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y-bed probe circuit ground contact may not be ideal arrangement.
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Description

There is a concern about the reliability of the ground under the bed plate. On previous designs it was stainless fastener -> ring terminal -> lock washer -> masked bed plate and now it is stainless fastener -> printed part ->ring terminal -> masked bed plate. The way the printed part is shaped there is space for the terminals to sit, but I'm not sure the variance on those parts is going to be small enough to be sure that those ring terminals will never sit in there loose.

Event Timeline

kent created this task.Aug 9 2018, 3:17 PM
kent triaged this task as Normal priority.
tutley added a subscriber: tutley.Aug 9 2018, 3:19 PM

@ kent i also was a little concerned about this so i threw a lock washer in there. So its stainless fastener -> printed part ->ring terminals -> lock washer -> masked bed plate

west added a comment.Aug 13 2018, 7:20 AM

I have spring washers in for this

nickp reassigned this task from kent to west.Aug 13 2018, 7:24 AM
nickp changed the edit policy from "All Users" to "LulzBot Hardware Products (Project)".
west closed this task as Resolved.Aug 27 2018, 11:02 AM

The lock washers that @tutley mentioned seem to work for this. It allows a little bit of variance in the printed part.
I'm going to close this for now until alphas or betas when we can test on a bulk amount

logan reopened this task as Open.Dec 21 2018, 8:01 AM
logan added a subscriber: logan.

With the ground screw tight I can still wiggle the ground terminals; not tight enough. Lock washer is in place.

As part of ESD mitigation, I am adding a second TVS diode at that same attachment point. The cathode (white line) side of the diode will be attached with a ring terminal along with the ring terminals of the green probe wires. The anode side of the diode with connect with a 16 gauge wire (via EL-MS0146 Solder Sleeve) that will run back the chassis ground. I have yet to design the details of the cable assembly but I had to carve out a trough in the plastic part over the ring terminals to accommodate the third ring terminal. Adding this third terminal was difficult so I would advocate a change in the design of the plastic part. I will discuss this with Josh.

@mjpelletier If possible i think we should utilize the shielding in the cable running to the bed plate as the return path for the added TVS diode. This will allow us to make a minor modification to the igus cable without needing to mate any other harnesses to the cable chain.

We may need to modify the y chain mounting bracket to make it easier to install the ring terminals on the bottom of the bed plate. As this adds another terminal and it is already difficult to install

west added a comment.Dec 27 2018, 11:44 AM

We are waiting on the approval of T5014