Traub Truab Tnl 18P nakup rabljenega (209)

Stanje: dober (rabljeno), Leto izdelave: 2002, Funkcionalnost: popolnoma funkcionalen, številka stroja/vozila: 344, skupna masa: 7.000 kg, skupna širina: 2.000 mm, skupna dolžina: 11.000 mm, skupna višina: 1.900 mm, proizvajalec krmilnikov: TRAUB, model krmilnika: SYSTEM TX 8i, TRAUB TNK 36 CNC Automatic Lathe - Operating voltage: 460 V - Connection power: 33 kW - Rated current: 56 A Main spindle: - Bar capacity: 36 mm - Max. speed: 6300 rpm - Drive power at 100/40% duty cycle: 6.7/10.7 kW - Torque at 100/40% duty cycle: 21/32 Nm Upper tool turret: - Number of tool stations: 12 - X-axis travel: 50 mm - Y-axis travel (option): ±20 mm - Z-axis travel: 100 mm - Rapid traverse X/Y/Z: 15/15/15 m/min - Measuring system resolution X/Y/Z: 0.0005/0.001/0.001 mm - Input force X/Y/Z: 4240/4240/4240 N Front unit: - Number of tool stations: 5 - Diameter: 40 mm - Spacing: 54 mm - X-axis travel: 370 mm - Z-axis travel: 250 mm - Rapid traverse X/Y: 30/30 m/min - Input force X/Z: 2800/2120 N - Measuring system resolution X/Z: 0.0005/0.001 mm Lrodeyh Hkzjpfx Al Nek Rear unit: - Number of tool stations: 5 - Diameter: 40 mm - Spacing: 54 mm - X-axis travel: 73 mm - Y-axis travel: ±50 mm - Rapid traverse X/Y: 15/15 m/min - Input force X/Z: 4240/4240 N - Measuring system resolution X/Z: 0.0005/0.001 mm - Includes the clamped tool holders as shown in the photos, a chip conveyor, and a coolant system by Resy, as well as a bar feeder by FNB, type: TURBO 5-42 Note: The item must be collected on a binding date, to be coordinated, between 01. and 02.04.2026. FCA D-97944 Boxberg – loaded onto truck

Stanje: dober (rabljeno), Leto izdelave: 2003, obratovalne ure: 18.538 h, Funkcionalnost: popolnoma funkcionalen, številka stroja/vozila: 431, skupna masa: 7.000 kg, skupna širina: 2.000 mm, skupna dolžina: 11.000 mm, skupna višina: 1.900 mm, proizvajalec krmilnikov: TRAUB, model krmilnika: SYSTEM TX 8i, TRAUB TNK 36 CNC Turning Machine - Operating voltage: 460 V - Frequency: 50 Hz - Connection power: 33 kW - Rated current: 56 A Main spindle: - Bar capacity: 36 mm - Max. speed: 6,300 rpm - Drive power at 100/40% duty cycle: 6.7/10.7 kW - Torque at 100/40% duty cycle: 21/32 Nm Upper tool turret: - Number of tool stations: 12 - X-axis travel: 50 mm - Y-axis travel (option): ±20 mm - Z-axis travel: 100 mm - Rapid traverse X/Y/Z: 15/15/15 m/min - Measuring system resolution X/Y/Z: 0.0005/0.001/0.001 mm - Thrust force X/Y/Z: 4,240/4,240/4,240 N Front tool unit: - Number of tool stations: 5 - Diameter: 40 mm - Pitch: 54 mm - X-axis travel: 370 mm - Z-axis travel: 250 mm - Rapid traverse X/Y: 30/30 m/min Lrodpfxsyh Ivlj Al Nok - Thrust force X/Z: 2,800/2,120 N - Measuring system resolution X/Z: 0.0005/0.001 mm Rear tool unit: - Number of tool stations: 5 - Diameter: 40 mm - Pitch: 54 mm - X-axis travel: 73 mm - Y-axis travel: ±50 mm - Rapid traverse X/Y: 15/15 m/min - Thrust force X/Z: 4,240/4,240 N - Measuring system resolution X/Z: 0.0005/0.001 mm - Including the clamping tool holders shown in the photos, as well as a chip conveyor and a coolant system from manufacturer Resy, and a bar feeder from manufacturer FNB, type: TURBO 5-42 Note: The item must be picked up on a binding date to be agreed between 01.04. and 02.04.2026. FCA D-97944 Boxberg – loaded onto truck

Stanje: dober (rabljeno), Leto izdelave: 2001, Ref. No.: 10551 Manufacturer: TRAUB Model: TNC 42/65 Year of manufacture: 2001 Control type: CNC Control system: TRAUB TX Location: Halberstadt Country of origin: Germany Machine No.: 93XXXXX Max. speed: 8000 rpm X-axis travel: 450 mm Turning length: 450 mm Spindle speeds: 4000 rpm Clamping diameter: 42 / 65 mm Spindle bearing diameter (front): 110 mm Tool mounts: 14 Max. torque: 170 / 230 Nm Rapid traverse (X-axis): 15 m/min Rapid traverse (Y-axis): 6 m/min Rapid traverse (Z-axis): 30 m/min Space requirement (L x W x H): 4354 x 2076 x 1917 mm Cross-section of tool slide (turning/milling support): 16 x 16 (20 x 20) mm Pressure: 70 bar Hydraulic tank: 70 l Ledjy Ed E Uepfx Al Nerk Total power requirement: 39 kVA Machine weight approx.: 5.2 t Feed force X-axis at 100% duty cycle: 5000 N Feed travel X-axis: 140 mm Feed travel Z-axis: 450 mm Feed travel Y-axis: 35 mm Ballscrew (Z-axis) (Ø x pitch): 32 x 10 mm Ballscrew (X-axis) (Ø x pitch): 32 x 5 mm Ballscrew (Y-axis) (Ø x pitch): 25 x 5 mm Additional Information: - Turret 1, number of stations: 10 - Turret 2, number of stations: 14 - Hecowpkfie Htlx Tfefh (text seems garbled/unreadable) - Driven tools: Yes The machine can be inspected under power by prior arrangement.

Stanje: rabljeno, Leto izdelave: 1993, Funkcionalnost: popolnoma funkcionalen, Traub CNC stružnica TNS26DG, TX8F, letnik 1993 • 2x 12-postajna revolverska glava z rotacijskim pogonom orodja VDI25 • C-os na glavni/vzvratni vretenu • 163E na glavni vretenu, 161E na vzvratni vretenu Lrodpfx Alsy D I Svj Nek • Transporter za ostružke, nalagalni magazin DN26 • Katalog rezervnih delov, električna shema, ATC optika Na lokaciji, neposredno iz proizvodnje Po dogovoru, cca. 2-3 tedne po naročilu 100% plačilo pred nakladom Brez kakršnegakoli jamstva. Na lokaciji/razstavljen, kot je bilo vidno in preizkušeno. Vmesna prodaja pridržana.

Stanje: dober (rabljeno), Leto izdelave: 2009, Funkcionalnost: popolnoma funkcionalen, CNC Lathe TRAUB TNX 65/42 Year of manufacture: 2009 Control: Traub TX 8i-s TECHNICAL DATA - Number of spindles: 2 - Number of axes: 12 - Number of turret heads: 2 MAIN SPINDLE - Spindle nose: A2-6 - Spindle drive power: 24 kW - Spindle speed: 5,000 rpm - Max. bar diameter: 65 mm Lrjdpfx Aljyw H Szj Nok - Max. main spindle chuck diameter: 175 mm - Minimum C-axis resolution: 0.001° SUBSPINDLE - Spindle nose: A2-5 - Spindle drive power: 28 kW - Spindle speed: 7,000 rpm - Max. bar diameter: 42 mm - Minimum C-axis resolution: 0.001° - Travel distance: 700 mm LEFT UPPER TURRET - Number of positions: 10 - Number of driven positions: 10 - X/Z travel: 175 / 650 mm - Y travel: +/- 40 mm - Tool type: VDI 30 - Driven tool speed: 6,000 rpm - Driven tool power: 5.5 kW RIGHT LOWER TURRET - Number of positions: 10 - Number of driven positions: 10 - X/Z travel: 175 / 650 mm - Y travel: +/- 40 mm - Tool type: VDI 30 - Driven tool speed: 6,000 rpm - Driven tool power: 5.5 kW ELECTRICAL SUPPLY - Supply voltage: 400 V - Total drive power: 95 kW WEIGHT AND DIMENSIONS - Footprint: 5,450 x 2,318 mm - Machine height: 2,258 mm - Machine weight: 10,000 kg ACCESSORIES - 3-color status lamp - Coolant tank: RESY * with high-pressure pump * with paper filter - Chip conveyor - Part removal unit - Parts conveyor belt

Stanje: rabljeno, Leto izdelave: 2005, Technical details: Turning diameter: 275 mm Turning length: 900 mm Spindle bore: 65 mm Drive power 100% duty cycle: 25/20 kW Spindle speeds: 1 - 5000 rpm Spindle diameter at front bearing: 110 mm C-axis: 1 - 500 rpm Number of tool carriers: 4 Turret: 1 X-axis: 290 mm Ledpewp D Nbofx Al Nerk Y-axis: 165 mm Z-axis: 360 mm B-axis: 360° Rapid traverse speed: 18/30 m/min Number of tools: 2x2 + 2x2 Number of driven tools: 2x2 + 2x2 mm Tool speeds: 8000 / 2000 rpm Drive power 25% duty cycle: 5.8 kW Tool holder: TRAUB 60 Turret: 2/3/4 X-axis: 170 mm Z-axis: 600/950 mm Y-axis: +/- 60 mm Rapid traverse speed: 18/15/30 m/min Number of driven tools: 10 mm Tool speeds: 1 - 6000 rpm Drive power 25% duty cycle: 5.8 kW Tool holder: DIN 69880 40 x 63 Total power requirement: 95 kW Approx. machine weight: 16 t Space requirement approx.: 10.0 x 3.5 x 3.0 m with CNC TRAUB TX 8i, bar feeder TRAUB Stamag DNH61 / 3000, main and counter spindle with C-axis 1 vertical tool carrier with B-axis 3 turret tool carriers extraction system, coolant unit with coalescence separator and chip conveyor 2 pcs. 3-jaw chucks SMW KNCS-N 170-43 2 pcs. HAINBUCH Spanntop collet chucks 40 pcs. various static tool holders 6 pcs. various driven tool holders Spare parts package

Stanje: rabljeno, Leto izdelave: 1990, Tehnične podrobnosti: Premer struženja: 445 mm Dolžina struženja: 2000 mm Premer struženja nad posteljnim suportom: 660 mm Vretenska izvrtina: 65 mm Vretenaste hitrosti: 16 - 3150 min⁻¹ Hitri pomik v smeri x: 10 mm/min Hitri pomik v osi Z: 15 m/min Skupna potrebna moč: 34 kW Teža stroja cca.: 7,5 t Prostorska zahteva cca.: 6 x 2,5 x 2,2 m z CNC krmiljem TX 8 D Lredpfx Alow I R Ndj Nsk C-os, pogonska orodja Revolverska glava s 14 pozicijami 3-čeljustna vpenjalna glava Ø 315 mm Konjiček, luneta SMW SLK 520 N kot NC-os različni pogonski nosilci orodij različni nosilci stružnih orodij Odvajač ostružkov in hladilna naprava

Stanje: rabljeno, Funkcionalnost: popolnoma funkcionalen, automatic lathe Traub Ljdpjwcqv Iofx Al Nork

Leto izdelave: 2022, stanje: rabljeno, Funkcionalnost: popolnoma funkcionalen, TRAUB suha kamnoseška žaga MULTI-STONE 520 — letnik 2022 Rabljeno, iz profesionalne najemne flote podjetja Kurt König Baumaschinen GmbH, Einbeck. Ljdpfxjy A E Nio Al Nsrk Stanje in opombe: - Stanje: Rabljeno iz najema, redno servisirano - Funkcija: Popolnoma delujoča - Slike izdelka sledijo — v primeru zanimanja nas kontaktirajte za aktualne fotografije - Ogled možen po dogovoru v 37574 Einbeck Cena: 3.750 EUR + DDV | EXW Einbeck | Dostava na zahtevo

Stanje: rabljeno, Leto izdelave: 1996, maks. premer palice: 65 mm maks. premer vrtenja: 175 mm maks. dolžina palice: 3.000 mm Krmiljenje: sistem TX 8F Hod – x: 140 mm Hod – z: 520 mm CNC stružnica | TRAUB - TNC 42/65 DG, opremljena z nalagalnikom palic. Stroj je v dobro vzdrževanem stanju. Ledpfjxbtq Nex Al Njrk Videoposnetke stroja na lokaciji z veseljem posredujemo na zahtevo. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #Tags: TNC65 | TNC-65 |TNC 42-65 DG | TNC 42/65DG

Stanje: rabljeno, Leto izdelave: 1997, Prehod vretena 80 mm Največji premer struženja 460 mm Največja dolžina struženja 1.000 mm Krmilni sistem TX 8F Največja hitrost vretena 2.800 obr/min CNC stružnica | TRAUB - TNA 500 Stroj je v vzdrževanem stanju. Videoposnetke delovanja stroja na lokaciji vam na zahtevo z veseljem posredujemo. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #Tags: TNA500 | TNA-500 Ljdpfx Ajxbtpxel Nsrk

Stanje: rabljeno, Leto izdelave: 1996, Prehod vretena: 80 mm Maks. premer struženja: 395 mm Maks. dolžina struženja: 750 mm Lsdjxbtqvspfx Al Nork Krmiljenje: Sistem TX 8H Maks. hitrost vretena: 3.150 obr./min CNC stružnica | TRAUB - TNA 400 Stroj je v dobro ohranjenem stanju.

Stanje: dober (rabljeno), Maximum bar capacity: 36 mm Maximum spindle speed: 6,300 rpm Number of spindles: 2 Control system: Traub TX8i Tool carrier 1: Lredpstrvzxjfx Al Nek Number of tools: 12 X-axis travel: 50 mm Z-axis travel: 50 mm Front tool carrier: Number of tools: 7 Spindle speeds: 150 - 3,000 rpm / 300 - 6,000 rpm Mounting diameter: 40 mm X-axis travel: 370 mm Z-axis travel: 250 mm Rear tool carrier: Number of tools: 5 Spindle speeds: 150 - 3,000 rpm / 300 - 6,000 rpm Mounting diameter: 40 mm X-axis travel: 73 mm Bar feeder: FMB Turbo 5-42 Bar length: 3,200 mm Bar diameter: 5 - 42 mm Country of origin: Germany Machine dimensions (LxWxH): 3,400 x 1,300 x 1,700 mm Machine weight: 4,000 kg

Stanje: zelo dobro (rabljeno), Leto izdelave: 2001, Funkcionalnost: popolnoma funkcionalen, Traub CNC Lathe TNC65DGY, TX8H, Year 2001 • 2x 10-position turrets with live tooling drive VDI30 • C-axis on main and sub spindle • Y-axis on turret 1 • Hainbuch BZI65 on main/sub spindle Hollow clamping cylinder • Chip conveyor, coolant tank • Spare parts catalogue, circuit diagram, ATC optics Very good condition. Machine can be inspected under power. Machine geometry has been checked and corrected/set. Lrsdpfx Aeyvfwfjl Nsk

Stanje: pripravljen za uporabo (rabljen), Leto izdelave: 1996, obratovalne ure: 46.282 h, Funkcionalnost: popolnoma funkcionalen, model krmilnika: TX 8F, največja hitrost protivretena: 4.000 obr/min, premer obdelovanca (maks.): 56 mm, Oprema: podajalnik palic, transportni trak za ostružke, No minimum price – guaranteed sale to the highest bidder! By placing a bid, you are committing to collecting the machine within one of the following periods: either between 11.05.2026 and 13.05.2026 or between 18.05.2026 and 21.05.2026! TECHNICAL DETAILS Maximum counter-spindle speed: 4,000 rpm Maximum workpiece diameter: 56 mm Rapid traverse: up to 15 m/min Fine interpolation cycle: 0.34 ms Maximum thread pitch: 999,999 mm Maximum radius: 99,999.999 mm Feed override: 0–200% Rapid traverse override: 0–100% Spindle speed override: 50–120% Workpiece discharge via counter-spindle Programming: EIA and ISO code Input/output resolution: X/Z: 0.001 mm, C-axis: 0.001° C-AXIS Main spindle: Maximum speed: 80 rpm Torque at 100% duty cycle: 100 Nm Accuracy: +/- 3 minutes Counter-spindle: Maximum speed: 80 rpm Torque at 100% duty cycle: 30 Nm Accuracy: +/- 3 minutes Tool Turrets 1 & 2 Driven tools per turret: 10 (14) Maximum speed: 4,000 (8,000) rpm Power at 100% duty cycle: 1.5 kW Power at 15% duty cycle: 4 kW Torque at 15% duty cycle: 12.4 (4) Nm Tool holder bays/turret: 10 (14) Cylindrical shank according to DIN 69880: Ø 30 x 55 (25 x 48) mm Tool cross-section: 20 x 20 (16 x 16) mm Chip-to-chip time (as per VDI 2852): 1.2 s Station change time: 0.6 s Across 5 stations: 1.5 s Counter-spindle (numerically controlled in Z-direction) Maximum speed: 4,000 rpm Maximum clamping diameter: 65 mm Continuously programmable three-phase motor: 11 kW Torque: 210 Nm Feed force at 100% duty cycle: 6,000 N Feed travel: 520 mm Ball screw drive: Ø 32 x 10 mm MACHINE DETAILS Control: TX 8F Operating voltage: 400 V Frequency: 50 Hz Control voltage: 230 V Nominal pressure current: 85 A Connection: 54 kW Connected load: 39 kW Noise emission at operator’s position: 71 dB(A) Lodeym A E Iepfx Al Njrk Hydraulics System pressure: 60 bar Tank capacity: 150 l Coolant/Lubrication Per tool turret: single-stage centrifugal pump Pump pressure: 5/12 bar Tank capacity without chip conveyor: 300 l Tank capacity with chip conveyor: 280 l Dimensions & Weight Dimensions (L x W x H): 11,000 x 2,000 x 2,600 mm Weight: 6,000 kg Read-off operating hours: 46,282 h EQUIPMENT STAMAG bar feeder Chip conveyor Hainbuch chuck system Two 10-position tool turrets with driven tool stations Counter-spindle External reference: L. Schaible

Stanje: dober (rabljeno), Odmikač brusilnih plošč, odmikač lončastih plošč, odmikač za dvostranski brusilnik, odmikač za ploščinsko brusilko, odmikač za cilindrično brusilko, glava za oblačenje, glava za uravnavanje za brusilne stroje Lredpfx Asd R Ikdel Njk - Količina: 1 kos na voljo - Dimenzije: 325/130/V135 mm - Teža: 7,3 kg

Stanje: rabljeno, Leto izdelave: 2001, Drehdurchmesser 340 mm Drehlänge 750 mm Steuerung SYSTEM TX 8H Spindeldurchlass 80 mm Umlaufdurchmesser über Planschlitten 530 mm Umlaufdurchmesser über Bett 665 mm Drehzahlbereich - Hauptspindel 3.150 min/-1 Antriebsleistung - Hauptspindel 22 kW Anzahl der Werkzeugplätze 12 Pos. Die Maschine befindet sich unserer Einschätzung nach in einem guten gebrauchten Zustand und kann nach Terminvereinbarung unter Strom besichtigt werden. Es sind 2 Maschinen verfügbar. Preis pro Stück. Maschine 1: Lredpfx Ajxwdw Ejl Nsk - Bilder 1-5 - Betriebsstunden ca.55.790 h Maschine 2: - Bilder 6-10 - Betriebsstunden ca.54.347 h Technische Merkmale & Zubehör: - Y Achse - Zubehörpaket mit starren und angetriebenen Werkzeughaltern -Späneförderer Zubehör, abgebildete Werkzeuge und Spannmittel gehören nur zum Lieferumfang wenn dies in den Zusatzinformationen vermerkt ist. Aenderungen und Irrtuemer in den technischen Daten und Angaben sowie Zwischenverkauf vorbehalten!

Stanje: rabljeno, Leto izdelave: 1992, Drehdurchmesser 480 mm Drehlänge 800 mm Steuerung System TX8F Drehdurchmesser über Support 240 mm Spindeldurchlass 65 mm Spannfutter-Durchmesser 200 mm Drehzahl 4000 U/min Antriebsleistung 30 kW Maschinengewicht ca. 4,3 t Nr.: 508 Die techn. Daten sind Hersteller- bzw. Betreiberangaben und daher für uns unverbindlich. Einen Zwischenverkauf behalten wir uns vor; es gelten ausschließlich unsere Geschäfts- und Verkaufsbedingungen. Über uns mehr als 400 eigene Maschinen im Lager Lredoyuqiwopfx Al Nok über 15.000 m² Lagerfläche, Krankapazität 70 t mehr als 10.000 Artikel Zubehör für Ihre Werkstatt Sie wollen Maschinen Produktionslinien oder Ihren Betrieb verkaufen, dann sprechen Sie uns an. Weitere Angebote finden Sie auf unserer Webseite. Besichtigungen sind nach Absprache möglich. Wir freuen uns auf Ihren Besuch. Ihr Markus Hirsch Team

Leto izdelave: 1997, obratovalne ure: 54.646 h, stanje: rabljeno, Traub TNA500 SN 253 Vreteno 2800 obr/min Ledoyt Slwopfx Al Nork 12-pozicijski revolverski nosilec orodij Ima gnana orodja Moč 46 kVA

Stanje: dober (rabljeno), Leto izdelave: 1989, 1 x Automatic Lathe Manufacturer: Traub Model: TD 16 Year of manufacture: 1989 with hydraulic bar feeder LNS Hydrobar Model: 3.16-HS 4.4 Ledpfevga A Tex Al Nsrk Year of manufacture: 1989 Equipment: 6-position turret head Quick-action material clamping Long turning device Central lubrication system by Vogel Accessories: See photos The machine can be inspected under power.

Stanje: pripravljen za uporabo (rabljen), Funkcionalnost: popolnoma funkcionalen, Enovretenski avtomatski stružnica TRAUB A-15 v brezhibnem stanju, pripravljen za uporabo Ljdpfxsyy Nz Re Al Nsrk Maksimalni premer struženja 15 mm

Stanje: zelo dobro (rabljeno), Leto izdelave: 2001, obratovalne ure: 47.600 h, številka stroja/vozila: 325, Dobro ohranjena Lrodpfx Alsh Dzqls Nsk

Stanje: rabljeno, Leto izdelave: 1988, Technical details: Swing diameter over bed: 360 mm Ledsu Rqabopfx Al Nork Swing diameter over cross slide: 160 mm Turning length: 800 mm Longitudinal travel (Z-axis): 810 mm Cross travel (X-axis): 205 mm Control system: TX-8 Spindle bore: 60 mm Spindle speed: 63 - 3150 rpm / 2-step Feed rate: 10,000 mm/min Tool turret - number of stations: 8 Operating hours: 8,834 h Tailstock taper: SK30 DIN 2080 Tailstock quill travel: 105 mm Operating pressure: 40 bar Total power requirement: 38 kW Machine weight approx.: 3.1 t Machine dimensions (LxWxH): approx. 1.8 x 3.3 x 1.8 m Hydraulic unit dimensions: 580 x 400 x 750 mm Equipment: Ø 200 mm hydraulic chuck (without jaws) Feed force Z-axis = 8 kN and X-axis = 5 kN Coolant system Control panel Accessories: Precision adjustment device for tool setting

Stanje: rabljeno, Leto izdelave: 1990, Zelo veliko nosilcev Vpenjalna glava z veliko silo 12-pozicijska revolverska glava Tip stroja: CNC stružnica Leto izdelave: 1990 Lrodpeyc Hgbsfx Al Nsk Krmiljenje: Traub TX 8 F Premer struženja: 480 mm Dolžina struženja: 800 mm Premer vretena: 65 mm Hitrost vretena: 40 - 4000 min⁻¹ Teža: pribl. 5000 kg Dimenzije (Š x G x V): pribl. 2950 x 1990 x 2000 mm Stanje: rabljeno

Stanje: pripravljen za uporabo (rabljen), Na voljo je stružnica Traub TND 400. Razdalja med konicami: 800 mm, premer struženja cca 250 mm, pomiki X/Y cca 220 mm/850 mm, prehod vretena: 65 mm, območje vrtljajev: 40-4000 rpm, 12-pozicijski diskovni revolver, držalo orodja: VDI40 DIN69880, vgrajena hladilna naprava, dimenzije X/Y/Z cca 3000 mm/2000 mm/2000 mm, teža cca 4300 kg-4500 kg. Ogled možen po dogovoru. Lodpfx Alsykutxj Nerk