How to avoid buying a bad Used FEELER
Core Principles: Be cautious, inspect thoroughly, prioritize condition over age.
I. Pre-Purchase: Conduct Due Diligence
Clarify Your Needs and Model: Determine your desired travel, spindle speed, torque, and accuracy requirements. Targetedly search for corresponding FEELER models (such as the FV/DMV series) and understand their common problems and market reputation in advance.
Verify the Equipment Source: Prioritize purchasing from the original user's factory or a reputable used equipment dealer. Inquire about the machine's usage history—is it used for year-round, heavy-duty batch production, or for intermittent mold processing? Mold machines typically experience less wear.
II. Machine Inspection: A thorough on-site inspection is essential.
This is crucial to avoiding purchasing a defective machine, so bring an experienced technician or specialized inspection tools.
Static Inspection:
Appearance and Maintenance Signs: Observe the machine's appearance for cleanliness and any significant damage to the sheet metal. More importantly, open the protective door and inspect the interior. If there's sludge or metal shavings everywhere, it indicates poor maintenance by the previous owner, a red flag. Check the lubricating oil tank and hydraulic oil tank for cleanliness.
Core Mechanical Component Wear: Inspect the three guide rails (X/Y/Z axes) for severe scratches or "furrowing." Touch the guide rail surface to feel for wear steps. Inspect the ball screw for rust or signs of wear.
Dynamic and Precision Testing (Critical):
Low Run and Abnormal Noise: With the Used FEELER unloaded, reciprocate each axis at different speeds. Listen carefully for any unusual knocks, friction, or sharp noises. Observe the smooth movement of the axis and any jitter.
Backlash Testing: This is a key indicator for detecting wear in the transmission system. Use a dial indicator to hold the worktable against the axis. Use system commands to move the axis forward a certain distance, then reverse it. Observe the dial indicator pointer's return value. The larger the backlash value, the more severe the wear on the screw and bearing, which directly affects machining accuracy.
Spindle Testing: Run the spindle from low to high speed, especially reaching and maintaining the maximum speed for a period of time. Listen for any unusual noises from the spindle bearings and observe for any excessive vibration. After shutting down the machine, feel the spindle nose to check if the temperature rise is within normal limits (abnormally high temperatures indicate a loss of spindle bearing preload or poor lubrication).
Test Cutting - The Ultimate Touchstone:
Never rely solely on dry run data. Perform a test cut on a real part.
The test cut material should be a material you commonly use (such as 45-gauge steel or aluminum). Create a simple program that includes a cavity, islands, drilling, and tapping.
After machining is complete, immediately use tools such as a micrometer, dial indicator, and roughness tester to rigorously inspect the workpiece for dimensional accuracy, form and position tolerances, and surface finish. Only when the test cut results meet your expectations can the machine tool's overall performance be proven to meet your standards.
3. Decision-Making:
Use any issues discovered during machine inspection (such as excessive backlash or minor scratches on the guide rails) as bargaining chips to request a price reduction or require the seller to complete necessary repairs and maintenance before the transaction. Be sure to retain the test cuts as proof.
