Frequently Asked Questions
1) The wrong kind of lubricant has been used. Never use oil, silicone, WD-40, graphite or another lubricant that reduces friction.
2) The load (for example a wire guide roller) is too heavy or it has been mounted in such a way that it is placing overturning moments of force on the Uhing drive.
3) The four screws used to mount the load to the top of the Uhing drive are too long.
4) The Uhing drive is very old (more than 10 years) and the bearings are worn down.
Used properly, a Uhing drive will not slip. Please contact Amacoil if your Uhing drive is slipping.
This is fine for heavy, robust applications requiring a lot of side thrust. But a Uhing drive may not be practical for an application with a long travel stroke and a very low thrust requirement. A long stroke requires a thick shaft which means the Uhing drive will have a lot of side thrust. This means you end up with a very powerful unit when all that is needed is a very light duty unit.
Contact Amacoil to see if a Uhing drive is right for your application.
Does anyone ever specify a maximum pitch that is larger or smaller than the maximum diameter of the wire being spooled?
When I received my Amacoil quotation for a Uhing drive assembly, I noticed a technical specification labeled "gear ratio." What is this?
In a basic Uhing set up, the Uhing shaft is driven via a belt & pulley system linking the Uhing shaft to the take up spool shaft. The gear ratio refers to the size relationship of the pulley wheels in this linkage. If the wheels are the same size (1:1) then the drive's maximum pitch will be as listed in the brochure. If the gear ratio is greater than 1, the pulley wheel on the Uhing shaft will be larger than the wheel on the spool shaft and the Uhing shaft will turn slower than the spool shaft. If the gear ratio is less than 1, the pulley wheel of the Uhing shaft will be smaller than the wheel on the spool shaft and the Uhing shaft will rotate faster than the spool shaft. Correct gear ratio and shaft speed is required in order to assure that the linear movement of the Uhing drive stays in synch with the rotation of the spool.
In a Uhing drive assembly, the L dimension is the distance between the outside edge of one end support to the outside edge of the opposite end support. The L dimension determines how much travel is possible in a Uhing assembly. The converse is also true -- the amount of travel desired will determine the L dimension. The L dimension is important because the mounting holes used to anchor the Uhing assembly are located in the bottom of the end supports.
Uhing drives are designed to provide side thrust only. If any other forces are imposed on the drive – such as weight or overturning moments – then a linear slide load carrier is needed. The linear slide transfers the forces to a separate support assembly. In an assembly model number a linear slide is usually designated as SLS.
Chances are you have a Uhing model RG drive and are rotating the shaft in the wrong direction. The RG drive operates with the shaft rotating in one direction ONLY. Reversal is mechanically controlled with a special mechanism on the drive unit. Reversing the shaft with a model RG drive will cause the drive to stop at the end of its stroke and create undue wear on the bearings. The Uhing model RS drive does require shaft reversal in order to change travel direction.
Is it OK to install a Uhing assembly without having the mounting surface of the drive facing upwards?
I am considering a Uhing RS linear drive nut for a CMM application. How can I compensate for the accumulated difference in linear travel?
To use the RS drive in a CMM (coordinate measuring machine) application, you need to incorporate a linear scale with the drive. Amacoil provides a pre-integrated assembly which precisely monitors both linear position and travel direction. The unit provides smooth, vibration-free movement with no backlash. Resolution may be specified for either 0.0004 inches (0.01 mm) or 0.004 inches (0.1 mm). The RS-Linear Scale Assembly operates on a smooth shaft at rotational speeds of up to 8,000 rpm. Linear travel speed is up to 4 ft./sec. with axial thrust up to 202 lbs.
Could be that your traverse unit is so old the bearings need to be replaced. Thrust requirements are at a maximum at the end of each stroke. Worn bearings could cause the skipping. We've had units sent back to us after ten years of 24x7 use, and the bearings hardly look worn. Other times we see a unit that's been in service for only a few years and the bearings are completely worn. This can mean the traverse unit size is not properly matched to the application requirements. Not only the diameter and line tension of the material you are winding, but also the physical set up of your winding assembly, go into determining the exact size of the Uhing traverse drive nut needed. For example, if angle "M" in the illustration below is too great, it can cause a drive that's too small to skip or even stall.
The best solution to your problem is to phone an Amacoil applications engineer and go over the specifics of your set-up. The next best solution is to go to http://www.amacoil.com/html/form1.htm and complete the winding assembly applications form. After you submit the form online, an Amacoil applications engineer will get back to you to discuss what might be causing your Uhing traverse unit to skip.
I frequently use spools of varying widths on the same winding system. Re-setting the traverse end stops every time I switch spools takes too much time. Is there any way to avoid this step?
Yes. The Amacoil/Uhing FA System uses a "light barrier" to electronically detect spool flanges. When the flange edge breaks the barrier, it triggers a pneumatic solenoid which turns the mechanical reversal lever on the Amacoil/Uhing rolling ring drive. You never have to set the end stops and you can use spools of any width. To install an FA system on an existing Amacoil set-up, you should consult an Amacoil applications engineer.
We don't recommend it. Pitch is factory-set by inserting a series of poly-based pitch wedges between the rolling ring bearings inside the drive nut. The pitch wedges determine the unit's pitch by holding the rolling ring bearing assembly at a precise angle relative to the drive shaft.
Changing the pitch is an inexpensive (less than $60) process whereby the pitch wedges are switched out for a different set. No other components of the linear motion system need be changed as opposed to other types of linear motion systems where changing pitch can require the purchase of major new parts such as screws, gearboxes and clutches.
The RS comes standard with a fixed pitch setting of 0.5 times the shaft diameter. (The model RS4-25, for example, runs on a 25 mm drive shaft and has a fixed pitch setting of 12.5 mm per shaft revolution.) Each RS drive is now also available with four other pitch settings - 0.1, 0.2, 0.3 and 0.4 times he shaft diameter.
We manufacture and distribute several gauges of electrical wire. Any way around having to design a separate spooling system for each wire gauge?
For each different material being spooled, the linear drive moving the wire guide back and forth, must travel a specific linear distance per one revolution of the shaft. This is the pitch of the system. Proper pitch adjustment ensures that material is laid onto the spool in evenly spaced rows.
To assure that a single spooling system accommodates as many different gauge materials as possible, the system must be designed around application requirements for winding the largest size material (see Figure 1). Additionally, planning around the largest spool (flange-to-flange width) is necessary to make certain the system will meet varying axial thrust requirements.
Designing around the largest diameter material - requiring the maximum linear actuator pitch setting -- ensures that there is enough "turn down" adjustment available to accommodate the winding of smaller gauge materials. Turning down the pitch on a linear actuator is much simpler and less expensive than, say, changing the motor speed or changing gears to properly wind smaller gauge materials.
Likewise, by designing around the requirements using the widest reel (flange-to-flange), when the linear drive reaches the reel flange, the angle (M) between the point of payoff and the material guide is at a maximum (see Figure 2). The resulting line tension imposes the maximum axial thrust requirement on the linear drive. Narrower reels may then be used on the same system without concern over exceeding axial thrust requirements. (Note: This is true only if distance B remains the same.)
For details, see the article at http://www.amacoil.com/articles06.html
My payload is a long rod with a spray nozzle fixture at the end. It's too heavy to mount to the drive nut, and I have very little vertical space above the traverse drive nut to add a linear slide. What can I do?
Is there any space behind the traverse unit? If so, you can mount an Amacoil L4 linear slide to the back of your drive nut. The L4 adds only about 1.0 mm in vertical height to your drive assembly, yet completely removes the load from the nut. All radial forces and moments of torque created by overhung or off-center loads are directed away from the drive nut and assembly, and you are assured your system is protected from torque-induced damage.
Rolling ring linear drives have a thrust set screw preset at the factory. It applies pressure (preload) to the rolling ring bearings so they maintain constant contact with the drive shaft. This assures accurate thrust and prevents backlash. When the free movement lever is actuated 90° (manually or pneumatically), the thrust set screw pressure is released and the linear drive is easily pushed, in either direction, to any location along the shaft. This eliminates the need to start-and-stop, or "jog," the system to position the linear drive.
As shown in these illustrations, a rolling ring linear actuator will simplify winding system design, set-up and operation. A rolling ring system eliminates the need for additional motors and controls saving time and money.Rolling ring system Screw-based system
Yes. If you are winding a material that demands extremely high accuracy or requires a complex or intricate lay line pattern, the Amacoil/Uhing RS linear drive, in an electronically-controlled system, is ideal for guiding the material onto the spool. The diagram below shows a typical custom winding set-up. For details on systems like this, contact an Amacoil applications engineer toll free at 1-800-252-2645.
My cutting application is set-up in a very dirty environment. Do I need to fabricate a bellows assembly to protect the Uhing unit?
Not really. Particulate contaminates rarely find a way into an Amacoil/Uhing rolling ring linear drive. Bellows assemblies are excellent protection against particulate contaminates but they can be expensive to design and build, and they often pose stacking space problems. A better, far less costly solution to meet your concern is to install "scrapers" in the shaft apertures on the linear drive. The scrapers effectively clean off any debris from the drive shaft. Scrapers are available with grease fittings for lubrication of the linear drive shaft.
|Scraper-wipers mounted on either end of the linear drive prevent build up of absorbent (dust, wood/paper pulp) and non-absorbent (metal chips) particulate contaminants. With grease fittings, scraper-wipers also facilitate lubrication of the linear drive drive shaft.|