Quick link of the Troubleshooting Guide:
A book of "Mold Standards" is a detailed description of what is required to match the mold with the molding factory, their equipment, machines, clamping systems, water hook ups, hydraulics for cylinders, air hook ups and cylinders, brand and type of steels/materials that are required, Hot Runner brand, electrical hook up and wiring requirements, brand and type of components (DME, Hasco), etc. This should never come from the mold maker, he'll build you what is cheapest for him.
You can get a larger shot size out of a hydraulic injection molding machine. There are times when you are pushing the injection capacity of the injection unit that hydraulic machines are a better choice than all-electric injection molding machines. However, if the job is within the range of the injection unit and specified properly, the electric machines outperform hydraulic for repeatability and energy consumption.
The main consideration when considering an all-electric injection molding machine is energy efficiency. Electricity savings of 20%-40% are typical when compared to hydraulic machines. Also, an all-electric machine can offer unmatched repeatability due to the servo drives that are used for injection forward and clamp rather than hydraulic pumps/valves.
Scientific Molding to me is a bit different than having a whole lot of data studies. To me, and to many of my peers, scientific molding is an disciplined elimination of multiple variables, which yields an range of conditions/settings/protocol/things that you must do. This will yields the highest volume of acceptable parts with the least amount of cost. I.E., when you do this, and you do that - the press operates thus and you get money. Going thru the methology checklist eliminates the variables in a disciplined fashion resulting in an updated group of setting, updated methods of handling material change outs, setting up a mold, scheduling jobs, etc. and reduction of scrap. Happy customers, happy plant operators, more money.
In injection molding, for any faults error on any 3M (Material, Machinery/Molding variables, Mold) maybe responsible. If you have earlier used similar combination of material & got satisfactory results (Reference sample may be available), then compare MFI values of base resins, if the values are same, then grade may differ & you have to get characterization results ( DSc/TGA) to ensure same combination being used.
For satisfaction, you may test MFI, density of raw material (Resins) used for product molding to compare with old raw material specs. Chemistry wise, materials molecular weight may differ (MFI will change) or MWD (molecular weight distribution) may not same as old stock. If you are getting compounded PC+ABS blend from compounder, then percentage of individual resin components (PC & ABS) may vary or they might have used different grades of PC & ABS in preparation of blend.
Rib is a frequently used feature in plastic injection molded parts design for the purpose to enhance the strength of the plastic parts, typical rib design see below figure.
The thickness and location is essential of the rib design. Usually, ribs should be designed with a thickness of 1/2 of the wall thickness to avoid a thick section at the base of the wall, which would cause sink marks on the part surface. Ribs are usually spaced at a distance at least twice the wall thickness to allow enough steel between the ribs for adequate cooling.
You will have to examine your application and choose accordingly, but I will try to explain briefly some of the advantages to a hot runner solution. As I currently work for a hot runner company I see many parts that benefit from this application. Here are a few basic reasons to look into hot runners:
- Less waste -which in turn reduces contamination
- Controlled melt temperature - reduces warping of part as well as plastic degrading
- Great gate vestige - Reduces the need for second operations
- Lower injection pressures - allows for more cavities per mold
- Shorter cycle times - improves production efficiency
Specific decisions for the best approach (material, process, design detailing) can only be made with a detailed knowledge of all the constraints (structural, dimensional and financial) and all the must-have, nice-to-have and absolute must-not-have features and attributes. Is there not a web address where we can get more detailed information? Another process (actually, a hybrid process) came to mind and this might suit the combination of requirements that I think you have. This is offered by a couple of machine manufacturers. You'd need to contact the machinery manufacturers direct for contact details of processors offering this service. A thin skin (can be vacuum-formed) is normally inserted in the relatively low-cost mold, to give high-quality surface. The robotic head dispenses PUR foam with reinforcing fibers - that are chopped in the head also - into the open mold. Once the mold is closed, the "B" surface is formed, complete with any ribbing and fixing points, etc. However, the total thickness will tend to be significantly well above the 5mm maximum that you have defined. Rigidity is very impressive. Impact strength will depend on surface material and density/reinforcement variables in the backing material.
The injection molding machine outputs cannot be set, but the inputs can be each time you set the injection mold. Some of these set points, like mold temperature and barrel temperatures can be set. Of course this depends on which factors are the most critical to the injection molding process
. If you had ability to perform a simple screening DOE before you put a specific injection mold into production, Minitab can pare to out the most significant inputs. If nothing else, these would be the ones to monitor. However, you'd likely want to capture fill time, cushion, screw recovery (loading time) and cycle time (especially if the machine is not run automatically.
Bottom line, if you have unlimited funds to purchase advanced monitoring systems and have employees that know how to operate them properly and analyze the data they produce, then by all means use them. But if you are dependent on your machine operators to produce good product, you must give them simple tools that they can understand and use while they are right at the injection molding machine. And they can monitor virtually every shot in real time, so if something does drift, or a machine or mold issue does arise, they can notify appropriate engineering personnel immediately.
Proper location of the gate point will be directly affect the quality of the injection molded parts gate location selection should follow the following principles:
- Gate location should be chosen in parting surface, so that it would be easier for machining and maintenance.
- The runner should be designed even, mold flow distance and sectional size in balance can achieved stable molding quality.
- Gating location should be on the thick-wall area so it ensure the cavity can be filled completed.
- The mold flow should not be right on the inserts or lifter, high pushing pressure of melt flow would probably deform the inserts.
- Try to avoid weld marks or weld lines created in the critical surface, changing location of gating and try to make the weld line on uncritical surface.
- Consider the venting when design the gating, make sure the end of the mold flow have good venting.
- Gates should be easily removed and gate mark should not affect the appearance of the molded parts.