Wire EDM, GOITI (DANOBAT Group)
Automated manufacture of dies for punching
press
Company
profile:
Firm: GOITI, S. Coop,
DANOBAT GROUP.
Address: Elgoibar, Gipuzkoa, Spain.
Business: Manufacture of bending machines and punching
presses.
Principal markets: All in Europe.
Year set up: 1961.
Employees: 825 (Danobat Group).
Wire EDM equipment: ONA PRIMA S-400, SODICK BF275,
JAPAX LDM50.
Person to contact: Iñaki Solupe.
Work
characteristics
| Application: | Automated manufacture of dies for punching press (DANOBAT). | Workpiece height: | 32 mm (1,26 in). |
| Machine: | PRIMA S-400. | Wire type: | Bare brass 900 N/mm² (Cu 63%, Zn 37%). |
| Workpiece material: | Steel. | Wire diameter: | 0.25 mm (0,0098 in). |
| Number of workpieces: | 33. | Number of cuts: | First at inclination of 1º and second at 3º, plus rerun. |
In
March of 1999, GOITI installed a PRIMA S-400 with automatic threader.
Working with the ONA Technology and Processes Service, it set in motion
a new process for the production of dies. This process features automated
manufacture 24 hours a day, seven days a week, with top precision and
quality guaranteed.
Today, a year and half later, GOITI remains entirely satisfied with the performance and reliability of the machine, having completely achieved its initial objective. In this article we explain how GOITI has its manufacturing system set up.
The
dies that GOITI manufactures are of cylindrical type, with diameters of
63 mm (2,48 in) or 30 mm (1,18 in). So that production could be automated,
first it was necessary to have tools for situating each workpiece on the
table with complete precision. A plate shoe measuring 500 mm x 400 mm
(19,68 in x 15,75 in) was made ready that would accommodate twenty-one
dies of diam. 63 mm (2,48 in) and twelve of diam. 30 mm (1,18 in). Thanks
to the die keys, the workpieces are set on the plate shoe with full precision.
Once the plate shoe had been set up and secured on the work table, the
next step was to prepare a program that would make it possible to manufacture
the dies without the operator's needing to centre manually or to take
reference points. With a precision of 0.01 mm (0,00039 in) on each axis,
offset figures were taken for each of the 33 dies and memorized. Thus
the point of origin of the cutting program for each of the dies would
always be the same, independently of the interior shape the die would
assume. The point of origin of the program is always the die centre, since
in every die a hole of diam. 2 mm (0,078 in) was made to accommodate automatic
wire threading.
Cutting time for the thirty-three dies on the plate shoe varies from 20 to 22 hours, depending on cutting geometry.
First thing in the morning, the operator removes the dies already cut. On the plate shoe he places a new set for cutting. When he has selected, on the CAD/CAM program, the new dies he wishes to cut, and when the macros with the new cutting shapes have been entered into the main program, the machine proceeds unattended until all the work has been done.In addition, a user technology was devised to enhance the specific cutting conditions. One of the peculiarities of this work is that the distance between the lower head and the actual cutting point on the workpiece is 44 mm (1,73 in), since dies are hollow inside and are mounted on the plate shoe. Although each die has a thickness of 32 mm (1,26 in), the actual cutting thickness is only 12 mm (0,47 in): 4 mm (0,157 in) of life plus 8 mm (0,315 in) output. The technology involves a first cut with the wire inclined at 1º. Subsequently, for the life only, a second cut is performed at an angle of 3º. This is followed by a skim-cut.
When all dies have been cut, the cuttings are attached to the workpiece by a wire, with thickness of no more than 0.55 mm / 0,0216 in ( at the point of union. The purpose is to ensure that when they fall, the cuttings do not collide with the lower head. Owing to the die's conicity, the wire or attachment point between the workpiece and the cutting affects only the die output area, and the cutting that corresponds to the life zone remains completely clean. When all dies have been cut, the operator separates the cutting from the die with a light blow.
