What is L/D Ratio
L/D ratio is the ratio of the length of injection molding screw (L) to it`s outer diameter (D). Frankly speaking, L/D ratio is a very important parameter to a plastic injeciton molding machine. As it affect a lot on the injection machine`s melting performence and final plastic injection molding products quality. As an professional plastic molding machines manufacturer, we would like to explain it more to help our customers to under plastic injeciton molding machines screw better.
What is L/D Ratio in Injection Moulding Machine
Length-to-diameter ratio or L/D ratio in injection molding machine is the nominal length of the screw divided by the nominal diameter in consistent units. Or we can simply say the L/D ratio is the flighted length of the screw to its outside diameter. The L/D ratio formula is very simple that you do not need the L/D ratio calculator. Plastic injection molding machine screw L/D ratio is calculated by dividing the screw`s flighted length by its nominal diameter. Today, most of injection molding machine manufacturers are offering mouling machines with the L/D ratio of 20:1 or around this ratio like in 19:1 or 21:1. And for some optimized plastic injection machines are have a bigger ratio like 24:1 to 26:1. Fewer injection screws are special to have a L/D ratio of 28:1.
So why some plastic injection molding machines have are have bigger length-to-diameter ratio? There mainly 3 reasons:
1. More shear heat can be uniformly generated in the plastic without degradation.
2. Greater the opportunity for mixing, resulting in a better homogeneity of the melt.
3. Greater the residence time of the plastic in the barrel possibly permitting faster cycles of larger shots.
Bigger L/D ratio in injection moulding machine are mostly used to produce products with a very high quality of appearance. Like cosmetic packing bottles and containers have smooth, bright, and clear to see what it`s packed in it.
And some medical plastic tools and containers and optical lenses will need this kind of plastic moulding machine as well.
Is Plastic Injection Molding Machine`s L/D Ratio the Bigger the Better?
As you know from above, bigger L/D ratio can bring many benefits to the plastics injection molding process. You may have the question about the what factors affect on the L/D ratio selection. Is it the bigger the better? The answer is NO. We should pick a right plastic injection machine with a science L/D ratio. For our standard plastic molding machines, there are 3 different screws with similar L/D ratio for your choice. And there are bigger L/D ratio for some other dedicated optimized machines for different applications.
For example, our PET preform injection making machine is with bigger L/D ratio but PVC/PPR pipe fitting molding machine is with smaller one comparing to the standard plastic injection machines. We pick the reasonal L/D ratio according to the plastics performance and characteristic. Our dedicated injection molding machines are optimized designed with the screws, nozzle, clamps, hydraulic parts, PLC controling system as well. That is why we will ask our customers for what materials they will run and what kinds of products planning to produce. Just to advise the most suitable injection moulding machine model to quote our best cost accordingly.
As one of leading injection machine manufacturing, Guanxin is always doing our best to provid our customer best quality machines and service. You are welcome to contact us to have your injection molding solution by filling below form.
