Edge Quality


In water jet cutting the edge quality varies based on the speed that the cutting head travels at, the slower the cut speed the better the edge quality. We offer a range of 5 different finishes; extra coarse, coarse, medium, fine, and extra fine, with the cost per inch incresing as the egde quality increases. We offer a variety of finishes(shown below) to fit our customer's needs and budget.


Extra Coarse- Rough cut; fastest speed and lowest cost. Sometimes referred to as a seperation cut.
Coarse-Better quality than extra coarse and a lower cost than medium edge quality
Medium-Slightly higher edge quality than coarse, the most common edge finish
Fine- High Edge Quality; not quite the tolerances of Extra Fine edge
Extra Fine- Best Edge Quality; Slowest cut rate but highest cost; tighest tolerances, in some instances can be +/- .005"


Varying Levels of Edge Quality
 



Stream Lag
There are other factors that take effect in water jet cutting that affect the edge finish of the cut part. Stream lag is one of the factors that affect edge quality.  Stream lag is the lagging of the water jet stream through the material as the cutting head travels the cut path.  A visual to help illustrate how stream lag occurs is shown below, the blue line on the right side of the picture shows where the jet stream enters at the top of the material and the blue line on the left side of the picture shows where the water jet stream exits the material on the bottom. The red line is the actual path that the water jet takes as it is cutting through the material. 

When cutting around corners with a water jet stream lag affects the cut quality greatly.  When a water cut arounds the corner the leading edge of the water jet stream has rounded the corner as the lagging end of the water jet stream has sometimes not entered the corner yet. In this situation the lagging edge of the water jet will flare out as it first rounds the corner then as the corner is rounded the lagging stream "catches up".  It is most easily described by stating that the leading and lagging edge travel in the same plane together that is always tangent to the edge of the material, the tangent point is based off of where the leading edge of the water jet stream is located. The leading and lagging points are always the same tangent distance from one another.  To help minimize this issue of stream lag we have written into our cutting program a sequence that reduces the speed entering a corner and then speeds back up as it exits. This slowing down into corners and speeding back up out of corners allows for us minimize the flaring out of the lagging water jet and to cut parts at a higher cut rate that still have good quality.









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