by Michael Paloian, IDS
In the previous issue of RotoWorld® published the first of a two-part series of design related interviews I conducted at the last ARM conference held in Denver. This second installment includes the opinions and comments of other highly respected individuals in the industry. The exchanges of questions and answers were intentionally conducted in a conversational mode to encourage honesty. My objectives in asking these questions were to gather opinions from individuals in different areas of the rotational molding industry concerning design, designers, and preferred design skills. Conversations were recorded and later transcribed by me in this article, which has been approved by each interviewee. I hope these impressions and opinions will stimulate further discussions pertaining to design, leading to improvements in the industry.
Interview with James Leitz
VP Sales Gregstrom Corporation, Woburn Mass
Question – What percentage of the designers you work with have a good understanding of rotational molding?
Jim – A very small percentage. Typically, 80% to 90% of the designers we’ve worked with have previously designed one or two rotationally molded products. But they don’t have a good understanding of the process.
Question – Have you had better results working with in-house corporate designers or design consultants employed by contracted design firms?
Jim – I haven’t noticed any significant difference in performance between either group. We have had an equal number of successful and very difficult projects with designers in either group. Most of the problems stem from the fact that designers don’t understand the rotational molding process or how the parts are molded. We’ve received design files from industrial design firms who have only designed one or two rotationally molded parts. We’ve sometimes found their CAD files to be better than those we’ve received from experienced engineering firms. It all depends on the designer. Just because a designer knows SolidWorks, doesn’t mean he or she knows how to design a rotationally molded part.
Question – So you actually encounter designers who attempt to design a rotationally molded part without having any idea of what they are doing?
Jim – Well, a designer might have previously designed a very simple rotationally molded part, like a ball, and is now attempting to design a pontoon with kiss-offs, undercuts and inserts. The latter is much more complicated and requires many more considerations.
Question – If you worked with these designers before, did you show them your process and discuss your capabilities, limitations, and design guidelines with them?
Jim – Yes, of course we tell them about tolerance limitations, desired radii in corners, and minimum distance between two adjacent parallel walls, for example.
Question – Anyone can get that same basic information from the ARM design manual as well. Why do you think designers don’t apply these parameters to their designs?
Jim – I’m not sure, maybe they forget. For example, we have to remind them that the minimum distance between two parallel walls is 5X the wall thickness or we have to remind them they can’t locate an insert near the edge of a wall where material can’t flow. We had one customer who designed a part with 58 inserts, which he wanted molded into the part and we had to inform him how impractical it was to load 58 inserts in a part. The added time required to load all the inserts combined with the high risk of omitting one, which would have resulted in a reject, would have made this approach very impractical. So, some designers may know the basic design guidelines but they lack an understanding of the process which results in very impractical design solutions from a manufacturing standpoint.
Question – Do designers typically complete a design and submit it to you or do they review the design with you as they develop it?
Jim – They typically submit a finished design, which we have to review and inform them of what they can and cannot achieve. They then go back make the revision and resubmit it to us. We review it again and discover new features they have added which cause other problems, resulting in another revision. This cycle can be repeated up to 4 or 5 times before the design is finalized and ready for production. There was one occasion where a designer specified 30 molded-in holes which weren’t a big problem except they were all perpendicular to the line of draw, resulting in a massive undercut. One of the problems we often face is designers collecting competitive bids from a number of molders after having invested many hours in helping them get their designs optimized for production.
Question – What percentage of the designs submitted to you have to be modified because there is a lack of understanding of tool design or tolerance limitations?
Jim – More than 75% of the designs we receive must go back to the designers for revisions to accommodate tooling requirements and up to 90% of the designs must be modified to comply with tolerance limitations. In addition, many designers don’t understand where to locate parting lines and its impact on appearance.
Question – How much time do all these revisions add to the design schedule or cost of the product?
Jim – Typically these revisions can add as much as one month to a design program but don’t add any significant amount to the overall cost of the part. Of course the added time does contribute to design and development costs.
Question – Are designers typically aware of the different types of polyethylenes or do they simply specific polyethylene?
Jim – They typically specify high or low density polyethylene. Specific resins are not often specified. We had a designer who forgot to specify crosslinked polyethylene for a tank application which was subjected to xylene. After molding parts for two years, the customer began discovering problems with the tanks stress cracking.
Question – Do designers often consider environmental conditions like temperature exposure?
Jim – Well we had a customer who wanted to autoclave hamster cages at 300F. Although their autoclave tests proved successful they discovered the cages were stained by hamster urine, which was not tested. It’s important for designers to carefully consider environmental factors that could affect the product. It’s very easy to overlook a seemingly insignificant detail that can later result in expensive recalls.
Question – Do designers consider the type of tooling to be applied to their application such as sheet metal molds vs. cast or machined tools?
Jim – No, they rarely consider the type of mold.
Question – In closing, if you had one recommendation for designers attempting to design a rotationally molded part, what would it be?
Jim – They should read and understand the ARM design manual which was developed by molders and Glenn Beall.
Steve ZAMPRELLI
VP – Engineering Formed Plastics
Question – When you first started working at Formed Plastics were you somewhat overwhelmed with the differences between rotational molding and injection molding part design?
Steve – Not sure if I would say overwhelmed, I have experienced many challenges. Initially it was quite an eye opener. I had come from a larger company with multiple resources. I had to quickly come up to speed to fill a void of a highly experienced senior member within the company, Ron Joannou. Although I felt confident in my basic skills, but I still felt there was a lot to learn.
Question – What was the special insight you gained working as a designer within the framework of a rotational molding company?
Steve – I quickly realized you never want to lead a customer to believe you can achieve something that is not possible or practical. You typically want to err toward the more conservative side of what is possible. For example, if a customer wants a highly polished part, you want to discourage him from expecting this because it is very difficult with the type of equipment we have.
Question – I saw a highly polished rotationally in the Roto Made Local exhibit. How was that accomplished?
Steve – I’m sure they have utilized special process controls and they are probably molding that part on
a dedicated machine.
Question – What is your primary role as an in-house designer?
Steve – I spend most of my time advising customers. We do not have the resources to invest time designing products for our customers since our primary business is molding parts. I try to guide our customers to the right process based on their design intent. If I feel that their requirements are better suited utilizing a process that we do not offer, I will suggest some process options to them.
Question – Doesn’t this concern you that you will not get their business?
Steve – If I guide a customer down the wrong path to suit only one of the processes we offer, I would be doing both the customer and the company an injustice. The customer will not be satisfied and the company will suffer for it. I know they will be back on the next project looking for guidance as we continue to build our relationship and trust. I don’t expect to get every project I review. Formed Plastics built its relationships upon 70 years of trust and customer service. Our customers depend on our honesty.
Question – What are the most important considerations you would like designers to
address in rotationally molded part designs?
Steve – I’d like to see designers being more realistic about tolerances expectations, locations of inserts, and their ability to be easily molded and provision of finished CAD files. We often receive napkin sketches from our customers, which accounts for fair percentage of the parts we mold. When we do receive finished CAD files, we must invest significant time revising the design and suggesting modifications for production, which is typical 50% of the time.
I would also encourage designers to consider rotational molding more for aesthetic applications, not just tanks and internal parts. Many rotational molded parts are very attractive, as you will notice in Rotoworld® magazine. The process is underutilized and underappreciated.
I would also encourage them to learn about the various materials that are available for processing. Rotational molding is not just for using various forms of PE. Although it is a major portion of the market, there are other resins that may be better suited for their design requirements.
I strongly believe that it is one of the most difficult processes for a designer to understand. When dealing with mating parts and fitment issues, most designers I have spoken with who have tried working with this process typically give it one chance and, due to their lack of knowledge of design constraints, tend to give up on it too quickly. Once I have the chance to show them the process and review how to deal with the design issues, they tend to get a better understanding how to design for it and welcome the challenges. They learn from their mistakes. We all learn from mistakes and the more the process is used, we become more knowledgeable and share the information to others so
that they are successful.
Tom Innis and I have been honored to be ambassadors for Roto Made Local, a joint effort between ARM and SPE Rotational Molding Division. We travel to IDSA International conferences to promote the use of rotational molding and educate designers. We educate educational faculty to at least make their students aware of the process.
Carlos Garcia
President Reduction International
Question – Based on your experience as salesman with extensive experience selling internationally, especially in South America, what do you think OEMs in South America expect from designers of rotationally molded products?
Carlos – The rotational molding market in South America is primarily based on water tanks because of the poor distribution of water in South America. This market is consistently growing and has hampered the application of rotational molding to other markets.
Question – Do water tank manufacturers design tanks as simple containers to store water or do they engineer them with proper considerations for creep, thermal conditions, stress cracking, and overall long term stress considerations?
Carlos – There are basically two types of water tanks in the South American Market. The first is the bottle type water tank molded on open flame machines. These tanks are often molded as dual or even triple layer tanks. In some cases, the second layer is foamed by simply adding the blowing agent PE layer into the open end of the mold. These tanks are sometimes molded with a 1mm outer layer and up to 10mm of foamed PE on the inner layer. There isn’t much engineering that goes into the design of these tanks since they are all virtually identical to one another. 80% of the machines in Latin America are open flame machines, which are dedicated to molding water tanks. These conditions have therefore limited the growth of rotational molding into new markets as well as stymied the use of professional designers. The other type is the conical single layer tanks that, even though they have a lower quality compared to the bottle type tanks, they have advantages since they can stack and have a much lower shipping and storage cost.
Question – Based on what you’ve described there doesn’t appear to be much interest in employing designers for rotationally molded products. Is this a correct assessment?
Carlos – Yes, design is often thought of as a luxury or unnecessary expense by most molders and OEMs in Latin America. They don’t acknowledge the benefits of good design unless they’ve experienced improved productivity, increased sales and a successful product launch from first shots all resulting from an investment in good design. OEMs begin thinking about investing in design when markets become saturated and profits dip. This is the point where companies begin considering introducing products that can be branded with a distinctive design and they look for qualified designers. However, the market for water tanks in South America is so large and still growing at a fast rate, that rotational molders are drawn to fill that non-stop demand with open flame machines. This dynamic dis-incentivizes rotational molders from pursuing other markets as well as contracting designers.
Question – Don’t you think rotational molders in South America would be attracted to higher profit products that would require an investment in design versus being limited to a very cost competitive water tank business?
Carlos – The very high demand for water tanks and the culture in Latin America introduce high barriers for investing in design. Well-designed products require well designed molding machines with good process controls. Most of the machines in Latin America are open flame machines with minimal process control limiting production quality and consistency, introducing another obstacle for investing in design. Many OEMs are also concerned about copycat clones of their products by competitors, thus discouraging them from innovating anything new.
Conclusion
I’d like to thank Jim Leitz, Steve Zamprelli, and Carlos Garcia for sharing their insight and perspectives about design with me and the readership of RotoWorld®. Each contributor generously shared their time with me to express their opinions about design and their expectations from designers. This second article will hopefully stimulate additional discussions in the industry as well as improvements which could be made in the development process.
Please send me your comments about this article; I am always interested in receiving your opinions to improve the content.
from an article at RotoWorld®
https://rotoworldmag.com/what-rotational-molding-industry-experts-expect-from-designers-part-2/
No comments:
Post a Comment