DE2313212C3 - Rolling process for the production of plastic gears - Google Patents

Description

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212

At a high temperature of the hot tool, gears can be produced in which the Tooth head is cylindrical and the tooth base is roughly the same as the underside of a ship. Here, too, the tooth shape is not correct, although it is formed a little better than in the cold rolling process is. Therefore, the most popular hot rolling process is for the production of plastic gears thus also inexpedient.

The object of the invention is to create a rolling process for the production of plastic gearwheels, with A m precise production of the plastic gearwheels is possible with little expenditure of time.

This object is achieved in a rolling process of the type mentioned at the outset in that in this way a tooth shape similar to the desired tooth shape is rolled in a roughing process and the exact tooth shape is obtained by a subsequent finishing rolling process in which a cold mill is used, whose temperature is lower than the operating temperature of the hot tool.

The method according to the invention has the following advantages.

a) The surface of the gear is particularly smooth and the coefficient of friction is minimal, so that results in good efficiency when using the gear;

b) the tooth surface can be considered very smooth, curved Area to be formed:

c) the fiber is not interrupted at the tooth surface and this results in a strong structure and increased strength of the gear;

d) machining can be carried out using a small and simple rolling machine:

e) the working hours are short;

f) a crown wheel is produced;

g) a tooth shape that is enlarged due to moisture can be corrected and rolled.

The preheating and heating of the raw material and the selection and changing of time two types of tools should be suitably matched to one another.

The method can be applied not only to a pinion type tool, but also to others Forming tools such as racks, internally toothed wheels and the like.

The invention is explained in more detail with reference to 9 figures. It shows

Fig. 1 is a partial section of a nylon gear a flank view, which in a known manner by rolling cold raw material with a cold Tool has been manufactured,

2 shows a view of the tooth shape (contour) of the gear wheel according to FIG. 1,

Fig. 3 is a partial section of a nylon gear with a flank view, which in a known manner by rolling a cold raw material with a hot Tool has been manufactured,

F i g. 4 is a view of the tooth shape of the gear according to FIG. 3,.

5 shows a schematic top view, partially in section, of a device for carrying out the method according to the invention.
6 is a perspective view of the device

according to FIG. 5,

7 shows a partial section with a flank view of a nylon gear wheel which is in a finish rolling process according to the invention.

8 shows a partial section with a flank view a nylon gear at a stage where the ridge has been cut away on both sides,

F i g. 9 is a view of the tooth shape of the gear according to FIG. 8th.

The rolling sequence for the production of plastic gears according to the invention is described in detail below described.

The manufacturing process includes a pre-rolling, in which a cylinder-shaped by pressure with a hot tool Raw material is deformed into a shape and dimension similar to the finished gear in a short time as well as a subsequent finished product in which the gear is brought to the exact shape and dimensions by means of a cold tool.

Based on the new theory that dimensional errors are necessarily due to fluctuations the distance between the axes when a tool is pressed into a raw material during the Pre-rolling occur and on the test result, according to which a better tooth shape is achieved with hot rolling is considered using cold rolling, the corresponding tooth shape is softened in as short a time as possible or melting the surface of the raw material with a hot tool.

It is possible that a hot one, at a temperature which is higher than the softening temperature of the raw material, the tool is placed on a cold raw material is pressed, but reduces preheating of the raw material in a raw material supply system, as described below, or by radiant heating or by oil bath heating the axis of the raw material, the machining time, and particularly good results can be achieved.

A "hot tool" should generally be understood to mean a tool that can be used by any means to a temperature above the softening temperature of the raw material (including temperatures higher than the melting point) has been heated while under "cold tool" should be understood in general a tool that is at a temperature which is lower than that of the hot tool and also includes the room temperature.

The introductory step of the finish rolling process "correction of shape and dimensions" is pretty much carried out in a short time, i.e. errors that occurred during Pre-rolling have been made, the raw material surface is still in the soft or molten state. before improved.

The "correction of shape and dimensions" is the most important process of the whole, which is why depending on the Properties of the plastic raw material a hot tool and a cold tool as appropriate must be used alternately or at the same time. In the final stage of the finish rolling process, the Raw material cooled in a short time with a cold tool and hardened in order to maintain the correct To effect shape and dimension.

The F i g. 5 and 6 show an example of a device, with which the rolling process according to the invention can be carried out.

At one end of a roll of raw material 1. the horizontally is mounted in a frame 14, 15 by bearings (not shown). are a drive gear 2 and a pulley 13, which is driven by a (not shown) Drive are driven, arranged. At the other end of the raw material shaft 1 is a raw material

tcrial bracket (not shown) for attaching the Raw material piece 11 is provided.

On both sides of the raw material shaft 1, driven shafts 16 and 17 are mounted in bearings (not shown), each of the driven shafts 16 and 17 being assigned a drive gear 3 or 4, which connects the shafts with the pinion gear 2 without play. Both shafts 16 and 17 are connected to two further shafts 18 and 19 by Oldham couplings 5 and 6 (couplings in which a coupling disk rotates between a drive disk and an output disk displaceable transversely to the axis of rotation).

The two shafts 18 and 19 are mounted in carriages 9 and 10 , which can be moved perpendicular to the shafts. The pinion-like hot tool 7 sits on the transversely displaceable shaft 18, while the pinion-like cold tool 8 is arranged on the other displaceable shaft 19, so that the shafts can be moved together with the carriage against the piece of raw material 11 .

The hot tool 7 is separately or simultaneously by high-frequency heating, radiant heating by means of a heater 20 which is arranged around the hot tool. can be heated by a heater arranged inside the hot tool or by an oil bath heater.

Numeral 12 designates a raw material supply device which is arranged coaxially opposite the raw material shaft 11. In the supply device 12 , plastic raw material cut in a cylindrical shape is enclosed, which, if necessary, can be heated. In this case, the supply device 12 is rotated and the raw material is heated uniformly by a radiant heater arranged around the supply device 12. The raw material can also be heated in an oil bath.

A trapped in the supply means 12 "ohmaterialstück is preheated and rotated so that the material surface is up to a pre-determined depth sufficiently softened. The crude material piece 11, which transferred from the supply device 12 to the raw shaft 1 and is held there, rotates with the shaft 1 At the same time, the Rit7el tools 7 and 8 rotate by the drive via the gears 3 and 4, the drive shaft 16 and 17. the Oldham couplings 5 and 6 and the sliding shafts 18 and 19.

As soon as the piece of raw material U is seated on the shaft 1, it is ensured that a drop in the surface temperature is avoided and the softening is accelerated, if necessary, by means of radiant heating (not shown). The rotating hot tool 7 is then pressed into the raw material 11 to a predetermined depth by moving the carriage forward to carry out the rough rolling as early as possible and then the other carriage 10 is advanced to bring the cold tool into contact with the tooth shape for finish rolling bring to.

If the withdrawal of the hot tool 7 takes place earlier than the contact with the cold tool 8 with the workpiece, the two tools are used alternately while both tools at the same time come into use when the withdrawal of the hot tool 7 later than the said contact takes place

In the finish rolling process are preferably up to

Completion of the correction of animal tooth shape and surface almost do the same conditions as with Vorwal / .cn. Because of the necessary wedge cooling to fix the tooth shape and dimensions then the finish rolling ends in a stage where, in principle, only a cold tool is left is applied.

In the case of finished goods, too, the options listed below can be used, depending on the ίο Properties of the raw material and the type and size of the errors to be corrected a wchsclweiser or simultaneous use of hot and cold tools may be advisable:

1. Pre-rolling ends with a hot tool and the finished product begins with a cold one;

2. Vorwalzcn ends with a hot tool and the finish rolling process is in an earlier one Step carried out with a hot tool, in a later step with a cold tool;

3. The rough rolling is in an earlier stage than hot rolling, in a later stage with a cold tool carried out and the finish rolling step takes place with a cold tool;

4. Hot and potash tools are used simultaneously in the final stage of roughing while das Finishwalz.cn is carried out with a cold tool:

5. Pre-rolling is finished with a hot tool while finishing rolling. Cn at the same time with hot and cold tools in an earlier stage and with a cold tool in one later stage is carried out;

6. Hot and cold tools are produced simultaneously in the final step of roughing and one after the other also with an earlier step of the finished rolling and a cold tool is with a later one Finish rolling step applied.

F i g. Fig. 7 shows a partial section with Fiankenansichi of a nylon gear in a finish rolling process was subjected to the rolling process according to the invention, the burrs 50 and 51, which are on both Ends have arisen, removed by machine or by hand. F i g. 8 shows the same view of the finished one Gear in which the burrs are removed unc F i g. 9 the tooth shape of this wheel.

Provided that Nylor 6 or acetal resin is used as the raw material, the raw material can be rolled ^{with or without preheating in the temperature range between about 220 and 280 s C.} Without preheating the best results at about 260 ⁰ C is obtained, while with additional pre-heating the gun stigste temperature is lower.

In the following two practical examples are given which give a concrete idea about the course of the procedure and the accuracy that can be achieved.

example 1

Raw material: nylon 6 Outside diameter of the gear body (without teeth) 50 mm

Width of the gear body

(without teeth) 10mm

Machining speed 30 rpm Temperature of the hot Tool 220-300 ° C

Feed rate of the

hot tool 0.065 mm / sec

Temperature of the cold

Tool room temperature

Total contact time 60 see

The nylon gear manufactured by this process had excellent dimensional stability.

Example 2

Raw material: nylon and acetalhar / outer diameter of the gear body (without teeth) 50 mm

Width of the gear body

(without teeth) 10 mm

Preheat temperature from 60 to 100 ⁰ C.

Machining speed 30 rpm

Temperature of the hot

Tool 250 to 260 ⁰ C

Radial feed of the hot

Tool 0.15 mm / scc

Temperature of the cold

Tool room temperature

Total contact time 40 to 50 seconds

Accuracy of the rolled nylon gear

a) Tooth profile error 12 μ

b) Division error 9 μ

Accuracy of the rolled acetal resin gear

a) Tooth profile error 8 μ

b) Division error 7 μ

As the examples show, the process according to the invention can be carried out with little effort and within A high-precision plasma gear can be rolled in a very short time.

For this purpose 3 sheets of drawings

Claims (10)

Patent claims: 1. Rolling process for the production of plastic gears, in which a plastic raw material by means of a hot tool whose temperature is above the softening temperature of the raw material is held, the desired tooth shape is rolled in, characterized in, that in this way a tooth shape similar to the desired tooth shape in one roughing process rolls and the exact tooth shape is obtained through a subsequent finish rolling process! is at which a cold tool is used whose temperature is lower than the operating temperature of the hot tool is. '5 2. Waiz method according to claim 1, characterized in that that for the roughing process only the hot tool and for the finish rolling process only use a cold tool! will 3. whale / method according to claim 1, characterized ge * ° indicates that the hot tool was used in an earlier production step of the roughing process is used, hot and cold tools at the same time in a later production step of the roughing process can be used. * 5 4. Rolling process according to claim 1, characterized in that the hot tool is used for the roughing process, while simultaneous hot and cold tools are used in an earlier production step of the finish rolling process and the cold tool is used in a later production step of the finish rolling process. ^s 5. Rolling method according to claim 1, characterized in that in an earlier manufacturing step of the pre-rolling process, the hot tool is used in a later production step the pre-rolling process and, in an earlier production step, the finish-rolling process at the same time Hot and cold tools are used and in a later production step of the finish rolling process the cold tool is used. 6. Rolling method according to claim 1, characterized in that that in an earlier production step of the roughing process the hot tool and in a later process step of the roughing process and then the cold tool is used. 7. rolling method according to claim 1, characterized in that that the hot tool up to an earlier manufacturing step of the finish rolling process and then the cold tool is used in a later manufacturing step of the finish rolling process will. 8. rolling method according to claim 6 or 7, characterized in that when exchanging the Tools the hot and cold tools can be used at the same time. 9. rolling process according to one or more of claims 1 to 8, characterized in that the Rolling process at room temperature of the raw material begins. 10. Rolling process according to one or more of claims 1 to 8, characterized in that the The rolling process starts at a temperature of the raw material which is above room temperature located. The invention relates to a rolling process Manufacture of plastic gears using a hot tool in a plastic raw material ges whose temperature is kept above the softening temperature of the raw material, the desired te tooth shape is rolled in. In general, gears made of thermoplastic resins such as ζ. Β Nylon uses an injection molding process or a tooth milling process. Compared to these processes, processes in which the gears are now machined without cutting are more favorable, because generally a higher Festigkeil de; Gear, in particular of the individual tooth reachi wire. The DT-Gbm 66 07 913 means that a device device for the non-cutting machining of gears made of a thermoplastic material became known, mii which finishes the gears at a temperature, d. h can be finely processed, in which the mass is plastic is. The gears themselves are previously manufactured as blanks by milling or injection molding and are made with a tool which; iul a temperature is maintained. which is higher than the softening temperature of the blank is. finished or finely machined. The procedure used with this device can be carried out is actually a polishing process, i.e. a process in which a work piece with a rough surface is provided by contact with a tool with a smooth surface. Although the rolling process is the most advantageous and widely used process for metal gears is, the rolling of plastic gears has not yet been carried out, not even researched. The has the following reason: a) With cold rolling, just as with the raw material metal, only one cold rolling tool (hereinafter referred to as a cold tool) in contact with a cold raw material made of plastic brought. Since in the case of metal as a raw material, the elasticity range is quite low The extent to which it has reached the plasticity range is the elastic recovery when the cold tool goes back rather small, so that an accurate tooth shape can be easily produced. On the other hand In plastic, the elasticity range and the plasticity range have approximately the same extent, and almost half of the deformation occurs when the cold tool retracts due to the elastic Recovery back. An exact tooth shape can therefore naturally not be created and even a similar one Tooth shape can practically not be achieved. That is, a cold rolling process for manufacturing of plastic gears is a hopeless thing. b) There are two following variants of hot rolling: As with metal, it is cold Tool brought into contact with a hot raw material. As with plastic raw material no high frequency heating can be applied, must be impractical means that take a lot of time in Claim, such as radiant heating with nickel-chrome wire or immersion in hot oil bath can be used. Another variant is the following: A hot tool is in contact with cold raw material brought. This rolling process leads to a low temperature of the hot tool same result as cold rolling while