Computer Controlled Cutting-
Tasks for the week:
Group project test runout, alignment, speeds, feeds, and tool paths for your machine
Individual project Make something big (on a CNC machine).
What is CNC Machine?
CNC stands for Computer Numeric Control it is a process used in the manufacturing sector that involves the use of computers to control machine tools. Tools that can be controlled in this manner include lathes, mills, routers and grinders.
The process involves creating a CAD(Computer Aided Design) file of the desired object. Then a specialized CAM (computer aided Manufacturing) software is required to convert the 3D CAD file into a set of codes which the machines can understand. CNC machining language, called G-code essentially controls all features like feed rate, coordination, location and speeds. With CNC machining, the computer can control exact positioning and velocity.
-I am first time using CNC Milling so I am learning basic command,CNC software and all the things.
Made sure i set the origins and used all the waste spaces of the boards used by the other students. So this complete shoes stand was in a way done for free from waste plyboards lying around. It meant i lost a lot of time doing this. 4 Days as we had access to the shopbot only 4-5 hours in COEP, pune enough for just about one cut with mounting and amounting of board (used c-clamps and drilled screws for securing those.)
ShopBot 3-Axis CNC Milling Machine
ShopBot PRSalpha
ShopBot PRSalpha
Shopbot is a large format CNC machine which can be used to cut timber, plywood, soft aluminum etc. It is a 3-axis machine and has a bed size of 4x8 feet. This machine is very modular. That means it can be easily disassembles and transported to a new location an reassembled. We have in our lab a.
The shopBot we are using is PRSalpha 96X48. Which has a Gantry size 96X48 i.e 8X4 foot.
Cutting logic: How to cut with a ShopBot
The ShopBot is like any other CNC machine which we have used previously. It runs on a series of commands which are called G-codes. These codes are like instructions executed line by line, they tell the machine where to move and what to cut. There is a whole host of processes involved in computer controlled cutting, and it all starts with a CAD design.
This is usually the first step in any CNC manufacturing process. You have to first design what you are going to cut. For cutting you need a 2D vector path of the part. You can design in your favorite design tool and export as a .DXF file which can be used by Vcarve. I used Solidworks for designing the path and Rhino for some light modifications as it is easier to edit DXF files in Rhino. Once the CAD design is done now we can move on to the CAM setup.
For controlling shopbot, we need to generate a G-code file from the CAD, in order to do that we need a CAM software. We use Vcarve for generating the shopbot file from the CAD design.
Test Cutting: Finding the Tolerances
Spindle Test:-
We made test part to check the dimensional error and finish while varying the speed and feed rate.
We cut some slots with 40mm thickness and we got this results which shows below:
We got our test parts and they look like this... |
For this results we concluded some points: |
We did a group task of finding the tolerance required for press-fit assembly. We have in our lab plywood sheets of 9mm , hence we cut slots from 9 to 8.5 in steps of 0.5mm. We found out that the right fits comes somewhere near 8.5 and 8.6mm. The material thickness does vary a bit hence I decided I would put a value in between these numbers.
Vcarve: learning how to use the software
ShopBot is unlike any other machine we used before, we cannot just click print, like we did with the laser cutter. There is a lot that needs to be taken care of before you can cut.
So to learn how to use the software and setup the machine I decided to cut something small. It would be 15x15cm with a pocket, a projection, a few slots and some text. I was aiming to use maximum variety of tools and learn how they work.
I designed it in fusen and exported as .DXF and imported it to Vcarve. In the first step it will ask you about the material, the thickness, the offset if necessary, and where you want the origin to be etc. Set them appropriately.
How to set up ShopBot
When working with a CNC tool always remember that you are not the one controlling the machine, you cannot predict where the spindle will go. As is you should never reach your hand into the machine when it is working. Never work with ShopBot when you are distracted or sleepy. Some Cuts can take hours and you should not leave the machine to run on its own.
Its important to wear eye protection and gloves at all times. The machine spindle is rotating at 12000RPM, it can and will spit out high speed projectiles at you, and If you are not careful it can seriously harm your health.
Once you have set all the tool paths in the software we can begin setting up the machine. First you have to load the stock into the machine, align it properly to the bed and fix it in place with screws.
Mane power switch
Power Switch
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Here I am learning shopbot software |
The top of the table has to be level at all the heights the table is designed for, hence I need to design the angles properly. The step of each teeth has to be fully resting on the key otherwise it cannot support the load.
Check the bed level-
{My design shoes stand in fusion software -}
export pdf file-:
pdf file part 1- |
pdf file part 2- |
Next
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connect the whole part- |
Next first inside cut-
Next second outside cut-
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There is a button with XY written on it this is the return to home button. The machine has a home position at the top right, near the control panel. Once you click it, an alarm will go off indicating that the machine will now move.
This would be a good time to put the bit into the machine, you can move the spindle using the arrows keys on the control panel.
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correct check and End mills.
Once done, get the wrenches out and remove the collect check. Put in our new bit and tighten it properly. Remember to never put the bit in too deep or too shallow. The chuck should close just above where the flute ends.
Group assignment
We are learning about tolls, bad size and all knowledge shopbot
Here we are Open the bit
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Tool inside hol-
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Bit 2.5mm-
assembling process-
Here I am filling
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So finely here my complete assembled shoe stand
Next step
perfect pressfit |
Final assemble-
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