Week 3:- BiW Fixture Design Methodologies Challenges

QUE 1) What is Design Methodology ?

ANS 1) Design methodologies is one of the pre design process which is the steps followed during the concept designing phases in fixture design.

DESIGN METHODOLOGY

Design Output

Percentage completion criteria

Inputs from customer

Purchase Order

Categories are described below

• Purchase Order –

A purchase order , or PO , is an official documents issued by a buyer committing to pay the seller for the sale of specific products or services to be delivered in the future.

• A PO specifies-
• Quality purchased
• Product or service being purchased
• Specific brand names , SKUs , or models numbers
• Price per unit
• Delivery date
• Delivery location
• Billing address
• It officially confirms to start the work on the design.
• Inputs for Customer-
• Designer needs following basic information to start the BIW fixture
• First understand scope of work. Means what is expected by customer. Every customer has its specific requirements and it may have own raw material, electric , pneumatic , cad, design standards. Every customer also gives different inputs and expects output.
• Bill of material of the component to be welded- spot welding
• CAD panel data or at least 2D drawing of assembly and individual panel data.
• Sheet metal panel thickness. Plays major role to decide 2 metal or 3 metal weld.
• Spot detail information like total no of spots and spacing between the spots.
• Weld information clarity from drawing like 2 metal or 3 metal welding.
• PLP of the individual panel and total assembly.
• Cycle time- if calculated or can be found out as per manual or robotic welding process.
• All clamping cylinder and fixtures standards.
• CAD- software guidelines
• Raw material standards
• Design guidelines

• Percentage completion Criteria –
• It consists planning of completion of total project. How much days the project will take to complete.
• It is followed in designing stages & dispatch stages of the welding fixture.
• It ensures that how much task we have decided to complete , within stipulated time complete or not & how much of it is rest to complete.
• Design output –
• Output consist 3D models , 2D drawing which is detailing part , BOM & other related documents.
• There are some tools which are multiple units on common base are called inutilized tools for ex fixture includes no of units on the same base.
• They required two types of drawing sheets as follows,
• Key sheet- It shows the index of unit & their placement on tool base.
• Layout sheet- it is detailed drawing individual unit to include all their component.
• Non unitized tools which can be completely detailed on layout sheet.

QUE2) What are the inputs required from the customer to designing a fixture ?

ANS2) Then following are the inputs required from the customer to start the fixture design work.

1. Functional requirement- it is basic requirement which defines the function of the fixture wheather it is being used for welding, hemming , checking fixture or storage racks . depending on design consideration are going to change while designing the fixture.
2. Preffered standards- The customer want to follow some standards. These standard part which we can use as it is in our design which saves are project time as well money.

ABB, NAAMS ,TUNKERS , ZYTRAN , DESTACO are some standards.

Some standard parts like riser, L-Blocks , Retainers etc.

Some components like clamps , cylinders , switches , sensors etc.

1. Car products – includes following inputs from customer

• GD&T – Geometric dimensioning & tolerances of the part for which the fixture have to be designed. GD&T provides information about locating pins , Rest , clamp, dumps & slides information of each station & sequencve & opening of clamps, Dumps slide strokes information.
• Part list – This is the list of part which are going top assembled in the fixture. It includes information about part name, part number, tooling revision , part thickness etc.
• Cad files of part – The 3D model file of the car part design using modeling software is given from the customer.
• Clamp plan- This is the clamping plan of the part while doing the operation. We cannot change the clamp plan without the permission of customer. It is very important input from the customer. It provides location of pins , Rest , Clamps , Dumps etc.
• Product assemply process sheet – it gives detail process of the completion of part from scratch to the finished product assembly.

1. Layout- it provides information about flow of parts , station pitch , robot stations, tool changers , Tip dressers , Platform height , Sub assembly links & loading/ Unloading sequence.
2. Ergo Data – it is the study of human behavior & movements during the assembly work.it provides data regarding loading height , working safety zone of operator.
3. Weld study – it includes the study of weld gun is going to be used for the operation depending on the size of the part, thickness of the part etc it also includes study of weld matrix & weld point position. There are two types in weld point one is geo weld point which ensures geometry of the assembly & second is Re-spots weld points which add strength to already welded point.
4. Standard detailing templates – Every customer have their standard of detailing & the templates which are used for 2D drawing & detailing .

QUE3) What is the input we get from “ Car Products” ?

ANS 3) Following is the input we get from the car products

1. GD & T- Geometric dimensioning & tolerance of the part for which the fixture have to be designed. GD & T provides information about Locating pins , Rest , Clamps , Dumps & Slides information of each station & sequence & opening of clamps , dumps & slide stroke information.
2. Part List – This is the list of part which are going to assembled in the fixture. It includes information about the part name, part number , Tooling revision , part thickness etc.

1. Cad files of part – The 3D model file of the car part given from the customer to study on it. The car part is designed using 3D modeling software . from this we can get some conceptual idea of the designing of fixture. The model is going to be the base of fixture design.
2. Clamp plan – A clamp is a force actuating mechanism of fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces. Clamping surfaces are subjected to the clamping forces obtaining invariant location. Clamp plan of the part while doing the operation. We can not change the clamp plan without the permission of the customer. It is very important input from the customer. It provides location of pins , Rest , Clamps, Dumps etc.
3. Product assembly process sheet – It gives detail process of the completion of the part from scratch to the finished product assembly. We can get details like the no of steps involved in the assembly process & sequence of operation.

QUE3) What is the input we get from “ Car Products” ?

ANS 3) Following is the input we get from the car products

1. GD & T- Geometric dimensioning & tolerance of the part for which the fixture have to be designed. GD & T provides information about Locating pins , Rest , Clamps , Dumps & Slides information of each station & sequence & opening of clamps , dumps & slide stroke information.
2. Part List – This is the list of part which are going to assembled in the fixture. It includes information about the part name, part number , Tooling revision , part thickness etc.

1. Cad files of part – The 3D model file of the car part given from the customer to study on it. The car part is designed using 3D modeling software . from this we can get some conceptual idea of the designing of fixture. The model is going to be the base of fixture design.
2. Clamp plan – A clamp is a force actuating mechanism of fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces. Clamping surfaces are subjected to the clamping forces obtaining invariant location. Clamp plan of the part while doing the operation. We can not change the clamp plan without the permission of the customer. It is very important input from the customer. It provides location of pins , Rest , Clamps, Dumps etc.
3. Product assembly process sheet – It gives detail process of the completion of the part from scratch to the finished product assembly. We can get details like the no of steps involved in the assembly process & sequence of operation.

QUE3) What is the input we get from “ Car Products” ?

ANS 3) Following is the input we get from the car products

GD & T- Geometric dimensioning & tolerance of the part for which the fixture have to be designed. GD & T provides information about Locating pins , Rest , Clamps , Dumps & Slides information of each station & sequence & opening of clamps , dumps & slide

1. Part List – This is the list of part which are going to assembled in the fixture. It includes information about the part name, part number , Tooling revision , part thickness etc.

1. Cad files of part – The 3D model file of the car part given from the customer to study on it. The car part is designed using 3D modeling software . from this we can get some conceptual idea of the designing of fixture. The model is going to be the base of fixture design.
2. Clamp plan – A clamp is a force actuating mechanism of fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces. Clamping surfaces are subjected to the clamping forces obtaining invariant location. Clamp plan of the part while doing the operation. We can not change the clamp plan without the permission of the customer. It is very important input from the customer. It provides location of pins , Rest , Clamps, Dumps etc.
3. Product assembly process sheet – It gives detail process of the completion of the part from scratch to the finished product assembly. We can get details like the no of steps involved in the assembly process & sequence of operation.

QUE 4) What is the Clamp Plan ?

ANS 4) A clamp is a force- actuating mechanism of a fixture. The force exerted by the clamps hold the part securely in the fixture against all other external forces.

• Clamping surfaces are subjected to the clamping forces for obtaining invariant location.
• Clamping is very important input from the customer. The clamping plan of the part is the plan which defines the location of the clamp while doing the operation to ensure the geometry of assembly.
• We can not change the clamp plan without permission of the customer. We have to design fixture which should not required change in clamp plan.
• It provides information regarding to the location of pins. Rest , Clamps, Dumps etc. The coordinates is also mentioned in the clamp plan so the design team can take the coordinates directly & start the designing of the fixture.

QUE 5) What is the purpose of a layout ?

ANS 5) layout is most effective physical arrangements , either existing or in plans of industrial facilities i.e arrangement of machines , processing equipments and service departments to achieve greatest coordination and efficiency of 74 M’s (men , material, method, machines) in a plant.

• Plant layout is a floor plan for determining and arranging the designed machinery and equipmenys of a plant, whether established and contemplated in best place, to permit quickest flow of material , at lowest cost with minimum handling in processing the product.
• It shows all objects of manufacturing line like Robots, Fixtures, Racks etc & also shows the reachebility of robot to fixture is called swept area of robot. It also show the constraint of space or the space available for the fixture that we are designing.
• Layout provides information about flow of parts, station pitch , robot station , tool changer, tip dresser , platform height , sub assembly links

Loading/unloading sequence.

QUE 6) What is Ergo data ?

ANS 6) Human factors and ergonomics is the application of psychological and physiological principles to the engineering and desingn of products , process and system. The goals of human factors is to reduce human error , increase productivity, and enhance safety and comfort with specific focus on the interaction between the human and the thing of interest.

• The final assembly of an automobile involves task of complex nature. These processes are on the least priority for automation. Manual labour is best suited for assembly operation with the aid of minimal level of automation. All the processes have to be improved continuously in order to reduce cost and increase productivity.
• The workers attain various posture , exerts force and work continuously in cycle time to accomplish the assembly task. Working along automobile assembly lines is characterized by repetitiveness.
• Ergo data is studied to identify and quantify ergonomics working postures that contributed to the serious development of muscle skeletal injuries and thus investigated possible contributory their related causes.

QUE 7) What do you understand by weld study ?

ANS 7) Welding is predominantly used in automobile industries and requirement for fixtures that ease the welding process is the process is a continous development task in any industry.

• Car Body-In-White is complicated steel structure including 300-500sheets with complex shape and are assembled by means of welding in ahigh rhythm through 55-75 robotics work-station.
• The foremost step taken before starting the design of welding fixture is to arrive at the spot weld locations. The location and orientation of other critical units of the fixture including clamps, locators etc, decided based on weld spot distribution . The weld spots for front door inner panel – side bracket assembly are located with respect to body line of car.
• It includes the study of weld gun (A portable device for semiautomatic welding of parts of various articles) which is going to be used for the operation depending on the size of the part, thickness of the parts.
• It includes study of weld matrix & the weld point positions. There are two types in weld point one is geo weld points which ensure geometry of assembly & second is the Re-spot weld point which add strength to the already welded part.

QUE8) What are the criteria for percentage completion in designing stage ? Explain it in detail.

ANS 8) The % completion criteria contain the current status of a task , expressed as the % of the task’s duration that has been completed. You can enter percent complete or you can have project calculate it for you based on actual duration.

• It consist planning of completion of project . how much days project will take to complete.
• It is followed in designing stage and dispatch stages of welding fixture.
• It ensure that how much task that we have decided to complete within stipulated time is complete or not & how much of it is rest to complete
• When a task is first created the percent work complete is zero percent . if you enter actual work for the task , project calculate percent work complete as follows.
• Percent work complete = (actual work/work)*100

1. Input & concept design – 0 to 25 %

The design inputs from the customer and then after studying those input concept fixture designs are created.

1. Concept approval and simulation check – 25 to 40%

The concept design approval from the customer after study of approval.

1. Design freezing & detailing– 40-85%

After the simulation result if no any changes are required then the design is freezed. After freezing 2D drawing which is detailing part is started.

1. Check & final dispatch – 85-100%

After detailing the quality check team inspection of all the data & it will dispatch to the customer if everything is ok.

QUE 9) Brief about “ Output “ in design ?

ANS 9) Each manufacturer shall establish and maintain procedures for defining and documenting design output in terms that allow an adequate evaluation of conformance to design input requirements.

OUTPUT IN DESIGN:

• The output is 3D models & the 2D drawings of the tools.
• For unitized tool( multiple unit in a common base) requires two types of drawing sheets.
• Example of unitized tool: A tool with multiple units like rest unit, clamp unit , fixed pin unit , rough locator unit, rectractable pin unit, sensor unit, etc in a common base
• The two types of drawing sheets are:

1. Key sheet
2. Layout sheet

1. Key sheet :

• Key sheet gives or shows the index of units & their placements on the tool base.
• It will have an orthogonal view of the fixture including a numbered balloon drawing mentioning the units.

1. Layout sheet:

• Layout sheet shows a detail drawing of individual units to include all of their components.
• For Nonunitized tool no need of keysheets. As they can stand alone , the drawing can be detailed completely on a layout sheets.

THE DESIGN OUTPUT SHOULD COMPILE FOLLOWING POINTS:

• Approved standard components are to be used wherever possible.
• Design must be as simple & economical as possible.
• Design must comply with all current safety & ergonomic requirements.
• Design must provide for controlled & damage free handling of product.
• The weight of moving part must be kept to aminimum while maintaining maximum strength.
• Frames & structure are to be simple & sturdy.
• Design clearance & accessibility for routine maintenance & service.
• Motion control must be considerd on any moving equipments.
• Designer is responsible to validate clamps & weld guns.

Hence, the output is design are briefed.

QUE 10) What do you understand by structuring a design tree ? How does it reduce errors during the design process?

ANS 10) Structuring a design tree implies to a process where all the assemblies & parts are named in a specific standard. Different customers have their different set of standards to structure a design tree.

• It is an important process which helps to identify a specific part or assembly as to which project, tool or unit, it
• This helps us to avoid the error during design study, manufacturing, assembly, inspection etc.
• If the parts or assemblies are not properly or the design tree is not structure properly, it will create confusion to understand the design & may create major possibilities of making an error.
• Naming of a fixture or a unit or a part, the information as to which project or zone or a assembly do they belong.
• It has help us to identify the quantity of items of same type or different types are being used in assembly.

Under the product there are main assemblies, sub-assemblies , child part , standard parts etc. these all parts are provided with specific no. zone etc to identify easily.

QUE 11) What are units? Mention 5 types of units.

ANS 11) A unit is a device that has specified function, specially one forming part of a complex mechanism.

• The BIW fixture is the assembly of different units which are designed to fulfill different purpose.
• The unit have the specified function like resting the panel, clamping the part, locating the part etc.
• According to the 3-2-1 principle of fixture design the units are designed to locate & clamp the car panel to its specified position in fixture while operation is going on.

In the following the different units are showed by different color

-following are the typical types of units used in BIW fixture design,

1) Fixed pin unit- It is non movable locating unit used for proper location of the part.

2) Retract pin unit- It is movable locating unit.

3) Rough locator unit- It roughly guides the operator for locating the part.

4) Rest unit- The panel is rest on this unit.

5) Base unit- It is the unit on which all other units are mounted

QUE 12) Describe fixed pin units & their purpose?

ANS 12) Fixed pin unit consist of riser, blade, block, shims or spacer, pin retainer & pin.

• Riser is the standard part which is used to rise up the height of the while unit. Blades are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.
• Shims are the small part which comes with the thickness of 0.1mm,0.2mm,0.5mm etc. these will compensate the stackup tolerance which reflects at the panel holding part Mylars. In fixed pin shims are used to adjust to translation motions.
• Pin retainer will support the pin & the locating pin which restricts movement of the car panel.

Purpose of fixed pin unit-

• Fixed pin unit is a unit designed to locate the car panel using pin.
• The fixed pin unit is the part of the 3-2-1 principle , it restrict 6 degrees of freedom of te car panel.
• It is necessary to have 2 pins to locate car panel. One pin must arrest 4 ways (4 translation) & other must arrest 2 way (2 rotational) of a car panel.

QUE 13) What are the different parts of Fixed Pin Unit?

ANS 13) Fixed pin unit consist of riser, blade, block ,shims or spacer, pin retainer & pin. All parts are described below.

• Riser- Riser is a standard part which is used to rise up the height of the while unit.

• Blade- These are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.
• Shims – These are the smallest part which comes with the thickness of 0.1mm, 0.2mm, 0.5mm etc. these will compensate the stackup tolerances which reflects at the panel holding part called Mylars. We give tolerance to all the parts of the fixture. Due to this tolerance Mylars will either lift up or go down from its defined position. If the Mylars goes down from the defined height it will make impression or dent on the panel. If the Mylars lift up then their will be distortion due to welding stress. To adjust the Mylar at its defined position we use shims so the panel won’t deformed & also don’t get any impression on it.
• Pin retainer- It will support the pin.
• Locating pin- Typically, locating pin are used for controlled, fine tolerance positioning of a work piece. For example, a pallet that is moved along one axis, where the drive mechanism is not accurate and stable enough to place it in a position sufficiently accurate to execute a particular process, the use of locating pins may be the best solution.

• The diamond shape is a critical feature that helps with machining inaccuracies and smoother locating operation. When two round head pins are installed into one plate, the distance between two mounting holes must be extremely precise and even then, the work-piece will not be placed on the base as easily as it would with the use of a diamond shape pin.

There are several styles of Pin Head shapes. They serve different purposes and can be utilized in a variety of applications.

QUE 14) What is the purpose of making a Rest unit & describe its parts?

ANS 14) The rest units are designed to rest/support the car panel by using NC blocks/ Mylar/Rest

-It is the simplest unit to design because it have less Parts to design & the purpose is only resting of the car panel.

-Because of this simplicity the rest unit is combined with other unit to reduce the cost of the overLL PROJECT.

-It can be combined with clamp unit to clamp ad well as to rest the car panel. It can be combined with locating unit to locate as well as to rest the car panel, also locating, clamping & rest-unit it can be combined together in one unit to reduce cost.

2) Blade- These are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.

3) Shims – These are the smallest part which comes with the thickness of 0.1mm, 0.2mm, 0.5mm etc. these will compensate the stackup tolerances which reflects at the panel holding part called Mylars. We give tolerance to all the parts of the fixture. Due to this tolerance Mylars will either lift up or go down from its defined position. If the Mylars goes down from the defined height it will make impression or dent on the panel. If the Mylars lift up then their will be distortion due to welding stress. To adjust the Mylar at its defined position we use shims so the panel won’t deformed & also don’t get any impression on it.

4) NC blocks/ Mylar/Fingers- Mylars is the component which holds the panel while operation. These are placed from top side as well bottom side also. The top side Mylar are called as Clamping Mylars & the bottom side Mylars called as Resting Mylars. Every Clamping Mylars have resting Mylars. It don’t allow deformation of the part due to welding stresses.

QUE 15)What are the basic fundamentals to design Sensor unit?

ANS 15) Sensor is a device which detects or measures a physical property and records, indicates, or otherwise responds to it.

-A unit designed to sense car panel using electrical sensor unit. The from the sensors is send to the PLC so the next process is executed by the signal.

-The sensor is very sensitive & easily damagable part so sensor cover is provided to the sensor for safety purpose.

-There are different types of sensors

1. Proximity sensor
2. Laser sensor
3. Photo electric sensor
4. Infrared sensor

-Fundamentals of sensor unit design-

1) Every single loose panel which are being welded in a tool should be sensed.

The assembly of car panel consist of no. of panels. The location of every panel is fixed. There are some locating units, clamping units, rest units are proper location and operation. The sensor is attached in this unit to sense the part is loaded or not. If the part is not loaded the sensor will segative signal to the PLC controller & operation will not start& viceversa.

• Each panel should be sensed by 1 to 2 sensors depends on the size of panel, preffered to be in diagonal opposite ends of panel.

Sensor is used to sense the part is loaded or not & start the operation by sending positive signal. But if part is big in size then there will be two sensors required because part will be loaded in correct position at one end & will be not positioned correctly at other end & due to which the assembly will not be ok part & get rejected at QC check stage. Hence to neglect these kind of situations the part should be sensed by 1 or 2 sensor depending on its size for proper assembly

• Every sensor should be mounted in a 3 direction adjustable way in general.

Sensors can be adjusted to a particular distance from the panel by using these 3 directional adjustable way. If we use proximity sensor it have range 5 to 10mm to sense part & for laser sensor the range increases.

QUE 16) What is a Rough locator unit & what are the basic fundamentals to consider while designing it?

ANS 16) A rough locator is a part designed to guide the operator, to locate the car panel on to the pins accordingly. A rough locator can be of standard part or make part.

It can be called it as fool proofing method also, Because due to the rough locator part cannot be loaded in correct position. The rough locator set according to the angle of respective panel hence part can only be loaded in correct position. The rough locators are set according to the angle of the respective panel hence part can only be loaded in defined direction & orientation.

Fundamentals of rough locator design-

• Rough locator should be placed at the edges of the car panel, which it has to guide.
• Rough locator has to be placed in the same angle of the car part edge with a minimum distance of 2-5mm from the edge of car part.
• Rough locator should guide the panel in pin arresting direction.
• Rough locator should start guiding the panel before 10 to 15mm to the start of the pin engagement.
• Rough locator should be designed with entry angle for the car panel. Generally it ranges between 30-45 degrees.
• Rough locator should be designed with two slots to mount the easy adjustments.
• The slots should be in the direction of car part guiding.

QUE 17) What is Base unit and describe it’s parts?

ANS 17) A base unit is the unit designed to mount all the other units (clamp unit, pin unit, rest unit etc) of the tool, also other part necessary for a tool like pneumatic valve box, trunking cable path will also mounted on base unit.

Base unit is the fundamental component of the fixture because all the component are mounted over it. So every fixture has base unit. The base unit design is different according to the panel. Design of clamp system, location system etc.

-fig 1 shows fixed base unit which is fixed to the floor by using nut bolts.

-fig 2 shows movable base unit which can be moved from one place to another by using wheel provided.

-fig 3 shows the rotating base unit. In this the base is fixed at two ends but the fixture can be rotate around it horizontal axis by using some rotating mechanism.

1) Floor plate- It is the plate which join the fixture to the floor by using some nut bolts. This plate surface is machined for maintaining the horizontal position of the fixture.

2) Weld bars & pedestal- pedestal is the base or support on which a fixture is mounted.

3) Eyebolt- An eye bolt is a bolt with a loop at one end. They are used to firmly attached a securing eye to a structure, so that ropes or cables may then be tied to it.

4)Measuring hole cover- The base plate have some drills to mount various units like clamp, rest, pin etc. & every drill have some coordinates to define the exact location of hole. Due to irregular shape of car panel the drilled hole coordinates are not like 110.0,150.0. the measuring hole drilled over the base plate which having exact coordinates so that all other hole can take reference from it .these holes are covered by using some plate to protect against dust, damage etc.

5) Valve box & trunking channel – the valve box is the box which consist different solenoid valves. The pneumatic fixtures work on air pressure inlet & outlet is done with this valve box. The trunking channel include all the pressure inlet cables going to pneumatic parts of the fixture & protect them from damaging while operation is in process.

6) Base plate- Base plate is the heavy plate of large thickness because it carries all the weight of mounted parts. So it must be able to bear the load. Base plate is machined to maintain the parallelity within the tolerance. It also consist some drilled holes to mount the different units over it.

QUE18) What is a Dump Unit and what are its functions?

ANS 18) when we have some geometrical constraints then we can not mount normal units like clamp unit, pin unit etc. In this case the dump unit is used.

-Dump unit is the complex unit to design due to space constrains there is less space available & have to adjust all the parts in available space.

- It consist of dump cylinder to perform the operation of clamping & unclamping car panel.

QUE 19) What is a slide unit? Mention where slide units are commonly used?

ANS 19) Slide units are positioning units which are used to position the fixture, weld gun , units, robot into position for further operations.

-Slide units can be classified into two types on the base of the type of guide-ways used as

1) hardened guide ways

2) LM guide way

- slide unit can be classified into three types on the base of the prime mover used

1) Manual slides

2) Hydraulic/pneumatic slides

3) CNC slides

- It may also be classified depending on application as

1) Horizontal Slide

2) Vertical Slide

3) Angular Slide

Guide line to design the slide unit

• LM guide ways preffered ver hardened guide ways due to least co-eficient of friction.
• Slide unit essentially consist of LM guides, linear cylinder , front & rear stoppers , front & rear shock absorber, two proximity switches for sensing the two end position, bellows or protection cover for rails.
• Centre trunnion/ rear clevis mounted cylinders are ideally used for slide unit application as this allow for some float to take up mis- alignment.
• Reverse stroke of 10mm to be considered in both forward & retracted condition.
• Cylinder & LM guides to be validate for load & stroke
• LM guide rail length should be standar and should be more than actual stroke.
• Mechanical hard stop to be considered for both extended & retracted condition.
• Shock absorber to be used for both extended and retracted condition to reduce impact load.
• The two end limits to be sensed externally by a proximity switch.
• The shock absorber should be mounted such that it is perpendicular to the pivot at mid stroke or within +/-5 degree.

Slide units are used when we have some space constraints. So we don’t have space to design different special units & to assemble it. In those case we use sliding units.