Assembly Methods for New Product Design

May 26, 2009

What means should I use to assemble my product? When we talk about assembly we are covering a couple of areas. We are referring to the methods we use to fasten one part to another and we are also talking about the processes used in the production of the item. Let’s do this one more time to ensure that we have this clear. In one respect we are considering the means of fastening parts. That is, are we using adhesives or screws? In the second respect we are covering the production process or tools used to perform the actual assembly. Are we using a manual screwdriver or a pneumatic driver with auto feed?

To be sure these two considerations are intertwined, will have a significant impact upon the quality of your product and, like many things we have discussed previously, need to be determined up front. How are they intertwined? Let us assume that your product will have a high production volume. That would drive you to use a fastening method that could be accomplished quickly and efficiently in production. If you have the choice between an adhesive then, or a screw, you would then opt for the screw as it is more conducive to quick, consistent and reliable fastening. (Yes, I know that there are a number of people reading this who are pro-adhesive. I have spent years working with both methods. There is a place for adhesives. They are unique in their application and serve a role that other fastening methods just cannot fill.)

How will the assembly method have an impact on the quality of your product? Let’s look at the use of a screw. There are several ways in which you can install such fasteners. Let’s look at the use of a manual driver as compared to the use of a pneumatic driver with the ability to set torque. As diligent as a person might be, when using a manual screwdriver they simply cannot tighten the fastener as consistently as someone using a settable pneumatic driver or electric. The end result will definitely show in the quality of your output. It should also be obvious by now why the assembly method needs to settled upfront as an integral part of the product design.

OK, what are some of the means we can use to fasten parts of a product together?

• Fasteners such as screws or snap clips

• Adhesives (cold, hot, UV cure, and so on)

• Ultrasonic welding

•Heat staking

•Molded in features such as snaps


Moving these methods to the production realm requires you to consider things such as consistency, reliability and durability (validated through your product testing process), ease of installation and cost. The costs to consider are not only the cost of the fastener itself but also the cost of the assembly equipment. Ultrasonic welding is a good example of this. There is no fastener cost as you are simply bonding the native materials together. But, behind the curtain is the cost of the welder itself, the horn used to focus the weld energy and the cost of the fixture to hold the parts while welding. This can run up to $30,000 and is certainly not the method you would use if you were only making 20 parts a year. Here come the adhesives!!


Product Testing or How do I make sure the Product will do what I want?

November 23, 2008

Product Testing or How do I make sure the Product will do what I want?

The success of your product and your company will depend largely on how well your product performs. Does it do what you want it to do and, perhaps more importantly, does it do what the buyer expects it to do? While the latter portion of this question deals with marketing, advertising and how you represent your product, the first portion is at the crux of this article.

A critical segment of your product must be the specification. This specification will describe not only what criteria you want the design to adhere to, but it should also include some consideration of the reliability and durability of the product. What is the difference? Reliability is simply how consistently the product performs its key functions. If a ball only bounces every third time you use it, it is not reliable. Durability is an indication of how long the product will perform its required functions. Back to the ball example, if the ball only bounces three times and then bursts, it is not durable (unless three bounces was your design goal!!).

In general then you must evaluate your product to determine if it meets the requirements that you had intended for it. In addition, in many instances, there will be government or organization mandated tests that must be passed. For example, UL (Underwriters Lab) certification is required for many consumer products. UL defines the specific test and how you must conduct it. Typically you would have these tests completed at a testing facility which meets the UL testing requirements. So, do your research on government and other organization tests to which your product must be submitted. Note that these tests will not typically test the functions you are concerned about. These tests are more focused on such items as flammability, electrical grounding, can a child swallow it, and so on.

Let’s talk specifically now about evaluating your product for those characteristics that you want your product to do. Typically product development professionals refer to a products’ “fit, form, function, reliability, safety and durability”. You will want to create and conduct tests which will validate your product in each of these areas. To do this you first need to define that feature that you wish to test. Let us say that your product is a new garden hose sprayer. Let us go through each of the characteristics we noted above and relate them to the garden hose sprayer:

Fit: You would be concerned with how it fits the typical hand. You may set up a test where you have a number of people (a mix of genders and sizes) pick up and hold your sprayer and evaluate it against a number of criteria i.e. is it too heavy, is the surface too rough, and so on. You can also do this using computer generated ergonomic models.

Form: Once again perhaps a mixture of objective and subjective measurement would be used here. Does it look sufficiently aesthetic? Is it the right color? Does it look like a garden sprayer or does it look like a hair brush?

Function: Here is where we get a little more objective. Does the trigger adequately control the spray volume? Does the control knob for varying the spray type work well? Does it fasten tightly and easily to the hose?

Reliability: Now we get much more objective. How consistent is the trigger’s operation? You may design and fabricate a machine that will repeatedly actuate the trigger. This machine would also measure the force required to actuate (does it change with repeated actuations?) and the amount of spray (does it decrease with repeated actuations?). Note that this same test can also cover many of the questions regarding durability.

Safety: This is very important. Does the users’ finger get cut by the edge of the trigger? Is the sprayer capable of sending such a high pressure jet of water that it penetrates your skin?

Durability: This product will be exposed to the weather most of the time. You will want to know if it fails to function when it is at 120 degrees F (a common temperature for a yard tool to reach if it is lying in the sun for some period of time). The make up of this test may be using the same test fixture you made above for actuating the trigger and placing it in an environmental test chamber. These chambers are typically something you will not have sitting around. You will have to engage the services of a testing laboratory to complete this. This same lab should be able to perform a UV (ultra violet) light test. Your sprayer will be sitting in the sun a lot. You certainly want to know if it falls apart after being exposed to sunlight for two weeks.

A lot of thought and research needs to be placed into defining these tests. You will find that a good testing lab will be instrumental in this work. You will also want to document the means by which all of these tests where conducted, the equipment used and the results. A good testing lab will do all of this as a matter of course.

How to Choose a Manufacturer and what to Expect

September 17, 2008

From your perspective you will be looking for two types of manufacturers. In the first category are those companies which will make the individual parts you need for your product. The second group of manufacturers are those who will put your product together.

All manufacturers will vary in their levels of sophistication. This sophistication will typically be a function of their current or desired customer base. For example those manufacturers who supply to the automotive, medical or aerospace industries will be required to have very rigid quality systems, controlled manufacturing processes, order entry systems and so on. Such systems are, more often than not, dictated by the customer and are a condition of doing business. Adherence to these systems on the part of the manufacturer are often reinforced by on site audits carried out by the customer. So, these types of suppliers are at the high end of the scale and will usually price their services accordingly. These systems are not inexpensive to implement and the company must recoup its costs in some manner.

On the other end of the scale are manufacturers which don’t have all of the high end systems, but do a good job within their area of skill. These companies typically will have their own means of ensuring quality. They will also be the most cost effective and will tend to treat you on an equal footing with their other customers. It will be well worth your time to visit these folks and review these items:

  • Ho w does the company take in and control your component specifications? You obviously want to ensure that each part made for you meets your requirements and that each part is identical to the next one. If a CNC program is written for your part, how do they ensure than no one messes with the program?
  • Will they make and retain a “first off” sample part? They should use this part to make any initial verifications against your specifications.
  • Do they have an equipment maintenance program? Do they have evidence that they follow that program? You do not want dull tools to be used to make your parts. If your part is a molded plastic part, how often do they tear the mold down and inspect for damage?
  • How do they plan on storing your parts? Will they be in an area which is safe from damage and the environment? How do they handle your parts once done? Do they toss ‘em in a box thus exposing them to possible damage?
  • How does the company handle your orders? How are they transmitted to the manufacturing operation?
  • How will they ensure that the raw materials used in the operation are the ones that meet your requirements?

To dwell for a moment now on those companies which would assemble or put your product together, many of the same comments above apply. You will want to find a company which has good, demonstrable control over its assembly processes. The key here is that the processes must be consistent and repeatable. If they use a pneumatic screwdriver sometimes and a manual screwdriver at other times, this is bad news. If they use a manual screwdriver (thus having little control over tightening torque) and they should be using a pneumatic screwdriver which allows for consistent torque, then that is bad news also. How do they handle your parts between operations? If there is a problem with some of the parts that go into an assembly, how they assure that only good parts are used?

In general you can expect good results from suppliers for whom you have verified references, but your best insurance is that you personally review these key process items and make certain that your chosen supplier has all of these systems in writing and that they actually use them.

How do I Get a Prototype Made and Why do I Need One?

September 4, 2008

How do I Get a Prototype Made and Why do I Need One?

Prototypes are a key part in any product development activity. I have yet to work with an engineer who does not see the value in prototypes. By the end of this discussion I hope that you will also see that same value.

What is the purpose of the prototype? In general a prototype provides confirmation that your product design is as you wanted it. Computer solid modeling is a huge step forward and eliminates many areas of concern, but it is not uncommon to find problem areas once you get a real part in your hands. Engineers, when introducing a new design option will even step back and build a “proof of concept” prior to entertaining a prototype. The proof of concept focuses on that one design feature that is new and is in need of evaluating further before it gets set in a prototype. I have often seen that a prototype will be used as a sales tool. In one recent instance the client liked the prototype so much that he had it painted and dressed up like the final product to show his customers. It looked very representative.

When should a prototype be made? Let’s talk for a minute about the various natures that products make take on. Some products are simply a minor variation on an already existing and validated product. A judgment call can be made at this point to make or not make a prototype. I would err on the side of safety when at this decision point. A few hundred dollars spent on a prototype could save tens of thousands of dollars downstream. You do not want to get your first manufactured parts in your hands (after spending $50,000) on tooling and find that the part is wrong!! As you ramp up the ladder toward a whole new product design, you will be faced with the decision of having a prototype made at various stages. At the extreme of an entirely new design, with no vestiges of a previous validated product, you will assuredly want a prototype. And, obviously, you will be prepared to make the prototype once the initial design is completed. In most cases, the organization making your prototype will need either computer generated solid models or drawings or both.

How do you get one made? There are a number of ways to make realistic prototypes. The key is to make the prototype of the materials (and possibly the processes) that are close to representing the final product. If your final product is made of metal, then a qualified machine shop will be able to fabricate one. If your product is to be made of plastic then you can also have it machined, rapid molded or you can choose one of the more gratifying tools in the product development arena. This tool is called “rapid prototyping” and it is gratifying because you can have a prototype in your hands in just a few days. There are several such services in most major cities. This process uses a variety of machines that operate in some cases like a printer that uses plastic instead of ink and in other cases uses a laser to remove the unwanted material from a block of material to reveal the final part. In most cases a part from this process can be handled roughly and can be quite representative of the real thing.

In some cases you will want to go a step further and obtain a prototype made of the exact materials and processes as the final production intent product. Having such parts also lets you get a head start on product testing and even lets you get a few “actual” parts in your customers hands well ahead of the timing for production intent tooling and at a much lower cost exposure than full blown tooling. If you are looking for a “real” injection molded part, companies such as ProtoMold can do this for you in a surprisingly short period of time and can also provide several hundred parts. The caveat is that you will not get thousands of parts out of these molds and you will pay more for each part. If die cast aluminum is your final material selection, there are companies such as RapidCast that can deliver these types of parts in a shorter period of time than hard tooling and the same caveats apply..

Once again, the goal of a prototype is to replicate the critical fit, form and function (and perhaps appearance) of the actual production part so that you can see the “surprises” before you put a lot of time and money into it.

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”.

What are the steps in a typical product development project?

July 13, 2008

What are the steps in a typical product development project?

In this segment we’ll talk about product development from a large scale and cover those portions that are not only design related but also those that encompass the entire process of getting your product ready for the market.

We’ll assume that you have defined a need for your product. In doing so you have a good idea of the features, functions and environment in which your product must excel. Ideally you would have done this taking input from potential customers and product users. But, wait…… can I talk with these folks and make sure that I do not lose my idea? Will one of these people take my idea and run with it? We feel it is better safe than sorry in this instance and suggest you obtain a provisional patent. Any patent attorney can set this up for you and it is cheap insurance. It will cost less than $2,000 in most cases. It is valid for one year. Once you have that in your hands, you are good to go. However, if you don’t proceed with the full scale utility patent within that one year period, then you wasted your money on the provisional and anyone can grab your idea.

So, the first thing you will do is get this provisional patent filed. Next you have the freedom to do some basic market research with provisional in hand. From this market research your product will fill out and may take on some new features or functions. Make sure that these are covered in your provisional unless you determine that they will not be a part of your product.

We mentioned environment above. Let’s cover that for a moment. I have seen more than one product fail because it was not designed to function in the environment or application that it ended up in. Environment includes such things as external temperature, moisture, impact and so on. Application means how will the buyer use it? Despite the fact that you intended it to be used as a pet food can opener, might someone also want to use it to pound nails? Make certain that you have done your best to cover these issues.

Now you know what the product will do and what environment it will function in and you have a good idea of how your customer will use it. How do you get it made? Here is where the engineer comes into play. We gave some good guidelines that an engineer should meet in our previous blog submission. Obviously the engineer should have education and experience in the field of application that your product will exist in. Remember that there are several different area of engineering expertise, so make sure you pick the right one.

Together with the engineer you will go through these steps:

  • Concept design: This is a basic design of your product as you see it. It should include all of the critical features. If your product has a significant aesthetic component, this concept model should take a first cut at that appearance. This is also the stage at which you and the engineer should get a good handle on the manufacturing methods. As we said in your previous installment, if your engineer does not have a good background in manufacturing and if he does not incorporate that knowledge into the design, go forth and seek out another engineer! It is also very helpful at this point to consult with your potential manufacturers.
  • After digesting what you have learned from the concept model, you will move on to a detailed model which should be an exact representation of your final product.
  • From this final model, you will want to have a prototype built. Depending on the type of product and its characteristics the method used to prototype could be anything from welded steel to a computer generated rapid prototype.
  • Having the prototype in hand will let you see many things that you may not have anticipated. Expect to make changes to your product after you have seen the prototype. This prototype can also be used to show customers.
  • The engineer at this point should (1) Prepare a DFMEA (Design Failure Modes and Effects Analysis) (2) based on the DFMEA, make changes as appropriate to the design. You may feel at this point that a second prototype is necessary.
  • The engineer should now prepare the piece part drawings. This is done for two reasons. One, it documents all of the dimensional details and other product specific requirements. And two, many of your piece part subcontractors may need drawings to work from.
  • With these drawings in hand, you should visit your manufacturers and verify the manufacturing processes (your engineer should be party to these discussions).
  • Now, it is time to cut your manufacturers loose, assuming that you have a good contract with them. You should have your manufacturers make a first article assembly for you. This first article should be compared against your parts drawings to ensure that they are made to your requirements. The topic of contracts and conformance to them by your suppliers is a whole subject unto itself and is critical to the success of your product and/or company.

OK, your manufacturers have done their jobs. The parts are all made to your specifications. They all fit together and the product works as you had wanted. Now, you get to do your job and get these products to your customers.









Product Development

July 13, 2008

How do I get my product idea from a napkin sketch to the buyers hands?

There are many books written about marketing and sales. But until you have something to sell, they make good reading but little else. So, you have a great idea for a new product, but the mystery begins here. How do I get it designed? How do I know it is designed correctly? What materials should I make it from? Should I make a prototype and how should that be made? How do I ensure that it is designed in the most cost effective manner? How do I get it manufactured? What is the best way to manufacture it? How do I know that manufacturing method is the most cost effective?

This series of articles will lead you through that process and provide you with some specific guidelines on getting through this process so in the end you have the product that you envisioned.

Assuming that you have satisfied yourself that you have a product that will provide you with wealth and fame, the first step is in your hands, and that is to define as well as possible what your product will be. To do so requires that you define how the customer will use it, what kind of environment it will be used in, what types of handling it may be subjected to, how big or small it can be and any other requirements which the designer (and yourself) will need to know. There are a number of sophisticated means to accomplish this. One of the most well known is QFD or Quality Function Deployment. I would not spend a lot of time using these types of methods, The keys for you are:

  • What does the product need to do?
  • What does it have to look like?
  • What, if any, restrictions may apply to it (for example does it have to be UL, Underwriters Lab, certified? Do all of the materials have to be biodegradable?
  • How does the user interface with it?
  • What are the environmental conditions that it will be exposed to, i.e. is it out in the rain? Is it exposed to fertilizers?
  • Any other specific information which will dictate how the product functions, looks or any regulatory requirements that it must meet.

In general your product will have either mechanical or electrical/electronic components in it or perhaps both. You will need to find a good mechanical or electrical engineer to see that the product is designed correctly. One important tip here: There are many good engineers out there. But, the key is to find an engineer who will not only design your product well, but will also design it so it can be manufactured and assembled easily. This is called DFMA or Design for Manufacturing and Assembly and it is key to holding your product costs in check. DFMA takes into consideration how each of the parts are made, how they fit together and how the completed end product is to be made. If this whole aspect is not thought out well and incorporated into the design, it will add excess cost to each unit that is made.

Your engineer, having satisfactory experience, should be able to work with you to develop a timeline for your entire project. While you may not adhere exactly to this time line, it will serve to give a good overview of all of the steps needed to get your product ready for market. In the next article in this series, we will list all of the items in a good project plan. This will give you a good useable tool to customize and use in your planning.