Eliminating Hazards with Safety-Focused Engineering: 5 Questions Every Engineer Must Ask When Designing Automated Equipment

Thursday, October 27th, 2011

“The design looks great, and I’ve met all of the productivity requirements…. Now, what parts need guarding?”

As a design engineer, safety tends to be an afterthought. Guards and safety lockouts are usually considered after all of the design requirements are met. In some instances, safety isn’t addressed until the equipment is built and undergoes testing.

Taking this approach can lead to equipment redesign if simple guarding isn’t good enough. Below are 5 simple questions to ask yourself the next time you design a piece of equipment to ensure a safe and effective product.

How could the equipment fail?

When we talk about equipment failing, it doesn’t have to mean a catastrophic failure with explosions and mass destruction. It could be as simple as a chain breaking under a peak load or a photoeye failing to read the product. To eliminate personal injury and equipment downtime, engineers must use redundant designs to act as a backup plan in the event of a failure. Elevator emergency brakes that engage when a cable fails are a perfect example of this practice. Hard mechanical stops to limit over travel of specific components or a safety mechanism that acts as a backup plan are ways that you can protect against equipment failures.

How will the equipment react to a loss of power?

Power losses are unpredictable and always seem to come at the worst time. Equipment must be designed to safely power down and come back online when power is cycled. Sensor selection is key when designing around power loss. Normally open (NO) and normally closed (NC) sensors allow the engineer to select the fail-safe mode for a piece of equipment. For more information about NO and NC sensor selection, visit AllAboutCircuits.com.  Other sources of energy, such as pneumatics and hydraulics, must also be taken into consideration in the event of a power loss with appropriate measures made to release stored energy.

How will the equipment be treated by operators?

This article is too short to tell some of the stories that are the purpose for this rule. Unless you have been an equipment operator or a maintenance technician (or had one of your designs destroyed by one), this is can be a very difficult idea to wrap your head around. I can only give you a few pieces of advice to steer you in the right direction. If it looks like a step, it will be stepped on. If it is designed to hold 100 pounds, at some point it will see 200. Every limit will be tested and every parameter could be changed. Try your best to anticipate the real-life environment your equipment will be in for the next 20 years.

Could the hazards be removed with a better design?

It still stands that the best way to guard around a hazard is to eliminate the hazard entirely! Instead of placing a guard over a pinch point, is it possible to redesign the equipment to eliminate the pinch point? What about the component that you are worried might fail and cause a safety issue? Can it be replaced with something more reliable or possibly removed completely? Think outside of the box to provide a safe alternative and you might find a more cost-effective approach staring you right in the face.

How do we ensure the equipment is used properly?

Operating instructions, safety manuals, warning labels, and instruction plaques are the last line of defense in protecting against hazards. You have worked hard to provide the safest design you can, and now is the time to communicate the potential hazards to people who will work around your equipment every day. Don’t overlook things like warning stickers or labels. These are simple additions that instruct the operators of dangerous machinery.

By applying these 5 tips, you can provide safety-focused equipment to your customers that will never be mistaken for a safety afterthought.

Decline Accumulation Conveyor: The Holy Grail of Material Handling

Wednesday, August 31st, 2011

Obtaining cost effective, belted accumulation on a decline is one of the holy grails of material handling systems. In systems that have a sorter before shipping lanes, accumulation provides buffer to the shipping lane, and the decline allows for a smaller accumulation footprint.

This is also true for declines that feed box toppers, shipping labels, or some other important process that requires singulation and product buffer. Once the decline angle and product weight require belted accumulation, the options to the system integration engineer narrow and become expensive.

With this in mind, Blue Arc Engineering introduced a belted, decline accumulation conveyor to the ZiPline product line that provides unique features unparalleled by other belted accumulation conveyors in the marketplace.

While developing ZiPline, a 24 Volt accumulating conveyor, we assumed that decline accumulation would be an easy design carryover from the horizontal and incline accumulation designs. What we found was a problem that many 24V conveyor manufacturers run into; it is difficult to control the speed on a decline once the product weight and decline angle cross a threshold.

The analogy to this is cruise control in your vehicle: as you descend a hill, the cruise control does not slow the car down. In a nutshell, it is much easier to add energy to a system to obtain a desired output than it is to take energy out to reach a desired output.

When you take energy out, it requires monitoring of the output as well as ensuring that you take energy out at a reasonable rate to not cause a violent shock to the system. This is a limitation of using a mechanical brake inside of motorized drive roller (MDR); the brake is either all the way on, or all the way off.

We evaluated several options to remove this energy in a controlled way, as shown in the table below.

Click to View a Larger Version of this Chart

Method 4 was chosen after some development and testing of different components to find the right setup that worked reliably.

When the electromechanical (EM) brake turns on, the resulting regenerated energy turns into an increase in voltage. This voltage increase is what needs to be monitored to ensure that the peak value does not cause any problems with the MDR control card, the field wiring, or the power supply.

The two scenarios covered in the graphs below show the increase in voltage for different weights at 140 feet per minute.

Click to View a Larger Version of this Chart

In conclusion, using an EM method to reliably introduce cruise control for belted accumulation is cost effective and reliable. Solving this problem with software causes no change to mechanical elements that make up the standard ZiPline conveyor, making it an easy option to decrease overall footprint of a system while increasing the flexibility and throughput with accumulation.

For more information, visit the ZiPline Decline Accumulation Conveyor Webpage.

How to Efficiently Design a “Same…But Different” Product

Thursday, July 7th, 2011

Can you tell a difference between these two systems???

In the world of custom material handling equipment we, at Blue Arc Engineering, spend the majority of our time designing and manufacturing “same but different” products.  This has become quite an affable catchphrase in our line of work.

After engineering and building a project from beginning to end in as little time as 6-8 weeks, customers come back to us wanting, “exactly what they had before, but…” Or within the same order, they need 14 of the exact same thing.  Come to find out, they are all, “the exact same, except….”

As the engineering team, we have to find the most productive way possible to re-use the information we have and while modifying it quickly. Many challenges arise with doing projects that are “almost” identical. Our CAD (computer-aided-design) software, SolidWorks, has a feature that allows us to do this with great efficiency.

Pack and Go, similar to Copy and Paste in Windows, is the feature in SolidWorks that is our lifeline. When customers request changes to equipment we have previously designed, Pack and Go allows us to copy all the information we used in the previous project and transfer it to a new one where we are free to edit, change, and replace where needed.  The changes don’t come completely without challenges, but it still reduces engineering time, which reduces the cost to the customer.

One of the biggest challenges this process presents is identifying what aspects of the equipment the changes will affect.  We try to figure this out before we ever use the Pack and Go feature.  If there is a new footprint; the product needs to be longer, wider, or faster; or if there is a new height restriction or a new stroke, we have to define which components are affected.  We also have to answer other questions like: Do we have room?  Will this cause clearance issues?  Because we use parametric modeling, the majority of these questions are hopefully answered before we ever start cutting material.

As soon as we identify the specific changes, we are off and running!  Just hit file, then Pack and Go.  We simply have to rename the parts that change and lay down the foundation for the new project, then we are ready to edit and make a whole new system that is the, “same…but different.”

What is your favorite CAD software feature and why?