Numerical Control Programming
Chapter 1
What Is Numerical Control & What Does It Do?

What are the Disadvantages of N/C?

Disadvantage 1: N/C Machines require a large investment.

The initial investment ranges from 25 to 50 thousand dollars for a small CNC mill on up to half a million dollars or more for a large machining center. That means they must be kept busy to pay off. Sometimes it means they must run two or three shifts per day and on weekends. Small firms often cannot afford the investment, especially when interest rates are high.

Disadvantage 2: N/C machines don't program themselves.

Programmers are highly skilled individuals and good ones are not easy to find. They command premium salaries. This problem can be partially offset by using computer-assisted programming (CAM) software to speed up the process and increase programmer productivity.

Disadvantage 3: High maintenance costs.

N/C machines can be very complex. The machine tool must be kept in tip-top mechanical condition to take advantage of N/C's inherent accuracy. The controller, while requiring relatively little maintenance, is an electronic device. Occasionally a switch, capacitor, transistor, or integrated circuit will fail. N/C machines that are down for repairs are not producing any income, while the expense clock keeps ticking. Repairs must be prompt to get the N/C back into production. Therefore maintenance personnel must possess expertise in both the mechanical and electronic realms, a combination not easy to find. They tend to command top salaries.

Disadvantage 4: Not cost effective for low production levels.

A skilled machinist could make one or two parts of a not-too-complex geometry in less time (and at lower cost) than it would take a programmer to write and debug a program for an N/C machine. However, as geometric complexity increases, N/C becomes more economical.

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Updated Jan. 9, 2002
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