Side stuffing is widely used for feeding fillers into twin-screw extruders.Many processors desire very high loadings of fillers that are oftenlow-bulk-density (fluffy) materials. The ultimateloading attainable is usuallylimited by two parameters:

A) Volumetric capacities of the side-stuffer and mainextruder screws.  The volumetric capacityis based on the free volume of the side-stuffer's   twin screws and of the main extruder screws,as well as the rpm of both screw sets. If material is test run through the sidestuffer unbolted from the extruder and discharging into a drum, it probablywill easily feed a high rate of material. But when the stuffer is attached tothe extruder, capacity is often limited by the amount of material the mainextruder screws can accept. Consequently, it is best to for the main extruderscrews to have flighted elements with a long pitch (long flight advance) at thestuffer location, extending 2D to 4D downstream of the stuffer. This is to keepthe melt in the extruder moving rapidly forward to allow the maximum freevolume for the filler to enter. If the screw design causes any"dam-up" of material downstream of thestuffer, it will severely limitthe amount of filler that can be fed.
B) Venting capacity to allow air to escape the extruder. The object of ventingis to allow air to escape easily, while preventing large amounts of filler frombeing lost out the vent. The best configuration is a top vent in the barrelimmediately upstream of the side stuffer. Sometimes a small half-slot ventinsert can also be used in the top of the side stuffer.
Here are some other factors to consider:
■feederdrop height: Ideally, the feeder should be positioned as closeas possible above the side stuffer to minimize the drop height. If a fluffymaterial is allowed to drop through air, it becomes aerated to the point whereits bulk density is significantly reduced. This can limit the throughput rateof the entire line.
■feederagitation type: Make sure the agitator in the filler feeder isn'taerating the material and reducing the bulk density. Many feeder manufacturershave special agitator designs for powders.
■make surestuffer hopper is vented: Along with the filler, thestuffer also introducesa lot of air into the extruder. An open top on the side-stuffer chute will takecare of venting. If you have a solid cover on the chute with a round stubup andflex connector to tbe feeder, it's important to also have a vent opening.
■aroundall hoppers/chutes to drain static electricity: Somematerials generate static electricity from friction. Static charge can causepowder to cling to the inside surfaces of hoppers and chutes, leading toproblems such as caking. An easy fix is to run a ground wire (10 gauge isrecommended) from the chute to a known good ground on the machine frame.

■compressed-airblaster: If caking persists, sometimes a special solutionis needed. Hopper vibrators can be used, but are tricky to size and mount. Analternative is a "blaster" witb air-jet nozzles strategically placedwithin the wall of the chute to break up any cakes before they get too large.The air jets are connected to a solenoid valve, which is actuated by a repeatcycle timer. This lets you set both the blast period and dwell time betweenblasts. It's best to have a small air accumulator tank just upstream of thesolenoid valve to provide a sharp pulse of air.

側(cè)喂料通常用于把填料喂進(jìn)雙螺桿擠出機(jī)。許多加工者需要做很高填充量的填料，這些填料往往又具有很低的堆積密度。最終的填充量受兩個(gè)因素制約：

A)側(cè)喂料的體積喂料能力和擠出機(jī)主螺桿的體積吃料能力。體積喂料能力取決于側(cè)喂料機(jī)和主螺桿螺桿的自由體積，以及這兩個(gè)螺桿的轉(zhuǎn)速。如果一種材料在測(cè)試中可以不受到主螺桿的阻力而流到儲(chǔ)料鼓中，那么這種材料喂料速度可以達(dá)到很好。如果側(cè)喂料機(jī)直接挨著主螺桿連接，那么助劑螺桿可以接受的材料量將受到限制。因此，主機(jī)螺桿最好有長(zhǎng)螺距的螺紋元件，在側(cè)喂料口下游延伸2D-4D長(zhǎng)度。這將允許熔體快速通過(guò)側(cè)喂料口，使填料最大限度地被主螺桿吃進(jìn)。如果主機(jī)螺桿設(shè)計(jì)引起任何側(cè)喂料喂進(jìn)材料的堆積，那么將嚴(yán)重限制填料的喂料量。

B)允許氣體從擠出機(jī)排出的排氣能力。排氣的目的就是使空氣容易逸出，同時(shí)還要保護(hù)填料不從排氣口大量逸失。最好的配置是在側(cè)喂料口的上游開(kāi)置向上排氣的排氣口。有時(shí)，在側(cè)喂料機(jī)的上部開(kāi)一個(gè)小的半狹縫排氣。還有一些其它因素要考慮：

---喂料機(jī)的落料高度。理想情況下，喂料螺桿要盡可能近地安裝于側(cè)喂料口頂部，以減小落料高度。如果某種蓬松的材料從空氣中流過(guò)，那么它可能變得充滿空氣，從而使它在落下后假密度大大減小。

---喂料機(jī)攪拌類型。要確保填料喂料機(jī)中的攪拌器不使填料流態(tài)化。許多攪拌器制造商設(shè)計(jì)了特殊的攪拌器用于填料喂料。儲(chǔ)料器會(huì)連同填料一起引進(jìn)空氣進(jìn)入擠出機(jī)。一個(gè)頂部敞開(kāi)的斜槽料斗有助于排氣。假如你的斜槽喂料料斗有一個(gè)實(shí)心蓋子并帶一個(gè)圓管，并且與喂料器是柔性連接，那么重要的要有一個(gè)排氣口。

---料斗斜槽要接地防靜電。一些材料由于摩擦產(chǎn)生靜電。靜電引起粉體對(duì)料斗掛壁，從而導(dǎo)致粉體餅狀化。一個(gè)簡(jiǎn)易的方案就是接地。

---壓縮空氣爆破器。如果料餅持續(xù)存在，常常需要一些特殊辦法。可以使用料斗振動(dòng)器，但是它們占空間，還需要安裝。一個(gè)替代方案是安裝一個(gè)帶空氣噴嘴的爆破器，安裝在斜槽的恰當(dāng)位置上，在料餅長(zhǎng)大之前將其吹破。

It's well known that turbulentflow m a pipe will induce far greater heat transfer from the pipe wall thanwill laminar flow. Laminar flow occurs with low fluid velocities caused bylowpressure delivery. In a laminar-flow situation, a stable boundary layerdevelops, which acts just like an insulator between the main fluid flow and thepipe wall. "Layers" of fluid slide over adjacent layers, withoutmixing and without removing much heat. With turbulent flow induced byhigh-pressure delivery, there is a high degree of transverse momentum exchange,which breaks up the boundary layer. As a result, the violent fluid motioncausesmuch greater heat transfer from the pipe wall to the fluid. The easiestway to induce turbulent flow in tbe barrel cooling bores is to increase tbedelivery pressure. Extruder cooling recirculation systems typically have supplypressures from 20 to 60 psi. To achieve turbulent flow, a pressure of approximately120 psi is desired. This can be attained relatively easily by changing the pumpin the recirculation system to a high-pressure type. Almost all extrudercooling system components (hoses and valves) are rated for at least 150 psi, so120 psi still allows some safety factor. The advantage will be apparentimmediately in a process that is highly exothermic. Temperature zone overridescan often be greatly reduced or even eliminated. A side benefit of turbulentflow is that it inhibits fouling of the cooling bores from scale buildup.

大家知道，水泵中的紊流比層流可以導(dǎo)致更多的管壁熱交換。層流出現(xiàn)在低流速低壓輸送條件下。在層流情況下，建立了一個(gè)穩(wěn)定的邊界層，就象在主料流和管壁之間建立了一個(gè)絕熱層。料流層沿著臨近的料流層滑過(guò)，沒(méi)有混合，沒(méi)有帶走更多的熱量。高壓傳輸中的紊流有高度的橫向動(dòng)量交換，它擊破了邊界層。結(jié)果劇烈的流體運(yùn)動(dòng)引起了管壁與流體之間大得多的熱交換。擠出機(jī)冷卻循環(huán)系統(tǒng)一般提供20-60psi的壓力。為了達(dá)到紊流，最好達(dá)到120PSI的壓力。把循環(huán)系統(tǒng)的水泵改成高壓泵就行了。擠出機(jī)幾乎所有的冷卻系統(tǒng)部件（軟管和閥）都要升級(jí)到150PSI,才能滿足120PSI的安全系數(shù)。優(yōu)點(diǎn)是在加工時(shí)馬上排出大量的熱。

■It improves the overall efficiency of the gearbox.

齒輪箱式雙螺桿擠出機(jī)的心臟。如果它完蛋了，那要花很多錢(qián)維修，而且頗為費(fèi)時(shí)。這時(shí)，我們能做的一個(gè)事情就是避免齒輪箱問(wèn)題：切換到合成齒輪油。合成油在潤(rùn)滑上是一個(gè)巨大進(jìn)步：

---更加滑膩，導(dǎo)致較小的摩擦；

---齒輪、軸承和密封將更持久；

---齒輪運(yùn)轉(zhuǎn)溫度更低，更安靜；

---合成油不因?yàn)闄C(jī)器剪切而損失粘度；

---它在高溫下維持較高的粘度；

---改進(jìn)綜合齒輪效率