.08 each, yet to install it costs $0.25. The total of $0.33 is now marked up by the fabricator to $0.50.If you were using Taptite 2000® screws, you would have only the cost of the screw and its installation – a cost which exists no matter what technique you use. A similar cost would be incurred with inserts in plastic.
Along with using common parts, standardization and reduction of parts used is an area it seems is always overlooked. Beginning with screws, use one type of drive system (slot, Torx , Hexagon, etc), use one type of material (steel plated, non magnetic stainless), minimize lengths, and where possible use one diameter. Take the time to review the sizes, styles and materials in Arnold’s on-line catalog at www.arnoldindustries.com – if they are not in that catalog they are “special”.
Washers are my favorite candidates for elimination, as they are frequently misapplied. Washers serve three purposes; the first is to provide a bearing surface under the head of a screw, or under a nut being tightened; the second is to use a tooth type lock washer to break a surface to insure electrical contact; the third is to use a Bellville spring washer to compensate for load fluctuations caused by thermal expansion and contraction. It should be noted that “lock washers” do not lock anything (you will not find any on aircraft). If you need to have a secure assembly, use a positive locking element of such as a Nylon patch or coating provided by Nylok Fastener Corporation on the screw or nut. These can be tailored to suit the application by varying the type of coating. Another approach is the “Sems” screw, almost seventy years ago the pre assembled screw and washer assembly was introduced. By using this “Sems screw” you reduce by 50% the number of components used compared to a loose screw and washer.
Riveting is probably one of the oldest fastening products after nails. In recent years the solid rivet has seen limited use in favor of the semi-tubular products. In any of this type of riveting the designer should consider the fact that the rivet will be peened or flared over and any plating will be stressed to the point of cracking. The holes need to be precise and the skills of the operators are important. The part has to be held and manipulated under the fixed riveting machine. It can be seen that the rivet with the low unit cost now has an increased cost when installed.
Recent developments by www.textronfasteningsystems.com Textron Fastening Systems have given us a high speed riveting system suitable to being installed by a portable tool or an articulated arm tooling system. The “Speed Fastening” version of this has a helix on the rivet body allowing removal and is installed from one side of the work. They also have developed and perfected self-piercing rivets which require no installation hole. The assembly will now be easy to automate as hole alignment is not required. Thus the rivet with a slightly higher unit cost now has a lower cost when installed.
As a 3-M distributor, Arnold Industries has access to the many truly unique 3-M products such as Dual-Lock® hook and loop fastener, a reusable system suitable for many electronic industry uses. 3-M has also developed VHB™ tapes which have incredible holding power actually equal to spot welding and are able to dramatically reduce “In place cost“.
The message is clear, true cost reduction is obtained by looking at the global view of cost, not just whittling pennies off each component. The best is for last; if you have a good supplier/ partner they will do it for you!
Art Boyson – VP/Operations Arnold Industries Inc.
Contributors to this article:
Bob Worth Textron Fastening Systems
Nick Panasian and John Moynihan Nylok Fastener Corporation
Ken Gomes VP Research Engineering & Manufacturing