7. Computer controlled machining¶
This week, I made a big object by industrial CNC machine. Eino Antikainen Fab Academy Alumi 2017 taught us how to design the big object and how to use the CNC machine in Fablab.
1. Group work assignment¶
Eino gave us a lecture of the production used bigger industrial CNC machine regarding the CAD design with NC data preparation, tool paths, machine usage procedure and its safety issues. After the lecture session, we observed the performance of CNC router with the sample.
For safety, wear the protect glass and ear muff. The mask was due to COVID restriction but also better in normal condition preventing from the cutting dust particles.
1. Measurement sample¶
The sample was produced by speed value was 15000 rpm and cutting feed rate was 6000 mm/min.
2. Measurement result¶
The result was quite close the target of 3D CAD data.
| Measurement | Measured length [mm] | Target values [mm] |
|---|---|---|
| Board Width 1 | 150.13 | 150.00 |
| Board Width 2 | 150.18 | 150.00 |
| Inlay circle 1 | 49.8 | 50.00 |
| Inlay circle 2 | 80.35 | 80.00 |
| Inlay circle 3 | 99.60 | 100.00 |
| Depth of circle 1 | 2.79 | 3.00 |
| Depth of circle 2 | 9.78 | 10.00 |
| Pocket length | 88.63 | 90.00 |
| Pocket width | 8.74 | 9.00 |
| Dog bone length | 79.86 | 80.00 |
| Dog bone width | 13.78 | 14.00 |
| Dog bone circle | 9.74 | 10.00 |
| Circle hole | 9.76 | 10.00 |
2. Individual assignment¶
My design is for my own CNC machine, recently bought from Neil’s recommended Sainsmart.
To put on garage at my home, I needed an enclosure preventing the dust from milling and smokes from laser cutter etc.
1. 3D design with Fusion 360¶
The design is made by Fusion 360 since used previous weeks for mechanical design especially for 3D models.
Here is the requirements of the enclosure,
- Enough space for locating the CNC machine, thinking for handling the operation of milling bit exchange, space for laser cutter module set up etc.
- CNC machine will be covered when using the laster cutter module in order to exclude the smokes.
- Space for drawer to put the tools.
- Space for locating a laptop on the top to control the CNC machine onsite.
CAM settings¶
After design of basic structure done, set up the tool path, to make the CNC machine run.
In Fusion 360, change the mode from DESIGN -> MANUFACTURE, and set the origin as following left bottom corner of the stock.
Create pocket¶
Making a hole type of work, use Pocket. Settings are following changes from the defaults, I applied to holes of press-fit joints and mechanical holes of object.
Create contour¶
The area which removed a big size, like window type of place, I used Contour instead of pocket. Pocket also can make the shape but it is milling, CNC operation time becomes much longer, takes more hours so it’s better to use contour then cut out the place. The settings are following changes and I applied to bigger cut out places.
Simulation, export the file¶
In Fusion 360, you can check how the CNC milling machine works. You can change the operation order by the sequence of folder order of pocket/contour settings. By this order adjusting, you can make the efficient moving operation of milling drill that can reduce the operational time.
If the simulation is okay, export the file by this settings.
2. CNC milling¶
The CNC router machine in Fablab Oulu is Rensi E2 1325.
start up¶
Before using the machine, make sure the buttons and start up.
1. Power source of machine
2. Start the CNC milling machine and emergency stop
3. Start the vacuum pump
board and origin setup¶
First set up milled OBS board into the base board on CNC stage by screwing.
Set up the milling bit, if wrong size of bit, replace the bit by removing the cover and collet.
Set the zero origin of X and Y axises. By using the jog keys on the screen and set the collect zero origin position on the board. Then make the X and Y axises Zero.
Set the Z origin, Operations -> mobile calibrator tool. Put the calibrator tool on the board, then carefully down the milling bit into near the tool. Then start (click Continue) the Mobile calibrator on screen, the calibration starts automatically.
NC data run¶
Open the NC file which created by Fusion 360, File -> Open and load then selected my file.
Before starting the operation, this can check by simulation.
3. Assembly¶
Milling done!
Moved to hand work place and removed all components from the board. Used a knife but if the space is allowed, the hand saw is also useful.
After removed, there are many burrs on the edge. In fablab Oulu, there is a polishing machine, this is very quick and handy to polish the edge surface nicely.
Press-fit issue¶
Due to the size of milling bit, pockets of press-fit holes and joints corners are not the right angle and round shape. So the joints couldn’t go into…
Used the rasp bar of the right corner for all joints then problem was solved.
Result¶
Satisfied!
Reflections¶
- For press-fit connection on OBS board, it is difficult to make the correct size of holes and joints. Also need to consider the thickness of OBS board is not always same. If allows the design, dog-bone joint is more safe side for assembly.
- When you handle the OBS board, recommend to use gloves. OBS board has many thorns and rough surface, easily make your hands damage (My hands were damaged…). With gloves it can be protected and better grip to hold the board and tools, highly recommend!
