Contamination Concern for CNC Ways And Drive Screw

Thinking over potential tasks to be tackled on our project CNC, we thought it might be occasionally useful to mill our own circuit boards. But before we start cutting bits of copper off fiberglass, we should make sure those flakes of copper won’t end up where they’ll do harm. One of the open questions involves how we should protect the ways and drive screws of our Parker motion control XY stage.

The XY stage was salvaged from an optical inspection machine, so it was not a surprise to see this mechanism has limited protection against contamination as most items under optical inspection don’t shed debris. Hence unlike real CNC mills, the ways here have no cover. On this machine they are exposed when an axis moves off center. Cursory inspection indicates the critical surfaces are those in the center facing to the side, so what we see as top surfaces are not areas of direct contact. But it’s still better to not have any contaminants build up here, because of the next item:

The drive screws have a thin metal cover to protect against dust, but the cover is opened towards the ways. When the table moves off center, there is a window for debris to fall from exposed ways to inside the screw compartment and end up sticking to the lubricant coating the mechanism. In the picture above we could see through this hole. While the screw itself is dark and out of line of sight, we could see colors of wires also living in that compartment. (They connect to three magnetic switches for the axis: a location/homing switch, and limit switches to either extreme.)

We realized this would be a problem once we started cutting into MDF and making a big mess. Powdered MDF may cause abrasion and should be kept out of the ways and screws if we can. Milling circuit boards would generate some shredded copper. I’m not sure if that would be considered abrasive, but they are definitely conductive and we should keep them away from machine internals as much as possible. A subtractive manufacturing machine like this one will always make big messes, how might we keep that under control?

2 thoughts on “Contamination Concern for CNC Ways And Drive Screw

  1. There’s another reason you’ll want to take care of dust, particularly with milling PCBs: inhalation. I worked with a professional PCB mill in the past, and after running that for a few hours, the whole room would smell of copper, even with a working dust extraction system.

    I don’t know exactly what that does, health-wise – but it’s probably not great.

    Like

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