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Zorluk: Çok zorPower Sanders

During a quality control inspection of a prepared hardwood surface, an inspector identifies two distinct defects: a continuous pattern of deep, spiral-shaped swirl marks (often called 'pigtails') across the main surface, and severe localized wood burning (scorching) at the outer edges of the panel. The operator used a power sander equipped with a 120-grit hook-and-loop abrasive disc. Based on these specific defects, which combination of equipment malfunction and operational technique is most likely responsible?

  1. A random-orbit sander with a worn pad brake that allowed the backing pad to spin at excessive high speeds, combined with the operator applying heavy downward pressure near the edges.Cevap
  2. B
    A pneumatic dual-action sander that seized internally due to a lack of daily lubrication, causing the abrasive to drag aggressively and erratically across the wood surface.
  3. C
    An electric orbital finishing sander operated with a bypassed ground prong, resulting in erratic motor oscillations and localized heat buildup from fluctuating voltage.
  4. D
    A rotary disc sander deliberately guided perpendicular to the wood grain to mimic a crosscut action, which aggressively tore the fibers and overheated the edges.

Cevap

A random-orbit sander with a worn pad brake that allowed the backing pad to spin at excessive high speeds, combined with the operator applying heavy downward pressure near the edges.
The correct answer accurately pairs the mechanical cause of spiral swirl marks (a failed pad brake on a random-orbit sander allows it to free-spin like a grinder, creating deep circular gouges called pigtails) with the operational cause of burning (applying heavy downward pressure generates excessive friction and heat, particularly near edges).

Adım Adım Çözüm

1
Analyze the first defect (spiral-shaped swirl marks or 'pigtails').
Recognize that pigtails are a defect unique to random-orbit sanders when they lose their random oscillatory pattern.
A functioning pad brake prevents the sanding pad from free-spinning. When the brake wears out, the tool behaves like a high-speed rotary grinder, leaving deep spiral gouges.
2
Analyze the second defect (severe localized burning at the edges).
Identify that burning on wood is caused by excessive, concentrated friction.
Lingering in one spot or applying too much downward pressure concentrates heat. This is especially severe at edges where the pad's contact area is reduced, rapidly scorching the wood.
3
Evaluate the distractors against the established symptoms.
Rule out pneumatic seizing, grounding issues, and cross-grain sanding as primary causes.
Lack of lubrication causes stalling; missing grounds do not affect performance; and cross-grain sanding leaves straight scratches, not spirals.

Anahtar Kavram

Random-orbit sander mechanics, defect troubleshooting, and the effect of friction during surface preparation.
Tahmini Süre:1m 30s
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