TECHNICAL ARTICLE:
| Linear Motor Technologies for Chipless Cutting | ||||||||||||
| By: T-Drill Oy, Finland | ||||||||||||
Introduction The use of coiled tubing is becoming more popular within Automotive and HVAC industries. The benefits are well recognised – coiled tubing brings logistical savings, less wasted material and crucially, it allows faster production.
The current outstanding issue is that today coiled tubing is available that has traditionally been supplied on straight lengths due to large diameter or material characteristics. In essence this means that small diameter steel tubing (4-12mm), as well as large diameter (15-25mm) aluminium and copper tubing, can already be supplied on coils. Some manufacturers are even joining tubes together just to make longer coils. Such tubes are typical for the automotive industry where they are used for making brake, fuel, power steering and air-conditioning parts.
Such large coils have set new requirements for decoiling and tube cut-off systems. To better meet these new requirements, T-Drill has developed a completely new chipless cut-off product and dedicated decoiling equipment that can fully meet all these challenges. Chipless Tube Cut-Off Basics Chipless cut-off has unquestionable advantages over standard practices in the field of tube cutting. The method makes no chips and noise level is low when compared to other tube cut-off methods. The tube cut-off method, pioneered by T-Drill, is also chipless. It is rotary cutting with a hallmark ‘pull-apart’ system. This means that initially the cutting disk penetrates the tube wall at about 95 per cent. Following this, the cut-length is separated by a pull-apart action. This eliminates the ID reduction that would occur if the blade were to pass through the tube wall. With this feature, the secondary operations are easier to carry out since the cutting quality is usually good enough for the secondary operations, without the deburring or chamfering of the tube ends. The method also allows easy chaining of different processes such as cutting and endforming/bending. This heralds a further efficiency bonus - tubes require no washing since the lubricant is biological and evaporative. Brazing or welding can be carried out even if there is still some left. Such an innovative concept - introduced by T-Drill - lies in the development of the feeding system that is based on linear motor technology. Linear Motor Principles Linear motors provide direct linear motion without mechanical linkages, such us ball screws. A permanent magnet linear motor can be thought of as permanent magnet rotary motor, whose stator and rotor have been cut along a radial plane and unrolled, so that it provides linear thrust.
The same forces of electromagnetism that produce torque in rotary motors are used to produce direct linear force in linear motors. The result is a flat linear motor that produces linear force, as opposed to torque, because the axis of rotation no longer exists. The motors are typically supplied as construction kits. They include:
Linear Motors offer the following advantages over conventional solutions:
Linear Motor Cut-Off Machine The new chipless cut-off machine from T-Drill, branded the TCC-25 LM, uses this described linear feeding system for cutting tubes to length. This new technology provides very fast and accurate cut-off for various cut-lengths (< 6000mm). It also has the power that is needed to feed and straighten tubes up to a diameter of 25mm, or coiled steel tubing up to 12mm diameter.
Until now T-Drill had used a pneumatic hitch-feeding system. However, the company saw a progressive opportunity to improve cutting technology and established intensive research to meet the challenge. This led to the proactive use of linear motors for tube cut-off and now the results are clear to see. With the TCC-25-LM, the heavy use of pneumatic air can be banished to historical dustbin.
With tube cutting operations it was impossible to use the full capacity provided from linear motors, as cut-length tolerance is set ‘only’ to +/-0.01mm. The reality remains +/0.1mm since there are still limitations that the natural laws of the tube cutting process establishes. An identical issue concerns the feeding speed and accelerations. By experience T-Drill has found out that 3m/s feeding speed and acceleration of 25 m/s2 are normally the maximum values – which, if keeping in mind the cut-quality and length tolerances - are very high compared to any other method. Multiple Differential Cut-Lengths Automatically with High Accuracy What makes TCC-25 LM special is the ability to cut several cut-lengths automatically based on touch screen parameters. These different lengths will be separated automatically after the cutting operation by the diverting table.
The automatic cutting of different lengths is a useful function when there is an assembly that requires several cut lengths from the same tube diameter. Another useful application is to have single TCC-25 LM for cutting different length tubes for several bending or endforming machines that are all making different parts. User Friendly Controls The operator interface is a touch screen control panel. It includes advanced functions and diagnostics which are making TCC-25 LM very easy to use – even for a non-skilled operator. From this control panel the operator can change tube cutting and general machine setting parameters.
Straightener with Quick Changeable Rolls and Digital Read-Outs In order to make tube straightening as easy as possible, T-Drill has developed a straightener that allows quick change of straightening rolls. Another improvement is the use of digital read-out for adjustment of the rolls. Those who deal with tube straightening practices will be aware of just how tricky it can be to adjust a tube straightener. T-Drill is now using digital read-outs for straightener settings. This will provide great help when the basic setup can be recorded and loaded.
Another matter is ‘quick changeable rolls’, an important feature if there is an important requirement to change a tube diameter regularly. This system is just matter of ‘pushing a button’ to release the straightening roll for switching it to another. Horizontal Decoiler for Heavy Coils Linear feeding, just like any other ‘hitch feed’ method is based on three operations: acceleration, feeding and stopping. In order to handle this kind of ‘feed-stop-feed-stop’ operation, the decoiling equipment needs to be able to accept all these high accelerations and stoppages while still keeping the tube tight to avoid coil jamming and tube damages. The new decoiler design meets all those requirements.
Auxiliary Equipment TCC-25 LM can be equipped with NDT (non-destructive testing) or colour detecting equipment. NDT equipment can be used for detecting defects and/or joints on coiled tubing. The advanced software will remove these bad sections from the coiled tubing automatically during the cutting process. It also makes sure that, in relevant scenarios, the wasted tubing will be minimized. If needed, the tubes can be marked or labelled by ink-jet/laser printer. Cut-Off with Integrated Endforming using Linear Motor Technology Beside normal cut-to-length systems, T-Drill has used the linear motor technology for cut-off machines with an integrated endformer. While all the linear motor feeding benefits have been explained, there is one important matter that needs to be explained when dealing with the issue of in-line cutting and endforming.
This is the inevitable change over any duration of time. Linear motor based feeding is accurate enough, and the machine can automatically cut and endform multiple cut lengths. Until now this kind of length setting had been time consuming work to do – on occasions it could take an hour to undertake. With T-Drill’s linear motor based cut-off and endforming system, it takes no extra time at all.
Summary It is likely that the industries will be using coils more frequently instead of straight length tubes. Coil sizes will also become larger. Tube diameters on coils are also likely to be larger and coiled steel tubing will be coming to use more frequently. With the TCC-25-LM linear motor based cut-off, a dedicated decoiling system, a new straightener with quick changeable rolls and advanced software, T-Drill aim to meet the most of these demanding cut-off applications.
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