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Turned parts common faults and solutions

Views: 93Date: 2013-09-12Typeface: Big Small
When turning screw thread common faults and solutions in the cylindrical surface of the workpiece along the helix formed with the same cross-section of a continuous convex and concave . In the machinery manufacturing industry, threaded parts application was very extensive. The method of turning threading , is commonly used processing methods. In horizontal lathe ( eg CA6140) can be turned on metric , inch system, the modulus and diameter control four standard thread, regardless of what kind of thread turning , lathe spindle and the tool movement must be maintained between a strict relationship : the spindle per revolution a turn ( ie a turn workpiece ) , turning pieces should be evenly moving a tool ( workpiece ) lead in the distance. Their relationship is such movement guaranteed : Spindle rotates together with the workpiece spindle movement spread through hanging round feed box ; feed box after the post-shift ( mainly in order to obtain a variety of pitch ) and then to the screw ; the screw and the opening on the apron drive nut holder with a straight line movement , rotation of the workpiece and the tool so that the movement of the spindle is driven to be achieved, thus ensuring the workpiece and the tool movement strict relationship between . In the actual turning thread , due to various reasons , caused by the movement between the spindle to the tool , in a certain part of the problem , causing failure when turning screw , affecting the normal production , then should be solved .

Turning thread when common faults and solutions are as follows :

First, eating knife Failure Analysis and Solution: The reason is installed too high or too low, turning , turning workpiece clamping is not strong or excessive wear .


1 Tool installed too high or too low too high, eating knife to a certain depth, the turning of the workpiece flank withstood , increasing friction , or even bend the workpiece top , causing eating knife phenomenon ; too low , then the chip difficult to discharge, turning the radial direction of the force of the workpiece center, with a cross-feed screw and nut gap is too large , resulting in automatic tendency to eat knife depth constantly deepened, thereby lifting the workpiece , there eating knives. At this point, turning height should adjust to the axis of the tool tip and workpiece contour ( tailstock can be used on the knife ) . Turning parts in roughing and semi- finishing car, tip position higher than the center of the workpiece about 1% D (D represents the workpiece diameter ) .

2 Workpiece clamping rigidity of the workpiece itself is not strong can not withstand the cutting force when turning , resulting in excessive deflection , changing the turning center height of the workpiece ( a workpiece is inflated ) , the formation of the sudden increase in the depth of cut , there eating knife , and you should firmly clamping the workpiece , tailstock , etc. can be used to increase the rigidity of the workpiece .

3 Tool wear caused by excessive cutting force increases , the top curved workpiece , there eating knives. Grinding tools to deal with at this time .

Second, the arbitrary deduction failure analysis and solution : The reason is that when the screw a turn , the workpiece is not turned integers instead caused .

1 When the lathe leadscrew pitch ratio and the workpiece if not integer multiples retraction , the use of open half nuts , shaking the saddle to the starting position , then closed again half nuts occurs when turning the tip of the knife is not the first car out of the spiral groove , resulting in chaos buckle. The workaround is to use positive and negative car retraction method , that is, in the first end of the trip , do not mention the opening and closing nut , knife radially exits, the spindle reversal, so that turning the longitudinal returned , then the first second trip , so forth process, due to the spindle , screw drive and there is no separation between the turret off , turning always in the original spiral groove , it will not appear arbitrary deduction .

2 pieces of lathe for turning women away from the workpiece spindle pitch ratio to an integer multiple of the workpiece and the screw threads are in the rotation , lift the opening and closing nut , turn the screw to wait at least one turn, to re- close the opening and closing nut , so that when the screw is turned one turn , turn an integer multiple of the workpiece , turning the knife will be able to enter the car out in front of the spiral groove , it will not appear arbitrary deduction , so that you can use to open the half nut , manual retraction . Such retraction fast , help to improve productivity and retention screw accuracy , while the screw is also safer .

Third, the pitch is not correct failure analysis and solutions :

1 thread length is incorrect because improper or hanging round feed box with handle position is wrong, check the feed box can be re- location or checking the handle hanging round .

(2) Local incorrect due to their pitch screw lathe local error ( usually caused by the wear and tear ) , replaceable screw or partially repaired.

3 . Thread length on uneven pitch reason: screw axial movement . Axial movement of the spindle . Apron opening and closing nut and screw shaft caused by different meshing bad . Apron dovetail rail wear and tear caused by the opening and closing nut closed unstable. Hanging round the gap too big. By testing : If it is caused by the axial movement of the screw can feed on the lathe screw and the adjustment of the junction box round nut to be adjusted to eliminate the junction thrust ball bearing axial clearance . If it is caused by the axial movement of the spindle , adjustable spindle nut after adjustment to eliminate the rear thrust ball bearing axial clearance . If apron opening and closing nut and screw shaft caused by different meshing caused by poor can trim and adjust the opening and closing of the opening and closing nut nut clearance . If dovetail rail wear, can be formulated dovetail rail and set pieces , in order to achieve the correct fit requirements. If the gap is too large hanging round , hanging round the gap can be re- adjusted .

4 turning pieces appear bamboo pattern due to the screw from the spindle gear between the errors caused by cyclical , such as hanging round inside the gear box gear because the feed itself, the manufacturing error , or local wear , or gear mounted on the shaft eccentricity caused by the low center of rotation , causing the screw rotation periodically uneven , uneven cyclical driven tool movement , leading to the emergence of bamboo pattern , you can repair for any error or worn gears.

Fourth, the path is not correct failure analysis and solution: The reason is eating knife too , dials allowed, but not timely measurements caused . The workaround is fine car to detailed examination of the dial is loose, finishing allowance should be appropriate vehicle to a sharp knife edge , a timely measure .

Five , turning pieces of thread surface roughness Failure Analysis and Solution : The reason is the car is not worn smooth blade mouth , improper cutting fluid , cutting speed and workpiece material and the cutting process is not suitable for generating vibrations create success. The solution is: correct wheel dressing or oil stone lapping tool ; selecting the appropriate cutting speed and cutting fluid ; adjust lathe saddle plate and medium and small slide dovetail rail inlay strips to ensure the accuracy of the guide clearance to prevent cutting vibration .

In short, turning threaded fault is generated when a variety of forms , both devices reasons, there are tools, operators and other reasons, when troubleshooting specific conditions , through a variety of testing and diagnostic tools to identify specific factors to take effective solution.