The Seven Secrets of Pressure Forming as a Prototyping Alternative

Pressure forming is an excellent alternative to injection molding or engineered blow molding. The lead times are shorter, the process flexibility is high, production parts in small quantities are comparable in price – but available much sooner. From a timing standpoint, pressure forming makes sense; however, pressure forming’s greatest benefits will accrue to those projects that start and stay with pressure forming throughout the development cycle and into production.

Pressure forming combines many risk avoidance features and, therefore, has many lower cost advantages. The design risk can be hedged because the tooling development time is short. Therefore, more time can be left for design alternatives, completing of internal parts affecting the outside design, or worst case, short turnaround to do it all over again. The desired part thickness to give the right customer feel can be hedged. Pressure forming is a one-sided process. Sheet gauge can be changed adding stiffness or lowering material content without changing tooling. Best of all, the overall project costs can be hedged because the hard prototype pressure forming tooling is ready for production. It is capable of cost effective piece part production without the need for additional hard tooling expenditures.

What are the Secrets of Pressure Forming?

Secret #1: Design for the Process

There is a processing window for every job – the bigger the window, the more easily controlled the process will be and the lower the costs of production will be. Lower costs should mean lower prices. The converse is also true. The tighter the processing envelope, the higher the uncertainty and the higher the production costs and prices will be.

With this in mind, it should be your goal to design a part for pressure forming that has as wide of a processing window as possible. There are a few rules or guidelines which cannot be violated, for instance, you cannot start with 0.125” gauge sheet, draw it down 5:1, and have anything but tissue paper left, even if the process were 100% repeatable.

The key design elements that must be understood and considered for any pressure formed part are:

  • Draw Ratio
  • Radii
  • Undercuts
  • Draft
  • Texture
  • Ribs and Louvers
  • Fastening
  • Tolerances
  • Dimensioning

The process must accommodate your design needs in each of these areas or you need not go any further with your evaluation.

Secret #2: Proper Tool Design

QUALITY TOOLS = QUALITY PARTS

Tool design and part design go hand in hand. The quality level and appearance you want to achieve with your parts will largely dictate the tooling costs. You can work the formula backwards and ask what is the best I can expect from a casting or an epoxy tool, but we recommend you start with as loose a requirement as possible and have it quoted.

Highlight what you have to have. Here is where you must decide what quantity of parts you will need and what future use you will have for the tooling.

There are several tooling alternatives to choose from:

  • Part or Model
  • Wooden Pattern
  • Epoxy Casting
  • Aluminum Casting
  • Spray Metal
  • Machined or Fabicated Aluminum

Each one of these has a place and strengths and weaknesses. Your particular application will generally dictate which one to use.

Since most applications include models or patterns, this can be very cost effectively used for prototypes or even a very complex pattern can be eventually used for the final production tooling. Decisions made at this state of the project can significantly affect total project costs.

Secret #3: Adequate Forming Equipment

Many pressure formed jobs require uncommon production equipment to cost effectively produce quality parts. Unlike injection molding where the pre tonnage, platen size, shot size and process control tell most of the story of production capabilities, pressure forming equipment is less standardized. By comparison to injection molding, the obvious part capacity concerns can be specified by maximum sheet size and depth of draw. The more artful variables of process capabilities and control of not only the forming cycle, but, also, of the heating oven are very difficult to put down on a process capabilities sheet. We believe the key to the forming in pressure forming is control. You must have a machine, set-up procedure and production operation that will result in uniform parts throughout a production run and from run to run.

Equipment-wise, we believe in pressure. Our equipment has 80 to 100 psi capabilities over 5′ x 10′ platens. This is very uncommon. Most new pressure forming machines are designed for 50 psi maximum over the entire platen. Some forming companies try to pressure assist their vacuum forming machines, which is even more limiting as to the pressure and the resulting detail that can be achieved.

Secret #4: Consistent Trimming Techniques

Over half of the art of producing pressure formed parts can be attributed to the process of freeing the part from the sheet. This must be done in a controlled production-like way to produce usable parts at reasonable prices. There are many techniques that can and have been used to do this. The trade off is usually one of speed vs. dimensional tolerances. As an industry, until recently, the process was very labor intensive and quality generally had to be “inspected in”. Profile Plastics purchased the second 5 axis CNC router that Thermwood built in 1979. Today we have many CNC trimming machines in production. Over the years we have learned that 99% of all pressure formed jobs require CNC trimming because it is the most cost effective way of accomplishing the sophisticated part designs the market demands. Because of this we highly recommend it. Without the control of CNC trimming, the dimensional control required for your purchased production parts would be nearly impossible to cost effectively supply.

This is a major dilema in the manufacture of prototype parts. The fixturing and programming cost of CNC trimming for only a few parts is very high. Instead, we recommend hand trimming by machinists for the few that are required. This is still generally very cost effective. It must be emphasized, however, that many trimming problems can be solved in the tool design stage. Part design for minimum trimming and open tolerance will pay big dividends.

Secret #5: Knowledgable People to Control the Process

Thermoforming is a people process.

Good people control their process and are not controlled by it. However, as with most other production processes, the greater the machine control, the narrower the process variation and the more uniform the quality will be. The industry is moving toward greater and greater process control but, compared to most other plastic processes, pressure forming is still an art. You will want to visit your prospective vendor and get to know their people.

Secret #6: Cost Effective Material Selection

The most important factor in specifying a material is part performance.  However, please do not use a computerized database to optimize that selection! Thermoforming is tied to the sheet extrusion industry. Fortunately, this is a very large industry and there are many resins available to be manufactured into sheet. There are several that enjoy very high volumes and are excellent starting points for your review. If your application can use HOPE, HIPS, GP ABS or FR ABS, one of these four should be your first choice.

The material component of pressure formed parts is directly related to the quantity of parts to be produced. Unlike other plastic processes, the smaller the production requirements, the smaller the material components. The larger the requirements, the higher will be the material component. This is because of the high labor component and the high set-up costs involved with pressure forming.

Thermoforming, in general, and pressure forming, in particular, requires custom extruded sheet to be cost effective. If “warehouse” sheet is less costly than custom sheet, it will be preferred. We rarely find this to be the case, however, except for very small quantities (ie., for prototypes). Custom sheet adds a lot of value to the pressure formed part. Part weight and forming time can be optimized, painting can be eliminated, and oftentimes excessive trimming or cleaning can also be reduced.

Initially, the key material decision that needs to be made relates to the design shrink factor to be used for the tooling. Materials with similar shrink rates, ie., HIPS, GP ABS, FR ABS, can be substituted even after the tool is finished. Final gauge decisions are best put off until first formed parts are reviewed. If the production material can wait until a molding trial is conducted, the gauge can easily be optimized without tooling modification. This generally saves you money. For gauge optimization, however, a heavier gauge with all of its higher cost disadvantages is much less risky than a lowest possible gauge, which more often than not is based upon wishful thinking.

For the lowest cost prototypes, use what is available and plan to paint the parts.  For production parts, the long term best buy is custom colored sheet in a high volume resin that meets the products requirements.

Secret #7: Tooling and Piece Part Costs

To properly compare two or more prototype or production alternatives, costs must be compared. We know the following relationships to be true for pressure forming.

Tooling Cost = f (Part Design, Forming Tooling, Trimming Fixtures)

Part Cost = f (Quantity, Material, Forming, Trimming, Tolerances, Yield)

But what do we compare? If we try to look at these two relationships separately, we find that we first have to make certain assumptions about one to draw any conclusions from the other. This complex relationship has plagued design engineers, buyers, sales engineers and even company presidents for many years. One solution is to look at competing alternatives on a total cost basis and then divide by the projected number of parts over the life of the product. Then, choose the one with the lowest cost.

This “total cost” approach still does not satisfactorily incorporate the cost effects of development time, the learning curve process yield and the risk that the product life forecasts will be wrong. What is the answer? That often depends upon the risks of being wrong.

We recommend for comparative purposes you use a piece part quote based upon the quantity of parts you will require for a three to four month period in year two after production start up. Use a five year project life and use your business plan sales volume numbers. Use tooling costs equal to the level of quality you feel fits the application. Plot the cumulative total costs per year of the competing alternatives. Where the curves cross each other will put time into perspective.  For instance, if pressure forming has a lower total cost until year four, consider the factors that might result in product changes prior to that. If they never cross, the answer should be obvious, and, if they cross in the first year, time is probably so important to your new product, you may want to develop parallel parts – one in injection molding and the other in pressure forming, just to get to the market faster.

Before making your final decision, look again at the lower level of risk associated with pressure forming because of the smaller up front tooling money and the opportunity for change being greater. Your total outlay for the parts will be less.

Pressure forming is a production process that bridges the gap between the need for a few parts and many thousands of parts. Because of this, it is exceptionally well suited for prototyping requirements as well as production requirements. Pressure forming is a new product manager’s dream come true! By taking full advantage of the process early in the product development cycle, high quality, functional prototypes can be available for customer trials and trade shows at costs not too different than “models”, and when production quantities are required, the tooling and trimming fixtures will be complete. If changes are required, they can generally be done quickly and at relatively low cost. This will allow the new product to get to market faster and at a lower total cost. Then, in a few years when an innovation is required to extend the product lifecycle, newly designed pressure formed parts can be retrofitted to highlight the product change to the marketplace.

Contact Profile Plastics today to learn more and see if pressure forming is a good option for your next project.

More White Papers

Let’s talk about how to make your part right.

Our guiding principle for doing business is simple but powerful: We’ll make it right.

Schedule a Call with one of our experts, or use our Contact Form to start a conversation.

 

Multi-part enclosure for panoramic dental x-ray unit.

Exceptional cosmetics have opened great opportunities for thermoforming, but satisfying high volume applications was a problem. Profile Plastics has built a business around high volume consistent, pressure forming, which has greatly expanded the market for all.

Pressure forming has proven itself as a great method for getting complex parts to market quickly without the high tooling costs and long lead times needed for injection molding. Unfortunately, because of the high per part costs and the artistic nature of the manufacturing process, pressure forming has most often been targeted to applications that require a lot less than 1,000 parts per year…Until now that is.

Profile Plastics of Lake Bluff, IL has spent the past ten years quietly perfecting a process that allows them to produce more than 10,000 of each part per year, consistently, and more importantly, cost effectively. They are now ready to reveal that they are the lowest cost manufacturer in the US for highly cosmetic, close tolerance, thermoformed parts, and that they have proven their process by consistently meeting the needs of customers who require tens of thousands of parts per year, year after year.

Who is Profile Plastics?

John Grundy, a pioneer in the thermoforming industry, founded Profile Plastics in 1960. Through his contributions to the growth of the thermoforming industry, John was chosen as Thermoformer of the Year in 1993. The company has a reputation for strong customer service and award-winning parts.

Profile Plastics' Thermoformed Medical Waste SystemThis Medical Waste System won thee 2023 SPE Thermoforming Award Winner for Pressure Form, Gold People’s Choice Award Healthcare. Throughout the years, Profile has remained on the cutting edge of technology and have been innovators in the commercial development and use of the thermoforming and pressure forming processes.

The company is currently led by Steve Murrill, whose mission is to create an organization and facility that allows Profile to anticipate and meet customer needs while opening up new high­ volume markets for pressure forming.

The entire Profile organization is structured around a team approach that is geared toward efficient,  continuous production. By having the best people organized into logical teams, Profile minimizes downtimes and creates efficiencies that reduce the total cost of operation.

To achieve highly detailed products using pressure forming, there is often a lot of hand finish work, which drives up the per-part price and makes it difficult to get consistent quality over a large number of parts. Traditionally, pressure forming has been almost more art than science. Each operator would get different results.

This meant that one shift would produce great parts while the next shift’s production would need to be reworked, deviated, or worse, scrapped. If key production went on vacation, some parts might not have been made at all. Inconsistent quality, high reject rates, excessive trimming time, slow production, and too much hand-labor per part were all obstacles that had to be overcome on the road to high-volume thermoforming.

The Profile Process for High Volume

Profile has developed a facility, an organizational structure, and a manufacturing process that allows them to consistently produce tens of thousands of each part per year. The process is as follows:

Sales Engineering.

Preparing for high volume starts with Profile’s direct sales people. Each project is unique, and the sales engineer’s job is to help the customer understand the right process for each application. Profile works to make sure that the customer understands what is possible and what is not possible with thermoforming. Many great sales opportunities are handed off to alternative processes that are a better “fit.”

Engineering.

Profile Plastics, Inc -thermoformed highly detailed cosmetic partsMuch of the cost of pressure formed parts comes from the CNC router trimming time and the manual labor needed to bond on blocks, hand trim out special areas, paint and so forth. Profile has always used molded-in color, which they believe provides a better end result and reduces production cycle time.

To reduce the other post­ production expenses, Profile spends a little more time during the engineering phase to prepare not only for the usage of the product, but also for the production process. In many cases, they are able to mold in features or eliminate blocks. By molding in these features, they reduce the time to make the part, lower the cost, and provide consistent quality.

Tooling/Process Development.

Profile engineers work to create accurate, robust, detailed production tooling, resulting in part cosmetics that are in many cases superior to injection molding. For higher volume projects, spending a little more on the mold tooling can have a dramatic effect on the consistence of production and the per-part cost. In order to take the skill of any particular operator out of the equation, Profile engineers also spend time upfront to create process check fixtures that allow the operator to regularly and precisely make sure they are making good parts. In this way, most prob­lems are caught before more than a handful of parts are made.

High Volume Production.

Custom Thermoforming PressOnce the tools are designed properly, the burden passes to production. As pressure forming has grown over the past 25 years, many of the manufacturing machines and processes were invented or modified by plant engineers as needed. This meant that each machine was a little bit different than the others. Most parts were tooled and set up to run on one particular machine. If that machine was down or busy, the part was delayed.

To get away from that restriction, Profile took advantage of a plant move and expansion to install multiple computer- controlled machines that allow for effective redundancy. If one machine is down or busy, production can be set up on an identical machine without any major problems. In addition, with more sophisticated process controls, the equipment can automatically alert the operator if something has changed. Profile runs multiple shifts on their state-of-the-art equipment, and they have developed their own quality control procedures that provide more consistent results, regardless of the operator. In fact, over the past ten years, Profile has reduced its reject rate by more than 75%. This reduces the high overhead of inspectors and rework artists, all of which result in lower costs.

Just in Time.

Traditionally, a thermoformer gets an order, makes the order, ships the order, and then waits. This approach means that there is a built-in delay in fulfilling each new order, and there can be a lot of uncertainty and downtime for the plant. Profile has implemented a different sort of “Just in Time” system.

Instead of waiting for an order, they work with each customer to understand his/her needs over time. They will then schedule production before they get an order, so that when the rush order comes in, they can meet the customer’s initial needs immediately, while they both ramp up for repeat production.

Profile also sizes the production runs to be the most efficient. They base the production run size on the customer demand, the degree of difficulty of the setup, and the physical size of the part, rather than arbitrarily stopping when the customer’s current requirements have been met. Of course, it is possible for Profile to get burned if they have parts on hand without an order and the parts are then discontinued or modified.

But Profile reports that by getting close to the customer and understanding the customer’s usage patterns, Profile can create production schedules that provide the parts right when the customers need them. This keeps the plant running more consistently and often lets Profile “be the hero” when a customer needs parts in a hurry. Over the past ten years, very few parts have been scrapped due to unauthorized overruns.

Customer Service.

While Profile has worked hard to develop a facility and a process that makes high volume production possible, company president Steve Murrill says that these actions alone are not enough. “For us, the key to transforming pressure forming into a consistent, high-volume process is an unswerving focus to customer needs. We have found that a close working relationship isn’t just a nice way to keep clients happy. It is what makes us successful. It is not enough to react to customer needs. We have to anticipate them. We combine knowledge of our process with knowledge of their needs in order to think on their behalf.”

Pressure Formed Exercise BikeBy creating a state-of-the-art facility, by helping clients design not only the part usage, but also to the production process, and by working to anticipate client needs, Profile has been able to break the volume ceiling for pressure forming. They routinely produce many parts in excess of 10,000 pieces per year. the panels for the Life Fitness Exercise Bike illustrates just this. Over 70,000 were produced using Profile’s “Just in Time” strategy.

Early Profile Plastics, Inc.'s Pressure Formed Color Printer Covers for KodakAnd over 5,000 multiple-part Electronic Printer Housings were produced in a matter of months to satisfy a rapidly developing market. Profile prides itself on complex part designs that have been recognized for excellence year after year at the annual Thermoforming Conference. Their motto, “Parts Under Pressure” is really a rallying cry to their employees to never let down and take anything for granted. The pressure is always on their parts and on their operations to maintain a high level of customer satisfaction.

More Whitepapers

Let’s talk about how to make your part right.

Our guiding principle for doing business is simple but powerful: We’ll make it right.

Schedule a Call with one of our experts, or use our Contact Form to start a conversation.