< <br>
2. [FabAcademy Kannai 2022](https://fabacademy.org/2022/labs/kannai/Weekly_Group_Assignments/week07/) <br>
3. [FabAcademy Nadieh 2021](http://fabacademy.org/2021/labs/waag/students/nadieh-bremer/blog/week-7/) <br>
4. [FabAcademy Vigyanashram 2022](https://fabacademy.org/2022/labs/vigyanashram/groupassig/groupassignment5.html)
## Safety Instructions
Safety was topmost priority. Mentor Steven placed effort to ensure we learn the risk and danger of CNC router. <br>
Steven also gave us our PPE (example: Safety Goggles, Muffers) and ensured that we are always properly geared (long pants). The vacuum should always be on and the emergency button was always in our hands when machining.
The medium was always properly screwed in place before usage. <br>
We finalised our terminology using the terms in the list referenced from 2020 SP FabAcademy Grp <br>
We also had safety briefing summarised in the list referenced from 2020 FabAcademy Grp<br>
We are advised to always look at the machining during usage.
<img src="https://fabacademy.org/2020/labs/singapore/group.assignments/assignment05/Assign05_images/Terminology.jpg" />
<img src="https://fabacademy.org/2020/labs/singapore/group.assignments/assignment05/Assign05_images/Safety.jpg" />
<img src="./listening.JPG" width="480" />
<img src="./screw.JPG" width="480" />
<img src="./button.JPG" width="480" />
## Test run out, alignment, speed feeds and toolpaths
### Workflow
There are two workflow for CNC which are made known to us as shown in figure below refenced from FabAcademy2020 Grp Students.
<img src="https://fabacademy.org/2020/labs/singapore/group.assignments/assignment05/Assign05_images/create_tap_files.jpg"/>
We used the VCarve Pro workflow. <br> <br>
** Updates to Global Evaluator**
### Test Methodology
Steven showed us the ropes of what parameters to start with. Initially, we wanted to test various speeds on our own, but were cautioned both
by our instructor and during the online lesson about the dangers if a tool breaks.
Therefore, we decided to use some reasonable settings
provided by the lab based on the recommneded tool, as well as do our own literature research on what the parameters mean.
<br/>
**Chip load**: measurement of thickness of material eremoved by cutting edge during a cut
**Flutes**: number of cutting edges of a tool
**Spindle speed**: speed at which the tool is rotating
**Feedrate**: tool engagement speed with the stock
<br/>
|Parameters|value|
|-|-|
|Chip Load| 0.1875 mm/min|
|Number of Flutes | 2 |
|Spindle Speed| 12,000 rpm|
|Feedrate| 4500 mm/min|
|Cut offset| 0.3mm|
<br/>
### Settings used for Wood CNC
We used the following formula to figure out what each values should be.
Feedrate = Number of flutes x Spindle Speed X Chipload.
However, since the Chipload is automatically generated from VCarve pro tools settings, we need to rearrange the formula for better comprehension
Chipload = Feedrate / (Number of flutes x Spindle Speed)
The tool we used was an Onsurd 6mm diameter, 2 flute, flat end mill.
<img src="./2_flute.jpg" width="240"/>
The recommended chipload by the lab for the tool we used was around 0.1875 mm/min.
As shown on the lesson website, the recommended range for chip load was between 0.01 inch/min to 0.001 inch/min,
which in mm are values between 0.254mm/min - 0.0254mm/min, which matches up with what was recommended by the lab.
We read the [documentation from Onsurd](https://www.onsrud.com/images/LMT%20Onsrud%20Product%20Cutting%20Tools%20Catalog%20PCT-19.pdf) and
cross verify if the chipload would provide a good enough cut. (see page 114/132, 1/4 inch cutting diameter for tool type 52-200 for soft plywood is around 0.006-0.008 inch/min)
We concluded the lab recommended chipload was within the manufacturer's specifications, and should function as per intended.
We thus followed Steven's recommendation of 4500mm/min feedrate and 12000rpm of Spindle Speed to be good.
<img src="./Setting.JPG" width="480" />
We further asked if we could increase the feedrate, but was advised against it. This is because if the feedrate is too high, we will not be able to generate
large enough chunks of chips, which will carry away heat generated from the rotating spindle. Furthermore, it might generate too much vibration, causing the
cut to have weird artifacts.
### Test results
For the actual test, Steven advised to cut a block along with some holes, and see if they fit properly. This allows the following tests:
1. alignment: place the wooden piece in the hole and check if the bottom is able to align
2. runout: measure the length of the actual cuts and compare with the expected length
3. kerf: how much offset is required in order for the piece to slot in the holes
The stock used for the test was measured to be 14.9mm in thickness.
We positioned our dxf as job into VCarve Pro.
<img src="./cncdesign.jpeg" width="480" />
<img src="./milled_grp_assignment.jpg" width="480" />
The cuts were rough on the edges because the plywood we got was of low quality. Even after cleaning up, the wood was still very fiborous. This is actually
an acceptable cut.
The width of holes from left to right have increments of 0.1mm to check for kerf agaisnt the stock. To check for runout, we measured the width of the 50mm Cut
with a digital caliper.
The results of our test is shown in picture below
<img src="./cnc1.jpeg" width="480" />
<img src="./nice_fit.jpg" width="480" />
We were able to fit it into the holes up to 14.8mm hole, which started to get very difficult to remove. indicating the kerf to be roughly 0.05mm (0.1mm/2 for top and bottom). When we are making
parts to fit into each other, we can have 0.05mm as kerf if we don't plan to disassemble the product, or not have any offset at all if we still want to disassemble it.
For alignment, we checked whether the wooden piece is able to fit in roughly perpendicular without any visible slants on either side, which passed the test. As long as we follow the SOP, we
should have no issue here.
<img src="./cnc2.jpeg" width="480" />
For runout, we can see that the stock has a 0.59mm increase from the expected dimension, meaning that we need to set a toolpath offset of roughly 0.3mm for outside allowance. Note: This has been
taken into account when generating the in-cut for the holes to test from lab provided parameters.
### Summary
|Machine Name | Versatil 2500|
|-------------|--------------|
|Software | VCarve Pro|
|Diameter of Mill | 6mm|
|Spindle Speed and Feedrate | 12000rpm, 4500 mm/min|
|Plunge rate | 600mm/min |
|Pass | 40% was advised |
|Chipload | ~0.1875mm/min |
|Runout | turned out 0.6mm in the test which matches the lab's recommended settings|
|Alignment | adjust positioning of end mill on the board via the controller to zero the x and y position to get a good cut|
|Fixturing | fixed board by screwing into sacrificial board|
|Materials | plywood|
<br><br>
** End updates**
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