You've searched the internet and talked to every servo drive manufacturer, but you just can't find a servo drive with all of the features that you need. What's going on? Are you being unreasonable? Are your specifications unusual?
It can't be this hard… can it?
Reasons you might need a custom servo drive:
- You need a feature that just doesn't make sense to include in a servo drive designed for general use.
- The your system components aren't compatible with each other. With all of the new features and technologies that are being introduced these days is it really a surprise that components from different suppliers don't always work together?
- They don't make a servo drive that fits in the available space. Modern robotics and mobile applications have forced the electronics to fit into ever smaller spaces making it even less likely that there's a servo drive that meets all of your requirements AND fits within the dimensions that you need.
Selecting a servo drive usually starts with looking at standard products to see if any will work for you. At ADVANCED Motion Controls we have over 200 off-the-shelf servo drive models to choose from which is a good start; if you find a match then great, the job is done! If not then you'll have to consider what compromises or workarounds are needed to get a standard product to work for you. If only a few minor accommodations are needed then it probably makes sense to stick with a standard product. But if you need to make too many compromises then you could be putting your project at risk. When you're at a point where a standard product is causing too many complications then a custom solution should be a strong consideration.
What Customizations are Possible?
Servo Drive as a Universal Adapter
In a motion control system the servo drive is the central connection point for these components:
- Power Supply
- Limit Switches
- Other Peripheral Components
When you consider every component that touches the servo drive multiplied with every option for these components, the number of combinations grows way beyond what can be offered with a standard product line.
This is where a custom servo drive with the right features can turn a messy design into a clean one.
For example we've seen systems where a resolver was required for the position feedback. This caused a problem because they couldn't find a servo drive that used resolver feedback but also had the right features and power capabilities for their application. Their solution was to home-brew a converter that would take the resolver signal from the motor and feed the corresponding encoder + commutation signal to the servo drive. What a mess, and what a lot of extra work! A better solution would be a custom servo drive that directly accepts the resolver feedback.
Another concern for machine designers is how well the servo drive can handle environmental conditions like temperature, humidity, vibration and more. For example, an arctic robot needs to operate in freezing conditions, while a tracking station based in the desert has to work in near boiling conditions. Agriculture robots need to be protected from mud and water, while a factory machine needs be protected against dust and hands.
Every application is different and there are numerous methods to protect servo drives in different conditions.
- Operating temperatures can be expanded by using subcomponents that are rated to the desired temperatures along with thorough testing to verify operability and performance.
- Ingress Protection (IP) is the protection from intrusion from the elements or foreign objects. Customizations can be as simple as adding a cover to protect fingers and hands from getting shocked, to adding a plastic cover with a gasket to prevent liquids from getting inside. The extreme is to encase the servo drive in potting compound to remove any possibility of contamination. An easy way to protect from dust and humidity is to spray the board with conformal coating.
- Mobile robotics have more bumps and vibrations than traditional factory machines. Over time components like capacitors can shake loose. We can redesign servo drives to use low-profile components and we can use adhesive to anchor components to the pcb.
Custom Layout to Simplify Installation and Connections
Have you ever pulled into a gas station and found that the only available pump is on the wrong side of the car? The same thing can happen with connectors and servo drives, but unlike at a gas station, you can't just wait for another pump to open up. If a cable comes from one direction but the connector is facing the wrong way this can force you to either use a longer cable or require you to rotate the servo drive to a different orientation. No matter how you look at it, you're being forced into a compromise for a pretty silly reason.
A custom servo drive can solve these kinds of problems because you can specify where to place the connectors. Also you can select between straight connectors or 90 degree connectors. Heck while you're at it, you might as well pick the mating connector that matches with the cables from your motor manufacturer and achieve instant savings because you no longer need a custom motor cable. Along with custom connectors comes custom pin assignments for the functions of the individual pins.
Round servo drives that fit in the back of a motor are the most obvious examples of servo drives with custom shapes. Servo drives configured to be long and narrow are a common request. We have several examples of drives with a notch in the middle, and one with a corner cut out. The point is the available space for the servo drive can be in an odd shape and this shouldn't be something to stress over. As long as there's enough surface area we should be able to figure out how to lay out the board so it fits.
In addition to just trying to get the servo drive to fit, another reason for custom shapes is to perform other functions. For example we've designed baseplates that become part of the airflow ducting system of a machine. In another example we made the baseplate so it functions as a sealed hatch that also provides access to the inside of a housing. In this case the servo drive sat on one side of the baseplate/access-plate while a MIL-spec connector came out the other side to provide power and control. This allowed the servo drive to safely sit on the inside of the machine and still be accessible from the outside.
Value Added Assembly
We don't stop at making custom servo drives, we can also do "value added" work.
If the servo drive is part of a bigger assembly, sometimes it's easier for our customers to purchase the assembly rather than do the work themselves.
For example we can place the servo drive (or multiple servo drives) in a larger enclosure and add: a power supply, controller, switches, fans and other components; then wire everything up and test it.
Realities of Customs
What's the reality of getting a custom solution for your project? Are they available for everyone? How much do they cost?
About 1/3 of our revenue is from standard products, 1/3 from modified products, and 1/3 from fully custom products. This means 2/3 of our revenue comes from products that have at least some customization. In short, the reality is we make customs all the time.
Modified vs. Custom Products
Let's clarify what we mean by "modified products" and "custom products". Both are considered to be customizations but the difference is in the degree of customization. The dividing line is with the PC Board.
If we can create a custom based on a standard product and we're able to use the existing PCB then we consider the end result to be a modified product. Things like adjusting the feedback scaling, command scaling, current limits, voltage limits, operating temperature, custom logo and markings, are all typically within the realm of modified products.
Once we start to change the shape, or add connectors with a different pole-pitch or layout, then we need to spin a new board which puts us in the realm of full customizations.
Availability of customizations depends on a number of factors but it often boils down to the resources required to complete the project and how available our engineering team is at the time.
|Lower Effort||Higher Effort|
|Modified product||Custom product|
|Few modifications||Many modifications|
|Similar to custom already in our portfolio||Something completely new to us|
|Reuse technology from other projects||Develop new technology|
|Uses existing components||Uses difficult-to-source components|
The size of the production run also plays an important factor. A project that's expected to be in production for several years with consistent monthly or quarterly deliveries would be a great candidate for a custom. While a project that's expected to have a single run with just a few units would be more fitting for a modified product.
Regardless of your needs you should always reach out to start a conversation. You may think you have a difficult request, but if we have already done something similar for other customers, it might actually be a really easy project.
If you have a need for a custom servo drive its always best to reach out to our sales team or your local representative/distributor/agent.
How Much Does a Custom Servo Drive Cost?
Considering just the cost of the servo drive, custom and modified servo drives can either be more or less expensive than their standard counterparts. Sometimes we can remove components that are unnecessary for the particular application to reduce the price. It all depends on the particular situation.
Considering the whole system-cost, custom and modified servo drives are almost always less expensive than using their standard counterparts. Including the added performance, increased reliability, greater ease of installation, better compatibility and synergy between components, many engineers conclude that they can't afford not to have a custom servo drive!
by René Ymzon, Marketing Manager