I just finished assembling a v7 microscope and the assembly ultimately went fairly smoothly. Everything is mostly working, and I’m able to capture some really very nice images of some assorted sample slides, but, the stage movement (and Z actuator) is exhibiting problems.
On any axis, the movement when traversing is generally okay. I see the servo rotate the small gear and engage the large gear. And mostly, I see the sample move in the appropriate direction. But occasionally the actuator seems to jump / slip / skip back to a previous position, and visually it looks like the movement is being rewound (quickly). This is a bit annoying, but not awful in the X/Y axis, but, in the Z axis, it seems to cause auto-focus to consistently fail. I initially thought maybe I was overstretching the bands, or running out of thread or something, but, the skipping occurs when traversing in either the positive or negative direction.
My first guess was that the Viton bands had broken (and indeed, I did snap a couple of these in the assembly), but pulling on the feet the bands still seem to be firmly attached. I thought next maybe I hadn’t adequately oiled the bolt threads, but dabbing additional oil onto the bolt through the nut-slot hasn’t seemed to have any impact.
For parts, I sourced the Viton O-rings, hex bolts, washers, and brass nuts as indicated in the parts list from McMaster-Carr – so I don’t think anything should be a knock-off or out of spec. The stepper motors are generic and cheap from Amazon, but, as best as I can tell they are not struggling and things are rotating as they should.
Sometimes near a skip it does seem like the motor begins to stall for an instant almost like something internal is seizing up and then breaking loose. But the stall doesn’t seem to line up precisely with the skip (though the slight lag in the video feed makes it hard to say for sure) and it doesn’t always occur before a skip. I also can hear a slight audible clicking sometimes associated with the stage resetting. If I try to push the stage around manually, other than the plastic flexing a bit, it seems to stay in place. Looking inside the nut-slot of the actuator, I do think I can see a piece of plastic inside that rotates a bit back and forth sometimes as I reverse direction on the stage, but nothing is obviously happening to it when the skip occurs.
Here is a video that shows the camera output on my monitor, along with the movement of the X-axis gear. The behavior is similar along the Y axis. The Z-axis seems to slip more quickly, but it’s also harder to tell visually since it is the focal plane, rather than the sample movement of the X/Y.
I’m hoping that this is a known problem and something with an easy fix, but I suspect that perhaps I’ve broken something inside the main body (or misprinted it) and will need to reprint, possibly with changes. Any insights or help debugging would be appreciated!
