MICROMOLDING- The Growth Market for Injection Molders in the Near Future
06/01/04:
Abstract
In our world of manufacturing today, there is a need for smaller and smaller components that fit into tiny circuitry, control the smallest droplet, or channel the smaller fiber optic light source. New advances in microfluidics, biomedical applications, micro sensors, microscopic implantables, and ultimately nanotechnology are growth and research initiatives that are requiring us to rethink how we manufacture using conventional methodology. Micromolding is an unconventional manufacturing method that can serve all of these initiatives. Growth and research, however, does not come without its challenges. This paper explores these challenges from a tooling perspective as total market potential for micromolded components. Several case studies and return on investment analysis are included that compare conventional molding methodology to a micromolding approach.
Introduction
Largely debated often misrepresented, true micromolding is defined as molded parts that are fractions of a pellet, and/or weighing fractions of a gram, and/or having wall thickness of less than 0.005”(0.127mm), and/or having tolerances of 0.0001-0.0002” (0.025-0.050mm). In most cases, micromolded components are a combination of some or all of these attributes.
Where is the need for micro molding coming from? If we look at the world of manufacturing in general, everything is getting smaller and smaller- fitting into tiny circuitry, controlling the smallest droplet, channeling the smallest fiber optic light source, etc. These problems require us to rethink how we manufacture in conventional methods.
Growth markets such as micro surgery- tiny parts on the ends of catheters, implantables such as eye drains and implants, filters behind the eye, ear tubes, etc. are all applications that require high precision micromolding. Biomedical labware such as 96 Well, 384 Well, and 1536 Well plates, all fitting into a 3 x 5” footprint have now forced research into lab-on-a-chip applications for hundreds of thousands of analysis in the same footprint and all stored computerized on a chip for future cell interaction. These small micro channels are all made possible from the advances in micro machining techniques using MEMS (Micro Electrical Mechanical Systems).
Microfluidics, (the liquid subset to MEMS), is the ability to move, mix, pump and control fluids on a microscopic level. Researchers in industry, government and academia are applying microfluidic technologies in such applications as protein separation, drug development, diagnostics, and environmental monitoring.[1] Another growth industry breaking out of the new product category and climbing into the growth, cash cow product life chart are micro sensors. These micro sensors, many found in GPS systems are being used in automotive behind the dash applications as well as in PDA’s and Cell phones.
The next step after micromolding is nanomolding. Nanotechnology (parts being 10 to the minus 9 in size) will have many uses from nano-robots that are envisioned to be injected into ones bloodstream to displace cancerous cells with nearby good cells to uses in khaki pants that made fabric that resist staining. Federal funding for nanotechnology increased by 17% this fiscal year[2] and many universities, including the University of Massachusetts-Lowell, WPI, Columbia, MIT, Princeton, and NYU, to name just a few, have been awarded grants to work in nanotechnology. These markets are a tremendous opportunity for U.S. companies to grow, not just stay alive. Micromolding is a serving all of these growth initiatives. Growth, however, doesn’t come easily. It takes first a visionary at the helm to see its potential, some risk-takers to purchase equipment and technology to set the stage, and then it requires the people who execute, that have experience with the challenges of micromolding.
From the initial concept stages of designing micromolded components, many challenges exist to manufacture them. Each and every step of the way, design and manufacturing engineers are paving the way by developing new technologies or using existing technology in a way they never did before in order to manufacture micromolded components. For example, even dimensioning micro parts on drawings or CAD, usually in thousandths of an inch must be converted to millimeters and/or microns, a paradigm shift for many engineers. Further down the design stage is conceptualizing the flow of the polymer in the mold. Most mold flow specialists are not versed in micromold flow analysis and therefore this is not yet commercially available as a tool for part designers. Figure 1 and Figure 2 show the known flow in the mold using a progressive short shot. Figure 2 shows the Mold Flow® analysis completed by the University of Massachusetts-Lowell Plastics Engineering Department, showing the effects of the last place to fill that match the known last place to fill in Figure 1. The physical properties of microfluidics offer challenges to researchers and product developers alike. Conventional methods of simulating mold flow in macroscale principles do not apply at this scale, therefore it is not possible to simply scale down with existing software and expect the same results as seen with larger parts. Fluid mechanics are dramatically different by virtue of the gate sizes the polymers are forced into, thus the shear heat generated by the gate must be taken into consideration much more so than macro sized gate designs. Other challenges include:
- Finding limitation of what is possible to mold, wall stock, L/D ratio, and gate sizes.
- Multiple cavity
- Using techniques developed by other industries (semiconductor, telecom) to improve capabilities
- Acceptable tolerances in “conventional” sized molds are unacceptable in micro molds
- Accurate positioning to smaller tolerances
- How all these vary with each material
- Part handling
With each micromold project comes a level of impossibility for many micromolders and micro moldmakers, but each project completed successfully brings a new level of confidence for the next one, more than likely more difficult than the last. Each smaller micron achieved, although barely measurable, is a huge accomplishment in plastics technology, paving the way for smaller and more complex micro components, pushing the envelope of theory to practice.
Figure 1: 
Figure 2:
® image courtesy of University of Massachusetts-Lowell Plastics Engineering Department
Description of Tooling Equipment And Processes
Many tooling processes are available to manufacture tiny geometry for mold cavities and cores. The methods employed for metal removal vary based on complexity of shape and steel tolerance requirements. This paper discusses a few of the many available methods and the pros and cons of each.
LIGA, an acronym for lithography is a 6-step process. A glass/chromium mask is created from a CAD file. The mask is used to build a master from SU-8, a commonly used photosensitive epoxy from MicroChem Corp. Layer by layer, the epoxy exposed through the mask is hardened by the UV light source. Curing follows. The finished master is electroplated with 2 to 3 mm of nickel or a nickel alloy. The master is destroyed and the resulting mold cavity is lapped down to finished thickness with tabletop lapping systems. [3] LIGA’s benefits include excellent surface quality and cost savings for multiple cavity two-dimensional geometry. Its challenges are maximum cavity depth of 1.5mm (0.060”) and since it’s a layer process, only two-dimensional shapes can be produced with no drafting surfaces.
Laser micromachining is another method for making micromold cavities. Using a precision laser, holes and other simple shapes can be manufactured. The advantages of laser micromachining are very fast metal removal rates, very smooth interior hole surfaces, and the process works on any material-ceramic, plastic, glass, diamond, and steel. The challenges for laser micromachining are exit burrs from the laser exit and subsequent secondary operation to remove them, the possibility of micro cracks in the material, and a maximum cavity thickness of 0.060” (1.5mm).
EDM (Electrical Discharge Machining) is another method of producing micromold cavities. EDM is a non-contact method that uses an electrode (mirror image of resulting steel) made from a electrically conductive material (in most cases graphite or copper). EDM cavities are produced in heat-treated, hardened steel producing tight-tolerance components without the need to heat treat after machining, causing no distortion to the workpiece. EDM works well for very hard materials and the electrode never touches the steel, it’s a non-contact machining method, therefore less stress is introduced to the steel during this process than many other micromold machining methods.
The most beneficial used of EDM for manufacturing micro mold cavities is that the electrode is produced and burned in the same setup using an orbit path of the electrode to “burn” away the electrode shape, allowing the component setup to stay in the same machine, therefore not violating the tooling setup by removing components and placing them back in again. This method of manufacturing electrodes addresses the need for very tiny three-dimensional shapes. Wire EDM is very similar to conventional EDM, except the wire acts as the electrode. Wires down to 0.001” (0.025mm) can burn through shapes straight or tapered at 30 degrees. In either case, EDM and Wire EDM are versatile methods for manufacturing micromold cavities.
It’s important to note that all machining methods, including milling, grinding, turning and some others not mentioned within are all necessary for particular applications of micromold manufacturing. Each piece of steel comprising a micro mold requires an individual process plan including processing method to hit the tolerances required for molding wall thicknesses of 0.0015” (0.038mm) or tolerances approaching 0.0001” (0.025mm).
Presentation of Data & Results
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Figure 3: 
Figure 4: 
Figure 5:
This medical cannula (Electrode for cavity shown in Figure 3, Molded part shown in Figure 4) was originally manufactured using heat forming with four additional assembly steps to forge the flange area, form the tip at the end, and trim. This part had four secondary operation stations with four operators. Due to the part geometry, this part was not known to be manufacturable using injection molding methods. The inside diameter was 0.007” (0.18mm), the outside diameter was 0.015” (0.36mm), and the resulting wall thickness was 0.004” (0.10mm) over 0.400” (10.0 mm) long, very much exceeded known L:D ratios in theory. This part was molded successfully clearing profit of $161,000.00 in direct labor savings over five years after the micro mold and micromolding machine returned in 23 months time.
Figure 6: 
Figure 7:
This nozzle component (Figure 6) was currently being molded in a 16-cavity conventional mold, which ran a 6-second cycle. This 16-cavity mold was compared to a 24-cavity micro mold, running in a micro molding machine in a 5 x 3” frame (see Figure 10). The micromold, because the runner is literally toothpick-sized, achieved a 5-second cycle, resulting in an 8-month return on investment, and profiting $713,000.00 in a 5-year period.
Figure 8: 
Figure 9: 
Figure 10:
These micro parts (Figure 8) were run in and 8-cavity conventional mold running 20 seconds. Issues existed with runner curling downstream automation and assembly problems arose, resulting in additional labor to the production line to aid in runner removal. This problem was solved using a new 8-cavity Hot Runner micro mold, with a Polyshot® hot runner manifold, achieving an 8-second cycle, and a 5.3 month return on investment for the mold only (this company was able to use an existing molding machine). For comparative purposes, another $100,000.00 on a molding machine produced a return on investment of 7.7months. After 5 years, this project resulted in a profit of $1,500,000.00 U.S. with this new micromolding process.
Application of Micromolding
Where is the need or growth of micromolding coming from? Micromolding is increasingly raising interest of injection molders because it fits on the product life cycle chart in many categories. (See Figure 11) Many of the products that have left this country to be manufactured elsewhere, whether to other countries or to any other competitor have historically been the mature products (see Circle #2 in Figure 11). Examples of such products are computer components, consumer and industrial goods. The sales of these products are starting to decline so they are forced to cost reduce just before they fall off the product cycle or get redesigned for cost purposes.
The growth products (see Circle #4 in Figure 11) are the cash cows of our business, these products are usually high volume products that are growing and feeding the business with profits. Some examples of micromolded growth products are GPS (Global Positioning System) sensors, insert molded grounding wires, and minimally invasive surgery components.
New products (see Circle #5 in Figure 11) are the products never to be seen before, never known to be manufacturable before, and are the future of molding growth for many companies that choose to implement micromolding. Examples of new products being researched or launched at this time are microfluidic plate applications, biomedical labware, in vivo medical implants, and research and test products for nanotechnology. Growth industries, new products, and continuous cost improvements are all initiatives that will sustain our future molding operations. Micromolding is an unconventional, yet largely necessary manufacturing method for all three of these initiatives.
Figure 11 
Conclusion
Many of the micromolding technologies and markets presented herein are currently under way, but in their infancy stages in terms lower volume applications. In order for micromolding to grow exponentially, more educational venues are needed to let product designers and engineers aware of their existence and possibility for manufacturing. What is also evident is that microfluidics, biomedical, electronics, and minimally invasive surgery applications are fueling the need for micro components today and in the next few years. This article presents a variety of challenges of micromolding and it is interesting to note the cross-disciplinary nature of this relatively new technology. The various players in this industry are combining engineering, micromachining, dimensional inspection, and product handling methods to create the portfolio needed to carry this technology in the future. The need for the each area of expertise to come together is paramount to allow micromolding to fully integrate into injection molding facilities abroad. This will result in large industry gains for the future of the plastics industry.
References
Carl Kirkland, (2002, June). Tiny molds, big marketing challenge. Injection Molding Magazine, Editorial Library Online: www.immnet.com.
M C Roco, (2002, September). “As the World Goes Nano, Here’s a Look at International Funding JOM: The Member Journal of The Minerals, Metals & Materials Society, Editorial Library Online: www.smalltimes.com.
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[1] http://www.micronics.net/news/news_release_detail.php?nr_id=34
[2] M C Roco, (2002, September). “As the World Goes Nano, Here’s a Look at International Funding JOM: The Member Journal of The Minerals, Metals & Materials Society, Editorial Library Online: www.smalltimes.com.
[3] Carl Kirkland, (2002, June). “Tiny molds, big marketing challenge”. Injection Molding Magazine, Editorial Library Online: www.immnet.com.
[4] Product Life Cycle courtesy of Graphic Technologies, Inc, http://www.graphtek12.com