Fused filament fabrication (FFF) continues to be among the most widespread additive manufacturing process for making polymeric functional prototypes, and in several cases end-use parts. There is a large installed base of serial-link industrial robots, some of which could be potentially retrofitted with an extruder head as an end-effector to serve as FFF systems with as many as six degrees of freedom compared to 3-axis gantry mechanisms that are typically deployed today. This paper identifies and proposes solutions to key engineering challenges that arise in retrofitting such robotic FFF systems in terms of integrating robot motion controller with extruder controller and evaluating the quality of the fabricated parts. Specifically, we propose an approach for integration and real-time synchronization of controllers to ensure that the extrusion velocity and deposition velocity match closely by building upon an analytical model for predicting road geometry as a function of process parameters. Compared to gantry mechanisms, this is challenging in serial-link industrial robots because of significantly larger and space-variant inertias. Furthermore, to compensate for distortion in the bed surface of the retrofitted robotic FFF system, a bed compensation algorithm based on bilinear interpolation has been developed. We have engineered a fully functional research testbed in which integration and real-time synchronization of controllers is achieved by (1) communicating space-variant process parameters in real-time using TCP/IP sockets, and (2) analog and digital I/O interfacing. Experimental testing shows excellent ($R^2$ = 0.9983) agreement between requested and actual volumetric flow rates and less than 5% errors in extrusion widths and heights in test samples fabricated across the range of physical limits of FFF process parameters. The testbed is also evaluated in terms of the impact of controller synchronization on the part dimensional accuracy for simple and complex geometries. This work can serve as a basis for further engineering innovations towards cost-effectively harnessing the capacity of industrial robots to manufacture geometrically accurate parts using FFF.

熔融长丝制造（FFF）仍然是用于制造聚合物功能原型以及在某些情况下最终用途零件的最广泛的增材制造工艺。串行链接工业机器人的安装基础很大，与3轴龙门机构相比，其中一些可以潜在地配备挤出机头作为末端执行器，以用作具有多达6个自由度的FFF系统。通常在今天部署。本文确定并提出了解决方案，以解决在将机器人运动控制器与挤出机控制器集成在一起并评估所制造零件的质量方面，对此类机器人FFF系统进行改造所遇到的关键工程挑战。具体来说，我们提出了一种用于控制器的集成和实时同步的方法，以通过基于用于预测道路几何形状与过程参数的函数的分析模型来确保挤出速度和沉积速度紧密匹配。与龙门机构相比，这在串行链接工业机器人中具有挑战性，因为它具有更大的惯性和随空间变化的惯性。此外，为了补偿改造后的机器人FFF系统的床面变形，已经开发了基于双线性插值的床面补偿算法。我们设计了一个功能完备的研究试验台，其中，控制器的集成和实时同步是通过以下方式实现的：（1）使用TCP / IP套接字实时传递空间变量过程参数，以及（2）模拟和数字I / O界面。${\mathrm{[R}}^{\mathrm{2个}}$ = 0.9983）在要求的流量和实际的体积流量之间达成一致，并且在FFF工艺参数的物理极限范围内制造的测试样品中，挤出宽度和高度的误差小于5％。对于简单和复杂的几何形状，还根据控制器同步对零件尺寸精度的影响来评估试验台。这项工作可以作为进一步工程创新的基础，以经济有效地利用工业机器人的能力来使用FFF制造几何形状精确的零件。