In my previous post (Building the FSR Circuit Boards) I showed how we assembly our circuit boards, using a manual pick and place machine that I designed and built. You can also find videos on that post. In this post I’ll walk through building the machine.
You can find all the 3D files here: http://www.thingiverse.com/thing:385567
Bill of Materials
You'll need to modify the Tetra air pump to convert it into a vacuum pump. There is a nice article and video on how to do this here:
Modifying the pump only take a few minutes.
Building the X/Y Assembly
Start by printing four of the Y Post parts, and then cut two pieces of aluminum tube about 18 inches long. You can make them longer, but I wouldn't go much shorter. A length of 18 inches will give you about 11 inches of movement along the X (left/right).
Next cut two pieces of aluminum tube about 12 inches long (or longer). Using 12 inches will allow movement of about 7 inches along Y. Print two sets of Y Carriage, Bottom Rollers, and Bottom Roller Clamp parts. Use the M8 x 30 bolts and washers to mount the 608 bearings to the Y Carriage. The washers go between the bearings and the part, and the M8 bolts are self-threading. Add the 608 bearings, washers, and bolts to the Bottom Rollers parts.
Place each Y Carriage assembly around one X assembly and then use the Bottom Roller Clamp with some M3 x 20 screws to clamp each Y Carriage assembly to the aluminum tube of the X assembly. This picture should help:
The bottom roller clamps don’t need to be really tight. They’re to keep the top rollers in place when you lean your hand on the carriage.
Now insert the two Y tubes into the holes of the Y Carriage and then mount to a piece of plywood. It's best to screw down one side first, with the screws centered in the slots so you have some room for adjustment. Then attach the other side, ensuring the assembly moves smoothly from left to right.
Building the Pen Holder
Print the Pen Holder and LM8 Cap parts. The 8mm aluminum tube slides through two LM8UU bearings. The tube will need to slide up and down smoothly, as well as rotate. I found I needed to sand the tube down a little to get just the right fit. Do this slowly, testing the fit frequently.
Insert the 8mm tube into the two LM8UU bearings, and then clamp them in place using the LM8 Cap part, held in place by four M3 x 12 screws. At this point you’ll still be able to remove the tube.
Insert two M8 x 50 bolts, as shown through the three holes. Add an M8 nut to the back of each bolt and tighten. Next add one 608 bearing to each bolt, along with an M8 washer, and put it up against the square tube, as shown here:
Add another 608 bearing to each bolt, followed by an M8 nut. Hand tighten each of the three nuts evenly, ensuring that the assembly slides smoothly without any slop.
Building the Pen
Print the Pen to Tube and Spring Stop parts. Add the spring, then the spring stop (which has a slot on the bottom for the spring). Use an M3 x 12 screw to clamp the spring stop in place. Apply some pipe tape to the tapered part of the Pen to Tube part and then push it into the aluminum tube. Finally, push the air hose onto the nib. When you’re finished, it should look like this:
Print out the Lock to Tube Adapter and Pen to Tube parts. Carefully push the Luer adapter into the Lock to Tube Adapter at the larger-diameter end. It should look like this (when you also have a needle in place):
In the photo above, I’ve also added some pipe tape to the tapered part to help create a tight air seal. You’ll want to push this into the tube after the tube is in place. When you’re done, it should look like this:
Optional USB Microscope
I initially installed a USB microscope in order to help with placement, but I found it to be more confusing them helpful. The problem is that it’s looking at the part from an angle, so it’s actually harder to line up parts with the microscope than with your eyes (stereo vision really helps). My friend uses a pair of Optivisors and found they work really well. I’m near-sighted, so I just take off my glasses. But if you do want to install a USB microscope, I purchased this one:
And the parts you’ll need to mount this microscope are Camera Cap Top and Camera Cap.