Cylindrical Grinding machine

Cylindrical Grinding machine Basic Data Category: Lathes Keywords: lathe, grinding machine, roughing, spindle, workshop, speed, feed, depth of cut, bed, tailstock, chuck, turret, grinding wheel License: CC BY-SA 4.0 Organization: OHO Project status: Active Certification status: In process Technical documentation Maturity of the project: prototype Contains PDF-drawings: Yes CAD files are editable: Yes Assembly instructions are published: Yes Bill of materials is published: Yes no yes yes

Description

Technical documentation

Project development

Based on the DIN 2221 standard, among others, OHO has established a series of stages in which the satisfactory completion of this project was carried out 1 Feasibility study Project justification Regarding the equipment for working with metals that may be needed in sustainable development initiatives, there are small and medium-scale lathes, for which OHO has proposed to evaluate the feasibility of designing and building equipment that serves to supply some cylindrical parts, where a certain level of quality is guaranteed in accordance with manufacturing processes that do not require very high precision. It was observed on the internet that there are already some DIY (homemade) devices, which, apparently, can fulfill this objective, however: The number of examples found is not very numerous, limiting the possibility of strengthening the idea of an open source lathe, made with totally accessible materials and processes, for practical applications, in low-income areas. Essential details about dimensions and assembly are not always well explained, plans are generally not available. The reviewed DIY cases are based on replicating commercial equipment or building a device with the necessary components, but without a technical analysis of the design and feasibility of the proposed solutions. Proposal (all aspects are subject to revision) The design and construction of a small-scale lathe is then proposed, which can be manufactured in a basic workshop, with the following characteristics: That can process non-hardened steel parts Maximum dimensions of the pieces to be processed: Diameter: 50mm, Length: 400mm That removes the material with abrasive wheels, this in order to reduce the forces transmitted to the structure and reduce costs for tool replacement See this link (cylindrical grinding machine) See this link (roughing with abrasives) The equipment must have a simplified design, for which some or all of these solutions can be applied: Main motor reused or purchased from other domestic components or adapt a high-performance manual drill (1/2”) In both cases, it must be possible to regulate the speed of rotation, which is facilitated in the case of the drill. See this link (with used engine) See this link (with drill) Includes a clamp head and tailstock, which can be purchased. See this link (chuck) See this link (counterpoint) The grinding subsystem can consist of a bench grinder adapted to the equipment, with the capacity for axial and transversal movement and rotation in the vertical axis. See this link (adapted bench grinder) The use of high precision linear bearings will make the project more expensive The equipment must have axial and transversal displacement guides, for which the use of tubes or calibrated bars is proposed, this to guarantee stability in movements and reduces costs and complexity compared to the use of bearings linear, dovetail, etc. See this link (bars) See this link (angles) Comparative analysis on the type of process to carry out A comparative test was carried out between the use of abrasive stones as a tool for a turning process, versus turning with usual cutting blades, for which an example was raised with the following premises: D1p: Initial diameter of the part: 38mm D2p: Final diameter of the piece: 25mm Lp: Piece length: 100mm It was proposed to know in both cases (grinding or turning): Machining time for one part Weekly production The force generated in the lathe and The cost in tooling for a production of 1000 pieces The following results were obtained: Grinding process Characteristics of the tool used Cost of an abrasive wheel: 11USD Abrasive wheel thickness: 25mm Abrasive wheel outside diameter: 152.4mm Internal diameter of abrasive wheel (useful): 50mm Machining parameters Abrasive wheel speed: 30m/s Speed of the piece in grinding: 0.22m/s Feed in grinding: 17.5mm/rev Depth of pass in grinding: 0.01mm Rotational speed of abrasive wheel: 5662rpm Rotational speed of the piece in grinding: 133rpm Performance Time of one pass in grinding: 6.4s Number of passes in grinding: 650 Time per piece in grinding: 69min Weekly production: 144 pieces/week Tooling cost Quantity of pieces per abrasive wheel: 632 Cost of abrasive wheels to make 1000 pieces: 17USD Mechanical load Absorbed power in grinding: 1.22HP Grinding torque : 1.5N-m Force transmitted in grinding : 1174N Turning process Characteristics of the tool used Cost of a tool: 25USD Number of sharps per tool: 10 Lifespan of a sharp tool: 50min Machining parameters Cutting speed in turning: 16m/min Feed in turning: 0.5mm/rev Depth of pass in turning: 1mm Rotational speed in turning: 134rpm Performance Time of one pass in turning: 89s Number of passes in turning: 7 Time per part in turning: 10min Weekly production: 1039 pieces/week Tooling cost Number of pieces per blade: 51 Cost of blades to make 1000 pieces: 485USD Mechanical load Absorbed power in turning : 2.5HP Turning torque : 129N-m Force transmitted in turning : 2384N Conclusions: Production performance drops significantly in the case of manufacturing the parts through the grinding process, achieving 15% of what can be produced by turning in the same period of time, this is due to the fact that the depth of past has a relationship of 3 to 100 with respect to both scenarios. When reviewing costs per tooling, the grinding process is far preferred over turning, grinding wheels were estimated for a wear ratio of 80 (volumetric ratio of wear to metal removed). Regarding the mechanical load resulting from machining, it could be determined that it increases in a proportion of 1:3 in the case of turning, so the respective forecasts must be taken when designing the bed, which It will support loads in the order of 300kgf, assuming a safety factor of 30%. Due to the above, this project will be oriented to the design and construction of a lathe that integrates the necessary components to carry out the cylindrical grinding process, mainly. Sub processes to be carried out in the machine The objective of this lathe to design is the production of parts that can usually be required in a non-industrialized workshop, with the capacity to manufacture machines and devices of medium complexity, through the use of Appropriate Technologies. In this sense, the operations that can normally be expected in a lathe to cover the aforementioned production and the fulfillment of such operations by the machine to be designed are indicated below: Operation Compliance Comments Turning Yes For parts that require the use of center point or steady rest, the non-interference of moving parts must be verified. Facing Yes The radius of the part must be less than or equal to the useful width of the abrasive wheel. Conical turning Yes The abrasive turning mechanism must be able to rotate and move obliquely on the cross slide (tool post grinder). Chamfering Yes The abrasive turning mechanism must be able to rotate and move obliquely on the cross slide (tool post grinder). Grooving, Cutoff Yes Requires the use of low thickness abrasive (cutting) wheels. Threading No It only applies to finishing processes and requires mechanisms for automatic feed Internal turning Yes Requires the use of smaller diameter accessories, for example, diamond-tipped tools. Drilling No It is an exclusive process for the use of drilling bits (metal in this case). Knurling No It is an exclusive process for the use of knurling accessories.

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