Wires pt. 5: Wire guides

In the last blog post the goal of "fixing the wire to the plastic" was achieved. However, the wire extruder itself also contacted the plastic surface when it punched wire into the surface (in step 2 of "Bond the starting pointing" and the step 3 of "Bond the consecutive points"). There are two problems with this direct contact: the plastic surface is messed up; also, some melted plastic is sometimes sucked up into the wire extruder, which may clog the extruder when plastic is cooled.

We have come up with an effective solution to avoid this direct contact - we printed holes on the plastic as wire guides. The holes are slightly larger and deeper than the tip of wire extruder, so the tip can get into the holes and the wire is underneath the top layer of plastic (Figure 1).

Figure 1

The advantages of guides are:
- plastic surface is neater;
- wire extruder stays cleaner;
- wire is more firmly bonded into the plastic;
- printed wire has less slack.

The way how guides improve bond strength is demonstrated by Figure 2. After the wire is fixed at the starting location (A), the wire extruder moves to the next location (B). Then the z-bed is raised, so the extruder tip and wire are underneath the plastic surface. Because the wire is very hot and it is forced down by the extruder, the wire easily melts the plastic around it and *cuts itself into the plastic* (as illustrated by the dashed line x).

Figure 2

Wire slack is undesirable because it may trap the extruder tip. Figure 3 shows how guides reduce wire slack. In both with/without guide cases, the real length of wire (MN, M'N') is larger than the distance between two fixing point. When there is no guide, points M' and N' are both above the plastic, so slack occurs. However, point N is beneath the surface when we have guides, so even though the length of wire MN is equal to that of wire M'N', wire MN does not have slack.

Figure 3
(Please click the picture for better quality)