Maryam's Fab Academy

The aim of this week group assignment is to test runout, alignment, speeds, feeds, and toolpaths of the CNC machine avaialble in our fab lab. The individual assignment is to design and build something big using the CNC machine.

Machines used:

CNC Machine: ShopBot.

Softwares used:

Fusion 360.
VCarve Pro.

This week assignment content:

8.1. Group assignment.
- 8.1.1. Test runout, alignment, speeds, feeds, and toolpaths for your lab machine.
8.2. Individual assignment.

Design resources:

Final version of this week files:

CNC Machine

It is a computer numerically controlled machine that can use different cutting bits rotating at a high speed rate. The machine use in the lab is the SnapBot. It can handle 4X8 foot sheet and has 3 axis, x, y and z.

cnc_machine

8.1. Group assignment.

For this group assignment we have test runout, alignment, speeds, feeds, and toolpaths (cut out, ingrave, drilling) for our lab machine "ShopBot PRSalpha". Click here to go to the group assignment page.

8.2. Individual assignment.

8.2.1. 3D Design.

I have designed a simple table that consists of multiple parts that can fit all together. I set all my design dimensions as parameteric variables so I can change them when I need. Material used for the cut is MDF of thickness 18mm, so I set the material thickness in fusion 360 as 18mm. All parameteric variables used in the design are listed below:

parametric_variables

Since the milling bit is round, the result of cutting in the corners will has round shape and the cutting parts will not going to fit in. To overcome this problem, DogBones are usually used. To add DogBones in Fusion 360, download the Add-in file from here, and simply add it from the top TOOLS menu > ADD-INS.

dogbone

You can find my final design below:

8.2.2. VCarve Pro Settings.

Parts is then exported separately from fusion 360 as dxf files and imported to VCarve Pro software for editing. First When open VCarve Pro, you will get the following page, click on Create a new file.

vcarve_create

Set the cutting sheet dimensions and the datum position. settings

Import parts from the left side icon “Import vectors from a file”. import

Then, my lab instructor suggested me to move the beams holes further to the sides and increase the height of the front and back sides parts so the beams holes become in the middle instead of in the bottom of the shape, which makes the design more rigid. In addition, the beams long increased to go for a further distnace inside the pocket holes.

To do that, I have removed the previous made holes in Fusion 360 using the Interactive Vector Trim tool.

trim

Add new holes by drawing rectangle shapes. holes

Increase the size of the beams by adding rectangle shapes of size 15x18mm to the sides of the beams beam beam2

Add dogbones to all holes in the design and make a fillet to the bottom corners of the front and back sides part. dogbone_fillet

Create cutting Toolpath by selecting the vectors you want to cut. Set the cutting depth to 19mm to make sure that the milling bit will go all the way through the sheet and can arrive a little bit to the sacrifice sheet. Set the Feed Rate, Spindle Speed, and Plunge Rate of the tool as recommended in the MDF table provided by ShopBot here.

cutting_tool

Add tabs to the cutting vectors to hold the parts after cutting from flying out of from the cutting bed.

tabs

Create pocket Toolpath and set the cutting depth to 15.4mm so the milling bit will not cut the sheet that has a width of 18mm. As mentioend before, set the Feed Rate, Spindle Speed, and Plunge Rate of the tool as recommended in the MDF table provided by ShopBot here.

pocket