Digital readouts (DROs) are a great way to maximize new lathe’s efficiency or turn a cumbersome manual machine into a thriving profit center again. The DRO essentially translates the direction, distance and location into an easily readable display. In the case of a lathe, there are typically two axes to account for, the X and Z.
DROs make lathes fundamentally simpler to use, which, in turn, improves productivity and raises the quality of machined parts. They help prevent common errors such as misreading the hand wheel dials or losing count of rotations requiring less energy-sapping wheel cranking and wasting less time. The right DRO also helps account for backlash (less important on a lathe) and inaccuracies that are often caused by the standard lead screws on most manual machines.
Choosing the right feedback for lathe DROs
The readout/interface itself pairs with feedback devices installed directly on the lathe. There is the option to use a rotary encoder on the hand wheel, but we don’t really consider that a DRO. Adding feedback to the handwheel measures turns of the hand wheels, and not the actual positions of the cross slide or carriage. Unless the rotary option is built specifically for the machine, you won’t know exactly where the cross slide and carriage are.
Differences between glass, inductive and magnetic DRO scales
Scales act as the measuring standard on the machine. A scanning head moves along with the machine, reads and transmits positioning from the scale to the readout. There are three types of scales commonly used on lathes: glass, inductive and magnetic.
With glass scales, light is shot through lines with different levels of opaqueness. On the other side of the scale a scanning head reads the changes in light. These are extremely accurate and available in a wide range of resolutions. The trade-off is that they have a higher risk of contamination, since their light is so sensitive is sensitive to distortions in the glass.
Instead of light, which requires a constantly clean line of sight, inductive encoders detect changes in capacitance-reactance and translates them into motion measurements. Inductive scales work along a guided rail and are almost completely resistant to contamination and vibration. They tend to take up more space and don’t offer high levels of accuracy and resolution.
Finally, magnetic encoders scan alternating magnetic poles as the machine moves and detect changes in magnetic flux fields. These have small profiles and can be cut for easier installation. Like inductive encoders, they are unaffected by most contamination and handle vibration well. Magnetic encoders have limits when it comes to accuracy and resolution performance as well as temperature resistance.
4 Lathe DRO buying tips
With the fundamentals down, you can start narrowing your search for the right DRO for your lathe even further. There are a variety of things that, if you get right at purchase, will ensure the DRO system pays for itself quickly and generates profit consistently thereafter.
Resolution and accuracy
Standard scales for lathes typically have a resolution of about 5μm on the Z axis and X axis, but there are other options. Before choosing a DRO system, you’ll want to understand the work you’ll be doing and what the tradeoffs are. If you need extreme accuracy, you may be able to sacrifice some protection.
For example, our most precise scale, the SENC 50, offers an accuracy grade of ± 3μm with measuring steps down to 0.5μm and has an IP 53 protection rating. Whereas our most rugged scale, the inductive LMF 9310, provides IP 67 graded protection and an accuracy grade of ± 20μm. The encoder of choice for these lathe systems, the SENC 150, offers an accuracy grade ± 5μm with IP 53.
It’s important to understand the environment where you’ll be operating the DRO system. What kind of risks are there to the performance or longevity of the DRO? If there’s heavy coolant, chips flying, dust, oil or vibration you may want to start by looking at an inductive-based system instead of glass.
The same goes for the console. The protection levels can vary quite a bit, so if you’re working in an area where splashing can happen, don’t overlook the IP rating of the console itself. Make note if there are different protections at different areas of the readout. Also, if there’s significant vibration, consider how the DRO will stand up to that.
The point of using a DRO on a lathe is to make it easier to use, so don’t skimp when choosing which bells and whistles to go with. The readout should have a consistent and intuitive logic and menu structure, not one where certain features are easy to use and others aren’t.
From the user’s perspective, dialogue messages, graphics and high-resolution color screens are often huge upgrades. That said, some DROs have dedicated modes for different kinds of machining operations like turning, milling, drilling, etc. All kinds of useful and specific features are unlocked that make work faster and make life easier on operators. Some of the turning functions our DROs feature include:
- Taper calculator
- Radius/diameter switching
- Vectoring: X/Y display of the traverse path with inclined top slide
- Lock Axis Feature: establishes tool offsets with the tool under load, resulting in reduced tool deflection
- Freezing the tool position for back-off
- Thread Assist: simplifies cutting metric threads on lathes with English leadscrews
Before you commit to purchase a DRO kit, be sure you understand what’s involved in installation. Every machine is a little different, and so are the encoders. As a result, the burden is on the buyer to adapt brackets and make sure everything fits tightly enough to achieve the desired results. How much time will it take, and will it matter if the machine is down?
As an alternative to the universal approach, we make custom mounting kits for almost every make and model of lathe still found on the shop floor. It saves a ton of hassle in the early research stages and we think it’s just about the easiest way to mount scales.
Mounting DROs isn’t the only thing we make easy at ACU-RITE. We’ve created a handy selector tool help you narrow down which ACU-RITE DRO would fit your lathe best. Do you still need to make the financial case to add digital readouts? We can help with that too. Give our ROI calculator a try to find out how quickly you’ll get paid back and how much productivity you can gain.