Product category:
Packaging, Conveyors and Materials Transfer
News Release from: Sandretto UK | Subject: Quick Mould Changes
Edited by the Processingtalk Editorial
Team on 16 March 2004
Plan, and be prepared, for Quick Mould
Changes
Gordon Crouch, Manager, Processing, at Rugby-based Sandretto UK, explains some of the Quick Mould Change (QMC) details and issues at the tool/moulding machine interface
Sandretto has for many years been able to offer a full side entry table style fully automated QMC system, capable of carrying out mould changes within a matter of minutes Sandretto also has the facility to pre-condition the mould in order to reduce the change-over time
This article was originally published on Processingtalk on 23 Jan 2004 at 8.00am (UK)
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However, due mainly to cost and space implications, these systems are rare.
This kind of mould system would represent the very top level of QMC.
In today's tough economic climate, shorter production runs have become a necessity for most moulders, simply because customers demand less inventory.
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However, in order to maximise profits, moulders need to keep the machine utilisation high.
These two ideals conflict with each other, as the mould change time is effectively lost time.
Obviously, if a company can improve its mould-change time, more changes for a given machine utilisation, or gain more utilisation for a given number of mould changes.
Mould change time is a very often misunderstood term.
There are many moulding companies that have shelled out large sums of cash for a quick mould clamping device, only to find out that the same device has not made drastic reductions in mould change times.
This is because the physical clamping of mould-to-platen, often does not take up a significant or large percentage of the overall mould-change time, which must be defined as elapsed time between 'Last off to first off'.
Quite often it is the overlooked manufacturing operations that contribute the most to lengthy mould-change time, for example water connections, ejector couplings, hydraulic core connections and so forth.
And the biggest factors involved can often involve material changes, material conditioning, and mould conditioning.
Material changing for example, can take days to achieve in some extreme cases, especially where clear material is used, and where even small amounts of contaminated material can cause rejects.
In these cases removing the screw and barrel for cleaning can become a part of the overall mould-change procedure.
Sandretto has recognised this fact, and has fitted quick change barrel mechanisms as standard to a large range of the moulding machines.
This allows for the complete change of injection unit screw /barrel assembly, together with heater bands and outer guards in a short space of time.
A second material specific barrel unit can be fitted in a much reduced time, which makes changing the unit a realistic proposition even on a daily basis.
The advice Sandretto UK gives to companies looking to reduce mould change times, is to break down all the components of operations typically required to change the mould, and to get a feel for the average times for each operation.
Often taking video footage of the complete operation is an invaluably reference both in the study of events, and also in the final training stages.
These individual operations then need to be categorised into online/offline operations.
For example - getting the next mould brought from the storage area to the machine can be carried out whilst the first mould is still in production.
Once this is done, all operations that can be carried out online should be structured so that they are kept online, and are ready before the change takes place.
All focus should be directed at reducing the time taken for the offline operations, as these are the ones that ultimately control mould-change time.
The secret is in preparation: in having everything ready in time for the proposed mould change.
Tasks include: material dried and ready; correct nozzle for next tool at press; correct location devices, clamps, ejector bars, tools, present and correct, so that as soon as the machine is brought 'offline', everything that needs changing is at hand.
Every effort must be made to get the next mouldings off as soon as possible, with perhaps QA ready to inspect and pass off the parts.
And once the machine goes back to being 'On-line', the old mould and all ancillaries can then be returned to their normal storage areas.
As long as this routine is regularly followed, effort can be concentrated on standardising time consuming tasks, to speed up the operation.
Planning is therefore a vital part of QMC.
Planning helps ensure that material changes are kept to a minimum, and rotated in the friendliest order, and that production run sizes are tailored for maximum efficiency.
Production runs also need to be intermeshed with each other.
After all, there is no point in carrying out two mould changes at the same time if there is only one overhead crane, or a lack of mould change personnel to carry out the task.
Shop floor communication is therefore critical to ensure planners are informed, up to the minute of all the goings on, in order to adapt the plan.
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