Videos – Performance Testing

 

Higher Accuracy and Better Finishes, in Less Time!

Sample Circle Diamond Square Part

Circle Diamond Square Test Part

Everyone agrees that reducing the cycle time greatly impacts the cost of production and the bottom line.

Time spent machining a part is the most significant contributor to part cycle time. Simply having a High Speed spindle does not result in automatic cycle time reduction. One can program faster feeds, but typically with most CNC equipment faster feed rates degrade the accuracy of the part. The limitation of the servos directly impacts the ability of the slides to move accurately and is directly proportional to feed rate. This limitation causes the tool to undercut or overcut the programmed path, requiring slower feed rates to accurately machine the part.
Adding acceleration / deceleration ramps only improves the starting and stopping, not the servo error in-between (Following Error).

With the NXGEN Control, the servo performance has dramatically reduced the Servo Following Error. Instead of having to contend with a Servo Error of .005″ or greater, we are now measuring results significantly less.
When compared to the Fadal Legacy control system, the NXGEN Control testing results shows it to be 40x more responsive. This improvement directly affects the part accuracy by closer tracking of the programmed cutter path.
Improved motion such as:
– contour shapes
– direction changes
– direction reversals
– holding position
– applying backlash

Servo Motor Lag

Typical Servo Motor Response At Reversal

The illustration shows one of the common shape errors that occurs with Servo Following Error. In this case, we are showing the error during servo direction reversal in the Y axis. This Flat Error is directly related to two characteristics: Servo Following Error and Mechanical Backlash. While Mechanical Backlash can be improved mechanically or by software compensation, the problem of Servo Following Error dynamically changes according to feed rates.
The Flat occurs when the Y-axis reverses direction. This is because when moving Y positive, the Following Error is a negative error, and when reversing to moving Y negative, the Following Error becomes positive.
The transition from negative to positive (Following Error) creates a servo dead-zone. The size of this dead-zone is directly proportionate to speed and is very difficult, if not impossible, to accurately correct with software, especially as feed rates increase.
With the typical machine today, the only solution operators have is to slow the feed rates to reduce the Following Error, which directly increases the part cycle time.

With the NXGEN Control, our approach has been to design a high performance servo system that virtually eliminates the Following Error from the system.

To illustrate how our performance improvements can directly reduce the part cycle time, we have three videos showing a standard Circle-Diamond-Square part being machined at various speeds with the part inspection results.

Feed Rate Test Specifications:
Machine: 1997 Fadal 4020 Box Way Machine. We adapted the NXGEN Control retrofit package, using the original Baldor/Glentek axis motors and Glentek amplifiers. The machine is mechanically in good condition. Doing a Ballbar test showed minor squareness error.
Tool: .500″ diameter carbide, 4 flute endmill
RPM: 10,000
Material: 6060-T6 Aluminum
Test Features:
OD Program Size 1.8000″
ID Program Size 1.0728″
Diamond Size 1.2728″

 


Video Showing Test 1 of 3

Test #1 Results – F40 inches per minute
Cycle Time: 72.7 seconds
Feed Rate = 40
Comment: A feed rate of F20 to F40 is in the typical range that machines use to achieve an fairly accurate part.
Inspection Results:
OD Actual Size  -.0004″,  Roundness .0002″
ID   Actual Size  -.0003″,  Roundness .0002″
Diamond Actual Size  -.0001″, Squareness ± .0003″

Crossover – XY No Measurable value (slightly visible under 10x)

 

 


Video Showing Test 2 of 3

Test #2 Results – F94 inches per minute
Cycle Time: Reduced from 72.7 to 30.9 seconds
Feed Rate = 94

Inspection Results:
OD Actual Size  -.0003″,  Roundness .0002″
ID   Actual Size  -.0005″,  Roundness .0005″
Diamond Actual Size  -.0001″,  Squareness ± .0003″

Crossover – XY No Measurable value (slightly visible under 10x)

 

 


Video Showing Test 3 of 3

Test #3 Results – F150 inches per minute
Cycle Time: Reduced from 72.7 to 19.4 seconds
Feed Rate = 150

Inspection Results:
OD Actual Size  -.0001″,  Roundness ±.0003″
ID   Actual Size  -.0006″,  Roundness ±.0004″
Diamond Actual Size  -.0002″,  Squareness ± .0003″

Crossover – XY .00025″ error measuring diameter at crossover, slightly visible

Comment: At this feed rate the mechanics of the machine begin to effect the dynamic operation. It was noted a better designed motor-ball screw coupler would be an improvement as well as correcting the squareness and checking the ball screw pitch error compensation.
Overall, the results are very impressive for a 1997 used machine.

 


Test Your Current Machine and Compare
Included is the program and drawing, we invite you to do your own tests to see how much you could be saving by reducing your cycle times.CDS Dimensions

%
N1 (DIAMOND SQUARE TEST CUT 2.0 BLOCK)
N2 T1 D1
N3 G90 G0 X1.5 Y-.7 M3 S10000
N4 Z-3.0 H1 (MOVE TO TOP OF PART)
N5 F150 (SET TEST FEEDRATE)
N6 G8 G1 X0 Y-.7 (CUT TOP OF PART)
N7 G2 I0 J0.7
N8 G1 Y0 X.1364
N9 Z-3.2 (.5364 ID)
N10 G41 X.4193 Y-.2829
N11 G3 X.5364 Y0 I-.2829 J.2829 (CIRCLE IN)
N12 G3 I-.5364
N13 X.4193 Y.2829 I-.4 (CIRCLE OUT)
N14 G1 G40 X.1364 Y0
N15 G0 Z-2.9
N16 X1.4303 Y0 (DIAMOND)
N17 Z-3.2
N18 G1 G41 X1.1652 Y.2652
N19 X0 Y-.9
N20 X-.9 Y0
N21 X0 Y.9
N22 X1.1652 Y-.2652
N23 G40 X1.4303 Y0
N24 G0 X1.8031 Y0 (OD .900 RADIUS)
N25 Z-3.4
N26 G1 G41 X1.538 Y.2652
N27 X.6364 Y-.6364
N28 G2 I-.6364 J.6364
N29 G1 X-.2652 Y-1.5380
N30 G40 X0 Y-1.8031
N31 G0 X-1.375 Y-1.375 (1.950 SQUARE)
N32 Z-3.6
N33 G1 G41 X-.975
N34 Y.975
N35 X.975
N36 Y-.975
N37 X-1.0
N38 G40 Y-1.375
N39 G9
N40 G0 G49 Z0
N41 X0 Y0
N42 M30
%