The Page 1 article titled ``New molders reject old machines'' written by Clare Goldsberry in the Oct. 14 issue grated on me enough to elicit a response. While I agree that the microprocessor controllers we have been seeing for the last 15-odd years are wonderful enhancements to our equipment, they are not the technological marvels one may think after reading this article. The injection molding press is still, all things considered, a fairly crude piece of equipment. Its basic function is to keep a mold closed while plastic is injected into it at very high pressures.
As an example of an industry that has truly changed with this technology, look at the metal machining industry. Before the advent of the microprocessor controller, a milling machine was also a fairly simple piece of equipment. Amazing things can be fabricated from a manual milling machine, but only with the assistance of a highly skilled machinist who is responsible for controlling the X, Y and Z axes of the bed and quill to form a close-tolerance, high-precision part.
Bring in the microprocessor controller along with a few servo drives and we end up with a truly new, revolutionary piece of equipment. This new computer numerically controlled milling machine can not only machine a close-tolerance part, but can do it faster and more reliably than even the most skilled machinist.
I work in a shop with 20 molding machines of various vintages. Many are early 1980s models with manual controls (PC-3s). A few of the older machines were upgraded with Maco digital controls with early cathode-ray tube displays, and we have four machines that are nearly new, fully microprocessor controlled. We are an FDA-regulated, proprietary molder of disposable medical devices - not the easiest molding around.
Do we get better performance out of the new machines vs. the older machines? For the most part, no. As a proprietary molder who runs some 150 molds year after year, we have a very good handle on the performance of our machines and molds. As with all molders, we run a few pretty lousy molds, some being the better part of 20 or more years old without having had a major refurbishment. The designs of some of these molds (or the parts themselves) are less than ideal - no balanced runners, no guided ejection system, very early hot-runner systems, etc. These are the kind of molds most custom molders also see and run on occasion - they may not want to run these kinds of molds, but for one reason or the other, they run them anyhow.
Do these molds run better in a microprocessor-controlled machine or in a manually controlled machine? It makes no difference. A contradictory paragraph in the article stated that ``90 percent of getting a good part lies in the mold'' - a statement that most of us molders wholeheartedly endorse. A poorly designed and built mold, or a good mold with a poor part design for injection molding will run like garbage even in that new whiz-bang, quad Pentium Pro 200-MHz, full-color CRT-controlled, Swiss-watch-company-built machine you just purchased to run these ``bad molds.''
How about that new, all-stainless-steel tool with all the best components money can buy just in from that megabuck tool shop down the road? I've got a 150-ton machine built in the early 1980s with manual controls, and a new 150 with a color CRT display that is fully microprocessor controlled. Which machine should I run this mold in? Assuming your older machines have been properly and consistently maintained and you have trained and experienced operators/technicians - it just isn't going to matter that much.
The new machine will be faster to set up. You probably will have statistical process control output and charting capabilities. This new machine will have the ability to see what is going on as the molding machine is cycling.
You can set up multistage injection, multistage holding, and multistage just about anything else, for that matter. The new machine may even have ``closed-loop'' design to provide feedback to the controller to allow for more consistent process control shot to shot. All great stuff indeed. But faster? A little bit, sure, but not much, unless the press was specifically designed for high-speed operation with hydraulic accumulators or other such devices - most of which also were available as options back in the 1970s and 1980s.
The injection molding industry still has plenty of room for the entrepreneur. The entrepreneur without the money to buy new presses, or the individual who doesn't want to have thousands of dollars' worth of machine payments still will be in the market for those old machines.
If someone is giving them away, I, for one, will be more than happy to take a well-maintained, late 1970s or 1980s machine off anyone's hands who will be setting them out to pasture. Microprocessor-controlled equipment is not required by the FDA's Good Manufacturing Practices, the federal government's military specifications or even ISO 9000. Quality or how one is able to compete in the marketplace has much less to do with the vintage of your production equipment than how you operate your business as a whole.
Lofgren is a molding supervisor at Kendall Health Products Co. in Ocala, Fla.