In control

6 min read

Following on from new machine interfaces (see feature 'A brave new face'), we take a more detailed look at developments in the controls behind them. New machine controls are not just faster, they incorporate software that improves milling performance elsewhere, reports Will Dalrymple

No matter how great the skill of the operator, the process of machining cannot avoid causing imperfections in the workpiece: even very rigid machines vibrate slightly in response to a stop or sudden turn, and the effects of even those small movements can be visible in cut metal. By the same token, the speed at which some operations can be carried out, such as simultaneous 5-axis work, or high speed roughing, is limited by the control, whose processing power is not infinite.

Control vendors are coming to the rescue with new software and hardware (much of it as optional extras) that aims to improve cutting performance and workpiece finish, generally without operator action. These features are often referred to as 'intelligent': 'intelligent machining' for Heidenhain; 'intelligent technology' for Okuma. New features promise benefits in machining speed, in reducing chatter and vibration to smoothen surface finishes, preventing collisions and improving a machine's simulation capabilities.

在提高加工速度时,其中一些技术就像汽车中的巡航控制:它们可以减少努力。例如,使用新的Heidenhain(01444 247711)TNC 640磨机和铣床的控制,操作员可以为给定工具设置最佳的主轴功率,并且机器将变化以补偿进料速率。由于在尖端边缘所需的主轴功率取决于切割的深度和工具的清晰度,因此控件将自动加快浅切割区域的主轴进料的速度,当工具钝化时。此功能的最大速度是在教学削减期间设置的,在此期间,操作员还设置了速度参数;低于最小速度,机器停止并发出错误。由于机器饲料除了最坏的情况以外的所有情况都增加了,因此此控制功能具有“巨大”的周期时间优势,尤其是在割切割深度(例如粗糙铸件或间歇性切割环境)中工作的区域(Heidenhein(Heidenhein))(Heidenhein(Heidenhein)(Heidenhein)(Heidenhein)(GB)董事总经理尼尔·普雷斯科特(Neil Prescott)。Heidenhain控件可在各种机器品牌上找到,包括Hermle(Geo Kingsbury,023 9258 0371)和DMG Mori(0247 651 6120)。

Graphics on Heidenhain's TNC 640 control are detailed enough to show a surface dig-in

This Heidenhain capability, called Adaptive Feed Control, has faster response times than alternative external add-on systems, he adds. It can also help new machinists work as effectively as more experienced colleagues. "Heidenhain controls have always allowed the programmer to enter a manual compensation through the [feed] override potentiometer to adjust for the actual machining situation. But this always depends on the experience and, of course, the presence of the operator," the company says.

另一种有益的切割技术是木铣刀铣削,其中主轴不仅具有线性进料,而且还具有切割插槽的圆形运动。该技术的主要优点是,它只会剥离每个圆形球的少量材料,因此可以进行更深的切割。这种方法更有效,可以更好地破坏芯片,并减少工具和机器磨损。Delcam(0121 766 5544)的CADCAM软件(例如PowerMill)提供了一段时间,现在提供了Trochoidal铣削工具路径,现在Heidenhain的TNC 640控件将其作为选项。可以通过自适应饲料控制来增强这两个系统,以减少周期时间。

Part programming screen on the new Mazak Smooth Technology interface

Faster machine movements are also a benefit of Mazak's (01905 755 755) new SmoothX control. Five-axis machines' linear axes generally have faster acceleration rates than rotary axes, points out Mazak product manager Mark Hall. This means that spindle acceleration in simultaneous 5-axis contouring has been limited by that of the slower rotary axes. Armed with this knowledge, the Mazak controller now allows multiple acceleration values, depending on the axes involved. Although rotary axes won't speed up any quicker than they did before, linear axes will, courtesy of Variable Acceleration Control, so the machine can, in effect, traverse more quickly.

It can corner better too. As any car driver will know, a moving body needs to slow down before going around a corner to hold a line. With its new Smooth Corner Control, the Mazak SmoothX controller adds a specific extra radius to corners to reduce the amount of deceleration during machining, helping maintain feed rates, and also reducing machine vibration that might show up on the workpiece.

进一步帮助提高速度来自于等优点ced Surface feature in the Sinumerik control from Siemens (08458 507600). This improves the performance of high speed machining where the limiting factor is not the machining process but the CNC control. Its algorithms speed up processing of challenging shapes, such as freeform surfaces, using techniques such as look ahead and dynamic compression of linear and circular blocks using a spline interpolation technique called non-uniform rational B-spline (NURBS).

BOX: Support with programming


  • Automatic calibration with pre-written machine calibration probing cycles on Heidenhain's TNC 640 control
  • 自动生成的袖珍铣削工具路径,该工具路径可保持持续的工具在Mazatrol(智能袋铣削)中,类似于Trochoidal铣削
  • Mazatrol中3D模型的形状自动数字化(3D辅助)。用户可以以寄生虫形式(扩展'.x_t')导入3D CAD模型,并数字化所需的形状几何形状。该系统足够智能,能够区分转弯和铣削功能,因此,在创建转弯程序时,它可以将转弯的配置文件包裹在铣削功能上,例如boss,以快速处理零件。马扎克产品经理马克·霍尔(Mark Hall)说:“它很快,不需要程序绘制,也没有机会在错误的维度中输入错误。”
  • 自动三维模型构建在压铸锌合金的快速Mazatrolconversational programming software. A 3D view of the part shape appears as the program is written. This reduces keystrokes; before, users would need to press the 'Shapecheck' button to create a drawing, and then flick back and forth between them. It also allows other software, Virtual Machining, to verify the program in 3D simulation.
  • 增强的3D图形,足够详细,以揭示Heidenhain 640控制中测试部分的表面上的挖掘缺陷。
  • 在西门子Sinumerik的最新更新中,简化了霉菌制造中加工路径的可视化;此显示可以排除插值和平面规格(G0和G1代码),因此工件很容易识别。现在,它还在生成的表面上显示钻孔模式,并考虑障碍物。
  • Easy jump from toolpath graphic to relevant section of G-code in Mazak's new Quick EIA G-code programming interface, and in Heidenhain 640 control.


由于主轴振动是ch​​at不休的主要指标,因此,在新的控制接口(CELOS)上至少显示了一个控制器的机器状态屏幕上的主轴振动也就不足为奇了。Heidenhain TNC 640控制更好地监测聊天的发作。它会自动更改机器的阻尼特性以减少颤动,因此声称它可以比以前更快或更快。

Okuma的最新P300控件(NCMT,024 7651 6600)出现了另一个反对手系统。加工Navi可以通过其他传感器检测chat不休,并建议更改主轴速度(加工NAVI L-G和M-G),或者自动调整速度(M-I)。控件上的实时图表显示了工具振动和最佳速度;聊天的实例也可以记录以供以后分析。

Vibrations and other machine movements that could lead to inaccuracies are compensated by several new features in the Heidenhain 640 control and are collected under the title of Dynamic Precision. Various programs counter low-frequency vibrations that are caused by a change in direction, the slight flexing of a portal-type machining centre's bridge's legs when it stops, the spindle nodding at the end of a pocket because of a change of direction, flexing within the machine when there are overhangs, and flexing in the machine when there is a load on the table. And to prevent minor jerks in the head that spoil a smooth surface, the Advanced Dynamic Prediction feature looks for clumps of points on a freeform surface that have been generated by a CADCAM system. It intelligently chooses to ignore some of them to enhance feedrate consistency, and, in so doing, surface finish.

Although programs written at a machine can be simulated on the same machine, and while G-code programs can be tested for collisions using offline software such as Vericut from CGTech (01273 773538), collisions still happen. Okuma says: "As machines become more complex, involving additional axes, automation and set-up changing, there's more room for human error. Many applications and development tools concentrate on the cutting and forget about the hazard of collision." The Okuma P300 control's Collision Avoidance System guards against the risk of clashes by generating a 3D image of the actual materials shape and running it in a cut simulation a fraction of a second before the cut happens. It protects the machine during automatic and manual (jogging) modes.

Similarly, the Dynamic Collision Monitoring function on the Heidenhain TNC 640 runs a simulation of the cut, including a model of all the machine components located within the work envelope (including the tool), in real time, for both automatic and manual modes. If a potential collision is detected, the system ramps down the machine to a stop and highlights the relevant parts on the screen. In fact, it has a two-stage warning: the first, at about 10 mm, stops the machine and warns the operator, but still allows manual jogging towards the collision – up to a second and absolute limit, 1 mm from the obstruction.

When there is a collision, it is often rotating tilting tables used in 5-axis milling machines that are on the receiving end, but even everyday wear and tear can throw off their kinematics and bring them out of level. Poor calibration of the table could affect machining quality. Several controls now offer an automated probing cycle that takes measurements from a datum sphere and then automatically adjusts the machine's kinematics. Okuma's system is called 5-axis Auto-Tuning; the Heidenhain system is called KinematicsOpt.