What should consider when choosing. using & maintaining ring die
What should consider when choosing、using、maintaining ring die?
With the growth of National economy and the living level of people, the demand of different kinds
of feed is improving, so it is with the demand of the main wearing part------the ring die, which
its quality directly affect the production cost and the feed pellet quality.
According to incomplete statistics, Ring wearing cost takes more than 30% of the total production
plant maintenance costs,and the feed pellet quality has tremendous impact on sales.Clearly,it
means a lot for feed producer to learn how to choose the right ring die.
The ring die is a wearing part with multi holes, densely covered die holes, high precision assembly
dimensions. and the wall of which is thin. When working, the feed is compressed by the rotating
extrusion ring die and the pressure roller, coming out from the inner wall outwardly through Die
hole into the strand, and then be cut to the desired length by the cutter particles. Then we make
some analysis about ring die selection, use and maintenance for your reference.
1、Selection of ring die
Ring die is generally made of carbon steel or alloy structural steel, or stainless steel by forging, machining, jig hole and heat treatment step system to do.
So far, the price of ring die sometimes high sometimes low, the main reason is the difference of material picking, process choosing and control. Some small factories producing domestic ring mold mainly composed of carbon or alloy steel by forging, die twist drill hole, and then processed by ordinary heat treatment together.Thus,this kind of ring die may emerge some problems,such as long-time process,high energy consumption, low production,bad quality of pellet. Another problem is low service life. A survey shows, the feed which produced by these ring dies have high iron content, which greatly affects the feed formula, the result mainly caused by poor wear resistance.
With the continuous development of market economy, China joining the WTO, only cheap feed got competitiveness on the market. For feed producers to reduce production costs and improve the quality of feed pellets is urgently needed, and these qualities are largely determined by the level of quality ring die.
According to ring die working conditions, feed producers should use those advanced production plant who can have reasonable selection and reasonable process in producing ring die.
You’d better use stainless steel ring die, ring die made of stainless steel forging stock, is the essence of high quality ring mold life assurance;
The die hole should use gun drilling process, the use of multi-position rifle drill holes ensure the smooth bore die without forming a crooked hole,so to achieve faster, better quality particles (particle surface is smooth, uniform, small powder rate, etc.).
Should choose the ring die who got by vacuum heat treatment, vacuum heat treatment of the ring mold is a further guarantee of the quality of the previous step process, which guarantees high wear resistance, high strength, and the smoothness of the orifice ring mold materials were effective protection (to avoid the oxidation of the die hole).
二、环模的使用
首先，在选用优质环模的前提下，应根据生产饲料品种、配方及产量选用合适的模孔形式、开孔率及压缩比（压缩比=模孔的有效长度/模孔直径）。一般来说，直形孔和阶梯形孔适于加工配合饲料；外锥形孔适合加工脱脂糠等高纤维的饲料；内锥形孔宜加工草粉料类比重轻的饲料。在保证环模强度的前提下，尽量提高环模的开孔率，对于有些品种的饲料，在保证合理压缩比的条件下，环模过于壁薄，以致环模强度不够，生产中会出现爆模现象，此时应当在保证模孔有效长度的前提下，增加环模的厚度和增开减压孔。通常来说，含谷物高的配合饲料宜选之间的压缩比；热敏感饲料及尿素饲料宜选用5-8之间的压缩比；含天然蛋白质高的浓缩饲料适于选用5-11之间的压缩比；奶牛配合饲料适宜选用7~15之间的压缩比。另外还可以在考虑饲料基本配方后，依据生产者自己要求的饲料品质调整具体的压缩比，比如选用稍低的压缩比对于增加产量、降低能耗、减轻环模的磨损等有利，但是这样一来将会降低饲料的品质，如颗粒不够结实，外观松散长短不一，饲料的粉化率高，反之，则对颗粒品质有利（颗粒外观光滑而有光泽，粉化率小），但会增加产品的生产成本。
其次，环模与压辊之间工作间隙合理与否对环模的有效使用具有重要影响。一般来说，环模与压辊之间的间隙为0.1-0.3之间，以实践经验来说，用手扳动环模旋转的同时，压辊达到似转非转的状态为佳。那么，如何调整环模与压辊之间的间隙呢？通过我们的实践经验得知，当新模装机后，首先，松动压辊调节螺栓将压辊调整到压辊外圆面紧靠环模内圆面的状态；其次，依次调整压辊偏心轴使各压辊与环模之间间隙适当，预紧调节螺栓，扳动环模，逐步调节间隙，使压辊达到似转非转的工作状态，最后紧固调节螺栓。当新模装机时，通常要求环模与压辊之间间隙比您所需要的稍大，这有利于新环模与旧辊之间的平稳过渡，等新模与旧辊完成一定的磨合期以后，可以将间隙调整到您所需要的间隙。在使用中，都是保环模而牺牲压辊，因为环模的价格是压辊价格的十几倍甚至几十倍，所以在使用中，在选用合理间隙的情况下，压辊的硬度不能太高，也就是说，压辊的耐磨性不能比环模的耐磨性高。
环模在生产过程中，对所使用的物料要求进行必要清理，避免物料混有大块砂石、砂粒、铁块、螺栓及铁屑等硬颗粒。因为这些夹杂加速了环模的磨损，而且大量的、大硬夹杂将造成环模多次受力，使环模产生疲劳，当某次受力超过环模的强度极限时，环模将出现爆模现象。
最后，操作者在新装或更换环模时，对于通过锥面装配的环模来说，新装模时，要求避免造成锥面的碰伤及刮伤，并对其锥面及其配合传动轮缘锥面进行必要清理，涂油装配。更换环模时，拆卸，不碰伤及刮伤锥面，涂油保护。对于经常需更换环模的颗粒机来说，要求定期对传动轮缘进行检查，防止其过度磨损而导致模具定心销的断裂，因为过度的磨损将会影响环模与轮缘之间的配合，配合不紧，当环模工作时将对模具定心销产生剪切力而导致断裂，当产生这种情况后，千万不要误认为是销的强度不够而换成高强度的销，最终只能导致环模损坏和安全销经常性的断裂。因此，对环模的配合锥面及配合的传动轮缘的锥面进行保护和定期的检查是相当必要的。对于抱箍式装配的环模来说，对其装配面及其配合的元件的保护与检查也是相当必要的。当压辊使用一段时间后，会出现磨损现象，影响了与环模的配合精度，从而影响了环模的生产产量，应对其进行必要的修理或更换新的环模。
三、环模的基本维护
俗话说，磨刀不误砍柴工。对环模进行合理的维护保养是环模经济、有效使用的一部分。
在生产过程中，操作者经常发现，环模在使用过程中，通常会出现堵塞、磨损、封口及内 翻等现象，这时，如果不对其进行必要维护，将造成产量降低，能耗增加，甚至不出料等现象。此时，对环模进行基本维护的方法是，先将环模工作内圆面进行磨平，然后进行倒角。
当更换环模时，要求趁热模将含油物料充填模孔，以便下次生产时使环模达到最佳状态。
综上所述，只有对环模进行正确选用、合理使用和有效的维护，才能降低成本，提高效率，创造颗粒品质，增强产品市场竞争力，迎接挑战，为企业创造更多的经济效益。