The most critical element is to have a good design first with special considerations to the structural stiffening members. Then use glass fiber reinforced PP, but remember the injection molding of glass filled PP is different from the injection of unfilled PP even if you are molding the same shape. The stiffness and the strength of the part depend on the fiber orientation pattern throughout the molded part. Such pattern is determined by the location and the type of the injection gate. The fiber length distribution which determines the quality of the compounded materials has huge effect on the creep modulus and hence on the long term strength of the par during application. It is not enough to use glass fiber filled PP without specifying the average fiber length. It is also important to consider the effect of the fiber orientation pattern and the fiber length on the warpage and shrinkage of the molded part which is completely different from those of the unfilled PP molded part.
There are many kind of steel, for long runs production, a durable mold is required, the tool steel must be selected properly, for small volume production, steel selection can be as economic as possible as long as it meet the requirement of production demands.
How to choose the injection mold steel? Important steel properties include:
- Ease of machining
- Dimensional stability after heat treatment
- Wear resistance
- Surface finish
- Corrosion resistance
In higher humidity conditions, apart from the increase in water content in the air in the tool void prior to fill, maybe you're getting condensation at times (if the press is held-up between shots), in which case you will be pushing lots of water into the weld-line. Worth noting, also, is that even if you have the same barrel settings and water temperature and flow settings throughout the year, actual conditions that the material encounters (precise melt temperature at point of entry into the injection mold and actual mold surface temperatures) will vary, because of the R.H. and temperature differences. Hire a thermal imaging camera at relevant times and look at the readings on the parts at point of ejection. You'll see differences, I'm sure.
There are possibilities to employ vacuum-assisted venting (by default, this would pull moisture out with the air) in the injection mold void prior to fill. Also, as I've seen with multi-impression PET preform molding, air-conditioning enclosures around machines.
The important consideration should be end product and what your definition of "REGRIND" is. Reprocessing your own internal scrap (if kept clean and uncontaminated with anything else) is a significantly different question basis than using unknown or unclassified "regrind" from outside sources.
Most folks that are quoting probably don't realize the write UP in material "cost" that should be considered when significantly less percentages of regrind are incorporated. If you DON'T use it up and end up selling it for a few cents on the dollar, the WRITE DOWN is actually a part of the COST of the product you originally bought the material for. And most don't have any idea of what the "true" cost to own of an 80:20 mixture is considering handling, size reduction, inventory holding and shrinkage costs etc are over the life of a business project. This should be part of the 'living business plan' for every product life cycle in your factory.
Mold is a kind of tool that form the molten plastic raw materials into designed shape and measurement, finishing, parts produced by utilizing mold is very common to see around your daily life, your phone case, most of the parts made in plastic in your car. When you want to product something in plastic massively, you would need employ molds to lower down cost and increase the efficiency. That's why the first issue would be discussed is mold when you send your unique design or sample for inquiry.
Mold making is a complex process, from the design, processing, assembly, commissioning and other steps to the final actual use. In the entire life cycle, the factors affecting the quality of the mold are mainly the following 10 aspects.
To decide an injection mold for unpredictable demand, I would see whether more cavities will change the mold base size. If part size is small and volume is low, a 2 cavities and 4 cavities mold may use the same mold base (hence use the same machine tonnage), then it may be wise to have a 4 cavity-capable mold with only 2 cavity cut, like a bridge mold.
However, I am still a little bit doubtful on the saving we can gain by just not cutting the remaining cavity. Building a small injection mold is still the 1st preference. Then we may end up with 2 small molds, which is more expensive. However, the second mold is a duplicate mold which will not need to design, program, and go through various mold modification as the first mold. Furthermore 2 small injection molds are sometime more flexible for production planning compared to one big mold.
Rounded pellets usually are hot-cut, cylindrical pellets are usually strand-cut so most likely different extruders were used. This (change in extruders) may effect compounding of the materials and thus properties, but your supplier should have done QC testing to know product is the same. Again, this may be where pellet-to-pellet differences could show up in FTIR analysis. Also, most suppliers don't mold sample test specimens that have knitlines that many production parts contain, and they wouldn't be able to catch differences in batches if you are having knitline issues. Poorly compounded materials (not enough mixing) might show up in drop dart impact test comparisons, as I have seen this in some materials I have evaluated in the past.
A couple of years ago I analyzed an FR-PC/ABS painted bezel for an electronic enclosure molded in China and found that their injection molder had sworn they used the same material, but the batch that had poor performance had a bunch of silicone oil in it. This caused failing the heat performance test and very poor paint adhesion.
Cushion is used to ASSURE colete material mold cavity complete FILL 2 PACK is achieved. Precise molding uses a "FIXED" VOLUME shot size of a PLUNGER or screw pot like the SODICK system, where an ASSURED excess melt VOLUME is injected to make up for SHRINKAGE.
Melt cushion is added the Screw Inject STROKE because the shut-off ring has a "FLOAT" distance and the added CUSHION ASSURES a final PEAK PACK AMOUNT. Both Barrel ID and screw shut-off clearance change with WEAR.
To ask about "Best Injection Mold Tool Designer" you must quantify what specific type(s) of tooling you are most interested in. Since this thread is under Injection Molds, I would add that the typical tool designers are experienced with certain industries and thus are familiar with injection mould tools that support products that typically use certain size presses, materials and key processes which complement the product requirements.
Like most processes, making plastic parts look like metal can be done poorly or well, and can be appropriate or not. If you want to look at some really beautiful metal coated parts, check out some of the bathroom and kitchen fixtures at your local Home Depot, Lowe's, etc. This requires specific material and design skill, but these parts are durable, wear reasonably well and look just like, particularly, chromed metal, in part because those items are chrome-plated.
As with any project, the hard part is to define as closely as possible what it is you want: Does it have to "sort of look like metal," does it have to look like a mirror, does it need to look like brushed stainless, etc., and how much abrasion, temperature resistance (e.g. will it sit on the top of a car dashboard where it could get to 180F), does the metal in the metallic look have to contribute anything other than aesthetics (e.g. conductivity)? The more time you spend closely defining the parameters, the better chance you have for success.
Here are some advantages and reasons for choosing:
- Easy manufacturing. All operations in milling, and saving up to 2/3 actual time if made by aluminum instead of steel.
- Weight plays more important role (example in bigger sized molds and with many loose inserts to be inserted manually, it is easy to handle).
So the Aluminum tooling is cheaper than steel tooling.