Effective deep drilling technology on TOS Kuřim machines

Deep drilling is used in the fabrication of holes which are much deeper than their diameter (eg. a hole of diameter 5 mm and depth 100 mm).
While making a hole with such parameters there may be some complications, such as for example removing chips from the place of cutting, sufficient cooling, lubrication etc. Depending on the hole’s diameter and its depth, every technologist must take into consideration the most suitable technology, with respect to the production time, financial cost and demand for existing machine equipment.

Possible machining technology:
System BT-A – an advantage of this technology is the possibility to make a hole to a depth of 170xD (with a diameter up to 50 mm), high surface quality, straightness of the hole, the VBD system and long lifespan. The disadvantage is a higher price (cannot be used on standard machines due to the special-purpose drilling head enabling the removal of chips centrally through the tool), demanding structure of guards on the machine, or the drilling may be time-consuming.
Ejector system – this system’s drilling principle consists in using a drilling rod tipped with so-called drill bits. Removal of chips from the place of cutting is through the drilling rod, which is hollow. Drill bits are manufactured as monolithic or with the VBD system. The range of hole diameters can be from 18 up to 200 mm. This solution is simple; however, it cannot be used for drilling of smaller holes.
Special drills system (monoliths) TB-T– they are a cheap and productive solution that can be used on standard machines with sufficient accessories. Holes can be drilled to depths up to 30xD. The disadvantage is the need to grind the tool on a special grinder (every grinding makes the drill shorter), limited life and the risk of breaking the drill in the hole.
All types of the above-mentioned hole-drilling technologies require accurate centre-drilling by so-called pilot drills mostly to the depth 2xD and a high-performance cooling system whose parameters differ in pressure, flow rate and coolant used (cooling emulsion, oil or even air).

All the above-mentioned deep hole drilling technologies can be used on TOS-manufactured machines thanks to a patented system of automatic exchange of spindle heads of own design and production: delivery of special heads at the customer’s request is possible TOS Kuřim machining centres of type FU(Q) EFEKTIV, FU(Q), FU(Q)150 B, eventually FO(Q) 80 are the most suitable for the fabrication of deep holes. As regards their design, these machines are independent of the clamping surface (size, loading capacity, height position in respect to the machine column) and are offered in capacities of 28 to 60 kW. These machining centres can be equipped with high-pressure and medium-pressure central tool cooling up to pressure 80 bar, flow rate 50 l.min-1 including continuous control of pressure and flow rate. The advantage of the continuous control of pressure is effective cooling, with the unwanted splash of cooling liquid to the working area limited to a minimum, making the fully enclosed machine cabin useless.
For illustration, we mention examples of designs to suit the customer’s requirements, including debugging of technology on a particular machine, with guaranteed required machining parameters (for example the overall machining time, diameter of holes, surface quality). In collaboration with the tooling supplier, we can also guarantee the lifespan of the cutting tool.
One of the contracts was the manufacture of holes in a steam turbine diffusion ring, or more specifically, fitting of the ring and the disc proper together with the vanes, with each component made of different material (steel ČSN 11 523 and stainless steel ČSN 17 021). The testing of technology was successful on the FO(Q) 80 machine (longitudinal travel X=2,600 mm, cross travel Y=825 mm, vertical travel Z=1,650 mm, VT cooling, two-axes VKE interchangeable milling head, 16,000 rpm, movable rotary table type CES 2 x 2), tools were supplied by WALTER CZ Kuřim. When TOS Kuřim’s proposed technology was tested, 68 pcs of holes was made, some were through-holes and non-through holes. The stainless steel was drilled first, sequentially steel, then stainless steel and then steel again. This includes the so-called hinge lock, with the drilled hole diameter of d9H7.
The operations were as follows:
1) Centre drilling by the pilot drill to the depth of 18 mm, time 3 s/hole
2) Completion of hole drilling to the depth of 73 mm, time 19 s/hole
3) Reaming to d9H7, time 78 s/hole
4) Hole edge bevelling under the angle 40°, time 8 s/hole
Based on the test, the customer purchased the FUQ 150 VR/8 machine with two tables type CES 2 x 2 (clamping surface 2,000 x 2,000 mm) with technological accessories as per the completed test + a special VAE-1 head with an integrated electrospindle, which replaced the formerly used VKE head.
The customer further required to test the proposed technology by fabricating 1,712 holes on the heat-exchanger tube plate. The original technology used by the customer was BT-A technology with which the customer was satisfied, but for reasons of higher production capacity this technology already failed to meet his expectations and he asked for a technological solution from TOS Kuřim. Taking into consideration the submitted documents and the customer’s requirement that the machine must be universal, the FU 150B type machine was selected. TOS Kuřim, in collaboration with WALTER, offered a technical solution taking into account a standard machine design. The proposed technology made use of a special twist drills system – monoliths that were made with respect to the exactly required hole diameter of 16.3 -0.1 mm, with a depth of 315 mm, workpiece material 15 020.
The operations were as follows:
1) Centre drilling by the pilot drill to the depth of 30 mm, tool diameter 16.25 mm
2) Final drilling of the through-hole of a depth of 315 mm and diameter 16.28 mm, time 57 s/hole
The resulting time of hole drilling in the whole tube plate was 34 Nh, with the original time being 242 Nh. The required surface roughness was Ra 6.3, attained roughness Ra 4.1 – 6.0.
The above-mentioned test vindicated the suitable selection of the proposed technology and the customer asked TOS Kuřim for cooperation in machining of 4 further units, which only proved that the proposed technology was suitable and this technology was deployed in serial production.
Subject to these results, the customer bought an FU 150B V/10 machine with capacity 60 kW, with a hydrostatic guideway, two automatic interchangeable milling heads VA1 and VP1; vertical travel 4,000 mm, plate clamping system 96 m2 in size.

TOS KUŘIM – OS, a.s., is a supplier of comprehensive machining solutions for customers including the design, construction and delivery of suitable machining centres as well as accessories and processing of technology for the customer‘s products.

Exhibitor Data Sheet