24. Group Assignment Week 7 - Computer Controlled Machining

This week we are working on Computer Controlled Cutting individually as well as in group. The following are the group assignments.

Group Assignment

• Do your lab’s safety training
• Test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine

Group Members:

• Kamal Kumar Chapagai
• Sonam Deki
• Tenzin Dorji
• Pema Yangzom
• Dorji Tshering Drugyel
• Thinlay Namgyal

LAB Safety Training

For the shopbot machine, since it is a large machine with moving parts consisting of three dimensional movements in XY in the range of meters and Z axis in the range of centimeters, the shopbot lab poses major risk in damaging the machine and causing physical harm to us. Therefore, we have to be extra cautious while handling the machine. While the basic precautions and safety measures are highlighed here, the detail of the machine runout and cut from toolpath is in HERE

Cutting using Shopbot and Aspire (ToolPath)

Dress Code

For the shopbot lab, the dress code is of utmost essential. There are a couple of things we have to take care of:

- Lab Coat/gown to prevent dust damages to our cloths.
- Googles to prevent eye from potential flying objects and dusts.
- Noise cancelling head phones to prevent ear damage due to loud noise.
- Gloves to prevent damage to hand.

We make use of all the above protection equipments when working with the shop bot machine.

Machine Allignment

For the machine we have to first check to see bit is not loose, or change the bit if a different tool is required. Then we may measure the thickness of material that we plan to cut. Once the material thickness is known, we need to calibrate Z AXIS on the table. We make use of the control on the shobbot software to slowly aligh the endmill to the bed of the machine. For the machine in our lab, the automatic Z-Axis callibration is non-functional and hence we had to manually align the Z-Axis. Then we have to raise the Z-AXIS by few inches in order to load the material to the table. Setting the new X and Y Origins is of utmost importance so that the machine cut only where desired on the material. Not setting the XY axis would take the machine to unknown location and damage the material or create unforseen effects. We have to make sure to raise the Z-axis so the bit won’t drag on the table Once the Origin is set, we can proceed with either the drill routine or cut routing. We can then Select Cut to proceed. We also make use of spirit label to check the labelling of the CNC bed and the CNC router. In a number of cases, the cut was not perfectly aligned and was caused due to misalignment of the CNC router. We make sure to check that the router is properly aligned or make necessary adjustment.

Cooling System.

The CNC machine we have in Lab is water cooled. The cooling system runs throuh the router and keeps it cool during cutting process. We have to make sure that the pump connected to the colling system is switched ON and in running condition. Further, we also look at the pipes connected to the pump to see if there is running water within.

Design data and visualization

We have to make sure to create proper toolpath for both the drill hole and profile. Only the drill hole is selected to create drill hole and drive the screw. This is to prevent the board from moving while cutting. Once the drill holes are drilled, we have to make sure the screw properly holds the material on the CNC bed. This is to reduce misalignment and movement of materials.

Once the drill process is completed, the profile is to be created for the parts to cut. When we create the tool path, we can visuallize the movement of the spindle on the toolpath. Care should be taken to remove the drill path from the profile while generating the toolpath. This is to avoid the spindle from drilling on the screws used to fix the material. This will break the endmill. we had this happen to one of the student during his individual assignment.

Adding tabs for smaller objects.

In one of the sessions, we had a student who created small shapes for machine cutting. While creating the toolpath, the student forgot to add tabs on this design and the small parts would move out of its position and collide with the spindle. This way he had an endmill broken. While tabs are not necessary for larger object or very small objects, for objects that are would possible jump up from the table and hit the spindle it is absolutely necessary. This will prevent the materials leaving its position and possibly colliding with the spindle can causing potential fire.

Emergency push button

One of the easy method that can get the machine to be interrupted abruptly is the emergency push button. Whenever there is possible unintended movement of the machine we can make use of the emergency button to stop the machine. Because of the shear size and speed of the machine, there is potential of major mishaps and hence this method can effectively stop the machine from its movements.

This is the preliinary precaunary safety that we have to follow while working with Shopbot. Further runout and toolpath works are presented HERE