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The Assembly - Taking it all apart
Now that the Plugs-in test is complete and the machine has been adjusted, filed, drilled and tweaked, it's time to take the whole thing apart in order to get paint on some of the parts, especially the steel ones.
Painting raw aluminum or raw steel for that matter requires some preparation. The first thing is to degrease and clean the parts by washing them with detergent and hot water. After rinsing and drying the parts, I need to deoxidate and roughen up the surfaces which is accomplished by a thorough rubbing with Scotchbrite pads. Another quick cleaning and drying gets the parts ready for a nice coat of Self Etching Metal Primer. It should be noted that all this is done wearing rubber gloves, the acids on your hands will ruin the surface cleanliness.
I kept the pan and end plates assembled for alignment purposes so the end plates need to be masked with some tape prior to any painting, also, I put scrap screws in all the threaded holes in the parts to keep them free from paint. Once this is done I primed the parts with steady even strokes and like that. I let the primer dry completely and then applied a nice topcoat of Hunter Green Satin Enamel. In deciding on the color, I tinted some shots of the cnc_drill in progress with Photoshop to see what color would look best. Well, I don't know if my choice is best or not, I like it however.
The Assembly - Putting it all back together again
Now that the paint is on and everything has been fabricated and test fitted I can put the thing together for real this time. When putting in screws I apply a bit of Locktite 242® Threadlocker to the threads of the screw. This helps prevent the screws from working their way back out from vibration.
When the machine goes together this time special care needs to be taken so that everything is square and perpindicular. The Y axis is the first axis to be attached to the frame. I aligned the Y axis perpindicular (90 degrees) to the Z axis mounting surface using some precision flats and a right angle square. I tried to keep this angle while keeping the axis in the center of the frame, this is not ultra critical, the angle however is. Once I have the axis exactly positioned I fastened it down, Locktit-ing the screws.
The X axis must be aligned perpendicular to the Y axis using much the same tools as before. It should be noted here that these alignment techniques are not a good precision method but they are good enough. Precision setup would require digital or dial indicators and some precision supports and flats, not to mention the precision granite block. Seeing that this is just a drilling machine and not a milling machine, a carefully measured visual alignment should suffice.
Continuing on with the assembly, I attach the table to the X axis and align it parallel to the X axis guide rods. This completes the X-Y table assembly. The last alignment job is to install the Z axis and align it perpendicular to the table top. This needs to be done in 2 planes to make sure the tool is square to the table top. This is kind of important especially if you do not want to break the fine drills used for PCB fabrication.
This is also where I seriously wire the machine. Up to this time most of the wiring was temporary and in many cases nothing but test clip leads. With a little figuring I determined that a 10 circuit, 20 screw terminal strip would buss all the sensor wiring using no more than two wires per terminal. I also decided to use jacketed 18 gage 2 wire cable for each limit switch pair and each home switch making a total of 6 sensor cables.
I opted for a looser more free form of wiring rather than the tightly routed wiring of most commercial products. This allows me to work on the circuits if needed because the room for the electronics and wire terminations is tight. I soldered all connections to the microswitches and put crimp lug terminals on the terminal block end of the cables. I did this because putting wires directly under the screws of a terminal block just has no class. A few tie wraps here and there to neaten up things a bit, connecting the motors, power and the limit switch leads to the controller and the final assembly of the CNC Drill is complete.
The Assembly - the Damages
Total elapsed time: 8 weeks from conception(10/12/04) to this point. This may be a long time in your estimation but I spent 2 weeks on the computer making solids models and in general designing the parts and then, all my parts were fabricated 2,400 miles away from me and there was a bit of shipping and receiving involved to make this project happen. If you have the machine tools locally available, then your time would be far less.
Total cost: Less than $1,000.00. I don't have accurate figures because I did not keep accurate records of the little trips to the hardware or electronics store. I do know that $500.00 of this cost was for machine part fabrication, which I consider a deal taking into account all the parts that needed to be fabricated. The motors and controller cost $130.00 and I splurged and bought a new flat panel monitor for the computer that cost another $200.00. I also got some things for free like the power supply and computer to name a few.
The Assembly - So... are we done?
Although the CNC Drill is fully assembled it is only partially set-up. All the home switch positions still need to be set and the speed and feed parameters need to be figured out, this will take a bit of trial and error. Aside from those little tid-bits, I need some drills, routing cutters, board fixtures and drilling substrate. I am not going to get away without some programming as well seeing that this is a computer controlled machine, so you could say that the CNC drill is done, if you wish to ignore these other realities.