4 Ways to Maximize Your Machine Tending Investment

Machine tending is one of the most common collaborative robot applications. But despite its widespread use, customers often ask, “Is machine tending right for me?”

To find out, let’s take a deeper look at machine tending by considering:

1. What is machine tending used for?
2. Common configurations and design criteria for setting up your cell.
3. How to reduce payback time and earn a higher ROI.

What is machine tending used for?

Machine tending most often involves loading and unloading CNC milling machines, but the term also applies to tending injection moulding machines, presses and manufacturing equipment of all sorts.

Any equipment with simple pick-and-place motions—where an object enters the machine, undergoes processing and leaves the machine after processing is completed—is a candidate for machine tending. Traditionally, this is a labour-intensive process that is highly dependent on the operator’s attention.

Why automate machine tending?

Let’s illustrate with a simple example. Say we have a machine-tending operation for a CNC mill with a human operator tending two different machines.

The red blocks are lost operator time, where the operator is probably not doing any value-added work because there’s not enough time between changeovers while the machine is operating.

Blue blocks are low-value operator time. They’re not programming the machine, just putting in parts, pressing start, and taking them out again.

The green blocks at the bottom are the CNC processing times. These are two different examples. At the top, the first example has a short machining time of around two minutes; the second, lower example, has a longer machining time of six minutes. In both cases, we can very quickly get into scenarios where an operator is going to be standing idle for two minutes at a time during changeovers or during machine-processing time.

By automating machine tending, you eliminate these inefficient periods of operator downtime, which are not just the red blocks but also the blue blocks. An automated solution will absorb this low-value work, allowing you to redeploy operators to higher-value work within the factory.

Examples of higher-value operations could be programming CNCs for new jobs or more intricate finishing tasks. Deburring, polishing, or general finishing might take a level of dexterity that is better performed by a human than a robot.

How to configure your machine tending robot cell

Now that we’ve looked at why you would want to consider automating machine tending, here’s how you can configure your machine-tending robot cell. Looking through all the different projects we’ve deployed, there are a few archetypal designs that come up time and again. These will be familiar to those who have been in the machining industry a long time.

The first is drawers, where a cobot is mounted on a mobile stand with a set of integrated drawers. Then there are feeder systems, which are common when you have cylindrical parts that can be fed automatically. Auto-feeder systems can have much larger capacities and include automation in the actual part presentation mechanism.

Trays are another simple example. These are better suited for smaller part runs, usually large or heavy parts. You can’t fit as many parts on a tray, so you’re going to need more changeovers by the human operator to refill the cobot’s station. But overall, this is a very economical solution and is easy to deploy.

Seventh-axis range extenders are another common configuration. These can shuttle a robot between two or more machines, or move the robot from an infeed to an outfeed station, which could include quality inspection as an intermediate station. Range extenders can be configured further with floor-mounted and overhead-mounted options available.

Key criteria for your configuration

When choosing a robot cell configuration, there are a few important considerations. This is not an exhaustive list, but they should be top of mind.

Next, you’ll want to select the end-of-arm tools.

Adding peripherals

The next thing to consider is whether you want to add more peripherals to your machine tending cell. One of the most enabling and versatile options is Vention’s MachineLogic for Universal Robots.

With MachineLogic for UR, you can integrate Vention’s MachineMotion controller with the UR controller and add a ton of peripheral equipment. Some examples include conveyors, small actuators, rotary tables, or full-size actuators for things like range extenders.

Justifying your investment in machine tending

Now that you’ve designed your robot cell, we’re going to look at how you might justify the investment. For this, we’ve built a payback model. Vention’s machine tending payback calculator lets you input 11 different parameters so that you can tailor the scenario to your needs. It allows you to compare your current process to what it could look like if it was automated.

Example

Let’s look at a process with two 8-hour shifts per day. We’re running roughly 75 parts per shift and the total cost of equipment is around US$60,000. There are a few more parameters, but we’ll keep those constant for the purpose of this example.

Those numbers give you a payback of less than eight months— a really attractive payback by industry standards. In the next couple of scenarios, we’ll look at the impact that different parameters have on the payback period.

The effects of increasing production on the payback period

The chart below looks at the effects of increasing production on shortening the payback period.

We’re varying two things: the number of shifts per day (from 1 to 3) and the shift length (from 8 to 12 hours). The small circle shows us the payback period from our previous example, which was about eight months.

This shows that we can drastically reduce the payback period if we increase production, whether it’s increasing shift duration or shifts per day. We can also see that running a 24/7 operation with three shifts a day, 12 hours a day, can lead to a payback period of less than three months.

It can be hard to justify a 24/7 operation for a number of reasons. However, having two 8-hour shifts a day can still be very attractive. As you can see, these fixed-cost investments in automation have a major effect on the payback period when we increase production.

The right-size equipment optimizes payback

The next graph looks at the effects of sizing the overall robot cell on payback. We’re looking at sizing in terms of parts capacity. The smaller the part capacity, the more often the operator will have to refill the station so the higher the labor requirement. We’ll look at what happens if we increase part capacity significantly.

Interestingly, past a certain point, we won’t change our payback significantly. That’s because after we have refilled once per shift, having the extra capacity doesn’t change much. It could improve it if, for example, there was one refill every two shifts, although that’s not something being captured here.

In simpler scenarios, our rule of thumb—one refill per shift— will ensure you’ve right-sized your equipment, you’ve optimized it, and you’re not paying for capacity that you’re never going to use. Past a certain capacity the investment is not going to be as effective.

The effects of labor on payback

Next, we’ll look at the effects of the labor rate on payback. This can be a sensitive topic since it can involve displacing the operator, although in many cases, it actually frees up skilled labour to focus on higher-value tasks - which are presumably more engaging as well. Since labor supply and wage rates vary regionally, the location of your facilities can be a determining factor.

We’ve added this as an easy-to-use parameter in the model. We can see that as we increase the labor rate, the payback period shortens drastically.

Higher cost means a longer payback period

Now, we want to see the sensitivity to equipment costs. As the equipment cost increases, our payback period is also going to increase. There’s a linear relationship between equipment cost and the payback period.

What this tells us is that you should only pay for extra features if they’ll give you extra performance. And even with extra performance, it must be a sizable improvement to “buck the trend” and invert the chart above.

Machine tending applications in the field

With a good idea of the different ways payback might be affected by the parameters of your use case, we can now look at some of the robot cells Vention has deployed in the past.

Overhead range extender

This is a 40-foot long overhead range extender is tending three HaaS CNCs with a single UR10 cobot. The range extender runs on a rack and pinion actuator, and everything is controlled from the UR robot. Vention’s MachineMotion controller drives the main actuator and plugs into the robot arm via MachineLogic for UR.

There’s an automated infeed station on the other side of the CNC machines. Since there are about two minutes of machining time here, the robot is busy shuttling back and forth between machines and infeed and outfeed stations the entire time.

This setup uses a dual gripper so the robot doesn’t have to take a part, drop it off, and pick up another part that is potentially 12 m away. Thanks to the dual gripper, it’s already carrying the next part so it can swap it out directly.

Part presenter with drawers

A 3-drawer machine tending cart with a Fanuc CRX-10iA plus a Schunk pneumatic gripper. The number of drawers can be configured and the surface can be customized to mount different part geometries.

Angled part presenter

This is a great example of a part presenter with a configurable tray angle, shown with a Doosan M1013 cobot. Using threaded pins lets you reconfigure the surface to support parts with several geometries very quickly, without any custom machining.

ActiNav Bin Picking

The next example is a robot stand with autonomous bin picking. It uses the Actinav system from Energid, which allows the robot to pick from a randomly sorted bin. So, if you have smaller parts or a disorganized assortment of parts and it’s hard to present them consistently, consider putting them in a bin randomly like this and adding a 3D vision system to your cobot.

Dual overhead range extender

This project is similar to the previous overhead range extender example but with two robots on the same rack and pinion track. These two robots actually tend two machines. One robot tends the infeed, picking parts off a conveyor and feeding them into the machines, while the other is dedicated to outfeeding, taking the parts out. This cobot cell also integrates an area scanner so operators can safely pass through the work area.