RepRap: Blog

To keep the angle of the point with the slide more vertical, I've put a kink in Probe 9. This keeps the width of the deposited line even regardless of the direction the probe is travelling in. One question I has was "Will the resin still climb the probe?" and the answer is yes. As you can see here it still accumulates nicely. Unfortunately the probe was a bit close to the edge of the foil, and this resin is mostly set solid:

Note that the probe still worked to some extent in this condition. I'll get it off by soaking in acetone, which has worked previously. This illustrates the importance of placing the probe's dipping point at least 0.9mm back from the edge of the foil, and preferably with the UV LED underneath the foil to avoid UV casting up onto the side of the probe.

The slide in this case was made using adhesive aluminium tape approx 60μm thick. The assembly process is as follows:

Clean slide with a razor blade and isopropyl alcohol to remove previous experiments. Cut a piece of adhesive foil on a cutting mat with a small box cutter approximately 1/3 the length of the slide.. It is important to cut the foil shiny side down.

Stick the foil on one end of the slide, leaving a 3mm gap to the end. The gap is so that the slide can be placed in a slide storage box after experimentation. Place a piece of printer paper on top of the slide and burnish the foil flat using a cylindrical polished chrome burnisher - I use the hex bit adaptor from a set of drill bits.

Place a second glass slide flat across the first perpendicularly and drive it in short motions against the edge of the foil. This curves the edge up slightly, creating a retaining wall for the resin.Run an isopropyl-dipped cotton bud up and down this edge to remove any exposed foil adhesive. When doing this, press the cotton bud against the edge of the foil laterally to give the retaining wall a crisp edge. The slide is now ready to be used as per the previous version, but the Touch Plate Height will need to be adjusted as the foil is thicker.

 

This is quicker to construct, and less prone to the probe tip penetrating the foil. It is, however, not as consistent, and I have found that making test dots of resin with the probe is the only way to be sure of probe height. It also tends to be more wrinkly, and might benefit from burnishing before adhering. However, if the wrinkles are not near the actual reservoir they are unimportant.

I have made another prototype gripper. This one is 13x larger than the one I intend to micro-print, which in this configuration would have a jaw spacing of 230μm (example has 2mm spacing, corresponding to 150μm). Obviously a version with wider jaws that don't completely close is possible. The hypodermic body and plunger would be replaced with a 0.5mm hypodermic needle and 0.23mm wire, assembled manually (I may add alignment stops). The actual actuator is undefined at this point but I has ideas. This one is a bit prone to torsion of the plunger, the plunger anchor is too short resulting in some curl, and the jaw tips need to be taller for more gripping area. All of these issues should be fixable. As it stands, it can grasp a sheet of paper and drag it along the desk.

 With minor changes it can be modified to close when pushing or pulling the actuator.