Custom CNC control engraves control panels to order
A custom computer numerical control (CNC) is the key to a unique router that helps Glastonbury Engraving (Glastonbury, Conn.) efficiently produce custom-engraved laminated control panels in very small quantities to meet customer requirements.The new machine has significantly reduced the cost of producing control panels, while remaining relatively inexpensive, because it was built complete...
A custom computer numerical control (CNC) is the key to a unique router that helps Glastonbury Engraving (Glastonbury, Conn.) efficiently produce custom-engraved laminated control panels in very small quantities to meet customer requirements.
The new machine has significantly reduced the cost of producing control panels, while remaining relatively inexpensive, because it was built completely with standard components. The control includes a PC-based motion control card, custom software that converts CAD files into motion files, and a crossed roller slide that provides z-axis travel to maintain constant cut depth despite possible material distortion.
Since 1971, Glastonbury engraving has been a leading supplier of panels to the printing, paper converting, and plastic extrusion industries. The firm specializes in providing one-of-a-kind solutions to meet its customers' individual needs.
Chuck McKinney, Glastonbury's plant engineer, says the firm has worked hard over the last several years to develop the equipment and processes needed to produce custom-built panels, while remaining cost competitive with off-the-shelf panels built in much larger quantities by competitors.
Easier operation, small quantities
Mr. McKinney states, "This makes it possible for developers of converting equipment and other machinery to add intelligence to their panels by providing diagrams and text that make their machines easier to operate. What our customers want is the ability to produce custom panels with a wide range of complicated designs at a price that is very close to plain standard panels. They don't want to keep a lot of inventory on the shelf. To meet this requirement, we need to be able to efficiently produce panels in small quantities often only one at a time. Yet, the panels need to match up perfectly with those we have produced in the past. Clearly, the only possible way to do this is through CNC machining.
"However, a traditional CNC machining center would be a very poor fit for our needs. The main problem was that we would have had to pay a minimum of $100,000, for a machining center with a working area big enough to handle our larger panels. This type of machine really would have been overkill for our work because it is designed to handle much heavier machining tasks. Another concern was that the laminate materials used to produce panels have a tendency to distort when laid out on a table for cutting. The tools used for engraving have angled sides, which means that if the workpiece lifts off the table, both the width and depth of cut will be too great. We needed some method to detect the location of the material and adjust the position of the tool."
Re-using existing programs
Glastonbury's team decided the only way to meet all these requirements was to build its own machine, custom control it, and minimize design time by using off-the-shelf components wherever possible. A base table from Techno-Isel (New Hyde Park, N.Y.) provides a 4 x 8-ft work area, sufficient to meet requirements. The Techno table features a positioning accuracy ofn, low wear, and long life.
Mr. McKinney designed the control system for the new machine, based on a $2,000 Acroloop ACR-1500 four-axis PC-Bus controller card. ACR-1500 is a 32/64-bit, floating-point, multitasking DSP-based motion controller with 48 TTL digital I/O points provided on 50-pin headers compatible with standard 50-pin optical-isolation boards. The controller card can perform independent or coordinated axis moves, including circular, linear, sinusoidal, elliptical, helical, and spherical interpolation in any combination of up to four and eight axes. In addition, the user can define up to eight coordinate systems for as many as 24 programs (16 motion and eight PLC programs). In typical applications, the preemptive multitasker will execute motion profiles and ladder logic PLC simultaneously.
There was an inventory of more than 1,000 programs previously written in C to be used on the new machine. Consequently, Mr. McKinney and Alex Sperduti of Microdyne (Plainville, Conn.) developed a program to convert these files to the motion files required by the Acroloop controller card. These files utilize standard G-code used by most CNC machines.
Del-Tron Precision Inc.'s (Bethel, Conn.) crossed roller slides met another important requirement of this application—very high accuracy. It provides straight-line accuracy of 0.0001 in. per inch of travel when measuring the line of travel to a master straight edge, using a gauge or indicator mounted on the slide. Positional repeatability of the slides is 0.0001 in. The coefficient of friction of these devices is only 0.003. At rated load capacity and moderate speeds, expected life is 10 million inches of travel. The expected life at one half the rated load is 100 million inches.
Small premium for complexity
"This machine has turned out to be the best we have ever seen for panel engraving," Mr. McKinney says. "We can produce any type of panel the customer wants with very short setup time simply by loading in a new program. Customers typically send us their designs in AutoCAD files, which means we only have to spend a few minutes programming each design. The size of the new machine and power of its control system means we can now produce very complicated custom panels at a very small premium to standard designs. For example, we recently did a panel with a flowchart that shows the entire web path of the converting machine in multiple colors engraved on the console."
Jerry Fireman, president, Structured Information and Gary A. Mintchell, senior editor, email@example.com
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