Pfauter P 400

Gear hobbing uses a rotating hob (a tool that looks like a worm gear with cutting flutes) to generate the involute gear tooth form. As the hob and workpiece rotate in synchronized mesh (hob rotation rate = workpiece rotation rate x (number of hob starts / gear tooth number)), the hob's cutting edges generate successive portions of the tooth flank involute profile. The axial feed advances the hob along the workpiece face width, completing one tooth space before the table index moves to the next tooth position. The generating motion produces the involute tooth form automatically without requiring a profile-form tool - the same hob cuts different numbers of teeth by adjusting the rotation ratio. This is the fundamental economic advantage of hobbing over milling: one hob module size cuts any tooth number in that module.

Pfauter P 400 achievable accuracy in production hobbing (soft gears, pre-heat-treatment): DIN/ISO Quality 6-8 (AGMA Quality 9-10). This is the standard accuracy target for automotive soft-hobbed gears - they are subsequently hard-finished (grinding or honing) after heat treatment to reach the final DIN/ISO Quality 4-6 (AGMA Quality 11-13) required for NVH compliance. For industrial gearbox gears that are used as-hobbed (no subsequent grinding): DIN/ISO Quality 7-9 is achievable with premium TiAlN-coated carbide hobs and careful process setup. High-accuracy hobbing (DIN/ISO Quality 6 or better) requires: rigid machine setup, temperature-controlled environment, premium hob tool quality, and minimal machine wear.

The P 400 uses standard DIN 3972 gear hob tooling in module sizes 1-10, with hob bore of 22, 32, or 40 mm depending on hob OD. Hob types: (1) High-speed steel (HSS) hobs - most common, suitable for most steel materials, wet cutting. Life: 50-500 gears per hob sharpening. (2) Carbide-tipped HSS hobs - increased cutting speed and longer life for production hobbing. (3) Solid carbide hobs - for dry hobbing or hard steel materials. (4) TiAlN or TiN coated HSS - extended tool life, reduced cutting temperature. Hob sources: Gleason, Pfauter original, Profilator, Star Cutter, Maxwell Tool. When specifying a hob for the P 400, provide the module, number of starts, hand of helix, and required AGMA lead accuracy class.

Hob shift is the axial translation of the hob along its own axis during production, moving the cutting engagement to different portions of the hob cutting edge as each portion wears. Manually controlled on older machines, the P 400 CNC automatically programs the hob shift increment and direction to distribute wear evenly across the full hob face width. Benefits: (1) Extends hob life by using the full available cutting edge before replacement; (2) Prevents single-point wear that causes tooth form errors from using a single worn section; (3) Reduces cost per gear by maximizing the number of gears per hob before resharpening. Typical hob shift increment: 1-2 mm per gear or per batch, with total shift limited by the hob face width minus chamfer zones.

Pfauter P 400 (used, $80K-$200K) vs Liebherr LC 3000 (new, $400K-$700K): The LC 3000 represents the current generation with higher spindle speed (enabling higher cutting speed with carbide hobs for dry cutting), better thermal compensation, automation interfaces for load/unload robot integration, and modern control with integrated gear CAM software. The P 400 provides the same basic hobbing capability at much lower capital cost - appropriate for shops with moderate production volume where the speed and automation advantages of the LC 3000 don't fully justify the 3-5x higher capital cost. For high-volume automotive production, the LC 3000's dry cutting capability and cycle time advantage may justify the premium. For job shops and industrial gear production at moderate volume, a well-maintained P 400 is economically compelling.