Simple adjustable slider clamp for He3D K200, K280 and similar kossel deltas

Replaces the stock injection moulded slider clamps of my He3D K280 kossel delta; the stock item is actually fine, but this version has a simple adjuster mechanism, and is sized for a 9mm belt upgrade I made.

### Updated with 4 new Models (March 2020) - This is a updated design with thicker pin supports and 4mm more adjustment travel.

Models are provided for 40 and 42mm pins, plus 6 and 9mm belts: A stock K280 has 6mm belts and 40mm pins.

The stock He3D 4 roller carriage backplate design