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● CNC-350 The test procedure of C axis position acuracy

Ans:

Our CNC slotting machine rotary table indexing operation only one direction , our CNC unit also only allow one (+) direction rotation .
Please explain it to your customer CNC slotting machine is not rotary table for CNC machining center , as you know the worm and worm gear driving at one direction which accuracy is good no backlash problem . For CNC slotting processing also no need forward /backward freedom rotating , so in our CNC program all run the rotary table at one direction only , when test accuracy you need also run the rotary table at  one direction testing.

Please also understand that our design is before keyway slotting , the first operation is indexing to first angle ,then next step execute slotting process , the accuracy basic from first angle .

The enclosed of photos are our program of below example for your reference .
For example  12 keyways , first angle is 30.000 degree , CNC unit will turn the rotary table to 30.000 degree then make the keyway , then next rotary table turn to next 30.000 …… So you must use first angle as basic standard because it can be no backlash problem.

Hereby we use 0.001mm dial gauge to test the rotary table accuracy in our factory , our method is use MDI to turn the rotary table at 30.000 , then put a 0.001mm dial gauge on ram to test T slot surface on rotary table .We set the dial gauge at 0 ,then we  ask CNC to turn 12 times 30.000 to come back original position , then check 0.001mm dial gauge error , we attached the video for your reference , the repeat is same at 0 , it means the first angle and last angle is same , so the rotary table indexing accuracy is not bad as your report.

Video link : https://www.dropbox.com/s/zryaw8ny1wy5jl1/Rotary%20table%20accuracy%20test.MOV?dl=0

We don’t know your customer measuring method , maybe your customer use not suitable method to test our CNC slotting C axis position accuracy , Please ask your Engineer to test CNC-350 as per below test procedure.

  1. Only +  one direction test because CNC  SLOTTING no use  two direction freedom indexing , use two side rotating maybe have backlash problem. 
  2. You need test 30.000 , then next 60.000 ,then next 90.000 ,then 120.000 , then 150.000 , then 180.000, then 210.000 ,then 240.000 ,then 270.000 , then 30.000 ,then 330.000, then 360.000 .

The you use first 30.000 as standard (basic) to compare every angle deviation .  Why use it to test because our CNC slotting real operation as it.

I don’t know how you can use 3D CMM to test CNC-350 ?
Do you real test cutting keyway then measuring work piece, then get the report  , if you test finished work piece  , the tool center is accuracy or not  , tool setting is good or not ?  Or work piece center etc.. are important ,then you just can get the accurate work piece then you just can use 3D CMM to test ? 
Please let us know your customer use what method to test by 3D CMM ?  Sometime because  wrong method  then it caused the wrong measure result.   

You can prepare real cutting tool and adjust the tool very well and adjust the work piece center well , roundness perfect align the tool direction well , confirm every adjustment and setting perfect then test cutting the work-piece , then just measure the work- piece.
But please notice that the Keyway is not suitable measuring by 3D CMM . Because the keyway depth is very small , while you use 3D CMM , the engineer must be very skill .Otherwise , there is possible to cause the measure report is wrong .
Please also double check your engineer checking method while he use 3D CMM.   Also notice Keyway depth only 5mm , it’s not easy to get long distance for keyway line, if engineer not very carefully and skill use 3D CMM , it will happen wrong inspecting report.

We think CNC-350 real operation , gear run at one direction , the index accuracy should be OK.  Please adjust machine condition and adjust tools setting accurate the check the finished work piece  ,  just notice tool setting and work-piece setting are very important , no accurate tool and fixture setting , you cannot get accurate work-piece and good inspection.

Solution:

  1. use 0.001mm dial gauge to test the rotary table accuracy, the method is to use MDI to turn the rotary table at 30.000 , then put a 0.001mm dial gauge on ram to test T slot surface on rotary table .We set the dial gauge at 0 ,then we  ask CNC to turn 12 times 30.000 to come back original position , then check 0.001mm dial gauge error , we attached the video for your reference , the repeat is same at 0 , it means the first angle and last angle is same.
  2. Follow above video of test procedure for C axis position accuracy.