Conceptual Designs

Design 1

This design uses a steel box section base clad with sheet steel, there are two ball screws each side driving the x axis, these are linked with a motor in the center and a pulley on either side and a timing belt. Tension on the belt is supplied by the motor sliding in its mount. The motor on the z axis is a direct drive onto a ball screw. much the same as the Y axis. The Y axis has two rails both supported round rails. The X axis has four to provide support when the X axis tries to rotate around the top rail on either side. This means that rigidity is not contained to the relationship at the top of the gantry. The whole gantry is rotated backwards to center the cutter between the carriages on the rails for the x axis in the Z direction.

The force when cutting in the X axis will be directed into X axis through a rotation of the Y axis and some force applied to the screws thus being controlled by the Y axis motor. This will create a force around the top of the gantry and the carriages on the Y axis. The only resistance to this load is the Aluminum plates that create the side of the gantry.

Out of the four designs this design scores Medium for cutting performance, Medium for ease of construction and medium in the cost category.

 Design 2

This design is primarily the same as design one however it is constructed with  aluminum frame rail for ease of construction and aluminum plates. It holds the same inherent issues as design one however is marginally weaker across the bed of the machine due to the material being aluminum as opposed to steel.

Out of the four designs this design scores Low for cutting performance, Medium-High for ease of construction and medium in the cost category.

Design 3

This design is very different from the other two, it has a single arm supported on one side. It used a singular profile rail. The intention of this design is to drastically reduce the complexity and component count thus reducing cost. It is constructed using aluminum frame rail with aluminum plates as required. However it is the weakest of all the designs. It is the easiest to construct and will be the cheapest due to the low component count.

Out of the four designs this design scores Low for cutting performance, High for ease of construction and High in the cost category.

Design 4

This design is primarily designed from square steel section that will be welded together. The tubes can be filled with an epoxy granite mix if resonance of the machine becomes a problem. The angular sections at the side are to provide support for the forces generated when cutting in the Y axis. This design will use profile rails sitting on the top of the of the frame work. This is to remove the cutting tendency for forces to rotate around the axis of the linear rail as per design one and two. Another change to this design is to fully encapsulate the spindle so it is help essentially between two gantries. These gantries will be 2 off 100x100x5mm steel box section welded together. Aluminum plate will be bolted to these to provide a fixing mechanism for rails and screws. Any welded component will be leveled off with epoxy resin to remove the effect of warping created by the heat of the welding. Although not shown there will be a removable section in the center of lower section. This will allow taller workpieces to be positioned within the machine. In this lowered section will be location stops to push the section up to. The bottom of this section will also be leveled with epoxy resin. The bed of the machine will be a thick aluminum sheet with tapped holes on a 50x50mm grid to allow mechanical fixing of components.

Out of the four designs this design scores High for cutting performance, Low for ease of construction and Low in the cost category.

Scoring Table

               

	Design 1	Design 2	Design 3	Design 4
Cost  (Weighted by a factor of 2)	2	2	3	1
Ease of constuction  (Weighted by a factor of 1)	2	2	3	1
Cutting performance (Weighted by a factor of 4)	2	1	1	3
Total points	14	10	13	15

               
Design one is a very well rounded machine with reasonable performance, reasonably easy to manufacture and put together and reasonable cost.

Design two has poor cutting performance but is well rounded in other aspects

Design three has poor cutting performance however is very cost effective and very easy to manufacture and produce.

Design four, will cost the most, will be hardest to manufacture however will have have by far the best cutting performance.