Arad use Autodesk Moldflow software to design, develop and manufacture top quality precision water meters

Background

Arad’s products are currently distributed in over 60 countries throughout the world and meet standards of quality and performance including ISO and AWWA. Every system is individually tested and inspected to ensure it meets the highest quality requirements.

The Arad Mould department has over 700 active moulds. On an annual basis they manufacture 70-100 new moulds and to support this activity they have 25 dedicated and skilled mould makers.

Water Meter Measuring Chamber

• A fundamental and important element of a water meter
• Original weight of the measuring chamber was 46g
• Single cavity mould tool
• Cycle time of 40 seconds

Case Study

The original weight of the measuring chamber was 46g and ran at a cycle time of 40 seconds. It had a cold feed, direct sprue that needed to be removed by machining after moulding.
The mould was a single cavity tool due to the incapability to produce more than one cavity within the required tolerances.

Therefore, the maximum annual run which the mould could produce was 420,000 parts. This was not enough to withstand the growing demand for the product.

Design Change

Arad reduced the weight from 46 to 30 grams using Moldflow software. The green regions show where wall thickness was reduced for the new design.

Injection Location Change

The Moldflow software also allowed Arad to try all different gating scenarios very quickly. Originally a single gate, Arad looked at 2,3 and 4 gates in various locations before deciding on 2 gates, close to the centre. This was chosen as the best being a compromise between quality, cycle time, dimensional accuracy, and materials selection.

By using Moldflow on the next generation design Arad fully optimised both the part and the mould designs, validated all iterations in Moldflow, and eventually produced a two-cavity mould.
Moldflow results confirmed a controlled flow and fiber orientation pattern within each cavity, low pressures to fill, no surface sink marks and internal voids and that the part dimensions would be within design specifications.

A 3 plate tool was designed which has the advantage that no finishing is required to remove the feed system since separation of the parts and feed system occurs automatically during mould opening.

Arad reduced the part weight from 46 to 30g -16g in material for each part. This means an annual saving of 9600kg (9.6 tons) of material.

The reduction of part weight helped contribute to a reduced cycle time of 28 seconds. This optimisation study now allowed Arad to manufacture more in the same amount of time, raising annual production to 600,000.

Arad’s biggest market place is the United States, with 80% of their products being exported there. This market is very competitive and the US market is very conservative and favours the traditional feel of metal solutions. A lot of Arad’s products are historically made from brass or bronze, however due to the rising costs of these metals it is becoming more common to replace metals with plastics.

It is very important to design for manufacture and not just for function. In this case, converting from brass to injection molded plastic required a few iterative design changes, to ensure the parts would be filled within the pressure limits of the molding machine from a choice of gate positions and have sufficient strength with thinner wall sections. The physical part ejection from the mold also has to be considered.

Even although Moldflow predicted the best gate location at one end for flow considerations, Arad continued to look at all scenarios. Moldflow enabled Arad to make good informed decisions while balancing all criteria. It is critical that both end openings are in line within a set tolerance. If it is out of tolerance than it can lead to a poor fitting when connecting to the inline piping installation and this can result in water leaks.

When gating from one end, an unacceptable amount of warpage was occurring. So Arad reviewed all gate locations and decided on a centre gate. The flow of the material is not as good but the deflection is within tolerance.

Simulation results showed that the part would :

• Fill with weld lines in non-critical areas.
• Be packed out adequately for good surface finish, control of dimensions and strength.
• Be free of distortion and high stresses.
• Efficiently cooled in the mould for minimum cycle time.

Business Benefits

Arad’s plastic products are cheaper in cost but still meet the performance requirements set by international standards. This savings is passed onto their customers which is then passed onto the end user.

• Arad produces 30,000 of these components a month
• Going from metal to plastic has saved 70% in cost
• The mould cost $30,000 so a return on investment in one month of production
• 20-30% saving in mould manufacturing costs
• Reduced time to market
• Control & validate moulds made in China
• 20% reduced time for mould manufacture
• Using Computer Aided Engineering (CAE) in-house to protect intellectual property

This new design was accepted by the US market dependent on NSF61 approval (a standard for drinking water in the USA by FDA). With a happy US market place they have branched out and now sell this product to the rest of the world as well.