Maximum neck reduction at minimum cost
Die necking: Process for die forming of stacking necks and multiple step necks
Die necking is the ideal process for DR material, specially when producing stacking necks.
Clear reduction in material costs for end manufacturing.
Single, double, triple or quadruple necking permits considerable savings on material.
NEW: multiple step neck with soft profile.
Combinations of die necking and die shaping offers a lot of can forming opportunities.
Tried and tested with DR material down to 0.10 mm.
Use of carbide or ceramic tooling ensures top performance over lengthy periods.
Increased axial load of necked cans made of thin DR material by using a second die necker for neck reforming.

The diameter of the can body can be reduced at one end or at both ends simultaneously.
A necking ring, a kind of drawing ring whose ring diameter equals the outer diameter of the unnecked body on one side and the desired necked diameter on the other side, is pushed axially onto the body. The neck geometry is thus shaped to the profile formed by the two ring diameters. An inner core prevents wrinkling and calibrates the exact neck diameter. The diameter reduction per necking step is limited and depends on material quality, sheet gauge and body diameter. Neck reductions in one step allow for reductions in diameter of up to 3 mm approx., whereas reductions of approx. 8 mm can be achieved by necks with multiple steps.
type of die necking unit  unit with upper controlled toolings  unit without upper toolings
range of application  neck on lower and/or upper position;
 use of bodies with and without preflage		  neck on the lower position only;
 use of bodies without preflange only

Neck reforming:
Process to increase the axial load with a second die necker

 

Diagram:
Sample: Can diameter 73mm
Difference in strength (%) - Material thickness (mm)
DR 550, T61, T50
30 degrees one step
27 degrees one step
21 degrees one step
21 degrees reformed
Re-forming of the necked shoulders of can bodies with stacking necks to increase their crush resistance.
Problem
Material savings dictated by the necessity to reduce costs have resulted in ever thinner sheet gauges. To compensate the reduced crush resistance of the cans, at least partially, materials with a higher strength (usually in conjunction with limited elongation) have come to be used.
When die-necking the bodies, the higher yield stress required to shape the neck is achieved with modified tool geometries with smaller drawing radii and/or larger necking angles.The resulting neck geometry, owever, impairs the crush resistance of the cans. Beaded cans with stacking necks are often crushed at the neck under axial load while the beaded sections are still sufficiently resistant.
The conflict we are facing here is that geometries enhancing the crush resistance can only be formed within certain limits (or not at all), while the targeted crush resistance cannot be obtained with the geometries which would be optimal from a process-related, technical point of view. This conflict becomes even more pronounced when dealing with reduced sheet gauges, harder materials and side welds protected by powder lacquer.
 
Solution
In spite of a long series of tests with necking tools with various geometries it has not yet been possible to produce a necking shoulder with sufficient crush resistance in a single operation. The only solution is to reduce the diameter first with a geometry which is be optimal from a process-related, technical point of view and to re-form the necking shoulder afterwards to achieve the necessary crush resistance.
 
CAN-O-MAT
Recent studies have now confirmed that the geometry of the necking shoulders can be re-formed after necking and that the crush resistance of necked cans can thus be increased.
This involves 2 operations:
1.
Diameter reduction using a tool geometry which has been optimised to meet processrelated, technical requirements so that the material becomes sufficiently elastic to flow around the necking shoulder without wrinkles.
2.
Re-forming of the necking shoulder without modification of the neck diameter (in particular reduction of the angle of the shoulder) to increase its crush resistance.
The re-formed necking angle is independent of the necking angle of the first process operation. For bodies for can size 73/70 x 112 mm (sheet gauge 0.12 mm, DR550 material), the optimum re-formed necking angle was 21°, regardless whether the necking angle had been 27° or 30° at the first stage. The necking angle of the first stage can thus be optimised to meet processrelated, technical requirements.

Subsequent re-forming of the necking shoulder is always recommended when the required crush resistance could not be achieved with the first process operation.
The enclosed diagram summarises the crush resistance figures measured on bodies for can size 73/70 x 112 mm with one-step neck and with subsequently re-formed necking shoulders. For bodies made from SR material, with appropriately thick sheet gauges, a necking angle of 21° is still sufficient. DR material with sheet gauges down to 0.13 mm requires a necking angle of 27°, or 30°, if the sheet gauge is reduced even further, in conjunction with a diametrically opposed reduction in crush resistance. Here, calibrating the necking shoulder to 21° can increase the crush resistance by approx. 12 to 18 %, as compared to a necking angle of 30°.

Information:  Basic technical conditions
  Material conditions for die necking . ( pdf   )
  Powder application for parting and necking. ( pdf   )

Press articles
  Smooth or stepped neck - a technological question.  ( pdf   )
  Neck reforming. ( pdf   )

Technical Data  
CAN-O-MAT I   die necking
  4 spindles 6 spindles 8 spindles 12 spindles
 Body diameter 49 – 105 mm 49 – 83 mm 49 – 105 mm 49 – 73 mm
 Body height 35 – 190 mm 35 – 190 mm 35 – 190 mm 35 – 190 mm
 Sheet thickness 0,12 – 0,25 mm 0,12 – 0,25 mm 0,12 – 0,25 mm 0,12 – 0,25 mm
 Max. capacity 400 cpm 600 cpm 800 cpm 1200 cpm

CAN-O-MAT II   die necking
  4 spindles
 small p.c.d. 		6 spindles
 small p.c.d.
 Body diameter 73 – 153 mm 73 – 127 mm
 Body height 70 – 250 mm 70 – 250 mm
 Sheet thickness 0,16 – 0,30 mm 0,16 – 0,30 mm
 Max. capacity 300 cpm 450 cpm

 Technical Data:(all CAN-O-MAT processes)