Special Purpose Machine servo driven axis movement for drilling holes on varying PCD at accurate angles.
Customer's Initial Machining Process:
Used a VMC.
Clamping sing a C washer and bolt mechanism.
True the job which would take around 5 minutes.
Machining cycle time for drilling of Ø31.75 mm for a depth of 56.3 mm using a U drill would take around 35 minutes.
A Total of 40 minutes used to be taken up for one job to be completed.
Our machine concept & Implementation:
Feature’s & Specs:
2 servo controlled axes for (a) rotational movement of the rotary table, (b) cross axis movement of 10 HP drilling head, which can do drilling upto Ø36 mm drilling.
Servo controlled linear axes movements & rotary movement are for accurate pitch selection & accurate indexing respectively.
Drilling head with special angular contact bearings arrangement for high level of accuracy & rigidity. Head driven by a 10HP motor with a combination of gears and timer belt and timer pulley arrangement for obtaining required speeds without torque drop.
Ball screw, box nut mechanism in combination with gear box for cross axis movements of the milling head.
Hydraulically operated vertical movements of the drilling head.
Swing clamp cylinder can be provided for automatic clamping.
Touch Screen enabled HMI (Human Machine Interface) for quick “on machine” program selection, program editing by the operator & quick troubleshooting.
Male sliding surfaces are with case hardened guideway strips and female sliding surfaces are with turcite lining for smooth axes movement & best wear resistance.
Centralized automatic lubrication to lubricate all rotating & sliding parts at pre-set regular intervals.
Machine enclosure & guideway protection
Machine to have PLC program.
High pressure coolant thru with rotary joint for quick chip evacuation
Total machine enclosure, required for high pressure coolant dispensation.
Chip conveyor for easy chip disposal.
Sequence of Operation of Machine:
Load the job onto fixture manually
Close the door and press auto cycle.
The servo driven horizontal slide moves from home to required distance to obtain the pre-fed PCD.
Spindle ON, coolant ON, Vertical hydraulic slide having head mounted moves in rapid to the cutting zone and slows down to the required feed rate while cutting.
Vertical slide retracts out of the hole and table indexes to the next pre-fed angle for drilling next hole.
Same indexing & drilling is followed upto 360°.
The slide and table moves back to home.
Job unclamps, unload job.
HMI Enabled Easy Programming:
One of the setbacks in owning a VMC is requirement of CNC programming knowledge to alter or change the program.
In our machine with a HMI, programming knowledge is not at all required. Simple instructions can be followed on screen to modify or change the program.
Working as shown in the upcoming slide.
Final Conclusion (Advantages of the Rotary Coordinate Drilling machine over conventional VMC) :
Cost is very high for high powered VMC which can drill upto Ø36mm holes.
Either a custom made fixture has to be made or job directly loaded onto machine. But in both case truing of job is required to start cycle, which eats up into cycle time. Manual clamping also increases the cycle time.
Cycle Time is about 35-40 minutes for Ø31.75 mm x 56 mm deep hole.
A skilled CNC operator is required to run the machine which increases wage bill.
CNC programming knowledge is required to change program in addition to skill required to true the job.
Different Jobs requires different fixture.
Rotary Coordinate Drilling SPM:
Cost is around way less that a VMC.
Being a custom made machine, a special fixture is provided, which does not require any pre machining alignment checks. Just load the job & press auto cycle. Clamping is also automatic, hence saving a lot of time.
Cycle Time is about 12 minutes for Ø31.75 mm x 56 mm deep hole
A semi-skilled or unskilled labour is required who only has load-unload the job & press auto cycle button.
HMI enables easy pre-programmed selection & if the program has to be altered only the PCD & angle value has to be entered into the HMI which will program itself for change in cycle.
Easy change fixture will accommodate a large variety of similar jobs.