Planning the first version

3.2 Planning the first version

When the Ormerod was assembled and tested, it appeared there were a few modifications that needed to be done on the original design to make it support a table/table configuration. The table/table configuration would add a rotary system on top of the Y-axis. This gives the Y-axis motor more weight to move compared to the original print plate on the Ormerod. To compensate this an extra motor had to be added to the Y-axis to make sure the Y-axis would be able to move the rotary system. The rotary system would also raise the print plate and be wider than the original print bed. To compensate these changes the platform and the Z-axis had to be expanded.

As mentioned in section 3.1.3 it is convenient to keep the origin of the machine coordinate system (MCS) at the point where the rotary axes intersect. To make sure this is the case the design of the rotary system should be designed with the print plate in focus. The print plate should also have an adjustment ability to make sure the print plate is laying directly in this origin.

In the worm gear system that was chosen for this system the worm have a different hole diameter then the axle of the motor, 6 mm and 5 mm respectively. One solution to this problem would be to add a lining between the worm and the axle of the motor.

3.2. PLANNING THE FIRST VERSION

When the A-axis is rotated to an angle, the nozzle must to be able to reach the print plate. In the design of the Ormerod the nozzle mounting has obstructions on both sides, as can be seen in Figure 3.4. One of these sides is the cooling system for the nozzle and needs to be there, while the other side can be improved upon. To avoid that the system has different relations between the print plate and the nozzle is depending on the A-axis being negative or positive, whereas the A-axis will be limited to 0° - 90°. By doing this the gear system in the A-axis will also be preloaded by the weight of the C-axis mount. This will, as mentioned in section 2.6, eliminate problems with backlash in the A-axis. The relation between the A-axis angle and the Z’ distance between the nozzle and the print plate (for the original nozzle mounting) can be seen in Figure 3.5. The values in this graph has been computed by measuring the distances in SolidWorks and then computing the A-axis angle and Z’ distance. An illustration of how these values where found can be seen in Figure 3.6.

Figure 3.4: The Ormerod nozzle mount, all distances are in mm.

CHAPTER 3. BUILDING A 5-AXIS SYSTEM

Figure 3.5: A-axis and Z’ limits for Ormerod. Computed limit is found as mentioned in section 3.2 and safety limit is the computed limit plus 10 mm. Values in red area will make the nozzle mount crash with the print plate, values in yellow area can make nozzle mount crash with the print plate mounts and for values in the green are the nozzle mount can move freely.

Nozzle

Obstruction

Z’

Figure 3.6: Illustration of how the relation between A-axis and Z’ distance between the nozzle and the print plate are found.

3.3. MODELING THE FIRST VERSION