If you had a choice, which machine would you choose to meet your spring production requirements?
(A) A machine that requires:
1. An operator with a highly developed set of skills, most often learned through experience.
2. An operator who “sees” or intuits the effect cam shape, size and position will have on the machine’s actions.
3. A machine that has few, if any, pre-sets to determine proper tool array or setting position.
4. A machine that is, in most cases, relatively limited in production rates.
5. A machine that demands incrementally longer and more difficult setups to produce complex shapes in springs.
or (B) A machine that:
1. Allows even a novice to make simple parts within a few hours.
2. Eliminates the need for complex cams.
3. Has pre-sets and functions that eliminate the need for specially shaped tooling while offering high repeatability in setting procedures.
4. Enhances production rates with no loss of accuracy.
5. Greatly reduces setup times on both simple and complex parts.
Obviously, we are talking about some of the differences between CNC spring coilers (as designed primarily for compression springs) and the old-fashioned mechanical coilers. As King Mongkut says in The King and I, “Etcetera, etcetera, etcetera.” The list of advantages for CNC machines goes on and on.
Why not CNC?
Equally obvious are the reasons more of these machines are not in use in North America today. Simply put: cost. Ironically, the transfer of spring markets in North America to offshore producers (especially China) has caused a great increase in the need for production machinery in these new markets. In virtually every instance, this need is being met by the purchase of CNC coilers. Ergo, we find ourselves faced with a stagnant market and competitors, both here and abroad, who are armed (in many cases) with better, more efficient tools. Add to this today’s increasingly demanding customers: “Give me better quality, faster deliveries, match your schedule to meet my needs – and by the way, lower your prices.” Welcome to today’s spring industry!
We live in an age where cell phones, Wi-Fi (wireless networking), e-mails, EDI (electronic data interchange), digital image transfer, etc. are part of our daily business regimen, yet we rely on production equipment whose basic technology was first put into widespread use over 80 years ago! I would suggest that, as the conduct of our business on a daily basis has changed, so too should the way we view our ways of producing parts. The old methods used to calculate cost vs. benefit ratios do not adequately reflect the demands of this new marketplace. Nor do they (the formulae) consider the consequences, both favorable and unfavorable, of a failure to modernize. But, again, the advantages of this modern equipment do not come without cost.
Add up the Benefits
It’s difficult to discuss precise cost vs. benefit because of the wide differences in price, function and features in the machines available today. For example, a new three-axis CNC in the 2mm size range could probably be purchased for around $55,000, plus or minus. An 11-axis machine in the size range may cost over $100,000. Typically, as the number of axes increases, so does the versatility, ease and repeatability of setup but so too does the cost. However, in virtually every instance, the following facts hold true:
• Setup times will be decreased by a minimum of 50%.
• Special tooling, such as custom-ground arbors (mandrels), pitch tools and coiling points, is almost universally eliminated. The savings in labor, coupled with the elimination of dedicated tooling, is quite significant.
• Repeat setup times will be decreased by the same factor.
• Production rates will be higher. In some cases we at RK have seen, the increase has been well over 200%.
• The increased machine accuracy in a well-
constructed, properly setup CNC machine will lead to dramatically improved part quality. In most cases, product scrap rates can be significantly decreased or even eliminated entirely.
• With the use of advanced 2D and 3D control devices, whether integrated or add-ons, automatic measurement AND correction of spring length, diameter, coil pitch and other relevant dimensions is possible with no loss of production speed. Safeties built into these systems make true “lights out” production a reality.
The modern CNC machine presents the owner with a “win-win” situation.
Special tooling, such as custom-ground arbors (mandrels), pitch tools and coiling points, is almost universally eliminated. The savings in labor, coupled with the elimination of dedicated tooling, is significant.
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Assume a situation where your company must produce a variety of small orders on straight compression springs (less than 500 pieces), each having different wire sizes and spring diameters, but all within the wire range of a given model of CNC machine. We have documented that, when used with inline stress relieving, it is possible to complete up to six of these orders in a single eight-hour shift on a nine-axis machine. Even if one is using a three-axis machine, it is still possible to more than double the output of a conventional machine.
On a repeat order, the conventional machine requires virtually the same amount of operator input as the original setup. The full CNC machine requires only minor adjustments caused by differences in raw material. With intermediate-to-long runs, the same savings in setup time occurs. However, there is the added benefit of dramatically improved production rates. Typically, the production rates will be a minimum of 50% faster, with increases of 200% (or even greater) quite possible. If the product as produced on a mechanical coiler requires a selector (sorter) gauge system, it is possible that it may not be required on a CNC, or, at the very least, scrap rates will be greatly reduced. The savings here is twofold: scrap rate reduction and higher piece-part yields. As mentioned earlier, the inclusion of 2D or 3D gauging devices in a CNC coiler makes unattended operation a reality.
Work the Numbers
Be specific as to how they relate to your individual situation. After the savings in man hours for setup and operation, reduced scrap, increased daily output, the elimination of special tools and cams, and greater flexibility in scheduling are added up, we think you will be surprised at how easy it is to justify the expense incurred. Not included in the equation are the possible increase in customer satisfaction and the major positive effect on employee morale.
What machine to buy? This will depend on your individual situation, such as the applications you have in mind, the features you require and, unfortunately, budget. When selecting a CNC, look with an open mind at functions and features, and examine construction details with a critical eye. Whatever your choice, you can expect to see the benefits, both tangible and intangible, as described in this article. These benefits will inevitably lead to increased profitability – a tough commodity to come by in these challenging times.
Chris Dix’s entire working career has been in the spring industry. Starting on the shop floor, he worked his way up to managerial positions with several different spring companies. He is currently the general manager of RK Trading Co., a distributor of machinery and testing devices to spring manufacturers. Readers may contact him by phone at (847) 640-9771 or e-mail at rkinfo@sbcglobal.net.
