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軟腳計算器
輸入各機腳的千分錶讀數以檢查機架變形。找出最嚴重的軟腳,確定墊片校正量,並驗證是否在可接受範圍內。
結果
| 機腳 | 讀數 (mm) | 讀數 (μm) | 狀態 | 所需墊片 |
|---|
什麼是軟腳?
當一個或多個機腳未與底板或基礎完全平整接觸時,即發生軟腳。當該機腳的固定螺栓被鎖緊時,機架會發生變形,產生內部應力,導致軸承和密封件不對中。
驗收標準
| 讀數 | 狀態 | 措施 |
|---|---|---|
| < 0.05 mm (50 μm) | 合格 | 可接受 — 無需校正 |
| 0.05 – 0.10 mm (50–100 μm) | 警告 | 臨界 — 建議校正 |
| > 0.10 mm (100 μm) | 失敗 | 過大 — 對中前必須校正 |
軟腳類型
- 平行(間隙)軟腳 — 機腳下方均勻間隙。由墊片缺失或錯誤引起。透過添加等於間隙厚度的平面墊片來校正。
- 角度軟腳 — 機腳在一側邊緣搖動的楔形間隙。由加工不平行引起。使用錐形或階梯墊片校正。
- 彈跳(反應/誘發)軟腳 — 由外部力量引起,例如管路應力、導線槽應力或定位銷卡死。機腳看似平整,但機架發生撓曲。必須處理外部力量來源。
測量程序
- 將所有機腳螺栓鎖緊至正常扭矩。
- 在機腳 1 附近的機架上安裝千分錶(或使用雷射對中系統)。
- 將千分錶歸零,然後鬆開機腳 1 的螺栓。
- 記錄千分錶的最大移動量 — 即為機腳 1 的軟腳量。
- 重新鎖緊機腳 1 的螺栓。
- 對其餘各機腳重複此步驟。
實務範例
讀數: 機腳 1 = 0.02 mm,機腳 2 = 0.08 mm,機腳 3 = 0.03 mm,機腳 4 = 0.15 mm
機腳 4 = 0.15 mm → 失敗 (超過 0.10 mm 限制)
機腳 2 = 0.08 mm → 警告 (介於 0.05 與 0.10 mm 之間)
機腳 1 與 3 → 合格 (低於 0.05 mm)
校正:於 0.15 mm 墊片 機腳 4 下方,然後重新檢查所有機腳。
💡 提示: 執行軸對心前,務必先校正軟腳。軟腳會導致對心讀數不一致且無法重複。
⚠️ 注意: 若鬆開螺栓時讀數為負值(機腳翹起),表示存在由外力引起的彈跳/反應性軟腳。請勿加墊片,應找出並解除外力(管線應力、電纜等)。
Soft foot is a condition where one or more machine feet do not make complete, flat contact with the baseplate or foundation. When the hold-down bolt at that foot is tightened, it pulls the machine frame down, causing internal distortion that misaligns bearings and seals.
The term comes from the analogy of a table with one short leg — it rocks and is unstable.
Soft foot is critical because it:
- Distorts the machine frame — causing internal bearing misalignment
- Makes alignment non-repeatable — readings change each time bolts are tightened
- Increases vibration — due to internal stresses and bearing preload
- Causes premature bearing failure — from uneven load distribution
- Wastes alignment time — if not corrected first, alignment will never converge
Always check and correct soft foot before performing shaft alignment.
Follow this procedure:
- Tighten all hold-down bolts to normal torque
- Mount a dial indicator on the machine frame near the first foot
- Zero the indicator
- Loosen the bolt at that foot (about 1/4 turn)
- Record the maximum indicator movement (positive = gap)
- Re-tighten the bolt
- Move to the next foot and repeat
Alternatively, modern laser alignment systems have a built-in soft foot check function that measures all feet quickly.
There are three main types:
- Parallel (gap) soft foot — A uniform gap exists under the foot, typically due to missing, incorrect, or worn shims. Corrected by adding flat shims equal to the measured gap.
- Angular soft foot — The foot has a wedge-shaped gap and rocks on one edge. Caused by non-parallel machining of the foot or baseplate. Corrected with tapered or stepped shims, or by machining the foot.
- Springing (reactive/induced) soft foot — No gap exists, but external forces (pipe strain, conduit stress, dowel pin binding) distort the machine when the bolt is tightened. Cannot be corrected with shims — must address the external force.
Parallel soft foot: Add flat shims equal to the dial indicator reading under the affected foot. Use quality pre-cut stainless steel shims. Avoid using more than 3–4 shims in a stack.
Angular soft foot: Use tapered shims, stepped shims, or machine the foot surface to achieve full contact. Sometimes a thin coat of epoxy or polymer can fill small angular gaps.
Springing soft foot: Identify and relieve the external force. Common causes include pipe strain, electrical conduit stress, tight dowel pins, and foundation settling. Do not add shims for springing soft foot — it will make the problem worse.
After correction, always re-check all feet to verify the fix.
本頁所述的操作流程由 Vibromera 團隊使用 Balanset-1A(一款用於現場轉子平衡的便攜式雙通道動平衡儀及振動分析儀)開發並經過實地測試。
具備內建軟腳偵測功能之專業對心與振動分析儀器。實現現場精密對心。已應用於 50 多個國家。
Nikolai Shelkovenko
Nikolai Shelkovenko是一名振動分析工程師,也是Vibromera的創辦人兼執行長。 15年多來,他一直在現場——而非在試驗台上——為旋轉設備進行動平衡校正:粉碎機、工業風機、破碎機、離心機、軸與主軸。正是這些實際工作催生了Balanset系列儀器——它們被設計為一種專業人員可以隨身攜帶到機器旁、在現場獨立使用的工具,而非實驗室設備。 Vibromera成立於2017年,自2023年起總部設於葡萄牙波爾圖。Balanset系列產品的研發、組裝與支援均在此完成。旗艦產品是Balanset-1A,一款用於單平面及雙平面動平衡校正與振動診斷的可攜式分析儀。 Nikolai親自參與客戶支援工作,處理各種棘手的動平衡校正案例,並參與軟體開發。他以任何語言為全球客戶提供服務。