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October 12, 2018

Why finished wire can be marked

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It is not rare for finished wire to be marked. This often happens on stripper blocks and causes quality complaints. Below is a series of specific steps you can take to identify the source of the marking.

  1. Lift up the coil overhead and examine the interior with a flashlight. Determine if it has a single mark per wrap or just a few marks and determine if the marks appear in a regular line on the inside of the coil. If you have random and frequent marks, this is a sign of marks caused by metal pickup. I will address this problem later.
  2. If you have marks that are more or less inline inside the coil, there should be a discernible cause for the marks on the block.  If there are four equidistant marks than it is obvious that it is the slots that are causing the marks.  If the edge of the slots are not rounded with an approximately 1/8” to 3/16” radius, rounding the edges might eliminate the problem.  If the slots are rounded and there are still four equidistant marks than it is an over drafting situation which has only two solutions.  Draw the wire in two passes or draw it on a larger block to diminish the effect of the overdraft.
  3. If you have one or two marks that are not in line with the slots than we have to look elsewhere.  Draw a few wraps and carefully unwrap the coils to determine where and when the marks appear. If the marks do not appear keep drawing wraps until they do and try and find the source of the marks.  Match up the marks as you unwrap the coils with any possible causes. Look for a raised edge on the face due to gripper or chain damage or a defective coating, a raised edge on a post, raised edge on a “come along hole” or gripper pocket, and possibly a sharp edge at the top of the block which should have been rounded with a belt sander same as the slots. If the marks are in the first wrap possibly the die box needs to be adjusted so the wire enters at the draw line and parallel to the floor (a level placed on the drawn wire can determine if an adjustment is necessary).
  4. In the case of metal pickup which is similar to welding splatter on the face of the block, the problem gets progressively worse. There can be a few different causes for metal pickup, but basically the drawn wire is being ripped apart and sticking to the face of the block.  It then builds on itself, causing more wire to be ripped apart and adhere to the block.  In order to solve this problem all pickup has to be removed from the block which is most efficiently done by grinding.

Possible causes:

  1. Not enough lubricant. This usually occurs by trying to produce a plating quality wire by minimizing a dry soap as opposed to using grease.
  2. Taper needs to be adjusted because the wire is too tight.
  3. Splintery rod
  4. A sharp edge on the face of the block is shaving the wire, and then the wraps adhere to the block and start the metal pickup.

Additional Info

  • Company: Parkway-Kew Corp.
  • Job Title: President
Read 50 times Last modified on October 12, 2018

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