Posts Tagged ‘product design’

Why is the Manufacturing Method so Important and How to Choose the Best Method

September 4, 2008

Why is the Manufacturing Method so Important and How to Choose the Best Method

In previous blog entries we have repeatedly noted how important it is to keep the manufacturing methods as a key focus of your design process. We mentioned DFM/DFA (Design for Manufacturing and Design for Assembly) and commented that a good design effort will be typified by bearing these two disciplines throughout the design process. Why do we keep harping on this?

There are several key points to consider. Let us assume that whatever your product is, that you will be making a bunch of them. That means that whatever initial work you put into the design and manufacturing processes will get replicated through each one you make. There are many ways to design any given product and there are many ways to make that same item. Let’s talk about the design input for a moment. Take for instance a part of a mechanism that is intended to provide friction. It does this by rubbing on another surface. You decide that the actual contact surface should be a polymer. There are two ways to carry this out. You can make the entire part from the chosen polymer or you can make another piece and fasten the friction polymer to that second piece. Either method would work, but the second method would have more cost both in labor and in part cost. It also may lead to reliability problems. Each time you add a component (and fasteners) you increase the chance of problems occurring during the use of the product. The time to consider these design issues is in the beginning, not after you are in production as you now have foolishly baked a lot of extra cost and problems into you product. Remember, it gets replicated with each one you make!! We are big on part reduction. One of our rules of thumb is if there are two parts next to each other and neither part moves relative to the other, then you probably have one more part that you need.

The considerations about the manufacturing and assembly methods follow a very similar thought process. Let’s take the example of a plastic assembly. You have two housing components that you have to join (Yes, we know that two housing parts violate our “no relative motion” rule but housings quite often are the exception to rule as you have to contain other parts within the housing). Let’s consider two ways of joining these two housing parts. You can use fasteners or you can use ultrasonic welding. If you use fasteners you have baked in the cost of the fasteners and the labor to install them (Sure, if the housing needs to capable of disassembly then the fasteners are an option). If you choose ultrasonic welding, then you have no fasteners (and you have the option of getting a water resistant seal without adding a separate gasket). You just minimized the cost of each product you ship out the door. Once again, in the design phase is the time to make these choices. One additional note here is that in the design process, each individual component of the complete product should be designed so that it can only be put together one way. This will be a tremendous aid to the manufacturing operation. Also if you can work this in, design your components so that if any one of them is missing, other components will not fit or function correctly. This allows you to catch errors in the assembly process prior to the product being completed and you are forced to toss it in the trash.

How do you choose the best manufacturing method? This is a text book in itself and would be much too lengthy to cover in detail here. However here some guidelines:

  • The method should meet the requirements dictated by the design intent of the product or part. That is, don’t use polymers where the structural needs demand steel.
  • The method you choose should be the minimum cost method that satisfies your requirements. Note that amortizing tooling cost in this is a key part of your analysis.
  • Once you choose a method, make certain that you qualify the supplier that will be executing that process. Do they know what they are doing? What is their experience with this process?
  • The method should be consistent. This means that every part that goes through the process should be treated identically to all of the others.
  • The method should be a commonly accepted practice. In other words ideally the method you use will be available at other suppliers. This reduces that chance of you being held hostage by a supplier or allows you to move your manufacturing for other reasons.
  • If you plan on implementing this method in your own internal processes, allow time for a learning curve if it is new to your production methods.

Not making wise decisions upfront regarding manufacturing and assembly will be a long term cost and possibly reliability burden to you.

What to Look for in a Good Product Design

July 21, 2008

Let us start off by re-iterating a point we made in each of the previous installments. That point being that a good product design needs to take into consideration two crucial aspects:

(1) The fit, form, function, reliability, durability and safety of the product and

(2) The manufacturability of the product

Let’s talk about (2) initially as it is a drum we have already beaten a couple of times. Having a design which takes manufacturability into consideration pays dividends in many areas. By considering the means of making your product up front, you ensure the most cost effective approach to achieve the design goals stated in (1) above. Note that this consideration fills two buckets. These buckets are the bucket of manufacturing and the bucket of assembly. The bucket of manufacturing includes the materials and processes that will be used to make each part. Choosing each of these wisely minimizes your cost and optimizes your design. The bucket of assembly has in it all of those methods to put your product together. In here is the key to minimizing fasteners or choosing environmentally friendly adhesives. It is also wise, if possible at this point, to include potential part manufacturers in this discussion.

There are a number of formal processes that you (your design group) should use in looking at manufacturing and assembly. DFMA (Design for Manufacturing and Assembly) is the overall discipline that defines the means for this process.

Now, let’s move on to (1). What do we mean when we say fit? We mean does it meet your customers’ needs in terms of interfacing with the user. Does the handle have a sharp point on it that hurts the hand? Form is aesthetic portion. Does the product look the way you want it? Will the customer like this appearance? Function is pretty obvious. Your customer wants the product to perform certain tasks. Does it do that?

Reliability and durability are sometimes confused. Reliability deals with how long your product lasts or how many repeated uses your product can withstand before it begins to not meet your customers’ needs. How long does the battery last? How many times can I adjust the nozzle before it no longer adjusts? Durability focuses on how rugged is the product. If it is a product to be used in the construction industry and it breaks after one, three foot drop on to a concrete floor, then it does not meet your durability goals.

There is no simple solution to the issue of product safety. You need to take a variety of factors into consideration. The first thing to cover are the industry or governmental regulations which may apply to it. Electrical items typically must be UL (Underwriters Lab) or CE (in Europe certified. Items which will be used by children must take into account the hazards from small parts breaking off or sharp points being exposed. The Consumer Products Safety Council may be involved here. A product which will be used on a motor vehicle will typically require DOT (Department of Transportation) or FMVSS (Federal Motor Vehicle Safety Standards) compliance.

There are standards for labeling which should be adhered to as well as materials which cannot be used in certain applications or coloring agents which should be avoided. Also keep in mind that even though you designed the product to conform, does not mean you are out of the woods.

All of the specifications you have created for your product design must be documented in the forms of drawings and specifications and possibly computer generated 3D models. These documents are you product. They are the keys to the city. They are the specific details to which you need to hold your manufacturers responsible. You need to put a quality system in place to make certain that your manufacturers are meeting your specifications. This system needs to include in it regular audits to verify compliance. We have direct, personal knowledge or more than one instance where suppliers made changes to products or materials once the production had begun. In one instance the cost to the company was over $1 million and a loss of reputation. In another instance it caused great confusion in trying to understand why the fully assembled product would no longer perform correctly. Only through diligent questioning and auditing of the supplier did we find that an unapproved material change had taken place at the manufacturer in a effort to “save money”.