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Improved milling at mouldmaker

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article image A CoroMill 20” cutter in action at Honyi.

NOT being dependent on any particular market, searching for new product areas with constant technology development in the company, and not being afraid of using external contacts when it is thought that it may improve the production, works well for Honyi Steel Mould Co Ltd.

The company was started in 1977 and in 1985 it moved to the current location in Taipei, Taiwan. Today it has grown to employ 150 people and also has a company in Shanghai where 40 people work.

Honyi's main products are thermoplastic injection moulds for the electronic, computer, automobile and consumer product industry. The largest segment is moulds for the TV industry, which is about 30 per cent of the production.

The company manufactures 300 moulds per year and 85 per cent of them are exported. Previously Japan was Honyi's largest market with 70 per cent of the export. Today Japanese customers only represent 30 per cent of the export.

"These figures vary and it is better not to be dependent too much on just one market" says general manager Y.C. Lin. "We would also like to get into the automotive business area more and get that figure up to about 25 per cent from the current 13 per cent - 14 per cent.

"The largest moulds we can manufacture at the moment are 2200mm x 1300mm x 1200mm but we also make moulds as small as 200mm x 200mm for injection mould machines from 150 ton up to 3000 ton. We have subcontractors who make all the rough machining for us and we only make the semi finishing and finishing of the components. When we get the machined components from the subcontractors there are 5 mm left in material stock for us to machine to the finished shape of the components."

High speed machining is something discussed much within the die and mould business, as well as other businesses, these days and Honyi is no exception.

"HSM is also something which we would like to be able to use, and will use in the future. Traditionally we have a lead time of seven weeks to make a mould, however, I predict that we could reduce that to only four weeks with HSM. Because of the CAD-CAM development there is more emphasis on the production planning and making better tool paths and so on to minimize the manual finishing of the components," Mr Lin says.

In its production Honyi has started to use Sandvik’s round insert cutter CoroMill 200, a type of cutter with which the company had no previous experience.

"Sandvik introduced us to a cutter and we started to test at the end of 1997 and found that the productivity was much higher with the CoroMill 200 cutter,” machining section vice manager J.C. Yang said.

“With the cutting depths we use it at, we can index the inserts 5 - 6 times compared to the 3 cutting edges we had on our previous triangular inserts for these applications. We found that the round inserts also have much stronger cutting edges compared to the inserts we were using, which broke quite easily,” he added.

Since Honyi makes a lot of moulds for television sets there is often a need for tools with long overhangs to reach into deep cavities. These obviously are applications where the vibration tendency is high. Therefore, Honyi uses anti-vibration adapters to reduce the vibrations.

"The overhangs we are talking about can be of over 400 mm and first we tried the use of conventional adapters for the operations but we got heavy vibrations causing very poor machining results,” Mr Yang said.

“To overcome this problem we started to use tuned anti-vibration adapters and now there are no problems. When we use these long tools we also remove two of the inserts in the cutters with four cutting edges to get lower cutting forces and further reduce the vibration tendencies.

“Since the adapters are tuned from the beginning they are easy to use and we do not treat these tools any different from conventional tools.

To reduce the vibration and noise, two inserts were removed from the cutter as explained before. The measures for reducing the insert breakage were several depending on the cause of the breakage.

In one case where the inserts broke due to vibrations the insert grade was changed from an old grade SM30 to the newer GC4030. The insert radius was also changed from 0.8 mm to 1.6 mm to get a stronger cutting edge.

To come to terms with the excessive spindle overload, causing the machine to shut off, the depth of cut was reduced from 3mm to 2mm and also the tool path was changed some what. It was also recommended to remove two inserts in this application as well to reduce the cutting forces.

Sandvik Coromant sales supervisor G.C. Ho also emphasised the importance of correct tool paths for a successful machining result, especially when machining corners, profiles and radii.

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