This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Planificar el mecanizado de moldes y matrices

Plan for the machining of moulds and dies

15/05/2002

Mold of a cover of trash

The machining of moulds and dies must be carefully planned. This article from Sandvik Coromant focuses on the planning phase of the process of machining, a planning which, in fact, also can be applied to high speed machining.

What bigger is a piece and what more complicated is, more important is the planning of the process. It is very important to adopt an open attitude regarding the methods of mechanised and tools of cutting. In a lot of cases can be of big value have an external collaborator that have diverse experiences in multiple areas and that it can provide a different perspective as well as contribute new ideas.
In our times, with the competitiveness like premise to survive, one of the fundamental tools is the computerización of the production. In the case of the industry of the moulds and matrices is a question to invest in equipment advanced and in systems of CAD/CAM. But even doing this, is of the maximum importance use all the potential of the softwares CAM.
In a lot of cases, the strength of the tradition in the programming is very strong. The traditional form and simpler to program the routes of the tools is the utilisation of the old technician of milling copied, with a lot of entrances and exits in the material. Often this means that a lot of very versatile softwares and powerful, machines and tools of cutting use with a lot of limitations.
The modern systems of CAD/CAM can take advantage of much more if they shelve forms to think old-fashioned and traditional habits.
If when it uses a technician of programming in which the main is to cut material with a value Z constant, use visited of tool of contorneado in combination with milling of recess, the result will be:

a time of mechanised enough shorter
better utilisation of machine and tool
better geometrical quality of the mould or matrix mechanised
lower manual polishing and time of proofs

In the election of the tool, the first thing to do is carefully studying the geometry of the mould or matrix

Has showed that, in combination with tools of tie up and modern cutting, this concept can reduce the time of production to the half.
In principle, a new work and more detailed is more complex and requires more time. The question that has to do is: where it is more elevated the cost by hour? In the department of planning of processes, in a station of work or in the machine-tool? The answer is quite clear, since the cost by hour of a machine is at least 2 or 3 times more than the one of a station of work.
Once familiarised with the new form to program/think, the programming will do increasingly routine and faster. The experience has showed that, on a long-term basis, can do with more rapidity a programming advanced of the routes of the tool that with the conventional programming.

By means of a programming advanced and the finishing
in a machine-tool of precision, the time of polishing can be reduced

Correct election of the tool of cut

The first thing to do is to carefully study the geometry of the mould or matrix. Other important steps are:

define the exigencias minimum of radius and the maximum depth of the cavity
estimate the quantity of material to delete. It is important to take into account that desbastar and semiacabar a mould or matrix of big dimensions is a task that does with more efficiency and of form more productive with the methods and conventional tools. For the finishing always is better to resort to the mechanised of high speed. This is due to the fact that the index of desbaste of material in the high speed is much lower that in the mechanised conventional, with the exception of the mechanised of aluminium or materials no férreos.
The manufacturing (milling and parallel surfaces) and fixation of the piece in the rough is of big importance, because it always is a source of vibrations. If It Is working with high speed, this point purchases even more importance. When it works with methods of high speed and even with mechanised conventional demanding regarding the precision of the mould or matrix, would owe always use specific machines for desbastados, semiacabados, finishings and superacabados.

Container mold for painting or mineral oil

The guides and husillos to balls are subjected to greater tensions when desbasta, for example. This will have a greater impact in the finishing of the surface and in the precision of the geometry of the moulds or matrices that are being object of mechanised of finishing in this machine-tool. This will result in a greater need of polishing manually and more time for proofs. If we remember that one of the current aims is to reduce the manual polishing, can conclude that the utilisation of the same machine for works of desbastado and finishing is a mistaken solution. For example, the time for pulir manually a mould for a capot of a big car can arrive to the 400 hours.
If it can reduce this time with a good mechanised, no only are going down the cost, but also improving the geometrical precision of the mould. A machine-tool mechanises with accuracy that for what has been programmed and thus the geometrical precision will be better what more can mechanise the mould or the matrix. However, when there is a lot of manual work of finishing, the geometrical precision will not be so good, by factors like the pressesure that each person exerts to the pulir or the method that use, for quoting only two causes.
Adding in total some 50 hours in a programming advanced (a small piece) and the finishing in a machine-tool of precision, the polishing can be reduced to 100 or 150 hours and even less. They exist besides other advantages if it mechanises with tolerances more precise and superficial finishing. One of them is that the greater geometrical precision requires afterwards less time of proofs. Another, that for example a mould for presses will have a longer life and that increases the competitiveness thanks to a greater quality of the piece.
A human being can not compete in precision, by a lot of experience that have, with a route of the tool computerizado. If we speak of applications of high speed is absolutely feasible to delete totally the manual works of polishing if it uses a programming advanced and adapted, machines-specific tool and tools of ideal cutting.

Mold for previous of Scooter

The modern systems of CAD/CAM can take advantage of much more if they shelve forms
to think old-fashioned and traditional habits

The versatilidad of plates of round cutting

If you are using a tool square to triangular plates steps will have relatively weak sections in the corners, thereby creating a behavior during unpredictable machining. Triangular or Rhombus-shaped plates create large forces of court radio and, as a result of the number of cutting edges, are a little economic alternative in this type of operation
On the other hand, if you use the round plates, allowing milling all materials and in all the
addresses, was mellow transitions between the steps and facilitate the later work of semifinishing, finally resulting in a better quality of the mould or matrix.
Another feature of round plates is that they create different chip thickness, allowing higher rates of food compared with most of the plates with other forms. Round plates cutting is very smooth as the angle of connection changes successively from almost zero to 90 degrees. In the maximum cutting depth onslaught angle is 45 degrees and when copying with peripherals, 90 degrees.
Round plates should always be the first choice for artefact. In five axes machining are very appropriate and have virtually no limitations.