Gate TI Indexing and Transfer

 

HomeFrequently Asked Questions

 

Frequently Asked Questions

1. How accurate or repeatable are Gate TI indexers?

All major components of our models are machined on five axis fully autonomous FMS work cell and inspected on Zeiss CMMs. Our IT-TR-HP series rotary indexers have repeatability listed to be +/- .02mm (+/-.0008”) at the cam follower pitch diameter. This is a standard tolerance which is conservative. Gate TI can maintain tolerances which are 50% tighter than this if required by customer.

2. How can I determine which type of indexer is best for my application?

Gate TI manufactures more than fifty model sizes of indexing and oscillating cam drives which are comprised of three different series of cam families.

  • IP Series: Paradromic Cam – parallel shaft indexers and oscillators.
  • IT, TR, HP Series: Barrel Cam – rotary dial indexing tables.
  • IG, IGA, TG Series: Globoidal Cam – right angle or roller gear indexing drives and oscillators.

3. Features of each series family are:

  • Paradromic Cams – IP Models: High torque, high speed capability indexing or oscillating motion. (Ex: Indexing conveyor, in-line feeds, inserting, pushing, tamping, probing)
  • Barrel Cams – IT, TR, HP Models: High torque, extremely rigid, heavy weight capacity, very accurate positioning. (Ex: Rotary dial tables, welding, positioners, transfer stations)
  • Globoidial Cams – IG, IGA, TG Models: High speed and torque capabilities indexing or oscillating, capable for special motions (Ex: Indexing conveyors pick and place devices, complex motion requirements)
  • Gate TI provides special motions (not listed in catalog) or left hand (LH) cams at no extra charge.

4. How does Gate TI’s manufacturing process differ from your competitors in producing cams?

Our cams are machined on five axis FMS work cells; induction hardened and then put through a grinding process. It is important to note that we use Low and High frequency six axis CNC machines induction hardening the cams. (Which is a Gate TI developed proprietary technology). Gate TI does not chemical harden or through harden, which can make a cam brittle and cause it to crack over time. The induction hardening is completely controlled via C.A.M software and allows the induction coil to follow the contour of the cam at exactly the right speed, the correct angle and at the optimal distance to produce a consistent and very hard surface (HRC 58-60).

We can regulate the CNC machine to provide the correct depth of induction hardening penetration for each cam.In this way, only the surface of the cam in contact with the cam followers is hardened while the internal core of the cam remains ductile. (Carbon Steel made to Gate TI’s specifications).Also, by hardening only a small section of the outer surface and quickly quenching it, we have minimal dimensional distortion of the cam caused by heat, which requires less grinding and maintains a more accurate cam profile.The induction hardening process causes a black scaling discoloration on the cam surface and the grinding process removes this as well as guarantees exceptionally tight dimensional tolerances.

Gate TI induction hardens all of its cams on every size and model we build. This is not the case for some competitors, which usually only through harden their bigger size cams or have an operator manually induction harden cams by hand.

5. How does Gate TI keep the cams from coming loose and drifting on the cam shaft?

Actually the keyway in our cam is machined to a very precise tolerance. Because of the way we control the hardening of our cams, our cams do not distort as would happen with other heat treating processes. When through harden heat treating processes are used, then it is necessary to leave more play in the keyway to account for dimensional distortion on the cam caused by heat treating. In this case, if the keyway is made too precise than the heat treating process may cause the cam to distort enough to cause the keyway and key to not join, and additional machining would be needed which is costly and time consuming. This is why most “key” type systems in use by our competitors have a wider tolerance.

Gate TI does it differently because we use the most state of the art equipment which can control these variables. Gate TI has in house five axis CNC milling centers, several with dual FMS work cells, 60 pallets for parts and 600 tool magazines which machine parts or cams to any profile and to extremely tight tolerances. We can machine the keyway to a very tight dimension and the cam and shaft are joined with a slight interference fit; the cam is slightly heated and then slowly presses onto the shaft. The cam is held on the shaft in a way to eliminate any cam drift. The cam is butted up to a shoulder stop on the shaft that is a ground surface and the other end of the cam has an oversized (more threads) Nylock type retaining nut to hold the cam in position, which is in addition to the interference fit of the cam and shaft.

6. What kind of bearings do Gate TI use at the point where the input/output shaft meets the casting?

We use only manufacturer certified bearings from the original manufacturers, (not from distributors). We use TIMKEN, SKF, FAG and INA brands.

Gate TI also manufactures “thrust cross roller bearings” to optimize the support of the output flange on all its heavy duty indexers. This is not the case for most competitors, which use low cost 4 contact ball bearings or thrust ball bearings that are prone to problems in the long term.

7. How are the cam follower bearings attached to the indexer output?

Gate TI has a few different cam follower designs, each for a different model cam drive mechanism, but they are all based on the solid friction roller bearing concept. Followers are pressed in the followers wheel and held in place with a top retaining screw. Some have threads and a grub type set screw.

Any system used to secure the followers is carefully designed for the specific type of mechanism and the different condition of work on the cam/follower-wheel.
I.E. In the rotary IT, HP and TR series, the stud has a set screw from the top and the follower stud is in a counter bored hole from the underside.
The top screw only holds the stud which also has the roller engaged with the cam on the other side.
The roller is just below the underside of the follower wheel and it has a shim bearing which acts as a spacer.
If the unit heats up, due to high cycle rates, the shim bearing will maintain enough clearance to allow the cam follower roller to rotate freely under the follower wheel and not bind up.

8. Is the cam follower bearing crowned or flat? When the roller cam comes into dwell, do we typically swell the dwell portion, thereby putting a pre-load on the cam follower bearing? If that is the case, with a solid journal bearing, does the shank deflect?

Gate TI cam followers are actually slightly crowned on a very large radius. The crown allows a thin film of oil to always reach all areas of the cam follower. Gate TI cam followers are always preloaded on the cam, either in the index or the dwell portion.

Gate TI do not need to swell the cam when it is in dwell. The barrel cam with its “conjugate profiles design” is the best type cam for heavy weight and high torque applications, but it also requires that the cam, cam-followers and follower-wheel are “perfectly” within tolerance to each other. We do not have a tolerance that allows adjustments of mechanism geometry by means of eccentric bushings like in other type indexers.

When using cam followers with needle bearings, the outer shell of the needle bearing will actually deflect and compensate for inaccurate machining tolerances, but this is not possible when using solid type cam followers. The tolerance inaccuracy cannot be adjusted by means of an eccentric bushing which is commonly done by other competitors.

Also having a large center stem section assures that the cam followers will not deflect; therefore, it is even more critical when using solid roller cam followers, that the tolerances are perfect to each other. Otherwise the cam will bind up and not rotate. Only a few competitors build a barrel cam type model. Most competitors engage “only one cam follower” during the index period in a loose cavity tract profile (what’s called a Z cam) and they have to swell the dwell portion to be able to engage two followers for a positive lock of the output flange. These competitors’ models are prone to backlash during the index period and they present poor kinetic performance but they are easy to manufacture with limited technological capability.

Gate TI barrel cam indexers use a modern “conjugate profiles technology” where a minimum of two cam followers are always positively engaged on a cam rib with conjugate profiles either in the dwell or the index cam portion; before one follower leaves contact with the cam another one is already engaged. This eliminates the possibility of any backlash during cam index period with improved load capacity and perfect kinetic motion making it possible to perform at very high speeds. This can be only achieved with exceptional technological capabilities.

9. Is there an increase in input torque required with our cam follower design or is there any other outward effect of that design vs. the needle bearing?

When a rotary table is sized for an application, the indexer, gear reducer and motor of the transmission are sized to handle the entire weight and load of the project.

When an indexer is in dwell, and the motor starts to turn the input shaft of the indexer there is no load to move other than the cam-shaft mass itself. The motor needs only to turn the input shaft as it proceeds through the dwell portion of the cam.

So even though the starting breakaway torque of a solid journal type cam follower is a little higher than a needle bearing type, it has absolutely no influence as it is minor of the comprehensive sized capacity for the entire transmission, once the motor starts, there is no difference for the application. Of course the indexers cannot be operated simply by turning the input shaft by hand, especially as the model size increases, but it can be done easily by means of a tool with a short lever arm.

People are typically not aware of the positive influence that this technology brings (better accuracy, wear resistance, extended life, no maintenance) and are more familiar with competitor’s model indexers and therefore sometimes, can incorrectly assume that an indexer is non-conforming.

Since the early 80’s, Gate TI can count thousands of units in the field with proven long term performance and positive results. This special type of follower is produced by “NADELLA” bearings according to Gate TI’s design.

10. On the TL Precision Link Conveyor series – how are the followers lubricated in the pallets? Do we use the same design for all of those followers?

The cam followers in the rear side of the precision link conveyor pallet are lubed for life by way of special sections in the pin or stud which retain Lubricant. The surface finish of our follower is designed to retain Lubricant even if the unit does not run for extended periods of time.

The followers at the top of the pallet need only have a few drops of lubricant placed on it from time to time (during routine machine maintenance). The top follower and bottom follower are on a common pin stud which is specifically designed to allow Lubricant to run from top to bottom.




Tel: 973.300.0090  |  Fax: 973.300.0061  |  E-mail: info@gateti.com

Gate TI has sales support offices throughout the world including main facilities in Italy, Germany, India, and France enabling support for our customers.

CATALOGS & TECHNICAL GUIDES

CLICK HERE TO DOWNLOAD
OUR PRODUCT CATALOGS

To view Catalogs and Technical guides in PDF,
you will need Adobe Acrobat Reader.