Grounding th chassis problem

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Grounding th chassis problem

Postby LeonS » Sun May 01, 2011 10:51 pm

I am in the throws of the last steps before testing the laser.

I grounded the chassis to the ground wire in the terminal block. The power supplies and other circuitry all share a common ground. The problem I am having is that the aluminum chassis is not conductive. I touch my multimeter's probes to the chassis members right next to each other and there is infinite resistance. I suspect the aluminum is coated with something non-conductive.

Have others had this problem? The angle bracket that I bolted the ground wire to is sitting right at ground potential but none of the aluminum is.

- Leon
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Re: Grounding th chassis problem

Postby whmeade10 » Mon May 02, 2011 12:29 am

LeonS wrote:I am in the throws of the last steps before testing the laser.

I grounded the chassis to the ground wire in the terminal block. The power supplies and other circuitry all share a common ground. The problem I am having is that the aluminum chassis is not conductive. I touch my multimeter's probes to the chassis members right next to each other and there is infinite resistance. I suspect the aluminum is coated with something non-conductive.

Have others had this problem? The angle bracket that I bolted the ground wire to is sitting right at ground potential but none of the aluminum is.

- Leon


I was experiencing the same problem until I took the point of my probe and scratched lightly into the aluminum frame. It seems that there is a clear finish of some sort on the aluminum.

- Bill
FSE 45w Deluxe CO2 Laser 5th Gen w/X7 DSP | CorelDRAW X7
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Re: Grounding th chassis problem

Postby r691175002 » Mon May 02, 2011 5:56 am

The aluminium is just clear anodized, its the standard finish for almost all aluminium. They cut the extrusion after anodizing so the ends conduct fine. The t-nuts and L-brackets break the finish when tightened so you just need to ground a single spot.
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Re: Grounding th chassis problem

Postby macona » Mon May 02, 2011 6:34 am

Aluminum instantly forms an oxide layer microseconds after it is cut. When grounding to the frame make sure you use star washers to get a good bite. An as mentioned, it is clear anodized which is a much thicker layer of oxide.
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Re: Grounding th chassis problem

Postby LeonS » Mon May 02, 2011 12:42 pm

Thanks to all. I'll abrade the connection point.

Today I do a "smoke test" on the laser itself. I am almost done with the initial construction and set up.

Cheers to all,
- Leon
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