Design method and procedure of electric heating pipe (heater, heating element)

Electric heating tube design methods and steps

The method used in the design process of electric heating tubes is essentially different from the design steps of ordinary mechanical parts or electrical components. It focuses on the practicality of the close cooperation between the environment and the functions used, while the design work content of electric heating tubes is: There are two parts: technical design and product manufacturing process design.

In these two parts of the design content, the technical design of the product mainly focuses on all state-owned characteristic indicators of the product. As a designer, the way of thinking and actual work ability level can be fully exerted and demonstrated through specific product design. The main content of process design: the process operation methods and process assurance measures determined during the production process to ensure that the end product meets the design indicators. What should be paid attention to in the process design process: the operating methods adopted under the premise of meeting the technical performance of the product and the process engineering auxiliary design to improve the operating efficiency, for example: the decomposition and positioning of the operating procedures in the production, the operating personnel Equipment, tooling, molds, fixtures, measuring tools design, etc. In short, the direct service target of process design is the production line. In other industries, technical design and process design have strict boundaries in nature. In the electric heating pipe industry, although there is a primary and secondary division of labor between the two, there is no obvious boundary. On the contrary, the two design processes are mutually exclusive. To complement and improve. The selection of rigid indicators for technical design can only be formally determined based on the prerequisite of process reliability, and the process design process must be connected in series with the engineering design based on technical design indicators. Therefore, in the electric heating tube manufacturing industry, it can be said that technology and process Design is a special department that is combined into one, which is the general concept of the design method of electric heating pipes.

1. Product design feasibility analysis

In the design process of electric heating tubes, there is first a design procedure issue. The specific contents include the following: Before the design work of electric heating tubes is carried out, whether it is a newly developed product or a simulated imitation work, the feasibility analysis of the product must first be carried out, and the product The content steps involved in the feasibility analysis work are:

1. Review, verification and estimation of main technical indicators: The main technical indicators referred to here include, an overview of the environmental system parameters in which the components work, and calculation of the main design parameter index values ​​of the components, such as: calculation of the effective heating area area, effective heating area The area load, etc., the temperature estimation of the working status of the pipe table, the above content can be judged based on conventional experience whether the product has design feasibility.

2. Feasibility analysis of main processes and materials: Does the mutual coordination of process characteristics and material characteristics involved in the production process of the predetermined reference design product meet the conditions? For example: Will the R of the tube shape requirement design meet the material properties? Another example is when the process involves surface treatment, can the pipe satisfy the various physical and chemical reactions during the treatment process? The determination of these factors is the preliminary preparation for the specific design steps.

3. The preliminary approval of product appearance design requires a certain comprehensive review process to prepare and calculate the appearance structure of the product.

① Review whether it meets the requirements of various assembly conditions;

② It should be considered whether it contains content that is inconsistent with safety regulations;

③ It is necessary to comprehensively review whether its appearance and structure meet the customer's requirements.

④ Consider whether there is anything that needs improvement in its products.

After the feasibility analysis of the above content is fully passed, the specific design work will be carried out. The first step is the technical design work. Now we will introduce the following parts on how to carry out the technical design work:

2. Technical design work

1. General drawing design of electric heating tube products

The general drawing design of the product includes the following work: (a) external dimensions of each part of the product; (b) cross-section of the internal structure; (c) marking of component combinations; (d) determination and marking of the main technical indicators of the product; (e) product parts Icon indication and specific design; (f) Other additional instructions. Now these contents are explained in detail:

(1) Appearance dimensions of each part of the product: The appearance dimensions of the product have different requirements for different types of pipes. For example, the appearance contour line of the stainless steel water boiler pipe only focuses on controlling the volume and size of the appearance, while The most important part to control is the quality control of the installation piece. Based on the current overall requirements for electric heating tube components in terms of product dimensions, the installation dimensions of the thermostat will be strictly controlled, with emphasis on the overall dimensions of the product. The accuracy requirements for other tubes in the forming process are generally lower, but: Empty fired tubes and die-cast electric heating tubes focus on the forming size, because these products are basically assembled and used as a whole in a fixed model cavity or a specified position.

(2) Internal structure cross-section: The internal structure cross-section in the general drawing focuses on the built-in length of the leading pin used in the electric heating tube, the tube mouth sealing method, the combination of the tube and components, etc. It is equivalent to a partial part of the mechanical part Sectional or assembly drawing. During the cross-section of the internal structure of the electric heating pipe component, try to enlarge and analyze key parts as clearly as possible, such as the detailed dimensional requirements of the brazing position, etc.

(3) Component combination method: The combination method between components refers to the welding or linking method in electric heating pipe components. Currently, the methods used in electric heating pipe components according to the welding method include: high-frequency brazing, furnace brazing, and flame brazing. Welding, spot welding, planting welding, argon arc welding, etc., when labeling the content, label it as clearly and completely as possible according to the specifications.

(4) Main technical index requirements of the product: On the one hand, a clear and focused explanation must be added in the description column of the general drawing. At the same time, some of the contents specified in the IEC351-1 standard are: model, specification, trademark, etc. should be on a certain part of the component. Give detailed instructions on labeling, exact location, shape and size.

(5) The content indicated by the product parts icon is exactly the same as the title attachment column in the general product design process, and will not be displayed or explained here.

(6) Additional explanations include layout design of the general drawing, comparison and translation of foreign languages, etc.

2. Product process master drawing design

The product process master diagram refers to the design of the product operation flow chart, which refers to the shape change diagram of the electric heating element during the process of sequencing the operation process. The process diagram design is a primitive and tedious technical work. Through the display of the process flow diagram, the basic requirements are: a clear operation sequence process, the decomposition of the workstation process, and the auxiliary design content of the mold modulus fixture. , the skill and quality requirements of each work station. During the design process of the process master diagram, attention should be paid to: ① The process flow should be concise and clear; ② Use the structure of alternating operations to strive to keep the main process roadmap in the shortest cycle; ③ The principle of the process master diagram consists of two parts: serial number indication and serial number description.

After the product master drawing design and process master drawing design are completed, preliminary approval work should be carried out in a timely manner. There are various methods of approval. Generally, the relevant design personnel conduct a joint review under the convening of the project leader of the product, and the approval is confirmed after revision. Under the premise that there are no principle issues, we can then enter the technical design and specific process design of the product.

3. Product technical application design

The technical application design of the product is to carry out specific work content based on the overall product drawing design. It includes: calculation of the current intensity of the heating wire, calculation of the rated resistance, selection of heating model specifications, calculation and design of the heating wire winding diameter, and calculation of safety. Arc creeping distance, calculation of relative spacing and spacing of heating wires, calculation of tube surface load, calculation of wire surface load, calculation of heating wire calorific value, checking of thermal parameters, selection of magnesium powder model, etc. are purely technical applications of heating tubes. , since various types of products have large design standards, parameters and projects that are different, we will not explain them for the time being.

Above we only gave a brief description of the technical application design content of the product, and the content of these tasks also needs to be displayed in a standardized form using the product technical design instructions. Otherwise, the work done is not conducive to the review work and is not in line with the technology. Management requirements are also not conducive to the accumulation of technical achievements for enterprises. The overall requirements are: standards, specifications, clarity, and completeness.

(1) Specific process design of the product

Its general working principle is to specify the working procedures of each station under the guidance of the overall process design. The main content is the determination of various process parameters: process operation methods, design of tooling molds, fixtures, measuring tools, and product manufacturing processes. In the preparation of instructions, product process operation instructions, etc., during the work process of this step, it is also necessary to fully express in this document all relevant content related to the entire operation process, such as related configuration equipment, operating precautions, and material lists.

(2) Sample production process

Guided by the overall process design, the designed products are initially produced under the guidance of specific process design. During the preliminary manufacturing process, on the one hand, the preset plan is strictly followed, but all phenomena and data during the production process must be fully recorded. Including the following contents: changes in winding (gauge wire) resistance, changes in resistance of powdered tube shrinkage, changes in forming and shaping resistance, tube shrinkage rate, built-in length of lead posts, powdered density statistics, shrinkage tube density calculation review, annealing …etc., everything in the specific production process must have digital original records and descriptions of conditions, including detailed record data on the difficulty of production.

(3) Inspection of samples

  The content of this job involves the largest amount of work. After this job is carried out, can all previous work be judged to be qualified or not? Does it still need to be modified or improved? The content of the inspection can generally be divided into three steps: A. Whether the appearance of the product meets the design requirements; B. Whether the technical performance of the product can pass experiments or tests, whether it meets the design indicators, user acceptance standards, and industry safety requirements. Standards shall be implemented together; C. Comparative analysis of recorded data during the production process and designed process parameters, and feedback of the above issues to relevant departments.