The origin of the error in CNC Machining and means of settlement are discussed

1 craft error machines craft to also make machine a method. Numerical control process designing person the each technology requirement that should understand treatment part above all, decide the treatment method of the spare parts according to technical requirement and tolerancepublic errand size next. Because machine a method,craft error is of undeserved generation error. 1.

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1 fixed position is standard unified fixed position should be used in wanting to unite 　 CNC Machining fiducial, the appearance that prevents to machine position of process occurrence outline and dimension and blueprint to not agree with and cause bigger error. To reduce such error, the process designing origin that chooses when process designing as far as possible and craft are fiducial with coincide of design datum mark. In the meantime, bring dimension catenary error to avoid dimension conversion, of the computation that the process designing origin of set should be helpful for coordinate numerical value, workpiece search, make go to the lavatory to the knife, process designing is handy. The process designing origin of general and symmetrical spare parts chooses the symmetrical center in the spare parts to go up, to the spare parts with a few irregular appearance, can ask to process designing origin chooses on taller datum plane in its precision, the spare parts that less than aperture locates, center of less than aperture serves as the origin of process designing. 1.

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Course of 2 treatment craft wants arrangement of course of craft of reasonable 　 CNC Machining reasonable, the error that order differs and arises in order to because machine,decrease. Design of course of CNC Machining craft should consider specific treatment details, machine on numerical control boring, milling machine especially form when the spare parts with tolerancepublic errand higher demand, should take each link seriously more. For example, treatment plane and plane have the demand of flatness; Treatment end panel and outside round, inside aperture has verticality demand; Inside, outside when columnar face has coaxial to spend a requirement, all answer to be finished in holding clip. 1.

Executive process can divide the compensatory of radius of error cutting tool that compensation of radius of 2 cutting tool uses undeserved generation commonly for 3 paces: The knife fills build, the knife fills carry out, the knife fills cancel. When the knife fills to build or cancel, must undertake below G00 or G01 instruction, cannot undertake below G02 or G03 instruction, and in same a G41 on treatment direction or G42 cannot be mixed with, do not allow to use two blame place to choose planar mobile statement continuously. Fill to build or cancel a course in the knife commonly in incidental be cut too or owe cut a condition, bring about be machined of the spare parts unqualified happening (see a picture 1) . Graph 1 had happened to cut position of the mistake in perhaps owing cut circumstance Zun Tu to bring about owe cut, wrong place has been brought about in right graph cut, want to notice when build or cancelling a knife to fill so: When contrail of shift of cutting tool center at ongoing direction is parallel (α =0 ° ) , build and cancel compensation to be cut nevertheless; When ° of <90 of α of 0 ° < , build cut nevertheless, had cancelled to cut; When α <0 ° , had built cut, cancel to be cut nevertheless; When ≤ of α of 90 ° ≤ when 180 ° , build and cancel to be cut nevertheless; When ° of <270 of α of 180 ° < , had built cut, cancel to be cut nevertheless; When α =270 ° , build and cancel to be cut nevertheless; When ° of <360 of α of 270 ° < , build and cancel to be cut too entirely. When milling is not linear outline, for example circular arc (one's duty is round the circle outside mixing) , normal direction avoids to be cut when the circle outside milling cutter mill, want to let cutting tool cut circular arc along tangent direction, knife of disappear of the reassume after cutting tool letting walk out of contour line along tangent direction after treatment is finished fills, lest had appeared to cut a phenomenon (see a picture 2) ; When the circle inside milling cutter milling, also want to be cut along tangent direction, establishing a method is circular arc and circular arc tangent (see a picture 3) . Graph the knife cuts the mill when the circular arc outside 2 mill to cut a method to pursue the knife cuts the mill when the circular arc inside 3 mill to cut a method besides angle problem should note when build or cancelling, the attention still answers when using: Cutting is bit more initiative the mobile distance that nods to the target on contour line must be more than cutting tool radius to compensate a value, and must move to just can be cut correctly continuously inside place compensatory plane cut; D00 -- D99 is code name of knife filling memory, d01 must choose when applied knife fills -- ability of a code name builds the random in D99 effective knife fills, d00 delegate cancels cutting tool compensation, in compensation memory must be being inputted before cost of cutting tool compensation is being machined. 1.

3 cutting tool and measure of cutting tool of error of cutting parameter choice have metrical below the static state, and treatment process is trends, cutting tool not only get cutting force and get even the influence of oscillatory outside force, the measure that can create spare parts treatment to come out so and blueprint dimension are abhorrent, the size of this error basically depends on the quality of cutting tool and dynamic character. The treatment quality that the function of cutting tool can affect a part directly reachs the manufacturing efficiency of numerical control machine tool, if treatment parameter choice is incorrect, of cutting tool wear away, the measurement of cutting tool error, the precision that can cause a part is unusual. Undeserved to choosing as a result of cutting tool and cutting parameter in CNC Machining the machining error that cause, can prevent through 4 kinds of methods: It is to machine precision to ask tall spare parts divides thick, precision work, the cutting tool that in the light of different cutting material choice different capable person pledges, different rotate speed and feed. 2 it is to reduce error of the fixed position that change a knife, choose an appropriate cutting tool to machine the content that can machine on the spare parts entirely after finishing, change other cutting tool to machine again. 3 it is the mental allowance with appropriate choice, the finish machining when allocating mental allowance should be taken 0.

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5 Mm. Mental allowance crosses congress to cause pull had moved cut and slant let owe cut, it is difficult to because be cut,also be met when mental allowance is too little cause owe cut, compensate the rework after surplus, can have caused cut. 4 it is to be when the treatment demand of groove is higher, use the intermediate part of the chamfer of mill of keyway milling cutter with lesser diameter first, radius of recycle cutting tool compensates milling two side. The cutting tool sort with all sorts of appearance, qualitative now material is various, different cutting tool applies in different situation, accordingly, in milling process, machine personnel to answer the effective demand that the basis machines, the cutting tool with the relevant element the most appropriate choice such as parameter of consideration workpiece appearance, rigid, material, cutting and cutting parameter undertake machining. 1.

Error of 4 pairs of knives is when numerical control process designing establish workpiece coordinate is, in CNC Machining, even affirmatory knife bit of position in workpiece coordinate. The method has pair of commonly used knives: Try cut a law to be opposite knife, right to Dao Yi knife, ATC is right the knife. Generation basically has to the reason of knife error: It is to use try cut a law to be opposite when the knife, basically result from to knife error the sum of errors that the range estimation in unit process of cargo bandling produces tries the measurement after cutting work error. 2 be after be being finished to the knife, should carry out to the numerical control equipment of opposite coder " the machine tool is answered 0 " operation, zero shift may produce in this process and cause a 0 errors, produce pair of knife errors thereby. 3 it is to use pair of Dao Yi to be opposite when the knife, the error basically originates the production of the instrument, installation and measure, additionally wrong instrument uses a method to also can cause an error. The main measure that reduces pair of knife errors has: It is to should be used try cut a law to be opposite when the knife, handlers is in attentive the compensation cost that the poor value between dimension of referenced to still answering after the knife spare parts and process designing dimension will come to amend cutting tool. The 2 zero shift circumstances that are machine tool of regular examination numerical control, adjust spacing switch position and systematic parameter in time. 3 it is to use an instrument to be opposite when the knife, install and measure precision what should notice an instrument, master the use method of special apparatus correctly. 1.

The 5 treatment content that measure an error to differ should choose different measure to undertake metrical. The competence that the measure itself precision, member that machine a person makes dosage is provided and place detect the measurement technique of the project is met produce an effect to the precision of the spare parts. Because this measure wants to send check regularly, want to undertake metrical a technology technically to groom to using personnel. Conditional unit can use 3 coordinate to measure machine etc to undertake metrical with quantity appearance only, will measure result and the measure that process personnel to measure a result to contrast, in order to analyse error reason, this has certain and direct effect to assuring spare parts precision. In recent years, online in measuring equipment to also apply the spare parts with taller precision to machine a process gradually, such making machine and measure undertake on same equipment, improved manufacturing efficiency not only, and nonexistent repeat fixed position error, can undertake detecting to processing medium work at any time, and can the basis is online measure a result to adjust craft parameter, raise treatment precision thereby. 2, the error that objective reason produces the error that objective reason produces basically divides amount to to accuse operating system error, mechanical error and tool error 3 parts. 1) error of numerical control system. The control means according to servo can divide numerical control system to control system, closed-loop control system and system of half closed-loop control for open loop. Among them closed-loop control system can detect in real time the real position of cutting tool, give numerical control the system result feedback, undertake feedbacking is worth what be worth with the instruction in the system to compare, the ability when be being eliminated till poor value can stop shift, control precision is very consequently tall. But, closed circuit position detects all sorts of not stable elements in feedback are more, because this debugs working difficulty, if all sorts of parameter do not match, can cause systematic oscillation, cause a machine tool to work to be not stabilized. Of error of closed-loop control system basically is the mounting error that feedback system produces in installing a process. The main method that reduces afore-mentioned errors is the installation precision that improves feedback system, choose the feedback system with more expensive precision as far as possible. The existence in system of half closed-loop control does not feedback link, the positional precision of cutting tool still can be not feedbacked link influence. Transmission catenary error is to show transmission catenary is medium an error that moves relatively between end drive component, its are the main factor that affects treatment precision, the method that can adopt parameter of system of modification numerical control undertakes compensating. System of open loop control does not contain the position to detect device, also do not have feedback circuit. Because feed system is medium,detect without feedback device, the error that its feed circuitry produces cannot undertake compensating through feedback information, caused factual position error thereby. For example, the main error that uses a pace to enter electric machinery has step pitch error, trends the error stops since sum of errors. Be aimed at above all sorts of errors, the electric machinery that can choose to be able to satisfy step pitch horn to ask or electric machinery of fractionize circuit drive will improve. 2) mechanical error. Machinery of numerical control machine tool includes guide screw of bearing of decelerate gear, bearing, ball partly deputy reach shaft coupling to wait. Transmission guide screw is put in backlash, when workbench moves reversely, this kind of clearance can cause motor racing and workbench does not move, produce an error thereby. Be aimed at transmission backlash, the method that eliminates ball guide screw and nut gap is to bring to bear on to tighten force beforehand; Introduce in open loop system cut with cut a direction to extend a capacity, prevent to owe cutting or the treatment quality that cross cutting and affect a part; Measure a closed circuit and the clearance value in half closed circuit system, can have set as compensating parameter of retrorse pitch error. Be out of shape to getting power by mechanical drive catenary and heat up the error that be out of shape and causes, can pass improve quality of machine tool component (treatment precision, stiffness and hot character) , reduce inner heat source calorific quantity and environment of strict control treatment and use condition will solve. 3) error of tool clamping apparatus. The fixed position error of tool clamping apparatus can affect the dimension precision of workpiece and positional precision directly, because clamping apparatus of this requirement tool should have good fixed position,precision, tigidity reachs structural craft sex. Dot of the fulcrum of logical choice clamping apparatus, fixed position and clamp are nodded, the deflection when assuring spare parts clamp is inside reasonable range, cross big deflection to machine those who affect a part precision otherwise. If adopt relevant measure still of incontrollable spare parts be out of shape, ought to consider necessary technology measure, have heat treatment to the spare parts for example, in order to eliminate stress, reduce be out of shape; Be out of shape to cannot using what heat treatment method solves problem, can use the method with apart mill of thick, essence, treatment of mill of thick, essence uses different clamping force. The place on 3, last word put together is narrated, the spare parts is being machined on numerical control machine tool is the result that whole machining complex and collaboration of treatment environment put together use, source of error is very complex, the treatment precision of the spare parts depends on all sorts of elements of the system. Accordingly, must consider each link integratedly, analyse and find out the source of error that affects spare parts precision, so that take corresponding step. CNC Milling CNC Machining