自由锻件与模锻件怎么选｜Open-Die or Closed-Die Forging: How to Choose

摘要：两种工艺没有绝对优劣：量决定成本，形状决定可行性。按批量、精度、交期、总成本四个维度给出选择路径。
Abstract: Neither process wins absolutely: volume decides cost, geometry decides feasibility. A path through volume, precision, lead time and total cost per piece.

正文： 客户拿着图纸来问锻件，第一个分岔路口就是自由锻还是模锻。选错方向，贵一倍是常事，交期翻倍也不少见。
Main text: Every forging enquiry hits the same fork first: open die or closed die. Take the wrong branch and the price doubles, lead time with it.

一、批量是第一分水岭
1. Volume is the first watershed

模锻要开模具，模具费摊到件上：批量低于几百件，摊完模费单件成本往往反超自由锻。自由锻免模具、柔性高，一两件能做，但每件都靠人工控制形状，工时随复杂度涨。
Closed die needs tooling amortised over parts: below a few hundred pieces, die cost per part often overtakes open-die pricing. Open die needs no tooling and flexes from a single piece, but labour per part grows with shape complexity.

二、几何与精度定可行性
2. Geometry and precision set feasibility

• 带薄腹板、高筋、变截面的件，自由锻做不出形状，只能模锻。
  Thin webs, tall ribs and variable sections are closed-die territory.
• 轴、饼、环类简单几何，自由锻加机加工反而更省。
  Shafts, discs and rings: open die plus machining is often cheaper.
• 批量中型、精度中等的件，胎模锻是中间路线。
  Mid-volume, mid-precision parts: open-die tooling (loose tooling) is the middle path.

三、按总成本比，不按报价
3. Compare total cost, not quotes

把两边的锻件价、机加工余量、材料利用率、交期资金占用拉到一张表：自由锻余量大、机加工贵；模锻件近净形、省刀但押着模具费和库存。批量越大，天平越倒向模锻，临界点用数字算，不用感觉。
Table both routes: forging price, machining allowance, material yield, lead-time capital. Open die carries big allowances and machining cost; closed die is near-net-shape but carries tooling and inventory. The higher the volume, the harder it tips to closed die — find the crossover with numbers, not feel.