Our CNC router has proven to be an invaluable tool in our shop. We completely designed and built it ourselves over six years ago, and we have been improving on it ever since. Originally, the machine was controlled using software called TurboCNC, however we have since upgraded to the Window-based Mach 3 by Vectric. This works in tandem with Vectric V-Carve, which we use to generate the G Code. Other upgrades included a new driver system and beefier stepper motors, more rigid linear rails on the Y-Axis, a new DeWalt router, and a wireless jog wheel used to set up the machine for a cut. We have logged hundreds of hours of cutting on this machine, so it’s only right that we maintain it and give it some TLC every once in a while.
Squaring the Gantry
One of the main issues that the router has had recently is that the gantry was out of square. This means that on all cuts, the Y-Axis was not 90 degrees to the X-Axis. This issue arises from the fact that the X-Axis utilizes two separate motors and ball screws to move the main gantry. Over time, as the gantry is pulled one way or the other, or it is crashed at its stops (which occasionally happens), the motors come out of alignment.
I ran several test cuts to determine by how much the gantry was off. A test cut and a square showed that the machine was off by .05″ over ten inches. This is pretty significant, because this extrapolates to being off by about .15″ over the thirty inch spacing between the ball screws. So, I first disconnected the X-Axis motors from the driver. Next, I loosened the set screw on the timing pulley linking the two ball screws. This belt was intended to keep the screws in alignment, but clearly this has not worked great. In the future, we will probably install a tensioning idler pulley on the belt. However, after loosening one of the pulleys, I was able to manually rotate one of the screws against the pulley. This took a little guess and check, but it took approximately three quarters of a turn to realign the gantry, seeing as how the screws have a .2″ lead. One final test cut proved that the gantry was once again square.
Oiling the Bearings
Next up, the linear bearings could use some lubrication. The Y-Axis rails and bearings had been replaced recently, so I focused only on the X-Axis for now. These bearings consist of two parts. There are the main bearings, which are mounted in aluminum blocks which are then mounted to the gantry. However, these bearings also have rubber wipers, which are held in place by an aluminum plate. After clearing the rails of sawdust, the wiper plates were removed and slid to the far ends of the table. Next, some heavy gear oil was laid on the rails, and I simply ran the gantry back and forth to work this oil into the actual bearings. The wipers and their mounts were cleared of old sawdust, and the wipers were replaced on the ends of the bearings, all while being careful not to get any dust inside the bearings. Following this procedure, the gantry moved noticeably smoother.
Installing new Fences
The fences mounted to the table were only temporary to begin with. They were mounted to the table and trued up originally, however they were no longer true with the machine, and there were many marks from running the cutter beyond the fence and marks from general use. It was time for some proper fences.
This table uses a 2″ grid with ¼-20 tee nuts with long ¼-20 bolts to secure the pieces to be cut. We have utilized some of these holes to mount the fence, and this has worked in the past. So, using the router, I mounted and drilled some fresh pieces of melamine with identically spaced holes. Then, the new fences were mounted in place using several of these mounting holes and washers. The upper piece was mounted with an overhang, so this upper piece would be the true reference. To true the fences, I ran the router in an “L” shape, cutting the leading edges of the fences true to the machine’s motion. One final measure with a square confirmed that the machine was now cutting true.
More upgrades for our router will be coming soon. We are experimenting with the idea of using a vacuum top surface, eliminating the need for the 2″ grid to mount the pieces to be cut. Furthermore, we will be implementing a much-needed, proper dust collection system. Also, we may soon connect the limit switches, to prevent the possibility of crashing the gantry of Y-Axis. We take care of our tools, because they need to be ready to work when we need them. By performing this small amount of maintenance to our router, it will now run smoothly for another couple hundred hours.