door line used for sale

Manufacturer: DMG Type: Sprint 42/10 Linear Year of Make: 2014 Technical data working space Max. travel X-axis: 50 mm Max. travel Y-axis: 350 mm Max. travel Z-axis: 120 mm Workpiece Max. workpiece diameter: 42 mm Max. workpiece length: 320 mm Max. bar passage: 42 mm Control: Fanuc Basic functions Sub-spindle Y-axis Accessories Bar Feeder Säneförderer Tool Holder Condition Perfect Availability Immediately after payment Terms and conditions of purchase: no guarantee, no warranty, no return Terms of delivery: Ex-works Terms of payment: 100% prepayment

Copilot system with touch-screen monitor Rounding and backing station 1st gluing station with viscosity control, book mark suction device 2nd gluing station Head and tail bending station Gauzing unit Kolbus BF 527 casing-in unit Kolbus FE 604 book forming and pressing machine Casing prestacking conveyor Gluing station with circulation and premelter Backlining and headbanding station pressing station with teflon band Case prestacking conveyor Case bending machine Case forming station Case magazine right hand infeed Kolbus DS 391 stacker Kolbus SU 651 Kolbus HD 142P three-knife-trimmer including all the cutting tables and knife changing unit Kolbus FS.A FS.L XMT 680

turning diameter: 20 mm turning length: 230 mm control: Fanuc 16iT total power requirement: 0,55 kW weight of the machine ca.: 2,6 t dimensions of the machine ca.: 2275 x 1300 x 1760 mm The data for this ad was created with ModulMWS - the software solution of LogoTech oHG.

Tool changer chain, chain magazine, tool changing system, tool magazine -for: max. 60 recordings -Hole: Ø 17 mm -Weight: 44 kg

The 2005 Deckel Maho DMC 104 V linear is a CNC (Computer Numerical Control) vertical machining center manufactured by Deckel Maho, a part of DMG MORI. This machine is known for its precision and efficiency in machining tasks, including milling, drilling, and tapping. Here are some key features and specifications of the 2005 Deckel Maho DMC 104 V linear: - Travel and Table Size: - X-axis travel: Approximately 1040 mm - Y-axis travel: Approximately 600 mm - Z-axis travel: Approximately 500 mm - Table size: Large enough to accommodate substantial workpieces - Spindle: - Spindle speed: High rotational speeds for efficient cutting - Spindle power: Sufficient for heavy-duty machining tasks - Linear Drives: - Equipped with linear drives for the X, Y, and Z axes, providing higher precision and faster movements compared to traditional ball screw drives. - Control System: - Typically equip ...

Indoor agriculture / vertical hydroponic farm, and the machines are associated with these operations. We are talking about leafy vegetables and herbs, to name a few examples: Iceberg lettuce, romaine, basil, mint, coriander, rocket etc. The machines are part of the same solution developed and manufactured by the Taiwanese company YesHealth. The machines are 2 years old. The drying machine has not been in operation for one year. Seeder, 2 kW Harvester, 8 kW Cleaning and drying machine, 20 kW Labelling machine, 300W Find more here - .ucymachines/

Control: SIEMENS - 840 D - - -: - - - - - - - - -: - - - - - - Milling Machine - Horizontal | DMG - DMC 60H linear The machine is in a well-maintained condition. The machine video from the production plant will be shared on request. Technical data of the machine will follow soon. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #Tags: DMC60Hlinear | DMC 60-H | DMG - DMC 60 H The data for this ad was created with ModulMWS - the software solution of LogoTech oHG.

AUTEX LINEA PRO spreading machine was built in 2015 in Spain by AUTEX-INT, S.L.L. The machine is designed for the precise spreading of layers of material on the work table during the automatic fabric cutting process. The use of this machine in production increases productivity while reducing the cost of orders. The AUTEX LINEA PRO is equipped with an automatic cradle system, which facilitates the loading of the fabric roll and improves the preparation of the entire process. A tension control system with material edge sensors keeps the fabric in the correct position without the need for additional grippers. Photocells automatically detect the edges of the fabric and the end of the roll, while an anti-collision system increases operational safety. The machine is controlled by an advanced control system with a touchscreen and intuitive interface. It enables a full spreading cycle to b ...

Complete Lacquering line - Feeding - Primer application unit - Dryer - UV plant - UV dryer - Stacking System components are all from Bürkler and Kontra Formats: 1860, 2800, 5600x2070mm Number of application units: 10 units, 3 of which are UV UV dryer: 1x 4 UV-tubes, 1x 5 UV-tubes: 1x 6 UV-tubes Output: approx. 3300m²/h Find more here - .ucymachines/ Contact us at - sales@ucymachines

RAKOBAK H-Line is a professional smoking and thermal processing chamber designed for small and medium-sized food production facilities. This multifunctional system allows multiple processing operations within a single unit, including cooking, baking, cold smoking, hot smoking, steam smoking, drying, maturing, and curing. The chamber is engineered to ensure uniform heat, steam, and smoke distribution throughout the entire processing area. A high-performance air circulation system provides consistent processing results and reliable product quality. Various heating options are available, including electric, gas, oil, and steam heating to meet different production requirements. RAKOBAK H-Line features an automatic cleaning system that simplifies maintenance and supports high hygiene standards. The unit also includes automatic flap control, humidity regulation, core temperature monitoring,  ...

Specifications: Working length: 6100 mm Bending capacity: 3.0 mm CNC control: 400 A Bending angle: 143° Distance upper beam – table: 200 mm Projection: 1,050 mm Foot step switches: 2 pcs. Motor power: 11.5 kW Dimensions (length x width x height): approx. 7000 x 1500 x 1850 mm Weight: approx. 9.5 tons

1 x Wohlenberg 132 guillotine equipped with : air table, 2 side tables, 2 knives, photo cells, program 1 x Baumann BA 3 MAN unloader 1 x Baumann BB5 stack lift

Reference ID PP-59633 Category Screen Printer Manufacturer - Model S-LINE Year Built 2022 Color - Impression - Working Hours - Speed - - Max. Size - Min. Size - Condition Good Location Europe Availability Immediately Machine Description Screen Printing Carousel for Textile Printing VERSATRONIC S-lim Number of stations / pallets: 8 Number of print heads: 6 Maximum printing area: 400 x 450 mm Pallet drive: frequency-controlled AC servo gear drive Squeegee Drive System High-precision AC servo drive 4-piston POWER squeegee system Main Control Rotary arm with control panel and 7" SMART touchscreen Microprocessor with diagnostic program Printing Programs 6 standard programs High opacity MULTIFLASH program Cooling stop Test print Start / stop Screen cleaning mode Pallet stop between print heads Free running mode Accessories 8 aluminium sandwich pallets 420 x ...

ID3469 Simec LM2000 – Grinding line year/Baujahr 1999 Grinding line consisting of: Protec tilting table, infeed conveyor table, pre-grinding machine with 4 grinding supports, warm air blower, Kirschner putty station, oven, grinding machine with 10 supports (pre-equipped for 12) Grinding line made of: Protec tilting table, infeed conveyor table, pre-grinding machine with 4 grinding supports, warm air blower, Kirschner putty station, oven, grinding machine with 10 supports (pre-equipped for 12)

1 x Wohlenberg 132 guillotine, equipped with : air table, 2 side tables, 2 knives, photo cells, program 1 x Baumann BA3 unloader (year 2008)

GeneralCNC Swiss type lathe with Fanuc control; Control: FANUC 310 iTB Working areaTurning diameter33 mmSpecial equipmentHinged belt chip conveyor with Discharge height 1200 mm Aut. bar feeder IEMCA BOSS 545/32 E, max_ L=3200 mm, incl. guide channel diam. 18 mm

Still Water PET Bottling Line – 16,000 BPH (2018) Complete still water bottling line designed for high-efficiency production of small-format PET bottles with thermoseal lids. The line is suitable for filling 100 ml, 150 ml, and 200 ml PET bottles and includes blow molding, filling, sealing, labeling, packing, palletizing, and wrapping equipment. General Information - Application: Still / non-carbonated water - Bottle Material: PET bottles with thermoseal lid - Output Capacity: 16,000 bottles per hour - Bottle Sizes: 100 ml, 150 ml, 200 ml - Year of Manufacturing: 2018 Production Configuration - Combi Machines: 2 units (Blow Moulder + Filler + Sealer) - Machine Speed: 8,000 BPH each - Preform Type: Flat Neck – 6.39 g - Sealing System: Thermoseal neck Filling and Sealing Stations - Filling Station: Two-step system with two stations - Each station equipped with 8  ...

max. Spindle speed: 5000 U/min. travel -x axis: 160 mm travel -z axis: 450 mm numbers of turret head positions: 12 tool taper: VDI 30 Control: Heidenhain iT Plus Dimensions (L x W x H): 4,5 x 2,5 x 2,5 m weight of the machine: 3700 kg CNC Turning- and Milling Center | DMG GILDEMEISTER - CTX 310 Additional equipment: - C-Axis The machine is in good condition. Please refer to further technical details in the attachement of the offer. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #Tags: CTX310 | CTX-310 The data for this ad was created with ModulMWS - the software solution of LogoTech oHG.

GeneralHSC-Precision Centre - Active chiller for main spindle and linear drives - Active chiller for electrical cabinet - Direct absolute measuring system with air purge - Coolant-airblast changeover - MPC (Machine Protection Control); Control: 3D-control Heidenhain iTNC 530 HSCI Technical DataSpindle taperHSK-E 50 Feed rate longitudinal/transverse/vertical1-80000/1-80000/1-80000 mm/minRapid traverse longitudinal/transverse/vertical80/80/80 m/minWorking area 1Cross580 mmLongitudinal450 mmVertical460 mmTool changerType of magazineChain ApplicationVertical Type of gripperDouble gripper Number of tools30 Rigid tableRigid table, clamping area 460 x 600 mm / 18,11 x 23,62 inch Loading weight max. 600 kg / 1322 lbsSpindle speed up to 40,000rpm with Shaft CoolingSpindle speed 20 up to 40,000 rpm within shaft cooling for tool taper HSK-E50 DIN 69893 AC-Main drive with 19,5/15 kW (100/40%DC) 14,5 ...

GeneralHorizontal machining centre - Horizontal milling head; Control: CELOS with Siemens 840D sl Operate Technical DataRapid traverse longitudinal/transverse/vertical60/60/70 m/minFeed rate longitudinal/transverse/vertical60000/60000/70000 mm/minWorking area 1Longitudinal800 mmCross1050 mmVertical900 mmCabineFull protection cabinDirect measuring systemDirect path measuring systemNC rotary table with pallet changerType of Measuring system Direct measuring systemTable surface 630 x 630 mmRotation speed max.4. Axis 40 rpmDistance between T-Slots 100 mmNumber of Slots 5Slot width 14 mmMaximum load (table centre) 900 KgCentre bore 50 mm4. Axes (swivelling range) 360 x 0,001 degreePackage recirculation ballscrew spindlePackage recirculating ballscrew spindle X-,Z-axis:max. feed speed: 60.000 mm/min Y-axis: max. feed speed: 70.000 mm/min (basic machine without linear drive X-, Y-, Z-axis)Motor ...

line for croisants

New longitudinal veneer splicer Brand: CASATI Type: LINEA 1250 Technical details: Arm length 1.250 mm Veneer thickness 0,4 - 4 mm Min. veneer length 350 mm Min. veneer width 45 mm Glue for pre-gluing: Urea and PVA Glue for integrated gluing: Urea Feed speed 10 - 40 m/min. Heating area length 1.250 mm Total connected load 7,4 kW Power consumtion approx. 6 kw Compressed air consumption 5 Nl/min Compressed air pressure 6 - 8 bar This machine permits the longitudinal splicing of veneer sheets by applying glue on their edge. Immediately afterwards the veneer will be passing through a heated zone in order to activate the glue reaction: the glue will be hardening thus bonding the veneer sheets. The integrated glueing device allows the joining by one only process. Its also possible to bond pre-glued veneer sheets Option for an extra charge: Cooling device for the glue po ...

CUTTING LINE - refurbished - consisting of 1) Polar137EM-MON AutoTrim = Cutting LINE 2) Unloader/palletiser TR TR1 EL145-1 LH standing 3) Jogger RA-B-5 with air removal roller 4) Paper Lift Full description of Equipment on request

swing diameter: 640 mm max. turning passage: 640 mm control: Simens 840 D Powerline - - - - - Main spindle - - - - -: - - - - - - bar material dia.: 65 mm chuck diameter: 200 - 315 mm spindle bore diameter: 80 mm diam. of main spindle in forward position: 120 mm --- Subspindle ---: - - - - - - bar material dia.: 65 mm chuck diameter: 315 mm spindle bore diameter: 80 mm forward bearing diameter: 120 mm - - - - - General data - - - - -: - - - - - - spindle distance: 1.500 mm turning length: 1.185 mm Main-/Counter -spindle turning speeds: 5.000 U/min driven tools turning speeds: 12.000 U/min Slide cross: X1, Y1: 550 / 180 mm Slide cross: Z1: 1.185 mm Slide cross: B1: 240 ° Slide cross: X2: 180 mm Slide cross: Z2: 1.050 mm Slide cross: Z3: 1.150 mm CNC Turning- and Milling Center | DMG GILDEMEISTER - GMX 250 linear equipped with main/counter spindle, chip conveyor, tool changer, a turret fo ...

Brazing line manufactured in 2018. This SCAME BRAZING LINE 50-20-350-GI-DR features a maximum temperature of 1150 °C and operates with an electric power source of 85 kW. The continuous longitudinal conveyor system efficiently moves parts along a passage chamber measuring 50 x 20 x 350 cm. If you are looking to get high-quality brazing capabilities, consider the SCAME BRAZING LINE 50-20-350-GI-DR machine we have for sale. Contact us for further details.

Hiwell batter and breading line

# ABB 15kV 8-Bay MV Switchgear Lineup Model: ABB-MV-15-8 Voltage Class: 15 kV Configuration: 8-Bay Lineup Fault Rating: 40 kA Product Overview The ABB 15kV 8-Bay Medium Voltage (MV) Switchgear Lineup is a high-performance power distribution solution engineered for utility, industrial, commercial, and infrastructure applications requiring safe, reliable, and efficient medium-voltage power control. Built on ABB's proven switchgear technology, this lineup provides superior operational safety, system flexibility, and long-term reliability for critical electrical distribution networks. Designed for indoor installation, the 8-bay lineup offers a compact footprint while delivering advanced protection, control, metering, and monitoring capabilities. Its modular architecture allows seamless integration with existing power systems and future expansion requirements. Key Features ...

Used Used Packaging Line Ital Pal: Year: 2008 Condition: As Is Used Packaging Line Ital Pal Year: 2008 Speed: 5.000 bph Box forming machine Boxes: american Type of closure: with glue Case packer Number of heads: 12 Type of heads: fixed heads Box closing machine Safety protections Code: JM 87 More details: https://bottlingscout.com

Used Used labeller Sacmi Linea Ra adhesive: Year: 2003 Condition: As Is Used labelling machine SACMI model LINEA RA Year: 2003 Speed: 9.000 bph Rotative carousel with 10 heads Counterclockwise direction Machine suitable for plastic bottle for detergents 2 adhesive group to apply front and back Code: EA 81 More details: https://bottlingscout.com

x-travel: 500 mm y-travel: 450 mm z-travel: 400 mm Control: HEIDENHAIN control: MillPlus iT table surface area: ø 500 x 380 mm B-axis: 0 - 161,955 ° C-axis: 360 ° spindle taper: SK 40 spindle turning speed range: 20 - 18.000 U/min spindle power: max. 35 kW max. torque on the spindle: max. 130 Nm feeds -stepless-: bis 20.000 mm/min rapid traverse X/Y/Z axis: 80 / 50 / 50 m/min rapid traverse B-axis: 40 U/min C-axis rapid feed: 50 U/min no. of tools in magazin: 30 tool diameter if 2 vacant positions: 130 mm tool diametre at full load: 80 mm tool length - max.: 300 mm weight of tools max.: 6 kg internal coolant system feed: 40 bar total power requirement: 52 kVA weight of the machine ca.: 6 t = 5-axis machining center with 2-axis NC swivelling rotary table Accessories: electron. handwheel, chip conveyor, coolant, band filter device The data for this ad was created with ModulMWS - the  ...

Used hermetic, self-cleaning centrifuge made by REDA, model: RE150T, capacity: 15.000 liters / hour, new: 1998 Centrifuge serviced. Last service on February 16, 2022.

This 3-axis DMG DECKEL MAHO DMC 104V linear was manufactured in 2006. It features an X-axis travel of 1040 mm, Y-axis travel of 600 mm, and Z-axis travel of 500 mm. The machine includes a robust table size of 1250 x 600 mm and a maximum table load of 800 kg. If you are looking to get high-quality machining capabilities, consider the DMG DECKEL MAHO DMC 104V linear vertical machining centre we have for sale. Contact us for further details.

x-travel: 750 mm y-travel: 560 mm z-travel: 600 mm Control: HEIDENHAIN iTNC 530 total power requirement: 70 kW weight of the machine ca.: 11.000 kg dimensions of the machine ca.: m D E C K E L M A H O (Germany) Vertical CNC Machining Centre with high speed linear drives in 3 Axis and in double column design for high precision work Model DMC 75 V LINEAR Year 2005 _______________________________________________________ Working range: Longitudinal stroke X Axis 750 mm Vertical stroke Z Axis 600 mm Cross stroke Y Axis 560 mm Table clamping size 950 x 650 mm Max. Table load 1.000 kg Max. height of workpiece 600 mm Tool holder Cone HSK 63 Spindle (KESSLER) speeds 18,000 rpm Torque, max. 86/1 ...

Control: Fanuc 310 i, Max bar diameter [mm]: 25, Number of linear axis + C axis: 6 + 2, Spindle speed [rpm]: 10.000, Spindle motor [kW]: 3,7, Z - travel [mm]: 80 | 300, X - travel mm: 50 | 240, Y - travel [mm]: 350 | 120, High pressure coolant: 20 bar, Auto bar loader: FMB Turbo 3-26/3200, Machine weight approx. [kg]: 3.800

Paper cutting machine Schneider Senator 078E-Line, machine number: M-078E-018-11/20-05E, year of construction 2005, air table, side table, light flashes, program control, in good condition, immediately available If you are interested, we will also be happy to inform you about other machines in our company. Rsbr Sb Nowivimewksu You are welcome to visit the machines in our house by prior appointment.

- Model: Classic Line 60 KK - Year of manufacture: 2022 - Load capacity: 400 kg - Collection capacity: 65 liters - Dimensions: 785 x 639 x 281 mm - With grating - Steel construction - Color: blue (powder -coated) - Weight: 37 kg

- Model: Classic Line 2 FE - Year of manufacture: 2022 - Load capacity: 800 kg - Collection capacity: 205 liters - Dimensions: 1,236 x 815 x 360 mm - With grating - Steel construction - Color: blue (powder -coated) - Weight: 64 kg

CNC punching machine manufactured in 2013. This Pivatic Punching Line PCC80-e TT HT is designed for serial production of flat sheet metal parts, featuring a punching force of 400 kN and a maximum coil weight of 5,000 kg. The line includes two punching sections for flexible and repetitive operations. If you are looking to get high-quality punching capabilities, consider the Pivatic Punching Line PCC80-e TT HT machine we have for sale. Contact us for further details.

Used RÖDER H-Line tent hall (built around 2020) in an excellently maintained condition. The hall is currently still standing and is available for dismantling at short notice. The most important key data at a glance: Area & dimensions: 20 × 50 m (approx. 1,000 m² usable area) Heights: Generous 6.20 m eaves height / 9.56 m ridge height (ideal for high-bay storage and smooth forklift/truck traffic) Construction: Bolted aluminium frame structure – no elaborate or expensive concrete foundation is required (ground nail anchoring on asphalt/gravel is sufficient). Statics: Snow load 0.85 kN/m², wind zone II (fully certified according to German building standards). Your decisive advantage – the complete turnkey package: The attractive total price already includes the complete, high-quality accessories: A high-performance diesel hall heating system (mobiheat / Thermobile, 150 ...

Used RÖDER H-Line tent hall (built around 2020) in an excellently maintained condition. The hall is currently still standing and is available for dismantling at short notice. The most important key data at a glance: Area & dimensions: 20 × 50 m (approx. 1,000 m² usable area) Heights: Generous 6.20 m eaves height / 9.56 m ridge height (ideal for high-bay storage and smooth forklift/truck traffic) Construction: Bolted aluminium frame structure – no elaborate or expensive concrete foundation is required (ground nail anchoring on asphalt/gravel is sufficient). Statics: Snow load 0.85 kN/m², wind zone II (fully certified according to German building standards). Your decisive advantage – the complete turnkey package: The attractive total price already includes the complete, high-quality accessories: A high-performance diesel hall heating system (mobiheat / Thermobile, 150 ...

Brand Name: GOPEL Model: OPTICON THT 600 LINE Year: 2015 Serial Number: TH-603 Notes: - The machine is in excellent condition and in working order. - No CE manuals and declaration of conformity have been provided. - The goods being sold are declared out of service and with the obligation to restore safety in the devices relating to Legislative Decree 81/08 on machine safety. - PROPERTY INTENDED FOR VAT HOLDERS.

Production lines: 1. Polyester fiber production line (Chinese brand) Polyester fiber production line, manufactured in 2008, put into operation in 2010. From the end of 2012 until the second half of 2019, fiber production was suspended. The productivity of the line is 10,000 tons of fiber per year. The possibility of producing fiber from primary raw materials - PET granules and from secondary raw materials - PET flakes (recycled PET bottles). The main default raw material (as cheaper) is PET flakes. The available spinneret can be used to produce solid fiber 3, 7 and 15 denier, and hollow fiber, 7 and 15 denier. Hollow fiber can be produced in the conjugated type. Can buy and use other denier spinnerete according needs. The main components of the line: Fiber extrusion line • Vacuum dryers, volume 8m3, heated with thermal oil, year of manufacture 2011 – 4 units. + In 2019 i ...

TBI VC 1270 HH New Line CNC machining center was built in 2023 in Poland by TBI Technology Sp. z o.o.. This extremely efficient and reliable machine is the perfect choice for precision machining of workpieces with a maximum weight of 1500 kg. The work space, in relation to the machine’s compact dimensions, has been fully maximised in order to make the operations easier and completely free. It consists, among others, of a large work table and a body made of the highest quality grey cast iron, whose stability ensures maximum precision and repeatability of the produced parts. The very precisely balanced spindle, in turn, allows vibration-free operation at any speed. Its excellent temperature stabilisation also ensures that the temperature remains constant during even the most intense challenges. The spindle taper and tool changer are continuously purged with air to protect them from ch ...

x-travel: 630 mm y-travel: 800 mm z-travel: 750 mm control: SIN 840D sl Siemens B - axis: 360 x 0,001 ° A - axis: -200 -- +25 x 0,001 ° spindle turning speed - stepless: 20 - 18.000 U/min power capacity at 100 % load: 28,00 kW power capacity at 40 % load: 34,00 KW max. torque at 40% / 100% load: 110 / 84 Nm tool taper: HSK 63 feed X/Y/Z/-axis: 1 - 100.000 mm/min rapid traverse X/Y/Z: 100,00 m/min feed capacity X/Y/Z: 9 / 6 / 9 kN feed B-axis: 1 - 14.400 °/min feed A-axis: 1 - 7.200 °/min size of pallet: 2x 500 x 500 mm workpiece weight max.: 400 kg max. workpiece diameter: 800 mm workpiece height max.: 800 mm tool magacine with: 63 diameter of tools max.: 280 mm tool length - max.: 550 mm weight of tools max.: 15,00 kg total power requirement: 65,00 kW weight of the machine ca.: 14,00 t dimensions of the machine ca.: 5,50 x 3,50 x H3,20 m 5-axis machining center with SIEMENS SINUMERI ...

Rüttler mit Ausstreichwalze - Jogger with air removal rollers Schneider Senator Profi-Line 0077 Year 2003 - Serial-No. P-7359003 Format / Size max. 790 x 1090mm Platzbedarf / Space required 1370 x 1700mm Einsatzhöhe / Infeed high 165mm CE-Zeichen-Zulassung / CE Certificate Elektr. Anschluss / Power supply 3 Phase 380V - 1,75/2,2kW

Schneidmaschine - Guillotine Schneider Senator SEN78 E-LINE Year 2000 - Serial-No. M-078E-004-10/30-09 Schnittbreite max. 780mm / Cutting width max. 780mm Programm - Duisplay / Program - Display Lufttisch - Chromtisch / Light guard - chrome table CE-Zeichen-Zulassung / CE Certificate Elektr. Anschluss / Power supply 3 Phase 380V - 10A Ersatzmesser / Spare knives