本批写法：讲清材料逻辑 + 诚实交代采购通道（这一批方向走石化厂专用料通道，不走改性造粒线）
上个月，一个做手板和功能件的客户寄来一盒 SLS 打印件。
盒子里一半是卡扣，一半是齿轮，边上有几件明显发黄。
他在电话里问得很直接：
"你们做改性尼龙的，能不能直接给我磨一桶打印粉？"
我先问了三句：这桶粉是新开封的，还是已经复用过几轮？件是哪个方向受力？那台设备的粉床温度是怎么定的？
他答：粉是回掺的，卡扣卡在侧向，粉床温度按设备默认值走。
三句答完，方向也就清楚了——问题不在件，在粉。
而且要先讲一句：打印粉的账，和注塑粒子的账不是一套。
SLS尼龙粉这个叫法，说的是选择性激光烧结用的尼龙粉末，基材以 PA12、PA11 为主。
这篇讲三件事：粉的判据有哪些、复用粉为什么会变、以及这类料的通道在哪。
一、一桶粉的四个身份：粒径、形貌、流动性、复用
先给一个反直觉的结论。
注塑看的是熔指和力学，打印粉先看的是能不能铺平。
铺不平，后面所有力学数据都无从谈起。
身份其一，粒径分布。
SLS 打印的粉，中位粒径常见在 40–60 μm 这个量级，比面粉粗，比砂糖细。
关键不是中位数，是分布的宽窄。
分布一宽，粗的那头撑起层厚，细的那头在粉床上结块。
一次换算：层厚常设 0.1 mm，也就是 100 μm。一粒 60 μm 的粉，加上铺粉辊的压实，正好铺出这一层。粗颗粒只要超过 100 μm，这一层就厚一块，激光扫过去的能量密度跟着变。
身份其二，颗粒形貌。
理想的粉是接近球形，业内用球形度或圆度来描述，好的粉常做到 0.85 以上。
破碎法磨出来的粉带棱角，堆积时互相咬住，流动性差一档。
球形的另一个好处是铺粉时的滚动性好，层与层之间叠得均匀。
身份其三，流动性。
流动性看不见摸不着，但它的替身有两个数：休止角与堆积密度。
休止角越小，粉越"滑"；堆积密度越稳，铺出来的层厚越稳。
身份其四，复用。
打印粉和注塑料最大的不同，是它要回收再用。
一缸打完，未烧结的粉要清出来、筛一遍、和一部分新粉掺回去。
复用比例是这套工艺里最贵的那个变量。
二、打印件的四个工况维度
其一，温度。
粉床温度通常压在熔点以下几度到十几度。
以 PA12 为例，熔点约 178℃，粉床常设在 165–175℃ 这一带。
这个窗口很窄：低了，层间结合不够；高了，粉床边上会结块。
其二，层厚与能量密度。
层厚常见 0.08–0.12 mm，激光功率与扫描速度共同决定能量密度。
层厚、功率、速度这三样是一组联动的参数，动一个要复验另外两个。
其三，复用轮次。
新粉与复用粉的掺配比，常见做法在 50:50 到 70:30 之间。
每打一轮，粉就多受一次热历史，颜色和分子量都在悄悄变。
其四，精度与外观。
尺寸精度常见落在 ±0.1–0.3 mm（按 100 mm 件计），表面的粗糙度受粉的粒径影响。
做手板看外观，做功能件看力学与层间强度，两边的侧重点不一样。
| 工况维度 | 典型量值 | 对粉的要求 |
|---|
| 粉床温度 | 熔点以下几度到十几度（PA12 常 165–175℃） | 烧结窗口要宽，抗氧体系要够 |
| 层厚 | 0.08–0.12 mm | 粒径与层厚要匹配，粗粉要压掉 |
| 复用 | 新旧掺配常 50:50 到 70:30 | 复用后的流动性与色差要能控 |
| 精度 | 按 100 mm 件常 ±0.1–0.3 mm | 分布窄、球形度好、含水低 |
三、三条粉末路线，各守一段窗口
路线一：PA12 粉末。
熔点约 178℃，吸水率低，烧结窗口相对宽，韧性与耐化学表现好。
它是目前 SLS 的主力。短板是单价高，而且来源集中在少数粉体厂手里。
路线二：PA11 粉末。
熔点约 198℃ 上下，韧性与低温冲击表现好，原料来自可再生来源。
它的吸水率略高于 PA12，烧结窗口相对窄一点，成本还高一档。
路线三：共聚体系与填充体系。
共聚类把窗口调宽、把收缩调下去；加玻纤或矿物的牌号做功能件，刚性和尺寸稳定性更好。
这一类更看具体应用，不是通用替代。
三条路线不是谁替代谁，是看件要韧性、要耐温、还是要刚性。
| 路线 | 熔点（典型） | 烧结窗口 | 强项 | 要当心 |
|---|
| PA12 粉末 | 约 178℃ | 相对宽 | 韧性、耐化学、吸水低 | 单价高，来源集中 |
| PA11 粉末 | 约 198℃ | 相对窄 | 韧性、低温冲击 | 吸水略高、成本再上一档 |
| 共聚与填充体系 | 按牌号定 | 按牌号定 | 窗口可调、刚性可补 | 参数要按牌号重做，不能套用 |
（表中为典型值，具体以牌号 TDS 为准）
四、SLS 尼龙粉的七项判据（这一页值得存）
门限值都是方向性建议，不是验收标准；实际数值由设备的粉床、激光与层厚共同确定。
| 指标 | 方向性门限 | 验证方法 / 标准 | 常见失效 | 通行解法 | 对应助剂体系 |
|---|
| 粒径分布 | 中位常见 40–60 μm，分布要窄 | GB/T 19077-2016（激光衍射法） | 铺粉不均、层厚波动、表面粗糙 | 分级筛分、按分布掺配 | 流动助剂（气相二氧化硅类） |
| 颗粒形貌 | 球形度常见 0.85 以上 | 扫描电镜观察与图像分析 | 堆积不实、件致密度低 | 选球形粉、去掉破碎料尾 | 无 |
| 流动性 | 休止角常要求 35° 以内 | GB/T 16913-2008（粉尘物性试验） | 铺粉起条纹、局部缺粉 | 加流动助剂、干燥后过筛 | 流动助剂（气相二氧化硅类） |
| 堆积密度 | 按牌号定，批间要稳 | GB/T 16913-2008 或 GB/T 1033.1-2008 | 层厚不稳、件重偏差 | 锁批号、按密度调铺粉参数 | 无 |
| 熔融与结晶（烧结窗口） | 熔点与结晶起始温度之差，越宽越好 | GB/T 19466.3-2004（DSC） | 翘曲、层间分层 | 控粉床温度、加深色遮蔽 | 抗氧剂（受阻酚与亚磷酸酯复配） |
| 复用后的热氧稳定 | 黄变与性能保留按轮次自定门限 | GB/T 19466.6-2009（氧化诱导时间） | 复用几轮后发黄、变脆 | 控新旧掺配比、补抗氧体系 | 抗氧剂（受阻酚与亚磷酸酯复配） |
| 含水率与细粉 | 干燥后含水要压到 0.1% 量级；细粉越少越好 | GB/T 12006.2-2009（含水量） | 粉床结块、气泡、扬尘 | 干燥、筛掉细粉段 | 无 |
怎么用这张表：先看头两行。
粒径分布与形貌这两项不进去，后面的力学与精度都测不出可比性。
还有一条顺序上的讲究：复用粉必须做循环试验，一次新粉的数据说明不了第几轮以后会怎样。
五、四种常见失效，和它们真正的根因
失效一：复用几轮以后，件开始发黄、变脆。
多数人头一个念头是"粉脏了"，其实更常见的是热氧降解。
粉在粉床里长时间处于高温，一轮一轮累积热历史，分子量往下走。
助剂侧的一条归因：抗氧剂是按消耗品算的，被消耗完了，后面每一轮都在"裸奔"。
通行解法：把新旧粉掺配比管住，按轮次做色差与力学的趋势记录，别等件发黄才回头看。
失效二：铺粉出现条纹，或者局部缺粉。
这一类通常不是激光的问题，是流动性与含水。
粉受潮会结小团，团一上去，铺粉辊就推出一条沟。
通行解法：干燥到工艺窗口、过筛去掉细粉段、必要时补流动助剂。
失效三：件翘曲、层间分层。
先别急着换粉，先看粉床温度场与扫描策略。
粉床温度偏低、或者件在缸里冷却过快，都会把应力留在件里。
这里有一条要直说的："换一桶新粉"经常是最贵的那种排查方式。
温度场与扫描策略排掉之后，再怀疑粉。
失效四：同一桶粉，前半桶好、后半桶差。
认真查下去，问题常常出在没有记录复用比例。
哪一桶掺了多少、复用了几轮、筛的是多少目，全靠师傅记忆，趋势就无从谈起。
通行解法：给每一桶粉建一张卡，掺配比例、筛分目数、轮次都写上去。
留粉的追溯，就是这套工艺的质量体系。
一段可以对照的时间线。
起点：那台设备刚上线时，师傅按厂家建议掺新粉，比例是拍着定的，件也做得漂亮。
潜伏：第三轮开始，件表面有一点点发黄，抛光一下就看不出来，谁也没提。
爆发：第六轮之后，卡扣装上去一掰就裂，客户那边开始成批退货。
追溯：翻记录才发现，账上只有"打了多少缸"，没有"掺了多少新粉、筛的多少目"。
结算：补做一批复用循环试验，重定掺配阶梯与筛分目数，前后停机的时间比省下的粉钱贵得多。
这条线里最该记住的一句是：粉的颜色是慢慢变的，件是突然坏的。
六、加工与验证：铺粉和复用各管一段
铺粉这一段。
层厚与粉床温度是一组参数，要按粉的粒径与烧结窗口定。
铺粉辊的转速与压实力，决定层与层之间的密实度。
复用这一段。
清粉、筛分、回掺，三步都要有记录。
筛分目数按细粉含量定；掺配比例按轮次阶梯走，不要一次掺到底。
干燥这一段。
打印粉比注塑料对水分更敏感：受潮的粉不是"打不出件"，是"打出来的件没人敢用"。
这里补一句实感：普通热风干燥机对尼龙基本是无效的，粉也一样要用除湿干燥；南方的梅雨季尤其明显。
验证顺序，建议这样排：
其一，粉端——粒径分布、球形度、休止角、含水率，进厂先做。
其二，单层与小块——看层间结合与致密度。
其三，标准试条——拉伸强度与断裂伸长、密度。
其四，零件级——尺寸精度、外观、装配。
其五，复用循环——按轮次复测色差、力学与流动性的趋势。
顺序不能换。 前一项不通过就往下走，后面的数据解释不了。
也不要拿一缸新粉的强度，去推第四轮复用之后的件。
七、这个方向的通道在哪：把话讲清楚
SLS 打印粉的采购通道，是粉体厂与聚合厂的专业粉末料通道，不是改性造粒线。
原因三条：
其一，形态不同。 这条路要的是微米级粉末：窄分布、球形度好、细粉含量低、流动性达标。改性造粒线的产出是 2–4 mm 的圆柱或圆片，中间隔着一整套制粉、分级与球形化设备。
其二，门限不同。 打印粉的判据是"铺得平、烧得住、复用得起"——休止角、堆积密度、烧结窗口、氧化诱导时间。这套判据和粒子料的熔指、玻纤含量、热变形温度不是一回事。
其三，用途不同。 打印粉常按公斤、按缸供，还要配套工艺参数与复用数据；改性粒子是按吨、按件供的。
所以这个方向，我们不接单，也没打算接。
写出来，是因为搜"SLS 打印粉"的人不少，而把复用这笔账算清楚的人不多。
你如果正在选粉，这篇里的七项判据与验证顺序可以直接拿去用。
至于粒子的方向——注塑件、挤出型材件要用的改性尼龙，那条线才是我们能陪你走完的路。
顺带说一句改性这条线上的事：配方里的助剂体系按件的工况配——常规助剂常备现货，特殊型号按需配套；你报工况和牌号，料和助剂一次配齐。
选型风险清单（换粉要动什么）
| 环节 | 要重新确认什么 | 最容易漏的点 |
|---|
| 粒径分布 | 新粉的分布宽度与细粉占比 | 只看中位粒径，不看两头 |
| 粉床温度 | 窗口要按新粉重定 | 直接套上一家的温度 |
| 层厚与能量 | 层厚、功率、速度要联动复验 | 只调一个参数就放量 |
| 铺粉 | 辊速与压实力、铺粉均匀性 | 出现条纹先怪设备，不查粉受潮 |
| 掺配比例 | 新旧粉比例与轮次记录 | 靠师傅记忆，没有台账 |
| 筛分 | 目数与细粉去除率 | 筛网长期不换，细粉越积越多 |
| 冷缸与清粉 | 冷却节奏与清粉方式 | 冷得太快，应力留在件里 |
| 验证顺序 | 粉端→单层→试条→零件→复用循环 | 前一项没过就往下走 |
一页纸汇报表（给要向上汇报的人）
| 项 | 一句话结论 |
|---|
| 选什么 | 先锁粒径分布与球形度，再谈烧结窗口与复用 |
| 管什么 | 粉床温度、层厚与能量、新旧粉掺配比 |
| 验什么 | 分布宽度、休止角、含水率、氧化诱导时间、复用后的力学趋势 |
| 通道在哪 | 粉体厂与聚合厂的专业粉末料通道，不在改性造粒线 |
| 什么时候能放量 | 连续几轮复用后色差与力学可控、零件精度与装配稳定 |
读者常问的两句
问：拿注塑级 PA12 粒料自己磨粉，能不能省钱？
不成立，而且难点不在磨，在磨完之后。破碎法出来的粉带棱角、分布宽、细粉多，铺粉这一关就先过不去；成形件的致密度与层间强度也跟着打折。这条路要补的是整套制粉与分级设备，不是一台磨机。
问：新旧粉按什么比例掺，可以一直掺下去？
比例由设备、粉床温度与件的用途共同决定，没有通用答案。可以确定的是两件事：掺配比要阶梯式验证，不能一步到底；每一轮都要留色差与力学数据，看趋势而不是看单点。
结语
打印粉的选型，说到底是一道闭环题。
判断链只有三条：分布与形貌定铺粉 → 烧结窗口定成形 → 复用管理定长期一致性。
三条都定完，"这桶粉能不能上我的缸"自然就有答案了。开篇那三句追问——新粉还是复用粉、受力方向、粉床温度——问的就是这三条里的头一条和第三条。
如果你手上正有一批粉要定，把三样东西发过来就能给方向：设备与层厚参数、当前新旧粉掺配比、现在卡在哪一项上（条纹、翘曲、还是复用后发黄）。
先把话讲清楚，再谈价钱——粉末这条线，我们先把通道交代明白。
副牌料到底能不能用，这个问题在粒子料那边有一整套判法；到了打印粉这边，答案更直接——批间差异会原封不动地印在件上。
微米级粉末的分布、球形度与复用判据，和改性造粒线做的件级粒子，是两套语言。这套语言的入口在粉体厂的专业粉末料线，不在我们这条线上。
我们能做的，是把粉末料与件级料之间那道分界讲清楚，让你少走一段弯路。件级改性尼龙这条线，选料与试模可以一起聊。
This batch of writing method: clearly explain the material logic and honestly disclose the procurement channel (this batch uses the dedicated channel for petrochemical plants, not the modified granulation line).
Last month, a client who makes prototypes and functional parts sent a box of SLS printed parts.
Half of the box contains clips, and the other half contains gears, with a few pieces on the side noticeably yellowed.
He asked very directly over the phone:
You guys make modified nylon. Can you directly grind a barrel of printing powder for me?
I first asked three questions: Is this bucket of powder newly opened, or has it been reused several times? In which direction is the part under stress? How is the powder bed temperature of that equipment determined?
He replied: The powder is recycled, the clips are fastened laterally, and the powder bed temperature follows the equipment's default value.
In three sentences, the answer is clear — the problem is not with the item, but with the powder.
And first, I need to say this: the accounts for printing powder and the accounts for injection molding pellets are not the same.
The term SLS nylon powder refers to nylon powder used for selective laser sintering, with PA12 and PA11 as the main base materials.
This article talks about three things: what the criteria for powder are, why reused powder changes, and where the channels for this type of material are.
1. The four identities of a bucket of powder: particle size, morphology, flowability, and reuse
Let's start with a counterintuitive conclusion.
Injection molding focuses on melt flow index and mechanics, while when printing with powder, the first thing to look at is whether it can be spread evenly.
If it is not leveled properly, all subsequent mechanical data cannot be discussed.
Identity one, particle size distribution.
The powder used in SLS printing typically has a median particle size in the range of 40–60 μm, coarser than flour but finer than sugar.
The key is not the median, but the width of the distribution.
The distribution is wide, with the thick end supporting the layer thickness, and the thin end clumping on the powder bed.
A single conversion: the layer thickness is usually set at 0.1 mm, which is 100 μm. A 60 μm powder particle, combined with the compaction from the powder spreading roller, exactly spreads out this layer. If coarse particles exceed 100 μm, this layer becomes thicker, and the energy density from the laser scan changes accordingly.
The second identity is the particle morphology.
The ideal powder is nearly spherical, and the industry describes it using sphericity or roundness; good powder often achieves above 0.85.
The powder produced by the crushing method has sharp edges, and when piled up, the particles interlock with each other, resulting in poor flowability.
Another benefit of spherical shape is its good rolling ability when spreading powder, allowing layers to stack evenly.
The third aspect of identity is mobility.
Liquidity is invisible and intangible, but it has two proxies: the angle of repose and the bulk density.
The smaller the repose angle, the 'smoother' the powder; the more stable the bulk density, the more consistent the laid layer thickness.
Identity four, reuse.
The biggest difference between printing powder and injection molding material is that it needs to be recycled and reused.
After one batch is finished, the unsintered powder needs to be removed, sieved, and mixed back with some new powder.
The multiplexing ratio is the most expensive variable in this process.
2. The Four Operational Dimensions of the Printed Document
First, temperature.
The powder bed temperature is usually kept a few degrees to more than ten degrees below the melting point.
Taking PA12 as an example, the melting point is about 178°C, and the powder bed is usually set around 165–175°C.
This window is very narrow: if it's too low, the interlayer bonding is insufficient; if it's too high, clumps will form at the edge of the powder bed.
Secondly, layer thickness and energy density.
The layer thickness is commonly 0.08–0.12 mm, and the laser power and scanning speed together determine the energy density.
Layer thickness, power, and speed are a set of interlinked parameters; if you change one, you need to recheck the other two.
Third, reuse rounds.
The mixing ratio of new powder to reused powder is commonly between 50:50 and 70:30.
With each round of grinding, the powder undergoes heat exposure again, and its color and molecular weight are quietly changing.
Fourth, precision and appearance.
Dimensional accuracy commonly falls within ±0.1–0.3 mm (per 100 mm part), and the surface roughness is influenced by the powder particle size.
For prototypes, focus on appearance; for functional parts, focus on mechanics and interlayer strength. The emphasis is different on both sides.
| Operating conditions dimension | Typical value | Requirements for the powder |
|---|
| Powder bed temperature | A few degrees to more than ten degrees below the melting point (PA12 usually 165–175°C) | The sintering window needs to be wide, and the oxidation resistance system needs to be sufficient. |
| Layer thickness | 0.08–0.12 mm | The particle size should match the layer thickness, and coarse powder should be pressed down. |
| Reuse | The mixing ratio of new and old is usually 50:50 to 70:30 | The liquidity and color difference after reuse must be controllable |
| Accuracy | Per 100 mm piece, usually ±0.1–0.3 mm | Narrow distribution, good sphericity, low water content |
3. Three powder routes, each guarding a window segment
Route 1: PA12 powder.
The melting point is about 178°C, water absorption is low, the sintering window is relatively wide, and it has good toughness and chemical resistance.
It is currently the mainstay of SLS. The downside is its high unit price, and the supply is concentrated in the hands of a few powder manufacturers.
Route 2: PA11 Powder.
Melting point around 198°C, good toughness and low-temperature impact performance, raw materials come from renewable sources.
Its water absorption rate is slightly higher than PA12, the sintering window is relatively narrower, and the cost is also a level higher.
Route Three: Co-assembly system and filler system.
Co-clustering widens the window and reduces the shrinkage; using grades with glass fiber or minerals for functional parts improves rigidity and dimensional stability.
This category depends more on the specific application and is not a general substitute.
The three paths are not about replacing each other; it's about whether the part needs toughness, heat resistance, or rigidity.
| Route | Melting Point (Typical) | Sintering window | Strength | Be careful |
|---|
| PA12 powder | About 178℃ | Relatively wide | Toughness, chemical resistance, low water absorption | High unit price, concentrated sources |
| PA11 Powder | about 198℃ | Relatively narrow | Toughness, low-temperature impact | Slightly higher water absorption, cost rises to the next level |
| Copolymerization and Filling System | According to the brand/grade | According to the brand/grade | Adjustable window, rigidity can be supplemented | The parameters need to be redone according to the grade and cannot be applied directly. |
(The values in the table are typical; please refer to the grade TDS for specifics)
4. Seven Criteria for SLS Nylon Powder (This page is worth saving)
Threshold values are directional suggestions, not acceptance standards; the actual numbers are determined jointly by the device's powder bed, laser, and layer thickness.
| Indicator | Directional threshold | Verification Method / Standard | Common Failures | Common solution | Corresponding auxiliary agent system |
|---|
| Particle size distribution | Median common 40–60 μm, distribution is narrow | GB/T 19077-2016 (Laser Diffraction Method) | Uneven powder spreading, layer thickness fluctuations, surface roughness | Graded sieving, proportioned blending according to distribution | Flow aid (fumed silica type) |
| Particle Morphology | Sphericity commonly above 0.85 | Scanning Electron Microscopy Observation and Image Analysis | Poor accumulation, low bulk density | Select spherical powder and remove the broken material tail | None |
| Liquidity | The repose angle is often required to be within 35° | GB/T 16913-2008 (Dust Physical Property Test) | Powder coating streaks, localized powder deficiency | Add flow agent, dry, and then sieve | Flow aid (vapor-phase silica type) |
| Bulk Density | Set according to the brand number, and be consistent between batches | GB/T 16913-2008 or GB/T 1033.1-2008 | Unstable layer thickness and heavy part deviation | Lock batch number, adjust powder spreading parameters according to density | None |
| Melting and Crystallization (Sintering Window) | The larger the difference between the melting point and the crystallization onset temperature, the better. | GB/T 19466.3-2004 (DSC) | Warping, interlaminar delamination | Control the powder bed temperature, deepen color masking | Antioxidant (a combination of hindered phenols and phosphite) |
| Thermal-oxidative stability after reuse | Yellowing and performance retention have thresholds set by round | GB/T 19466.6-2009 (Oxidation Induction Time) | Turns yellow and becomes brittle after several uses | Control the ratio of new and old blends, and supplement the antioxidant system | Antioxidant (a combination of hindered phenols and phosphite) |
| Moisture content and fine powder | After drying, the moisture content should be pressed down to the 0.1% level; the fewer the fine particles, the better. | GB/T 12006.2-2009 (Moisture Content) | Powder bed clumping, air bubbles, dust | Dry and sieve out the fine powder | None |
How to use this table: first look at the first two rows.
If particle size distribution and morphology are not included, the subsequent mechanical properties and precision cannot be measured for comparability.
There is also an order-related consideration: recycled toner must undergo iterative testing, as the data from a single batch of new toner cannot indicate what will happen in later cycles.
5. Four common failures and their real root causes
Failure 1: After several rounds of reuse, the parts begin to yellow and become brittle.
Most people's first thought is 'the powder got dirty,' but in fact, thermal-oxidative degradation is more common.
The powder stays in the powder bed at high temperature for a long time, accumulating heat history cycle after cycle, causing the molecular weight to decrease.
An attribution from the additives side: antioxidants are considered consumables, and once they are used up, every subsequent round is 'bare running'.
Common approach: Control the mixing ratio of new and old powder, record the trends of color difference and mechanical properties in rounds, and don't wait until the parts turn yellow to look back.
Failure 2: Stripes appear in the powder coating, or there is partial powder loss.
This type is usually not a problem with the laser, but with fluidity and water content.
When the powder gets damp, it forms small clumps. Once clumps form, the powder roller pushes out a groove.
Common solution: Dry until within the process window, sieve to remove fine powder, and add flow agent if necessary.
Failure 3: Warping of the part, delamination between layers.
Don't rush to change the powder; first look at the powder bed temperature field and scanning strategy.
If the powder bed temperature is too low, or the part cools too quickly in the cylinder, stress will remain in the part.
Here's something to say straight: 'Changing to a new toner cartridge' is often the most expensive way to troubleshoot.
After eliminating the temperature field and scanning strategy, then suspect the powder.
Failure Four: The same bucket of powder, the first half is good, the second half is bad.
If you investigate carefully, the problem often lies in not recording the reuse ratio.
Which barrel had how much mixed in, how many times it was reused, and what mesh was used for sifting—all rely on the master's memory, so there is no way to discuss trends.
Common approach: Create a card for each barrel of powder, writing down the mixing ratio, mesh size, and number of rounds.
The traceability of residual powder is the quality system of this set of processes.
A timeline that can be used for reference.
Starting point: When that device was first launched, the master added new powder according to the manufacturer's recommendation, the proportion was determined by tapping, and the pieces were made beautifully.
Latent: At the start of the third round, the surface of the item was slightly yellowed. Polishing it made it unnoticeable, and no one mentioned it.
Outbreak: After the sixth round, the buckle would crack as soon as it was fastened, and the client began returning goods in batches.
Tracing back: Only when reviewing the records did I realize that the accounts only show 'how many jars were made,' but not 'how much new powder was added or what mesh size was sieved.'
Settlement: Conduct another batch of reusable cycle tests, re-determine the blending steps and sieve mesh size. The time lost due to stopping the machine before and after is much more expensive than the saved powder.
The sentence you should remember most from this line is: The color of powder changes gradually, but a piece can break suddenly.
6. Processing and verification: spread powder and reuse each tube for a section
Apply the powder in this section.
Layer thickness and powder bed temperature are a set of parameters and should be determined according to the powder's particle size and the sintering window.
The rotation speed of the powder roller and the pressure determine the density between the layers.
Reuse this section.
Cleaning the powder, sieving, and remixing—records must be kept for all three steps.
The sieve mesh size is determined according to the fine powder content; the mixing ratio is done in steps per batch, do not mix it all at once.
Dry this section.
Printing powder is more sensitive to moisture than injection molding plastic: damp powder doesn't mean 'no parts can be printed', it means 'the parts that are printed are unsafe to use'.
A realistic note here: Ordinary hot air dryers are basically ineffective for nylon, and powders also need dehumidifying drying; this is especially noticeable during the plum rain season in the south.
Verify the order, it is recommended to arrange it like this:
First, powder aspects — particle size distribution, sphericity, angle of repose, moisture content, should be checked upon entering the factory.
Secondly, single layers and small pieces—look at the interlayer bonding and density.
Third, standard test strips—tensile strength and elongation at break, density.
Fourth, at the component level — dimensional accuracy, appearance, assembly.
Fifth, reuse cycles — retest the trends of color difference, mechanical properties, and fluidity by rounds.
The order cannot be changed. If the previous item fails, you move on, and the subsequent data cannot be explained.
Don't use the strength of a jar of new powder to push parts after the fourth reuse.
7. Where is the passage in this direction: make your point clear
The procurement channel for SLS printing powder is a professional powder material channel between the powder factory and the polymerization factory, not a modified granulation line.
Three reasons:
First, the morphology is different. This process requires micron-level powder: narrow distribution, good sphericity, low fine powder content, and acceptable flowability. The output of the modified granulation line is 2–4 mm cylinders or pellets, with a complete set of powder-making, classification, and spheronization equipment in between.
Secondly, the thresholds are different. The criteria for printing powder are 'spreads evenly, sinters reliably, can be reused'—including repose angle, bulk density, sintering window, and oxidation induction time. This set of criteria is not the same as the melt flow index, glass fiber content, or heat deflection temperature of particle material.
Thirdly, the uses are different. Printing powder is usually supplied by kilogram or by drum, and also requires matching process parameters and reusable data; modified particles are supplied by ton or by piece.
So in this direction, we do not take orders, nor do we plan to.
I wrote this because many people search for 'SLS printing powder,' but few take the time to clearly calculate the reuse costs.
If you are choosing powder, the seven criteria and verification sequence in this article can be used directly.
As for the direction of the particles—for injection-molded parts and extruded profile parts that require modified nylon, that is the path we can walk with you to the end.
By the way, a note about modification on this production line: the auxiliary system in the formula is matched according to the operating conditions by batch — conventional auxiliaries are kept in stock, special types are matched as needed; you report the operating conditions and grade, and the materials and auxiliaries are prepared all at once.
Selection Risk List (What needs to be done when changing toner)
| link; segment; part | What needs to be reconfirmed? | The points most easily overlooked |
|---|
| Particle size distribution | Distribution width of new powder and proportion of fine powder | Only look at the median particle size, not the extremes |
| Powder bed temperature | The window needs to be reset according to the new powder weight. | Directly use someone's temperature |
| Layer Thickness and Energy | Layer thickness, power, and speed need to be re-verified in conjunction | Just adjust one parameter to increase the output |
| apply powder | Roller speed and pressing force, powder spreading uniformity | When stripes appear, first blame the equipment instead of checking if the powder is damp. |
| Blending ratio | Record of Old and New Powder Ratios and Rounds | Relying on the master's memory, no ledger |
| Screening | Mesh Number and Fine Powder Removal Rate | If the sieve is not replaced for a long time, fine powder will accumulate more and more. |
| Cold Cylinder and Clear Powder | Cooling rhythm and powder cleaning method | Cools too quickly, stress remains in the part |
| Verification order | Powder end → Single layer → Test strip → Parts → Reuse cycle | If the previous item fails, just move on. |
One-page report sheet (for people who need to report upwards)
| item | A one-sentence conclusion |
|---|
| What to choose | First focus on particle size distribution and sphericity, then discuss the sintering window and reuse. |
| What does it matter? | Powder bed temperature, layer thickness, and energy, ratio of new and old powder |
| Test what | Distribution width, resting angle, moisture content, oxidation induction time, mechanical trends after reuse |
| Where is the passage? | The specialized powder material channel between the powder plant and the polymer plant is not on the modified granulation line. |
| When can the volume increase? | After several rounds of reuse, color difference and mechanical properties are controllable, and parts accuracy and assembly stability are maintained. |
Two questions readers often ask
Question: Can grinding injection molding grade PA12 pellets by myself save money?
It doesn't hold, and the difficulty is not in grinding, but after grinding. The powder produced by the crushing method has angular edges, wide distribution, and a lot of fine particles, so it can't pass the powder-spreading step; the density and interlayer strength of the formed parts are also compromised. What needs to be improved on this path is the entire set of powder-making and classification equipment, not just a single mill.
Question: At what ratio should new and old powder be mixed, and can it be mixed continuously?
The ratio is determined jointly by the equipment, the powder bed temperature, and the intended use of the part, and there is no universal answer. What can be confirmed are two things: the blending ratio should be verified step by step, not all at once; in each round, color differences and mechanical data should be recorded, focusing on trends rather than single points.
Conclusion
The selection of printer toner, after all, is a closed-loop problem.
The decision chain has only three links: distribution and morphology determine powder spreading → sintering window determines forming → reuse management determines long-term consistency.
Once the three conditions are set, the question of whether this bucket of powder can go into my tank naturally has an answer. The first three questions at the beginning—new powder or reused powder, direction of applied force, powder bed temperature—are asking about the first and third of these three conditions.
If you currently have a batch of powder to determine, sending over three things can give some direction: equipment and layer thickness parameters, the current ratio of new to old powder, and which issue it is stuck on (striping, warping, or yellowing after reuse).
Make things clear first, then discuss the price—regarding the powder line, let's first clarify the channels.
Whether sub-card materials can be used or not, this question has a whole set of rules for particle materials; when it comes to printing powders, the answer is even more straightforward—the differences between batches will be printed on the parts exactly as they are.
The distribution, sphericity, and reuse criteria of micron-scale powders, and the batch-level particles made by the modified granulation line, are two different sets of terminology. The entry point of this terminology is in the professional powder material line of the powder plant, not on our line.
What we can do is clearly explain the boundary between powder materials and part-level materials, so you can avoid taking a detour. For the part-level modified nylon line, material selection and trial molding can be discussed together.
