GB2298604A

GB2298604A - Profile forming

Info

Publication number: GB2298604A
Application number: GB9604586A
Authority: GB
Inventors: Roland Graham Whiteing; Dennis Hugh Sansome
Original assignee: Design & Dev Eng Ltd
Current assignee: Design & Dev Eng Ltd
Priority date: 1995-03-06
Filing date: 1996-03-04
Publication date: 1996-09-11
Also published as: WO1996027458A1; TW327613B; IL117387A0; GB9604586D0; ZA961823B; GB9504433D0; AU4885496A

Description

PROFILE FORMING This invention relates to profile forming and more particularly to forming a profile on an element of elongate shape.

According to the present invention a method of forming a profile on an element of elongate shape comprises passing the element through an ultrasonic resonating die. The element may be of any desired shape for example, round a square bar, or in fact any irregular shape, eg a jigsaw puzzle.

However, in a particular application of the method of the present invention the element is in the form of a hollow body, for example a tube.

Where a hollow body is to be produced the method may include inserting a mandrel in to the body prior to its being passed through the die.

Preferably the mandrel is at least partially shaped so that the interior of the body when passed through the die will conform to that shape. The hollow body may be of any desired shape, but in one preferred arrangement it is in the form of a tube. In this case the shaped portion of the mandrel may for example be tapered and may be provided with one or more different tapers. The shape of the mandrel is only limited by the ability to withdraw it from the tube.

By using ultrasonic vibrations it is possible to produce a product with a very high quality surface finish. Also when a mandrel is used this may further assist in producing a very high quality interior surface finish corresponding to or better than the surface finish of the mandrel. The method is particularly suitable, but not limited to the formation of irregular shapes and varying diameters which can be achieved by ultrasonic frequencies being transferred to a hardened die eg. carbide or other similar material.

The interfaces between the die and the element are lubricated and where a mandrel is used, between the element and the mandrel. High frequency vibrations do not affect the lubricant viscosity but by increasing the effectiveness of the lubricant they improve surface finish on both the inside and the outside of the tube.

The vibrations contribute to a burnishing of both the inner and outer surfaces of the body. Moreover, greater work hardening occurs throughout the wall thickness of the tube when additional advantage is taken of the reduction in stress produced by the vibrations.

In the invention the element is preferably provided with means by which it can be pulled through the die. In the case of a tube the means by which the tube can be pulled through the die may comprise for example a nozzled end on the tube which is engaged by an abutment on the mandrel, the mandrel may have a portion extending through the nozzled end and by means of which the tube can be pulled through the die.

In an alternative arrangement the element may be provided with a reduced diameter portion which extends beyond the die and by means of which the remaining portion can be pulled through the die.

In a further alternative arrangement means such as a pin may be placed through the mandrel and die so that the tube is drawn through the die.

The element may be drawn in either one pass or two or more subsequent passes, depending on the total deformation required and the ability of the drawn workpiece material to sustain the draw stress The present invention also includes within its scope an element made by the method set forth. Where the element is a tube such a tube may be used to form a gun barrel.

Previously gun barrels have been made by taking a suitable tube and drilling it and then subsequently reaming, honing and polishing or possibly using a rotary swaging technique to work harden the barrel. This traditional method of manufacture is time consuming, wasteful and very noisy.

The drawing of a tubular element in accordance with the present invention is a particularly effective, environmentally acceptable and quick method for manufacturing a very high precision gun barrel with a smooth surface finish. Further reference is made later in the specification to the parameters which can be established with the present invention compared with a conventional gun barrel.

The invention may be performed in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawings in which: Figure 1A and 1B - show a mandrel for use with the present invention Figure 2 - is a view of the mandrel in a tubular element about to be drawn Figure 3 - is a view of the workpiece partially drawn Figure 4 - is a view of the tube passing through a second die Figure 5 - is a chart showing the surface finish parameters of a conventional smooth bore barrel, and Figure 6 - is a similar chart showing the same parameters in a gun barrel produced by the present invention Various methods of drawing a tube in which a mandrel has been inserted can be used and one example is described below.

In the Figures 1A and 1B the mandrel 10 consists of a series of concentric groves at one end and shown at 11 by means of which it can be gripped to draw it. This is joined to a constant diameter part 12 which extends to an abutment 13 and joined to the part 12 by a chamfer 14.

This is turn is joined by a chamfer 15 to a reduced diameter part 16 which in turn is joined by a chamfer 17 to a tapered portion 18. The tapered portion 18 is joined to a second tapered portion 20 having a greater taper than the portion 18. This latter portion is then joined to a further constant diameter portion 21 which extends to a datum reference formed by a shoulder 22, then a further constant diameter portion 23 which extends to a further series of concentric groves 24 by means of which this second end can be gripped.

Reference is now made to Figure 2. In this it will be seen that the mandrel is inserted in the undrawn tube 25 and which is provided with a nozzle end 26. Surrounding the nozzled end is a first ultrasonic die 27. The tube is then drawn through the die by the mandrel being pulled from the end with the groves 11. The abutment 13 is drawn against the nozzled end 26 and pulls the tube through the die thus reducing its diameter in the process to conform to the shape of the mandrel and the die. The mandrel is formed with a very high precision finish which is imparted to the tube.

This completes the first pass at this point. However, to obtain the required deformation a further reduction may be necessary and it is then passed through a second die as shown at 28 in Figure 4.

The mandrel with the different tapers 18, 20 and 31 produces different internal corresponding tapers in the tube.

Although two passes have been described a third pass may be required to avoid putting too much strain on the mandrel.

At this stage the mandrel is not withdrawn from the tube.

Before doing so the datum point reference on the mandrel ie, the shoulder 22, is noted by being measured from the end with the grooves 24 and a mark made on the exterior of the tube. This then enables the position of the recessed portion 16 of the die to be determined and the tube is then parted off as indicated at 30 in Figure 3.

Subsequent to this the mandrel is withdrawn from the tube. The withdrawal may be made by any suitable means, either mechanical or inductive, sonic or ultrasonic means.

The entire process which is substantially silent and takes approximately 30 seconds to complete a one meter gun barrel which has the chamber, the firing cone and the barrel completed to size with a high quality finish as will be described with reference to Figures 5 and 6.

Although the drawing process has been described with reference to a nozzled tube and an abutment on the mandrel, it may be drawn by alternative methods. For example, the tube may be provided with a reduced diameter portion which extends beyond the die and by means of which the remaining portion can be pulled through the die.

Alternatively, means such as a pin may be placed through the mandrel and tube and by means of which the tube is drawn through the die.

A very high precision finish can be achieved in both the exterior and interior of the tube particularly the latter which can be conformed to the shape of the mandrel.

Reference is now made to Figures 5 and 6. These Figures show the results as applied to gun barrels but similar results will be achieved from any tube made in accordance with the invention. In Figure 5 the parameters are shown for a standard 12 bore shotgun barrel and Figure 6 shows similar measurements for a similar bore barrel made according to the present invention. It will seen that this is a very high degree of smoothness in the interior of the tube made according to the present invention compared with that of Figure 5. In particular it is to be noted that the projections above the reference line of the Applicant's tube are very small thus indicating that smoothness is produced where it is required.

The parameters shown are calculated in accordance with the definitions of BS1134, ISQ468 or other internationally accepted standards and are as follows: Definitions:

Rp = maximum peak height (above mean line) Rv = maximum valley depth (below mean line) Rt = Rp + Rv ii Rti = maximum peak to valley separation within a single sampling length Ry = the greatest of the 5 Rti values within the evaluation length Rtm = RZ(DIN) = (Rts + Rtz + Rt3 + Rto + Rt5Q) / 5 Rz(ISO) is assessed on the unfiltered profile and is the mean separation between the 5 highest peaks and the 5 lowest valleys Peak parameters such as R and R are very susceptible to large fluctuations in value caused by isolated singularities on the surface, or even minute particles of dirt on the component being measured. Rtm and Rz are both parameters designed to offer a measure of peak height, but using different averaging techniques to reduce sensitivity to individual freak peaks.

where Q(x) = root mean square slope of profile at x

Deltaq is the root mean square slope of the profile over the evaluation length. Surtrace software calculates and displays it in degrees.

Lamdaq = 2 x Rq/Deltaq (Deltaq in radians) Lamdaq represents a measure of the average (root mean square) spacing of peaks and valleys along the surface, sometimes referred to as the average wavelength along the surface.

R3yi = the separation between the third highest peak and the third lowest valley in one sample length R3y is the largest of the n R3y values in the evaluation length R3z = l/n (R3yl + R3y2 + ...R3yn) (where n = no of sampling lengths in the evaluation length - usually 5) R3y and R3z are, like Rtm and R=, designed to give a measure of the maximum peak and valley characteristics of the surface, but without the extreme sensitivity to individual freak peaks or valleys.

Claims

1. A method of forming a profile on an element of elongate shape comprises passing the element through an ultrasonic resonating die.

2. A method as claimed in Claim 1, in which the element is in the form of a hollow body, eg a tube.

3. A method as claimed in Claim 2, which includes inserting a mandrel in to the body prior to its being passed through the die.

4. A method as claimed in Claim 3, in which the mandrel is at least partially shaped so that the interior of the body when passed through the die will conform to that shape.

5. A method as claimed in Claim 4, in which the hollow body is in the form of a tube.

6. A method as claimed in Claim 4, in which the shaped portion of the mandrel is tapered.

7. A method as claimed in Claim 6, in which the mandrel is provided with one or more different tapers.

8. A method as claimed in any of one the preceding Claims, in which the element is provided with means by which is can be pulled through the die.

9. A method as claimed in any one of Claims 5 to 8, in which the tube has a nozzled end which is engaged by an abutment on the mandrel, the mandrel having a portion extending through the nozzled end and by means of which the tube can be pulled through the die.

10. A method as claimed in Claim 8, in which the element is provided with a reduced diameter portion which extends beyond the die and by which the remaining portion can be pulled through the die.

11. A method as claimed in Claim 4, in which a pin is placed through the mandrel and die and by means of which the tube is drawn through the die.

12. A method as claimed in any one of Claims 5 to 11, in which the tube is in the form of a a gun barrel.

13. A profile formed by the method set forth.

14. A gun barrel formed by the method as claimed in any one of the preceding Claims.