RepRap: Blog

So, what's wrong with this picture?

 

Peer in and observe those little yellow hooks at the bottom of those bands. Now observe the diameter of the blue pillars. Yes, that's right. The hooks do not fit into the gap between the pillars!

This is because doofus here reused some pillars off an old axis, and didn't check to see if they were the ones that were compatible with the new hooks.

Net result is that when the Drive Screw attempts to lift or lower the yellow mechanism in the middle, it tries to snap the hooks off. Well, the good news is that the yellow bit canted over and snapped off its flexures before the hooks came off, so I guess they're strong enough...

Now of course I have to reprint all the bits, reassemble them, and redo all the pictures I took with the wrong pillars before I can finish the build docs. *Sigh!*

If you're assembling a V0.05 Axis Driver, insert all the nuts, then put the silicone bands on. You can hang them up out of the way on a couple of screws like this:

 (The blue bit and 50mm M3 screw was added after I'd hung the bands on, but it propped it up at a photogenic angle...)

Then you can pull them over the top of the Nut Bar once it is in place over the Drive Screw. 

Back in NZ. μRepRap is in bits in the suitcase. It survived the outgoing trip well, and the Everything Open trip was a success. Might be doing some colabs on YouTube, and there is a video that is going up (and I quote) "soon." Last time that meant six months...

I'll post the slides once I've sorted my unpacking.

 

Footnote: The X and Z axes got smashed on the return trip. Nothing 16 hrs of 3D printing can't fix, but the machine will be down for a bit.

 

Time for a hotel room reassembly session. Updating the github wiki on V0.05 as I go. Fortunately I also took this photo of the RAMPS board wiring.

 

The gold has turned up. Small flakes rather than sheet, but we'll see what tests can be done. Also in the package was vark, or edible silver foil. The μRepRap is now in bits in the Everything Open suitcase, so testing will have to wait. Back in 10 days, got a house-sitter so the pets have good company.

Will post snaps of Maus on holiday. 

Meanwhile Siddharth has published his joystick control code for μRepRap, so that'll be something else to play with. Should be more accurate than trembly hands, with less opportunity to wreck things when waving stuff around. I've checked and I can just about get Maus under the binocular microscope, giving a view in 3D.

https://github.com/Siddharth2308/RepRapMicron/blob/main/Joystick%20Control/gamepad.py

This image shows a 1000μm (1mm) long, 5-step staircase. The treads are 200μm square. Each step is 5μm (notionally) taller than the step to the right. Top right above the staircase is a series of 10 dots. These were used in an attempt to determine the probe height empirically:

As you can see (now I have my gimbal slide holder and the new microscope imager going) it has gone all blobby. Now, when initially trying to determine the probe height manually, I ran some GCODE that did 10 dots, each one 1μm lower than the previous one. Through the USB microscope, I could only make out the last 7 dots and so lowered the probe an extra 3μm, but as you can see I was in fact already in contact. This put the probe at least 3μm too low when commencing the first square, and things got horribly chewed up and uneven by the time we got to the 20μm tall square.

If you look at the top edge of the staircase, you'll see an indication of the change in step height. The random small blobs scattered around are where the probe lifted from the surface to recharge the probe. These may decrease if I get the height right.

Anyway, if I can't show you something going right, I can at least show you where I'm going wrong. If I write it down, it's science...

I'm going to have to take a break now to prepare for a μRepRap presentation at Everything Open in a week or so.

FYI Probe 9, 2.3μm layer height, 34μm line width, solid infill, lines drawn as segments not dots, 150 x 15μm segments (2.25mm total linear distance) deposited per probe "dip".

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.