7. Computer-Controlled Machining (Indonesia)¶
This is group assignment page of Electronics design (Indonesia Student) :
Group assignment:
- do your lab’s safety training
- test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine
Big CNC Machine in our Lab¶
Zhongke ZK-1325
Specification¶
- Working Area : 1300mm x 2500mm x 200mm
- Table material : Thicken welded steel Bed, Aluminium Alloy table
- Maximum feed height : 200mm
- X,Y,Z Guideway rails type : Square guide rails Taiwan HIWIN, rack transmission
- Max Engraving Speed : 20000mm/min
- Resolution ratio : 0.002mm
- Repetition accuracy : ±0.02mm
- Spindle power : 3.5KW air cooling spindle or 3.2KW water cooling spindle
- Spindle Rotating Speed : 6000 -18,000rpm(6000-24000rpm)
- Spindle cooling : Water Cooling
- Drive motor system : Stepper Motor and Driver
- Engraving Command : G code, u00, mmg, PLT, HPG
- Command language system : English Version, Windows 98/2000/XP Operation System
- Operational Software : Original Type3 Software, ArtCam software or Wentai Software
- Command language system : English Version, Windows 98/2000/XP Operation System
- Software Compatibility : Support CAD/CAM software, PLT format, Corel Draw, Auto CAD
Safety Operations¶
Things that must be considered in safety during machine operation:
- safe glasses
- don’t put gloves(while CNC working)
- Put gloves when carrying material
- always put hand on emergency stop
- don’t control together
- Don’t leave from working machine!
- Put Fire extinguisher
- Take care for clothes, scurf
In our lab we already use safety glass, face masks, ear protection, first aid kits, fire extinguishers
Procedures¶
Handheld controller¶
Machine operation using handheld controller
Install the material¶
To operate a ‘big’ CNC milling machine, there are several procedures that must be followed. Large machines can easily injure the operator or damage the material or the machine itself. Therefore operating procedures must be clear and adhered to.
- pump the lubricating oil (1x)
- Switch on the machine, position the tool/spindle in the home position
- slide the spindle on the side outside the area (y+) of the workpiece to make it easier to put the material
- put the base wood material (choose a flat material), we can use MDF board as a work base
- put the cut material on top of the base material.
- clamp the two materials tightly and straight the surface of the material
- material ready to use
Install the tool¶
We need to install a cutting tool for the process of cutting wood material. Incorrect tool installation will cause the tool to fall, damage the material or the machine itself. Installation steps as follows:
- open the locking ring (black) if needed use pair-wrench to release,
- if using the pair-wrench, turn both towards each other to loosen the lock ring
- after the locking black ring is removed, attach the collet (adjust the collet size to the diameter of the tool to be installed)
- Collet installation to the ring by hitting the collet quickly towards the black ring so that it locks up
- make sure the collet surface is flat with the lock ring surface
- attach the collet and locking ring to the spindle (turn the screw to tighten it sufficiently)
- install the mill tool (e.g., flat end mill 2 flute dia 2 mm) on the collet and hold it so it doesn’t fall down
- move the spindle position in the area above the material (wood) so that if the tool falls it is not broken
- adjust the flute distance about 5 - 10 mm from the gripping position
- tighten the black ring until it is tight and make sure the tool does not fall and the collet surface is flat
- Tighten again using a pair of fasteners, the direction of tightening is opposite to each other until it is really tight
- after the tool is installed, the machine is ready to use
Information about the collet
Collet is a tool in the arbor tool that serves to clamp tools that have small diameter variations. we don’t need to replace the arbor, just replace the collet if we want to change the tool. The collet size also varies depending on the size of the arbor. This CNC machine uses an ER32 size arbor, so the collet size also adjusts to the ER32 size. The inner diameter of the collet varies depending on the size of the tool to be used.
Setting the origin¶
There are two types of “origin” in this machine which are machine origin and working area origin. One important thing to remember is that all software we use to control CNC machine has “virtual board” where the height and width is as same as the real working area. Eventhough in some cases, its dimension is adjusted according to height and width of an object to be milled or cut. Origin of our CNC machine is adjusted using handheld controller. When origin button is pressed, the end-effector will move to the most left-bottom. The position of end-effector can be readjusted to specific position by pressing X+ X- and Y+ Y- button. To save new position, X->Y button is pressed. Then it will go to coordinate (X-Y) or position where the milling will take place.
Running Test¶
The rectangular object test¶
In this test, we draw simple 5 x 5 cm rectangular in vector software like Inkscape or Coreldraw or Illustrator. Then we import the SVG image to Cut2D Pro software and position the object inside the working area. The endmill we are using is 6mm radius with appropriate collet. The test that we did is to see precision of milling result which is supposed to be 5 x 5 cm. Below images depict the results. Two upper images are the milling result when we select “cut outside” with two tabs. It can be seen that the discrepancy over real dimensionality is small. The lower image depicts the “cut inside” selection where the error are bigger than the former test. Both of the milling process are conventional process. The other parameters we set are speed = 10000 RPM, F = 6 mm/s, P = 1 mm/s.
The assignment object¶
How to run the program