Introduction: CNC Milling Machine
Heavy CNC milling machine project started in 2015.
A lot of different working steps are necessary to build a big CNC machine with good milling performance;
Building a big and accurate mold for casting the epoxy granite.
Aligning the linear guides and ball screw.
Setting up the electronics; stepper motors, spindle and the home switches the power supply and the connection to the computer with the CNC controller Linux CNC.
And finally a housing for clean and optimal machining experience.
Step 1: Planning and Making Decisions
It took me some time researching about CNC constructions, CNC parts, casting and possibilities before i could start. I decided do make a heavy epoxy granite CNC for high speed milling. The components are low price CNC parts from China. One first thing to decide is the working space for the x, y and z axis. In my case 450mm x 350mm x 200mm.
Step 2: The Plan
My working space was defined and i made a plan so i could order the right length guiding rails and ball screws, also the amount of epoxy resin had to be calculated, inserts bolds, and plywood for the mold.
Step 3: The Mold
The heavy CNC machine granite is a two part structure, the base and the bridge. Therefore i had to make two big molds. The molds are made out of thick plywood with the lamination on the inside. Some dry layers of liquid wax are important for separation after the cast is cured.
Threaded bolds, made on the lathe by modifying big hexagon bolds, are positioned through previously precisely drilled holes and fixed with screws. They are for mounting the guiding rails, ball screws and stepper motors on the cast.
The aluminium pipes inside the mold make the holes for the bolts that hold down the bridge on the base.
Every inside corner of the mold is sealed with silicon bevor waxing all laminated faces.
The bottom side of the mold must be perfectly flat for casting, the mold has to be positioned on a reference granite plate.
The mold is now ready for casting.
Step 4: The Epoxy Granite
The epoxy granite is a mixture with epoxy and gravel filler with different grain sizes. The sizes are chosen to make the most possible dense gravel mixture. This saves expensive epoxy and it makes the machine heavier and more stable.
One important thing is to make sure that the mold lies flat on a reference surface.
Thick layer of epoxy can get hot during hardening. the heat can bend the wooden mold and destroy the surface. Clamped down the mold on the reference surface to prevent it.
Mix the epoxy with the dry gravel and sand, carefully by hand, not to get to much air bubbles inside the epoxy granite mix.
Pure the epoxy granite inside the mold and use strong vibration device to shake out every air bubbles. The impact drill is just a tickle for 300kg (The epoxy granite the granite reference plate and the mold with claps)
Hope for the best and let it cure.
Step 5: The Linear Guiding Rails
The guiding rails need to be positioned perfectly to each other in any direction, starting from the x rails.
The X rails must be parallel and straight. The Y rails than need to be aligned to the X rails and they also must be straight and parallel. The Z than has to be aligned to the Y and Z rails.
Step 6: The X Y and Z Axis
I made the moving parts on the x y and z axis primarily from wood to be able to machine them from aluminium later. It was my only option since i had no other metal cutting machine.
Step 7: The X Thread Grid Plate
The x axis is moving the grid plate in x direction. To machine a part, it has to be mounted on this plate by screwing it to the thread grid.
The z axis moves the spindle motor up and down. For clean and straight cuts the spindle must be mounted perfect vertically to the x fixing plate. The construction must also be rigid to hold up the forces during heavy milling.
Step 9: Machining the Aluminium Parts
I machined all the aluminium with my wooden CNC setup. It worked great but at the end i noticed that the wooden structure was about to get retired, luckily not until i finished all my parts.
Step 10: Electronics, Cover and Lubrication
One big subproject was the electronics with the stepper motors, spindle setup and limit switches. Also the covers to protect the linear guides and the central lubrication for the sleds and the ball screws.
Step 11: The Housing, Dust and Cooling System
The machine than needs a housing for water cooling, dust collection and safety. I made the frame from stainless steel and plexiglas doors and windows. The working space is covered and sealed so every drop of water should run back into the cooling water system.
For dry dust collection while milling wood i have made a dust shoe to remove dust directly from the cutting tool.
Step 12: Cover
The x axis rails and the ball screw is covered with a telescope cover made from 2mm aluminium sheets. I cut it with the Jigsaw, made the V-grooves with the router and bend it by hand.
Step 13: Cooling Water Drain
The water for cooling the milling tool has to be directed into the collection container with a filter to circle the water.
Here is how the water drain was made with an angle grinder. We bend it by hand and weld the corners.
Step 14: Testing and Milling
Finally milling with the own machine is the best part when everything works well. I still need some upgrades and some more steps to complete the machine in total. Although i am milling since 2016 and constantly making my CNC upgrades alongside. Here are some projects i made with the machine.
Step 15: Testing the Performance
By cutting high quality aluminium with the CNC machine.
Step 16: Experimenting
There are many possibilities wit a router on 3 axis. One experimental milling project was engraving a round wooden bar.
Step 17: Find Milling Projects
Now its time to continue to be creative and start some milling projects like artistic 3D models, engravings or just parts for a new project.
Step 18: Let the Machine Do the Work
When everything worked out well you can relaxe, whats left is to feed the machine with material and it will replicate your part.
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