Cam Design 电子凸轮 设计 案例

1、Copyright 2011 Rockwell Automation, Inc. All rights reserved.Insert Photo HereRockwell AutomationMid Range Competency DevelopmentCam DesignOEM TeamCopyright 2011 Rockwell Automation, Inc. All rights reserved.2Topic Lists1. Definition of Mechanical CAMs & Related Systems2. CAM Design Math analysis 3.

2、 Prototyping CAM using RSLogix50004. Use of the RSLogix5000 ToolsetCopyright 2011 Rockwell Automation, Inc. All rights reserved.3Topic Lists1. Definition of Mechanical CAMs & Related Systems2. CAM Design Math analysis 3. Prototyping CAM using RSLogix50004. Use of the RSLogix5000 ToolsetCopyright 201

3、1 Rockwell Automation, Inc. All rights reserved.4Mechanical CAMs and related SystemsCopyright 2011 Rockwell Automation, Inc. All rights reserved.5Definition of Mechanical CAMs Mechanical CAM translates a primary unidirectional motion into either reciprocating (returning) or oscillating type of motio

4、n CAMs are typically repeatable and allow the designer to share geared, reciprocating and oscillating movements in the same system. CAMs can be flexible to an extent by allowing more than one secondary shape to be used alternatively in the same stage. CAMs can be very complex (Single stage vs. multi

5、stage) and contain additional mechanical systems (linkages, ) CAMs can be designed in a 3D fashion to allow changing shape with velocity Camshaft moves to alter the shape of movement progressively INOUTINOUT In todays world mechanical CAMs have been largely replaced by Servo Motors due to the follow

6、ing reasons 20-15 years ago Flexibility 12-8 years ago Price 6-4 years ago Accuracy 2 years ago and ongoing Dynamics Design Cycles changed with these developments A purely mechanical CAM system was typically sized with one large motor with high inertia to overcome the unbalanced reflected load gener

7、ated by the CAM shaft. The science behind CAM Design gradually improved to work with a secondary source of motion to provide optimized synchronization and dynamics. In mechanical systems the most crucial parameter on top of displacement (distance from center) was to generate jerk-limited (smooth) mo

8、tion, while for Servo Motors Velocity, Acceleration (current) and jerk-limitation are all equally important. Copyright 2011 Rockwell Automation, Inc. All rights reserved.6Need for Electronic CAMsCopyright 2011 Rockwell Automation, Inc. All rights reserved.7Topic Lists1. Definition of Mechanical CAMs

9、 & Related Systems2. CAM Design Math analysis 3. Prototyping CAM using RSLogix50004. Use of the RSLogix5000 ToolsetCopyright 2011 Rockwell Automation, Inc. All rights reserved.8CAM Design Math analysis On the right the equation set for different standardized algorithm sets that describe a Velocity “

10、jump” Any CAM can be separated to be displayed as multiple “Position Segments” using these Velocity segments.Velocity Accel Jerk V*ACopyright 2011 Rockwell Automation, Inc. All rights reserved.9Differentiating “restricted” to “free” CAMs Restricted Example Moving rotary tools restricted over a radiu

11、s, synchronous to material, shape of movement is predefined during this area Free Cam Example Rotary Tool needs to match product position on the conveyor to apply label, or glue. Velocity of tool does not match product velocity Linear movement.Copyright 2011 Rockwell Automation, Inc. All rights rese

12、rved.10The “math details” available from VDI(German association of Engineers)Copyright 2011 Rockwell Automation, Inc. All rights reserved.11CAM Design From Math to PLC code The algorithms displayed allow the designer to specify a movement that Reaches a Target Using a defined Velocity Providing Acce

13、leration and Jerk patterns The math behind it is very cumbersome in particular, when multiple different segments need to be combined that require different goal settings (parameter set of distances, velocities, accelerations is different). We will take on a real-world example of a simple bagger mach

14、ine (VFFS) and provide input in how Logix supports the design processVelocity Accel Jerk V*ACopyright 2009 Rockwell Automation, Inc. All rights reserved.12VFFS? Vertical Form, Fill, and Seal (VFFS) machines are used in the consumer products industry for a wide variety of products packing. The machin

15、e receives raw material, typically dry goods such as cereals or snack foods and non-food items, and places the product into formed pouches, which are finally sealed. These pouches are made of material that is flexible and heat-sealable which are usually plastic based. These machines are designed and

16、 built by OEMs for packing various products like salt, tea, sugar, spices, coffee, snack foods, wafers, detergent, henna powder, candies, and many other products.Copyright 2009 Rockwell Automation, Inc. All rights reserved.13VFFS PartsCopyright 2011 Rockwell Automation, Inc. All rights reserved.14VF

17、FS OperationSequence The Bag is transported with a constant pitch (“bag length”) per cycle.Product is inserted intermittently (start/stop) into a tube at a defined moment in the cycle using an individual synchronized transport (Auger Screw, Weigher) The Bag is formed into a Tube continuouslyThe Bag

18、is transported downwardsThe Length Seal is applied continuously or intermittently1.The Cross-Seal is applied using two reciprocating servos (one down and up, one open and close) or one servo (open and close during standstill of film)Copyright 2011 Rockwell Automation, Inc. All rights reserved.15Inte

19、rmittent vs. Continuous (Seal Transport) An intermittent VFFS is limited by the speed of the packaging material and the standstill required to seal the bagSimple filling mechanisms are typically sufficient to achieve between 50 and 90 packs/minute output.Ulma, Spain A continuous VFFS moves the seali

20、ng bar continuously up and down with the packaging material avoiding unnecessary standstills for the sealing cycle In conjunction with improved product filling mechanisms (such as an auger) will provide a performance increase of 50-100%VFFS HMI Template,Rockwell AutomationCopyright 2011 Rockwell Aut

21、omation, Inc. All rights reserved.16CAM for a reciprocating Vertical Sealing Bar Accelerate the pair of bars to material speed (Close the sealer) Maintain material speed until the sealing action has finishedConstant Seal time - will result in a variable distance due to line speed variation Decelerat

22、e & stop the Sealing bar (Open the Sealer) Return to original positionAccelSealStopReturnCopyright 2011 Rockwell Automation, Inc. All rights reserved.17Topic Lists1. Definition of Mechanical CAMs & Related Systems2. CAM Design Math analysis 3. Prototyping CAM using RSLogix50004. Use of the RSLogix50

23、00 ToolsetCopyright 2011 Rockwell Automation, Inc. All rights reserved.18Prototyping CAM using CAM Editor Simple entering of coordinates (positions) and selecting Linear or cubic interpolation will provide a valid profile This profile will run But it is not smooth And it is not an optimal usage of t

24、he motor With a ball screw or a belt this type of profile can result in mechanical damage The built-in Cam Editor is still a valid tool to prototype and test. Shows resulting Velocities, Accelerations and Jerk Can be used to understand exact real time parameters.CAM Editor Manual PrototypingCopyrigh

25、t 2011 Rockwell Automation, Inc. All rights reserved.19Optimization using additional points Adding additional coefficient and manipulating the data will smoothen the profile This profile will run better than the previous profile It is still not optimal for the motor Lets look at the key outputs to u

26、nderstand, what the results are Given a Master Velocity of 200mm/second we would get a slave max velocity of 413mm/sec and a max acceleration of 18000mm/sec or around 2G.CAM Editor Prototyping OptimizationCopyright 2011 Rockwell Automation, Inc. All rights reserved.20CAM Calculation using advanced M

27、ath When optimizing the same profile for acceleration using a modified Sine algorithm the following results can be obtainedProfile is smoothAcceleration down from 18m/s to 12m/s (-30%)Velocity down from 0.413m/s to 0.37m/s (-10%)Max Acceleration at low motor velocity (avoid de-rating)This is now com

28、pletely adjustable (further optimize velocity or acceleration) With a smaller motor machine speed can increase by 10-15%Advanced Math OptimizationCopyright 2011 Rockwell Automation, Inc. All rights reserved.21Optimization a complex mechanical CAM On the left original mechanical CAM and on the right

29、advanced Math algorithm. The mechanical CAM had been used for over 5 years Result Reduction of Acceleration by 20%, Reduction of Velocity by 25%Copyright 2011 Rockwell Automation, Inc. All rights reserved.22Topic Lists1. Definition of Mechanical CAMs & Related Systems2. CAM Design Math analysis 3. P

30、rototyping CAM using RSLogix50004. Use of the RSLogix5000 ToolsetRS Logix 5000 Toolset Application VFFS Sealing Cam (Flying Cutter)Copyright 2011 Rockwell Automation, Inc. All rights reserved.23Copyright 2011 Rockwell Automation, Inc. All rights reserved.24How to use the Toolset Need PHD?Over 5 mm t

31、ransportcome up to 1mm / mm speed (material speed) Over 45 mm transport keep velocity at 1mm / mm speed (material speed) Over 40 mm transport go from 1mm to 0mm speed and run -47mm (distance travelled up to this point)Copyright 2011 Rockwell Automation, Inc. All rights reserved.25Joining CAM Profile Segments Each subsequent segment receives the end point (Master, Slave, Index) from the preceding segment Each segment provides its end point (Master, Slave, Index) for use in the subsequent segment or for calculation Last segment will tell us length of the CAM in master (total 90mm