Edge-Polishing Machines: The Clear Advantage
Manually polishing plastic edges is tough and time-consuming. The moment an individual begins handwork on an edge, he or she introduces distortions and deformities in the piece: slight bends, rounded corners, microscopic air pockets, and other defects that compromise the quality of the product. Despite your best efforts, you cannot sand a three-foot edge into a truly flat plane by hand. And working with outdated technologies can cause many of the same problems.
New machines and tools offer plastics manufacturers, fabricators, and distributors updated capabilities for clean corners, straight edges, true joins, and a surface that’s ready to be glued or viewed. Edge-polishing machines for flat or contoured edges can reduce the risk of error in the production and fabrication of plastic components, reducing cost while increasing production and quality.
FLAT EDGE POLISHERS
A dedicated edge-polishing machine is used exclusively for flat edges and bevels. (Contours, interior radius and pocket polishing can be achieved on a CNC polisher.) Edge-polishing machines are used for transparent plastics, such as PMMA, GS, PMMA XT, PC, PETG, and SAN; technical plastics, such as PP, PE, and PS; and decorative plastics such as composite sheet and CORIAN®.
In addition to solving many of the problems of manual edge polishing by eliminating distortion and producing a truly flat edge, these machines offer several other benefits.
First, they increase production by greatly reducing the amount of time needed to polish a single piece. While it might take 45 minutes to manually turn a saw cut edge into an ultra-clear finished product, the same or better result can likely be achieved on an edge-polishing machine in 60 seconds or less. The ability to stack and polish multiple pieces at one time further improves production speed and efficiency.
Second, the newest edge-polishing machines include features that dramatically reduce operator error. The Weeke ABP 155 or 310, for example, includes a database that prompts operators with a series of questions: What material am I finishing (acrylic, polycarbonate, phenolic, etc.)? What finish do I want (ultra-high gloss, medium gloss, matte/frosted, etc.)? Once the material type and finish are selected, the database automatically calibrates the machines parameters for feed speeds, RPM and other variables. It also directs the operator how to set up the required tooling. This user-friendly process reduces operator error and saves labor costs.
Finally, edge-polishing machines will produce a flat edge no matter how inaccurate the initial cut is. Ideally, the piece will have been cut to size on an accurate panel saw with a true edge, as high-quality saw-cut edges produce the best results. If the lines are straight and the corners are square, the process is more efficient; if it’s not, multiple passes may be required. For a truly efficient process and a high-quality end product, look at every process in the production chain: How accurate is the material I am bringing to the edge polisher? How accurate is the material my supplier brings to me?
For fabricators that join acrylic, polycarbonate, and other plastics, an edge-polishing machine produces a flat surface for a high-quality glue joint that cannot be achieved manually. This flat edge is free from voids, air gaps and other deviations that can interfere with the fabrication process by introducing visible imperfections to the plastic. These machines are capable of producing a rough, or frosted/matte, finish to help your choice of solvent weld bond to both pieces.
Thanks to the exacting tolerance and true angles made possible by edge-polishing machines, many fabricators are creating seamless corners by joining two 45˚ angles together, effectively hiding the polished edge and reducing the fabrication needed to produce a finished product. In contrast, creating a corner by joining two perpendicular edges at 90˚ leaves one cut or polished edge exposed, requiring additional sanding and buffing to achieve the finished look.
For point-of-purchase applications
Point-of-purchase and retail fixture manufacturers can similarly benefit from an edge-polishing machine. The ability to create computer-aided true angles (some machines can bevel at angles of up to 48˚ degrees) with a flat edge saves time and reduces imperfections introduced by manual polishing.
Top-quality, ultra-clear or high-gloss edges are available with a single pass. In many instances (depending on the application and client requirements), no manual follow-up work is needed. For more demanding visual appearance, some manual sanding and buffing may be required—but a polishing machine will quickly bring you most of the way there.
CONTOUR EDGE POLISHERS
As mentioned earlier, contour edge polishing can be accomplished using a CNC router. In this process, a solid carbide tool is used to remove the majority of the raw material, then monocrystalline or polycrystalline diamond tooling is run along the edges at approximately 22,000 RPM, removing 0.2 mm of material and creating a high-gloss or ultra-clear edge.
Contour edge polishing produces only a high-gloss or ultra-clear edge; frosted or variable glosses are not available through this process. Most contour polishing is used for flat-face, 90˚ edge corners, 45˚ bevels, and bottom polishing for pockets. Depending on the machine, 5-axis polishing is possible.
Using the proper tooling is especially important for contour polishing. Monocrystalline diamond tools are preferred for contour polishing; these are expensive, but many fabricators have found that the value is worth the cost. More affordable polycrystalline diamond tools can often be used instead, and tend to last at least three times longer than monocrystalline tools. Many highly regarded companies, such as EURACRYL, offer proven tooling options for quality edge-polishing machines.
Additionally, tool holding needs to be as accurate as possible. Some older machines or components that use a spring collet may need to be upgraded to a hydraulic collet or a heat-shrink tool holder. Using new or upgraded equipment eliminates one of the variables that contributes to runout, which is detrimental to tool life and product finish, and can create unnecessary heat.
Because there are more variables involved in contour polishing than in flat edge polishing, it requires more operator involvement. Factors such as interior and exterior diameter, cut lengths, angle degree, inside radius, material thickness, and application directly impact the selection of appropriate tooling and machine parameters.
Potential increases in production quality, speed and output—and the decreases in labor costs—cannot be overestimated. A properly trained operator will be able to remove approximately 95 percent (and, for some applications, 100 percent) of the handwork from the process. Polishing tight inside radiuses and bores by hand can be especially time consuming. Using a contour edge-polishing machine can realistically reduce a three-hour process to less than 15 minutes.
SAVING WITH AN EDGE POLISHING MACHINE
Many plastics fabricators choose to go without an edge-polishing machine in their shop. Citing cost of entry and up-front expense, they continue to polish edges manually, flaming or sanding and buffing them by hand—despite the slow process, comparatively expensive labor costs, and likelihood of introducing defects to the piece.
Yet an honest measure of real changes in the production process reveal that edge-polishing machines contribute to significant costs reductions, resulting from labor cost savings, higher and more consistent product quality, increased productivity. Even with a modest up-front investment, an edge-polishing machine can provide a clear advantage for your business.
The same statement is as true for your business as it is for creating an ultra-clear edge: an edge-polishing machine won’t get you 100% there, but it can take you closer.
For more information on edge-polishing technologies and techniques, please contact James Swanson