Introduction: This series of articles is directed toward the entrepreneur or business and is focused on products as opposed to services. The goal of this series is to provide you with the background needed to bring your idea from wild thought to a product ready for market.
The writer has over 30 years engineering experience in industry and product development, is a member of the Board of Directors of Inventors North West, the Product Development Management Association and is a principal in a Bend firm that provides machine design, product design and development services (www.smithherrick.com).
Manufacturing and Production
First, let’s try out some definitions. In our discussion we will use the terms “manufacturing” and “production” to mean two different things. Manufacturing is the specific means by which a part is to be made. For example, injection molding for a plastic part is a manufacturing method. Wave soldering for a printed circuit board is a manufacturing method. Machining is a manufacturing method. Production, on the other hand, is the means by which the components or product will be made in the quantities planned. So, production of a populated printed circuit board in some quantity would be the process of stuffing the PCB using a pick and place machine and then using a pin check fixture to verify the goodness of the connections before placing it in the “good” pile.
Or if you are producing a rotary position sensor, the production process may be the manual placement of the spring, rotor and PCB in the housing, and then placing it in an ultrasonic welder to close the case, then to a test and programming station.
We have shown in previous articles how the methods you are going to use for manufacturing the individual parts and for producing your complete product need to be considered in the design process. To go into a discussion of all of the possible means of doing so is way beyond the scope of this article. However, we can talk in generalities and still cover some important points.
Your manufacturing and production methods will be chosen based on two major parameters: Suitability and cost. By “suitability” I mean does it provide the quality and is it capable of meeting your volume requirements in a timely manner. Cost is obvious. You want the best method that gives you the quality you need at the optimum cost. This certainly needs to consider the ability of maintaining the production rate necessary.
We see that suitability and cost are intertwined in most cases. Let’s look at making plastic parts. Say you plan on selling 100 of your product (assembled from several injection molded parts) in Year 1. From a quality standpoint you could use a rapid molding process (such as that used by Protomold) or you could go for the gold and have high volume production tooling made.
You would get nearly the same quality part from both processes. The Protomold tooling would cost a fraction of the high volume tooling, but it has two drawbacks: the parts will be several times the cost and the tooling will only last for a fraction of the number of shots as the high volume production tooling.
Let’s take another example that deals with the assembly process. Typically any product requires a process of assembling individual parts into the finished product. This entire assembly process can take place at one of several levels.
The process can be completely manual. Everything is done by hand. The next step up would be the inclusion of some semi-automated segments, such things as using a powered screw driver or an articulated fixture to install springs. The last step in this escalation would be a fully automated production process. Perhaps an automated parts feeder positions parts to an automated fixture that positions a second part, applies an adhesive and sets the two halves.
I have seen many production setups which are an amalgamation of these various approaches. (Note also that “poke yoke,” or mistake proofing, can and should be an integral part of any of the processes we have discussed). And here, once again, we see that our criteria for choosing the best avenue are suitability and cost. When considering the suitability of the level of assembly automation we are looking at whether or not the method used gives us the product correctly and effectively assembled and if it does so a the optimum cost.
I was involved with a project a few years back where we were designing the production process for a Hall effect rotary position sensor. In the part design phase we had assumed a semi-automated assembly process. This decision was based upon the annual forecasted sales quantity (20,000 pieces) and the realization that the cost of automating all of the assembly stages would be in the $500,000 plus arena (for a product that had a $2.50 margin, that investment in equipment did not make sense).
So our choice was to automate those assembly segments that were potentially the greatest source of product variation. We automated the adhesive, lubrication, enclosing and test process. We used manual assembly methods for the insertion of the individual parts. The automated test sequence also tested for the correctness of the assembly. This semi-automated approach was suitable for the desired product quality and gave us the overall cost picture we wanted.
Next month we’ll talk about supplier selection.
John Herrick, Jr. can be reached 503-799-3580, firstname.lastname@example.org. He is a principal in a local design and product development firm (www.smithherrick.com). The company’s focus is on electro-mechanical design and product development.