RAPID PROTOTYPING SYSTEM

Transcription

1 24 RAPID PROTOTYPING SYSTEM

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3 Scientific equipment: Racking for contains (e.g.) eppendorf tubes, Test tubes, Support systems for standard Equipment Turntables for plant biology Advertising: Automata base frames and Mechanical actuation Point of sales moving graphics Display systems Introduction Unlike familiar construction kits, the K lik system was not designed as a toy but for commercial prototyping. Now available as robustly moulded polypropylene consumable parts, it offers virtually unlimited design and making opportunities for education. The system can be extended with the use of other materials and tools and in what follows, the underlined part numbers refer to items in the current Teaching Resources catalogue. There are four basic K lik units: See fig i These parts can either be slotted together in an infinite number of permutations or joined by other mechanical methods such as screws, proprietary clips or some adhesives. fig i Point of sales moving graphics Architecture: Conceptual modelling Structural modelling Technical plant layout and modelling Film and TV: Animatronics modelling (e.g.) armature for cyborg figures Micro-camera support and articulation Plate Corner joiner Half plate H joiner 22 3

4 Getting started The system invites immediate experimentation since the parts fit together so easily, but as a system of slotted parts the important principle to bear in mind is geometrical repetition. This enables the user both to grow basic forms and to scale them up to practically any size. Robotic vehicles: Signal controlled vehicles Guided vehicles Microprocessor controlled vehicles Robotic arms: SCARA (semi-compliant) robot arms XYZ movement robot arms Robot elements (e.g.) grippers Automatic sorting: Sorting actuation mechanisms Feed troughs and channels Assembly line modelling: Scale equipment layouts Mechatronic assembly elements Lighting: Theatre gantry modelling Special effects source units (e.g.) revolving mirror units The repetition principle provides for growth in three dimensions: Instrumentation: Laser levelling system Optical benches (e.g.,) supporting lenses mirrors, light sources, filters Spinning mirror Laser diode Plates Box sections Laser levelling system 4 21

5 Shape memory alloys (SMA) For small or mechanically amplified movements, smart wire (PAC SW1) can provide an ideal solution. It is simply heated by an electric current to cause contraction and is capable of a useful pulling force. Other SMAs include two way memory springs (PAC SW7) and memory wire (PAC SW6) both of which can be used to produced useful controlled movement. Clockwork Smart grease (SM1 003) can be used to release stored energy slowly and uniformly giving a new life to elastic band motors used in models. The powered turning element e.g., a wheel - has to be pulled against a greased friction surface such as the end of the tube containing a wound elastic band. The grease retards the movement of the wheel. Rails Enclosures Applications, design & the spirit of Bauhaus It would be impossible to list even a fraction of the known applications of the K lik system, but some uses are listed below. Actual products range from simple technical assembly solutions to designs that creatively embody the industrial aesthetic of the system. Electronic assembly enclosures: Case enclosures PCB mountings Acoustic enclosures Frames It also provides for scaling. For example: enlarged box sections. It is worth trying out a number of random shapes using the slots to get used to what the system will do and what it won t. The hole spacing was set up for specific commercial needs and so, for example, the holes will not line up if two plates are turned at 90 O. It has to be emphasised, however, that the parts were intended to be modified for use for example, by cutting, drilling, reaming and heat forming. 20 5

6 Modifying the parts The holes in each K lik part are 4.2mm in diameter: a default fit for 4mm screws. For most precision purposes, these can be enlarged by hand with a small range of twist drills rising from 4.5mm to 5mm in 0.1mm increments (e.g., HIL 201) or using a tapered reamer (e.g.,too 043). Sources of movement Motors and gearboxes The K lik system will accommodate practically any small motor or gearbox unit. Motors can be secured using mounting clips such as PIP 001 or The clunk click gearbox ( TG1 010) can be fitted directly using 4mm screws through two of the holes in the base. Since the plastic is soft, the twist drills can be turned between finger and thumb. Radio control servos can be fitted to the system using either screws or tape adhesive. The precise method can only be determined by the size and detail of fittings. Hydraulics Movement from A to B can be effected using very basic accessories such as interconnected syringes for hydraulic actuation. 5mm syringes can be accommodated in plates or half plates by drilling or reaming out selected holes to 10 mm. 6 19

7 - parallel sliding elements can be cut from other sheet materials to fit within assembled K lik parts as shown. Please note that the K lik system is also supplied with a disposable reamer (HIL 200) for the nylon shoulder bushes. - running shafts in bearings will accommodate push-fit wheels, cams or gears. If two gears are meshed, one shaft can be supported on a swinging arm to ensure correct depthing or meshing. The use of these bushes is described below. The parts can be cut to create several different components. This can be done with tuff cut snips a PCB guillotine or the precision slitting saw (SAW 008). Even more components can be created by localised heating and folding using a proprietary line bender or oven (e.g., ). The parts can also be slowly folded cold but need to be over-folded to compensate for relaxation. 18 7

8 Combining generic materials The K lik slots provide an excellent interference fit for 2mm thick materials such as carbon fibre simulated sheet (CS6 010), mirror polystyrene (CS6 004P) or ABS sheet. Mechanisms The K lik system is an ideal starting place for creating mechanisms using other components that can be time consuming or awkward to combine: - cranks can be formed from aluminium axle rod (CW3 018) which has the unusual property of consistently defaulting to the same radius - however bent. Alternatively, for example, a crank can be formed from a combination of plate parts and 4mm screws. Practically any other material can be attached using the methods described below. Mechanical fastenings Screws & nuts K lik system parts can be joined other than by slotting together. The most obvious method is to use screws and nuts. - push rods can be formed from aluminium axle rod or rails made from H sections - bell crank elements can be formed from K lik parts or other sheet materials 8 17

9 Plastic hinges Polypropylene sheet makes ideal hinges because of its fatigue resistance. It can be cut up, drilled and fastened to the plates with screws. In extremis, duct tape can also be used for hinging. These can be used very creatively to extend the number of permutations: e.g., joining plates in parallel, the spacing of plates - or for articulation (see below). Tubing The K lik holes can be drilled or reamed out to provide very tight interference fits for nuts making the plates pre-ready for screws. PVC tubing or equivalent passing tightly through enlarged holes will facilitate universal movement. Alternatively, the same tubing forced over screw ends will provide hinges. Softlink tubing a thick walled silicone material provides excellent flexibility in this context. This is useful only if the screws are lightly tightened. A better method is to use proprietary threaded brass inserts designed to bite into plastics. A suitable insert (HIL 203) with a 4mm internal thread is typically 5mm in length and 16 9

10 ideally two or more plates need to be sandwich together. (The interference fit hole for these is 5.7mm diameter.) Threaded bush Rods and shafts Rods or tubes can be passed through enlarged plate holes to create running fits. Studding 4mm diameter studding can be widely used with or without spacers to join two or more plates. Very large structures can be built in this way including bases for complex assemblies. (Studding can also, of course, be used as a screw for moving sliding elements.) Ideally, the holes should be 0.1mm larger than the rod or tube O/D. Nylon shoulder bushes (WAS 001) can also be used as bearings. With an internal diameter of 3.2mm, these are ideal for either 3.2mm aluminium rod (CW3 018) with an interference fit or 3mm steel axle shaft (HIL 202) for a running fit. Nylon shoulder bush 10 15

11 Heat-shrink tubing Whole or modified K lik components can be joined with a suitable diameter heat-shrink tube. This also provides a method for fastening to other components having an unusual shape. Rivets Proprietary plastic rivets up to 4mm in diameter can be used to join the plates. These include the TR range. Magnets Articulation Articulated joints can be made in several ways: Screws Screws are probably the easiest method of providing articulated joints. In a simple joint, the screw is secured to one part with a single nut to provide a stub axle and the articulating part is then secured using a locking nut or two ordinary nuts locked against one another. Rare earth magnets can be used to create K lik sub-assemblies that can be linked together and easily broken down. For example, any hole can be drilled or reamed out to provide a very tight interference fit for smaller magnets which are then carefully forced fitted into place. A suitable magnet is EM5 019 which is 5mm in diameter x 2mm. The ideal hole size for his is 4.9mm in diameter. Magnet 14 11

12 Adhesives Adhesive tapes are now widely used for permanent joining of sheet materials particularly dissimilar materials. Tape pads can be used to join part to part or the system parts to other materials such as plastics or metals. Please note, however, that tape adhesive is pressure sensitive and its bond strength increases over time. Hot melt glues are also suitable. or it can be moulded over screw ends to make permanent joints. (It is interesting to note that formula One pit stop technicians are using Polymorph to rapidly fasten loose body parts together.) Tubes and rods The plates can be fitted together using force fitted rods or tubes. The holes can be drilled or reamed out, for example to accommodate butyrate tubing ranging from 4.8 mm to 9.5mm external diameter. For example, CP8 063 has an external diameter of 4.8mm and fits tightly in a hole drilled out with a 4.7mm drill. CP7 002 is a light gathering rod that fits tightly in a 5.9mm diameter hole. Metal rods provide the added advantage that they can be angled. Always remember to remove the burrs at either end of the metal rods before working with them. Polymorph This thermoplastic melts at just 62 o C and can be moulded into practically any shape. It is ideal for making specific parts to supplement the K lik system or simply for joining. For example, it can be squeezed between plates to make spacers, Any two K lik components can be joined using plain (brightly coloured) plastic bushes ( ). These fit tightly into a hole drilled or reamed out to 4.7 mm