Week 5:- Rest Unit & Clamp Unit Design Challenge
- Design 3 Different types of Power Clamp Unit with Different Riser, Blade and Clamp Arm for the given Car Panel.
- Design 2 Different types of Rest Unit for the given Car Panel.
Aim/Introduction/ Objective: In this challenge we have to design 3 Different types of Power Clamp Unit with Different Riser, Blade and Clamp Arm for the given Car Panel & 2 Different types of Rest Unit for the given Car Panel with the optimum use of material & space constraint. Also we learn different types of rest & clamp unit configuration.
Report & theory:
3-2-1 principle achievement:
3-2-1 principle is basis of any fixture design. Holding fixtures used in assembly operations often follow a 3-2-1 locating scheme to position parts. Under this scheme, three locators position a part in a primary plane or direction (e.g., high/low).
(3) minimum: Three locator blocks to establish part plane. Three locators or supports are placed under the workpiece. Three locators are usually positioned at primary locating surfaces. This restrict two translation motion i.e. upward & downward & four rotational motion ( i.e. clockwise or anticlockwise). Together tree locators with clamp restrict six degrees of freedom. Below figure shows how (3) minimum in 3-2-1 locating scheme achieved by clamping & resting
Clamp unit: Clamp unit is unit designed to clamp / hold the car panel with NC blocks/ mylar/ rest by using a pneumatic clamp cylinder & below are different parts of a clamp unit in general. Usually clamp open position is 90°. Fingers are attached to clamp mylar. In clamp unit shim to one side is more enough because it will restrict translation motion in upward & downward direction only. There is another type of clamp unit knows as swivel type. There is pivot pin around which clamp arm rotate.
Below are 3 designed power clamp unit:
Unit 1:
Below unit is named as P001_Z01_ST001_03_00_POWER_CLAMP_UNIT & is designed with power clamp cylinder. It is very simple in design. It has clamp mylar, rest mylar & riser.
Below fig shows clamping of car panel & also retracted position of clamp arm at 90°.
Cylinder designation: V_50_1_BR3_A40_T12_TUENKERS.
Vario clamp with toggle joint mechanism and continuously adjustable opening angle, Over-centre-lock, Enclosed aluminum housing, Oval-shaped cylinder in the sizes 50, 63, 80, Forked clamping arm, standard hole pattern for adapting contour blocks, Continuously adjustable opening angle 5°-135°, optional: Weld immune inductive sensing of closed and opened position (T12). It has four M8 tapping holes for its mounting & two dia. 8 dowel holes for locating. Also clamp arm has two free hole of dia. 9 to mount mylar on it with M8 screw & two dia. 6 dowel holes for locating purpose.
Below figure shows mounting holes on cylinder.
Below figure shows mounting holes on clamp arm.
Unit 2: Below unit is named as P001_Z01_ST001_04_00_POWER_CLAMP_UNIT & is designed with power clamp cylinder.
Below figure shows clamping of car panel by unit
Cylinder designation: APH_50_BR5_A40_T12_TUENKERS
Compact clamp with curve-driven lever mechanism for constant clamping force and tension reverse, Enclosed mono-block housing of aluminium material with integrated mechanics and flat cylinder, Sizes 50/63/80, Forked clamping arm with standard hole pattern for adapting contour blocks, continuously adjustable opening angle 15°-135°, Pneumatic cushioning for open position, Optional: Weld immune inductive sensing of closed and opened position (T12), Intelligent sensor identifying components and wear (T60), Pneumatic locking of dead centre positions (V+R position) (HD), Hand applied version. It has same mounting as above described cylinder V_50_1_BR3_A40_T12_TUENKERS.
Unit 3: Below unit is named as P001_Z01_ST001_05_00_POWER_CLAMP_UNIT & is designed with power clamp cylinder. It has clamp & rest mylar, L-blocks, mounting bracket & riser.
Below figure shows clamping of car panel using power clamp unit.
Cylinder designation: APH_50_H_BR5_A40_T12_TUENKERS
Compact clamp with displaced sensing system, alternatively equipped with knee-lever mechanism or curve-driven mechanism, self-locking type. Encapsulated monoblock housing made form aluminium material with integrated mechanics and flat cylinder sizes 50/63/80. Fork shaped clamp arm with standard hole pattern for mounting of contour blocks. Step less adjustable opening angle in the range of 15° to 135°. Option: Integrated stop valve for self-holding, Inductive sensing (weld-resistant) for opened and closed position (T12), hand lever (Z). It has same mounting as above described cylinder V_50_1_BR3_A40_T12_TUENKERS.
Rest unit: Rest unit is unit designed to support car panel using Mylar/ NC block/ rest. Component is rested only, no upper clamp or force applied there. It is the simplest unit to design because it has fewer 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 overall project.
It can be combined with clamp unit to clamp as 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 can be combined together in one unit to reduce cost. There is no cylinder attached to it. It has rest Mylar, blade & riser & below is different parts of rest unit. Rest unit is also divided into simple support unit, multiple support units & retractable support unit.
Below are two designed rest unit. Rest unit has rest mylar, blade or L-block & riser.
Below figure shows resting of car panel.
The minimum distance between any two units should be 30 mm as described in below figure.
Below figure shows clamp units with car panel.
Below figure shows clamp units without car panel.
Below are different parts of clamp & rest unit in general.
- Mylar/ NC blocks/ Fingers: These are parts are used to hold panel. They are globally called as Mylar. Top side Mylar is called as clamping Mylar & bottom side is called resting Mylar. Every clamping Mylar should have resting Mylar. It is jaw type. It prevent panel from deforming while welding. It is hardened to increase its wear strength.
- The clamp & rest mylar has the same size. It has standard size of 20mm x20mm. It has flat surface or sometimes its profile follow contour of car panel. As described in below figures
- Clamp & rest mylar have two dowel holes of dia.6 & one M8 tapping hole. Also clamp mylar have same mounting hole pattern as like clamp arm. Also minimum centre distance between holes should be 15 mm. & reference dimension should be 8 or 10 mm. as described in below figure.
- Minimum distance between clamp mylar mounting face & car panel should be more than 5 mm.
b) Riser: Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly. It is machined at mounted ends only to save cost. Below figure shows how other component mounted on riser.
c) Shims/spacer: In fixture, we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stack up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc.
We provide shim to accommodate clamp as well as rest mylar in two direction. Clamp & rest mylar can be adjusted in two direction only i.e. up or down.
d) Hardware: These are standard parts. Parts are assembled together with help of washer and bolt. for better assembly should use two dowels and four bolts for riser and blade. Where for bolting one part should have tapping hole and on other part simple hole (1 to 2 mm larger from bolt size.)
Length of the bolt is decided by width of part + (1.5*D)
For ex. where
L=Length of Bolt
D=diameter of bolt to be used
Let’s, take M8 Bolt
L= 25 + (1.5 * 8)
L=25+12
L=37 mm.
But length of 37mm bolt is not available so we have to select 40mm Bolt. (Additional 2 to 3 for washers).
Similarly minimum engagement length for M5, M6, M10 & M12 must be 7.5, 9, 15, 18 mm respectively.
e) Dowel pins: These are standard part. There are various types of dowel pin like split, parallel, taper, clevis, and spring, grooved. Dowel pins are used to locate part precisely & to restrict movements. For mylar dia. 6 or 8 dowel pins should be used. For blade, shimming block dia.8 dowel pin should be used & for riser base dia. 10 or 12 pins are used.
f) Washer: Standard steel grade A plain normal series washer used. also making counter bore if possible instead of washer reduce cost.
Clamp plan: It provides information about position of clamp unit, pin unit, rest unit, dump unit etc. This is major input from customer & it should be never changed without permission of customer. Clamp plan provide exact location of pins, rest, clamp etc. It is in more detail. It gives exact location in X, Y & Z co-ordinates value to start designing. Below figure show location of units.
Structuring a design tree:
Structuring a design tree implies process where all the assemblies & parts are named in specific manner. Different customers have different set of standard like how to structure a design tree? So they will be give standard template based on that design tree structured, which helps us to identify specific part of assembly. It specifies the Project number, station number, unit number; part number of each component so that it is easy to identify the parts.
It is an important process which helps us to identify a specific part or assembly as to which project, tool or unit, it belongs to.
This helps us to avoid error during design study, manufacturing, assembly, inspection etc.
If parts or assemblies are not named properly or the design tree is not structured properly, it will create confusion to understand & create major possibilities of making an error.
Naming of a fixture, a unit or a part gives the information as to which project or zone or assembly they do belong.
It can help us to identify quantity of items of same type or different types that are being used in assembly for e.g. bolt. It actually tells you how many bolts are particularly required in that assembly or unit.
For e.g. as in below figure highlighted in blue
P001 stands for project no 1.
Z01 stands for zone no 1.
ST001 stands for station no 1.
01 stands for unit no. e.g. Rest unit
01 stands for part no. e.g. Rest mylar