This large-scale CNC was designed to carve artist-scale deep reliefs in 3D, for less than $1000. This machine was built with a cutting area of 10×8 ft, and depth travel of 18″, and an accuracy of 1 mm. While similar machines can be found for around $4000, this CNC has a larger travel area at on quarter the cost. Design goals included the following:
1. Large-scale – The design uses a flying gantry with an independent table that allows for cutting of works of any depth, with easy change out of materials. It’s large enough that I can walk around inside the axes of the machine.
2. Portability – An unusual requirement for a large CNC machine, I wanted to avoid moving a heavy steel frame when moving the machine. This machine can be relocated by one person in about 1 hour. The main gantry contains all 3 drive axis mechanics.
3. Deep relief – A key design feature was to cut deep relief into foam for wax casting. The GiantCNC uses a 36″ lead screen to provide up to 18″ of Z-axis travel, with a unique fin-shaped mount for lateral stability. To keep down costs, cabinet slides are used for guide rails.
4. Low cost – The total cost of the machine is about $800, and is the lowest cost CNC machine for its size. Costs were reduced by using LVL lumber instead of steel, drawer slides for the Z-axis, lightweight chain, and common L-stock aluminum for X/Y-axis rails. Other costs were reduced with a special bearing box which allows the use of the same 1″ bearings throughout the machine.
First run was achieved on Aug 6th, 2012. A standard shop router was mounted to the Z-axis, and two circles were cut using a 1/2″ flat end mill. The speeds and feeds were way off, causing the darkend (burnt) wood, and several bits to break off during initial attempts.
Testing with a pencil allows for greater control, and demonstrates the precision of the machine despite its size. Here it draws a standard g-code pattern and text for ShapeOko.