Here are few topics that need to be brought up or answered.
- Ensure all necessary data are completed and authorized; usually there will be 3D drawing for 3D design and NC programming, 2d drawing must be available especially when there is precision requirement, mold factory need pay special attention to the tolerance specified. If any of the tolerance are no able to fulfilled, bring it up to customer in advance, otherwise it would be a disaster when you found it after mold is build.
- Check with customer about the resin that they are going to use for production. If it happened to be a kind of resin that is not available in local market, the mold factory needs to come a solution with customer where the resin will come from. In most occasions, customer will accept to provide material for trail if it's a very special resin. If the resin is special or you don't have much experience of it, ask opinions of the customer for the shrinkage rate.
- Discuss through with customers about the primary design by presenting parting line, ejector pins location, sliders, lifter, engraving, surface requirement etc. this would save a lot of time afterwards for official design approval. Sometimes the product design against the manufacturability, compromise needs to be made to achieve the best result.
- It's important to deeply understand the demands of the customer, it's a key factor to influence the mold project cost, let customer know what steel you are going to use and how many shorts it guarantees, make sure it fits the demands.
- Timeline need to be settled down during meeting.
Finding the right software is not easy. So the best is to do a benchmark of the software systems, cause it depends a bit of what you want get out of the simulation. It depends on if your company wants to simulate for part design, or is a mold manufacturer or a plastic part producer. Also is depends on the size of parts. Big Parts, small parts, flat parts. Big parts like bumper is hard to do in 3D, cause it takes too much time in simulation. It also depends on if you want to do simulation of assemblies with mold inserts or part inserts like core shift analysis. Not everybody needs everything.
Guiding system of injection mold works as guides to ensure precise mechanic movements. Generally the standard mold base all have guiding design, like guide pins between cavity side and core side, mold designers can just choose the proper mold base. Typical mold guiding system include, guiding between A/B plates, guiding for stripper plates, guiding for runner plates, guiding for ejector pins. All this guiding system can be customized when you order the mold base.
Plastic enclosures are plastic cases or housings manufactured by injection molding process. Usually a popular consumer product with great enclosure design catch people's eye immediately without promoting how good the function are, a very success example is Apple product, success industrial design contribute a lot to the success of Apple in worldwide.How to make a custom plastic enclosure?
First you need to make a design for your custom plastic enclosure, a complete and professional design will includes plastic parts size, structure, selection of proper plastic materials, assembly method, finish. Then you need a plastic mold maker to make a custom injection mold for it, mold price and lead-time will be determined by the quantity demanded, complexity of structure, size finish of the plastic part. If your plastic parts are in high volume demand, then a high quality and long durable mold is a must, get a warranty for how many plastic parts the mold can produce before you sign a mold manufacturing contract with your injection mold supplier. After the custom mold produced, you need to run the mold on an injection molding machine, finally, you get your custom plastic enclosure done.
There are many types of injection mold and tooling in using today, such as two-plate, three-plate and stack molds. Two and three- plate molds are more commonly used for heavy wall and non-packaging products. Both cold and hot-runner systems are used for two and three plate molds. All stack molds use a hot manifold to convey the melt to the cavities. Each mold component must be machined and finished to exact dimensions with very tight tolerances and must be heat-treated to be able to withstand very high injection and clamp pressures. Injection molds are the most expensive molds used in plastics processing with very long lead times, required for their design and fabrication. Every injection mold must be tested and debugged to prove-out the ejection system, cooling and/or heating system and operating components before it is placed in production.
Amorphous resins such as ABS, Polycarbonate, and Polystyrene have much lower shrinkage values than the polyolefins. The higher shrinkage of polyolefins is due to the fact that, in their molten state, they take up more volume than in the solid state because polyolefin resins are semi-crystalline. When the resin solidifies, the chains in the crystalline regions pack tightly together resulting in a reduction in volume. In general, the polyolefins can be ranked for shrinkage:
HDPE ≥LLDPE ≥LDPE ≥PP
Once a resin has been selected, shrinkage can be controlled, to some extent, through mold design and processing conditions.
A gate is a designed small opening to allow the melted plastics into the mold cavity, a successful gate design is determined by gate type, dimensions, location, it's deeply related with the materials been used, the type of mold plates, and economic factors. Gate design is one of the most important elements to influence injection mold quality and productivity.
Single gate has always been selected as a priority unless the distance of the mold flow is too big and beyond the limits of the injection molding pressure. Multiple gates always cannot avoid the problem of weld line where the flows meet from different gates. This weld line are not allowed sometimes specially when the injection molded parts have critical appearance or strength requirement, single gate also have good performance on packing, part strength, lower scrap rates, which gating way to employ will be determined by the structure, dimension appearance requirement of the molded parts.
A good mold flow analysis has lots of benefits, although it is time consuming, the cost is much lower than the cost of trials during nights and days on a production injection molding machine. The difficulty is not to produce colored pictures but to explain to the customers the different results, some customers have enough knowledge to understand some others no.
In 90% of cases, I work before the injection mold is cut, so I am ready to take the responsibility of cycle time, warpage, sink marks and so others issues. I am specialized in gas assisted injection molding and I assist Chinese companies to produce plastic parts for the German automotive industry which generally use overflow. With short shot process, we can obtain a production costs reduction of 20% by simulation and 30% in practice.
The differences between the two styles:
- Toggles generate tonnage via tie bar stretch, Hydraulics based on ram diameter and hydraulic pressure. Toggle injection machines tend to increase tonnage as they run due to thermal expansion of the mold, tie bars, toggle links and plattens. Without a tie bar strain gauge, you never know what the true tonnage is! Hydraulics remains the same as long the pressure stays the same.
- Toggle machines open with near full close tonnage ratings. Great for deep draw parts. Hydraulic machines are limited due to the ram design as the pressure is exerted against the shaft seals and wiper. For that reason, the opening pressure is limited. Now with newer clamp designs, the hydraulics is faster and more efficient than ever. Engel uses a smaller high speed cylinder to open and close the clamp; the ram is for clamp tonnage only. That is true of their Duo and Tie Barless machine design. With a Duo the small tie bar mounted clamping cylinders are used to break open large or deep draw parts.
In a fast-paced market, it is critical for a company to get new custom products into the market quickly, in most of the cases, it could be just a market-testing product with 10,000 units' volume or even less. But the plastic parts still need to be customized by injection molding to achieve the specified tolerance, finish, function. Traditionally, a hardened steel injection mold would requires a very high investment before you get a piece of sample, and it usually take 8-12 weeks to complete, which are unacceptable for a new product developing at the earliest phrase.
We need a solution to reduce the cost of injection molding and shorten the lead-time of for companies to launch new custom plastic products. Low volume plastic injection molding is what you are looking for, which means low cost, quick turn around and on budget.
Many years ago we molded golf clubs driving heads much thicker than 25mm. One solution (also used for a number of other thick walled products) was to mold an insert to leave say a minimum 3mm wall depending on strength needed. The insert was made of all the regrind sometimes contaminated material. Molded at quite a fast cycle as distortion was not usually important for the insert. An extra mould and an extra operation but often proved economical with reduction in overall cycle time and material costs.
The marbling effect or tortoise shell effect developed in the last century was typically achieved by adding 2 or more different colors of the same basic resin and processing through a plunger style machine versus a reciprocating screw machine as is commonly found today. The reason it worked was because that type of injection molding machine did not mix the materials very well and you would have streaks of the dissimilar colors showing on the surface of the product.