Process Settings

Last time, we introduced four types of parameters necessary for most automated CFRP manufacturing processes. Feeds, distances, pressures, and temperatures are essential parts of every layup operation. See here which types exist, and which function they fulfill.

In this article, we will highlight the most important parameters of the types of feeds and distances. The last article already hinted at some parameters and how they can be used to control different scenarios when manufacturing. If you are new to this series, we recommend starting with the article about end-effectors – the layup tools used to place CFRP material. From there you can easily catch up.

The term “feed” comes from machining technologies and describes the movement across the part, while “speed” is used to describe the rotational speed difference between the cutting tool and the component. In CFRP manufacturing, feeds describe the movement speed (velocity) at which the layup tool traverses across the layup surface. The most common units are given in mm/min or m/s. “Distances” in this context refers to the distances between trigger points along the movement path. They are usually given in mm or in. When reaching a trigger point, the feed may change, or certain pressures or temperatures may be adjusted.

To describe a layup path, at least 6 different feeds [m/s] are necessary:

• Approach Speed: The velocity that is used to reach the beginning of the touch-down movement operation.
• Touch down Speed: The velocity with which the first position on the layup surface is to be reached. This velocity stays constant until the first layup position is reached.
  
• Initial Speed: The velocity used when one or more material stripes start to be placed. This is either at the beginning of a course or when replacing after a gap present in the course.
• Layup Speed: Is used during material placement from all slots.
• Cutting Speed: This speed is used when one or more tows are cut. It is lower than the layup speed, so the cutting units can safely cut the material.
  
• Rapid Traversal Speed: This is used when the end-effector moves from the end of one course to the beginning of the next course.
  

These trigger points need to be defined by certain distances [mm]:

• Approach: A vector that describes the movement component used to approach the position where the layup surface is first touched by the compaction roller, as defined by the “Roll in” position.
• Departure: A vector that describes the retreating position after a course is laid, as defined by the “Roll out” position.
  
• Rapid: The distance towards the layup surface that the tool must maintain when traversing from the end of one course to the start of the next.
  
• Roll in: Describes the additional distance before the layup of one course, which describes how long the compaction roller needs to keep surface contact, so that the material is safely and correctly placed at a given position.
  
• Roll out: Same as Roll in but after the layup has occurred. This is used to ensure that the ends of all material stripes are in their correct position. If retracted too early, they may fall on top of each other or shift sideways.
  

Let’s look at an example from last week’s article:

Figure 1: A course on a curved surface. 

The blue arrows (1, 10) denote the start and end vectors of the whole movement path. They surround an orange line segment, whose length is defined by the rapid distance. Starting from right to left, the following red line (2) denotes the approach vector, which defines the distance and velocity used to reach the „Roll in“ position (3). This is the first surface contact point. The light blue line (4) denotes the area in which the „Initial speed“ is used since this is the first area in which tapes will be placed. The long blue line in the center (5) tells us that the „layup speed“ is used until reaching point (6), where the „Initial speed“ is used again. Take a look at the bottom left side – an additional, short tow is now also being laid. Since a new tow is to be laid, the „Initial speed“ needs to be used. Shortly thereafter, all tows need to be cut as the course ends (7). The light gray area denotes the „Cutting area“, which surrounds the actual cutting position. The remaining layup is done using the layup speed (8). Just as we used the approach vector on the right side, the „roll out“ (also 8) and departure vector (9) are now being used to safely lift off the surface (10). The rapid traversal speed is used in (1 and 10) and to move towards the subsequent course, omitted in this example

In this article, we went in-depth into the process settings and how they can be used to influence the movement path of the layup operations. Next week’s article will cover pressures and temperatures – what they are used for and how they can be optimally used.

Until then, stay safe and stay tuned.