Diamond drag engraving doesn’t put much sideways force on the platters, so taping the CD in place suffices to hold it:
Wrapping a flange around the screw-down platter fixture provides plenty of surface area for tape:
Which looks exactly as you think it would in real life:
Admittedly, masking tape doesn’t look professional, but it’s low-profile, cheap and works perfectly. Blue painter’s tape for the “permanent” hold-down strips on the platform would be a colorful upgrade.
It’s centered on the platform at the XY=0 origin in the middle of the XY travel limits, with edges aligned parallel to the axes. Homing the 3018 and moving to XY=0 puts the tool point directly over the center of the CD without any fussy alignment.
The blue-and-red rings around the center hole assist probe camera alignment, whenever that’s necessary.
The OpenSCAD source code as a GitHub Gist:
#1 by RCPete on 2019-09-12 - 16:37
For what it’s worth, there’s a chance mail costs from the usual eBay suspects might go up: https://www.freightwaves.com/news/us-to-leave-global-postal-union-next-month
Apparently, US subsidies for foreign shipping have been out of line, and this could impact parcel post rates for small packages.
#2 by Ed on 2019-09-13 - 10:25
If it helps get rid of the absolute bottom dollar sellers, I’m all for it.
I’ve been paying a few bucks more to “US Sellers”, which seem to be US-based front offices / reshippers of Chinese sources: the eBay seller name (a friendly ‘Murrican string) rarely matches the PayPal biller name (generally a set of Chinese characters).
Tracking down the physical mailing addresses suggests they’re parceling a containerload of assorted stuff, so foreign-postage increases may not matter.
Tariffs, on the other paw, should definitely apply and, if the eBay / Aliexpress pool get vacuumed, I’ll call ’em a net win.