CNC Milling ABS plastic (and outstanding issues)

Sacrificial wood clamps the piece so the cutter doesn't hit the steel vice. We have a new cutting lubricant in the bottom of the photo. A bottle of red helps the time pass.

Maria and I were working last week fabricating four identical complex pieces out of ABS plastic. Initially we though a lowish feed rate combined with a fast cutting speed would give the best results but actually that’s not true. ABS suffers from the material melting and reattaching tangental to the circular cutter, so the effect is that when you cut, you end up drawing frayed lines over the surface. This is particularly noticeable on 90 degree corners and in deep pockets (concave regions). The first fix we tried was running the same program a second time. This did improve the situation but not enough to give it a finished look.

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A Java implementation of persistent red-black trees open sourced

Make search go mega fast! O(log(n)) inserts and deletes on ordered lists, but with the twist that the original list before modification remains intact! Implemented by using path-copying as per “Making Data Structures Persistent” Driscoll, Sarnak, Sleator and Tarjan. PersistentRedBlackTreeSet This was quite tricky to implement, because you are not allowed parent pointers, so you Read more about A Java implementation of persistent red-black trees open sourced[…]

Android androids

Meet Arnie Android (rev0) !! Based on a desk toy from Dealextreme he as 2 servo driven arms,a buzzer two flashy eyes and a PIR sensor in the head. Those foolish enough to approach within 10 M of my desk can now be detected ans suitably “processed” by Arnie 😉 http://www.dealextreme.com/p/android-mini-collectible-series-action-figure-doll-android-09-yellow-51733 Designed by yours truly Read more about Android androids[…]

Talks at the lab on Sunday 17th July

Following the success of last months talks, this month we have a selection of Scotland’s ambitious tech start-ups talking about their areas. Anarkik3D — develops software applications using virtual 3D touch, with a haptic device taking the place of the standard mouse to provide more natural and familiar 3D interactions. Robomotic — develops embedded wireless sensor platforms. Read more about Talks at the lab on Sunday 17th July[…]