Palmary CGC-25

Palmary occupies the mid-market tier of cylindrical grinding — Taiwan-built machines with solid specifications at 40–60% below European premium brands. Studer (United Grinding, Switzerland) represents the top tier of cylindrical grinding: highest achievable tolerances, most advanced software (StuderGRIND), deepest global service network, and commensurately higher price ($200,000–$500,000+ for comparable class). Palmary CGC-25 achieves similar dimensional tolerancing in production (±0.003–0.005 mm) at a fraction of the price, with a trade-off in software sophistication, maximum achievable finish, and brand prestige. For job shops and manufacturers where Studer precision is not required and where capital cost is the primary constraint, Palmary offers genuine value.

Plunge (or infeed) grinding feeds the wheel directly into the workpiece at a fixed Z position to grind a single diameter — the wheel plunges on X until the target size is reached. This is the fastest method for grinding a single OD diameter but requires the wheel face width to equal or exceed the feature width being ground. Traverse grinding moves the wheel across the workpiece (Z axis) while feeding on X, allowing the wheel to grind diameters wider than the wheel face by traversing back and forth. The CGC-25 supports both methods; plunge grinding is preferred for high-volume production of single-diameter parts, while traverse grinding is used for longer diameters and stepped shafts where the wheel traverses between shoulders.

Water-soluble metalworking fluid at 4–6% concentration in the machine's flood coolant system is standard for steel and alloy grinding. The coolant is delivered through a flood nozzle positioned at the wheel-work interface at a flow rate of 10–30 L/min. Use a coolant specifically formulated for grinding (not cutting) — grinding fluids are formulated to control foam and fine swarf suspension. Tramp oil contamination from the machine (way oil, hydraulic oil) should be controlled with a skimmer. For stainless steel grinding, a sulfur-free coolant is recommended to prevent staining. Replace coolant per the fluid manufacturer's maintenance schedule — contaminated coolant causes rust, odor, and degraded surface finish.

The standard CGC-25 with 45 m/s wheel speed is not suitable for vitrified CBN wheels, which require 80–120 m/s peripheral speed to operate in their designed cutting conditions. Running a CBN wheel at 45 m/s produces poor stock removal, rapid wheel wear, and inferior surface finish compared to optimized CBN grinding. Palmary offers high-speed spindle options on some CGC models capable of 63–80 m/s — consult Palmary's specification sheet for the specific spindle option. For shops requiring CBN capability for hardened steel production, the standard CGC-25 is best used with conventional aluminum oxide or SG (seeded gel) abrasive wheels, which perform well at 45 m/s for most precision grinding applications.

The CGC-25 provides an interface for optional in-process gauging systems from Marposs (Marposs E35 or similar) or equivalent suppliers. The gauge head mounts on the machine and contacts the workpiece OD during grinding, continuously feeding the measured diameter to the CNC. The CNC uses this feedback to switch between rough, finish, and spark-out grinding phases automatically when target diameters are reached, eliminating manual measurement stops. In-process gauging is strongly recommended for production applications (same part, large quantity) where size consistency is critical — it is less necessary for job shop work where each part may be a different diameter requiring manual setup adjustment.