Thinking Inside The Box

Thinking Inside The Box

The GX 1000 B's tables ride on enhanced boxways.

Bridgeport returns to its boxway roots with the introduction of the GX 1000 B vertical machining center. Highlights of the machine include the company's special rigid boxway design that significantly dampens vibration at the cut and a generous 24-in. Y-axis travel not typically found on other comparably priced machines.

Bridgeport, now part of the Hardinge Inc. ( family, says it manufactures its boxways to standards that are higher than other builders'. For instance, the company spaces ribs in its boxway castings at smaller distances than other builders use. Typically, ribs in castings run every 11 in. to 15 in., but Bridgeport positions them every 3 in. to 5 in., nearly doubling the amount of ribs used to provide a solid, stiff base with high dampening capabilities for the GX 1000 B's boxways.

After hardening its boxways to 55 Rc and grinding them, Bridgeport applies a layer of Turcite B, a wearresistant material, to the mating surfaces to reduce friction and extend the life of the boxways. The Turcite B layers have handscraped fits to 16 points of contact and deeper oil channels that are designed to keep more oil between boxway mating surfaces. Bridgeport says these deeper channels are possible because it uses thicker layers of Turcite B than other builders. A volumetric lubrication system automatically keeps all points along the boxway's full length and all the machine's gibs supplied with oil.

All the GX 1000 B's boxway mating surfaces are handscraped to 0.0004 in. The result is machine movement accuracy of ±0.0002 in. and a repeatability of ±0.00008 in. While these accuracies are common among similar type machines, the difference is that Bridgeport builds the GX 1000 B to the stringent ISO 230 specifications that aren't typically used for comparable machines. (See "All accuracies are not the same," AMERICAN MACHINIST, Sept. 1991)

A vertical machining center with a 24-in Y-axis table travel usually is a premium machine, Bridgeport says, but the GX 1000 B has a mid-range price. Table travels for the machine's other axes are 40 in. in X and 22 in. in Z. The rapid-traverse rate for all three axes is 1,181 ipm.

Using mandrels, Bridgeport aligns the GX 1000 B's ballscrews to 0.0004 in. for smooth axis motion and long ballscrew life. Afterwards, the company pre-tensions and stretches the ballscrews to ensure rigidity and lower harmonics and less expansion due to heat during extended duty cycles. Double supports maintain ballscrew alignment over time and in case of impact.

Bridgeport's mid-range GX 1000 B vertical machining center.

More GX 1000 B specs

Spindle horsepower —17.3 hp
Spindle speed — 8,000 rpm
2-speed gearbox (optional)
Table capacity — (X/Y) 47.2 by 19.68 in.
Table weight capacity — 1,540 lb
20-tool automatic tool changer
Fully digital Fanuc iSeries control

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