Beli Mesin sekap dan pembentuk profil otomatis bekas (496)

Kondisi: siap digunakan (bekas), Guilliet KXR III dengan spindle bergerak untuk lebar yang dapat diubah + Paket joinery ukuran akhir 240x160mm + Pengumpanan sebelum perataan Hodpfovq Rnhsx Aazopa + Motor diperkuat Jumlah spindle: 4 buah, diameter 40mm Diameter alat untuk profiling kiri/kanan maks.: 180mm Penyesuaian poros vertikal: 40mm Ukuran akhir lebar: 240 mm Ukuran akhir tinggi: 160 mm Panjang meja perata: 2500 mm Kecepatan pengumpanan: variabel 4,5-27 m/menit Daya motor diperkuat: Perata: 7,5kW Spindle kiri/kanan: 11kW, 1 motor Ketebalan: 9kW Pengumpan: 2,2kW Dimensi sekitar (P x L x T): 3160 x 1420 x 1440mm Berat mesin sekitar: 1700 kg Dijual dari lokasi, sesuai kondisi saat ini Opsi pemeriksaan dan rekondisi tersedia dengan biaya tambahan

Kondisi: bekas, Tahun pembuatan: 1990, Weinig Profimat 22N Tahun pembuatan: 1990 Jumlah spindle: 6 buah Lebar penyerutan: 220 mm Tinggi penyerutan: 120 mm Diameter spindle: 40 mm Panjang meja masuk: 2.000 mm Penggerak: Kardus Urutan spindle: Bawah Hodsx Dbbnjpfx Aazjpa Kanan Kiri Atas Bawah Universal

Kondisi: sangat baik (bekas), Fungsionalitas: berfungsi sepenuhnya, tegangan masuk: 400 V, diameter alat: 140 mm, masa garansi: 3 bulan, diameter poros: 40 mm, jumlah spindel: 5, diameter sambungan ekstraksi: 140 mm, frekuensi input: 50 Hz, diameter rol pengumpan: 140 mm, lebar meja: 230 mm, diameter poros pisau: 40 mm, Perlengkapan: kabin, rem mesin, Four-sided planer Weinig Unimat 500 Working width: 230 mm Hpodjv Nkufspfx Aazoa Working height: 130 mm Number of spindles: 5 Spindle arrangement: 1. Bottom 7.5 kW 2. Right 3. Left 11 kW 4. Top 7.5 kW 5. Bottom 5.5 kW Powercom system Pneumatic pressure rollers divided into 4 sections Feed speed adjustable via inverter Feed drive via cardan shafts Infeed table length: 1970 mm CE certificate

Kondisi: sangat baik (bekas), 7817 TECHNICAL DATA DDCA – Double-end Tenoner - Min. workpiece width: 180 mm - Max. workpiece width: 850 mm - Min. workpiece thickness: 10 mm - Max. workpiece thickness: 45 mm - Spindle diameter: 30 mm - Max. blade diameter: 250 mm - 4 blades included 5 spindles: Left side: 1) Vertical upper 2.2 kW 2) Horizontal lower 2.2 kW Right side: 1) Vertical lower 2.2 kW 2) Vertical upper 2.2 kW 3) Horizontal lower 2.2 kW - Spindles adjustable up/down, left/right - Material hold-down: 2 pcs - Infinitely variable feed speed: 0–10 m/min - Central lubrication via oil pump - Pump motor: 2.2 kW - Extraction connection diameter: 5 x 100 mm - Dimensions (LxWxH): 1900 x 2230 x 1530 mm DDGA – Four-Sided Planer/Moulder - Max. workpiece width: 130 mm - Workpiece thickness: 10–60 mm - Min. workpiece length: 200 mm Spindle configuration: 1) Bottom 5.5 kW 2) Right 5.5 kW 3) Left 5.5 kW 4) Top 5.5 kW - Spindles adjustable up/down - Top and bottom spindle diameter: 40 mm - Left and right spindle diameter: 30 mm - 4 feed speeds: 13/20/26/40 - Central chain lubrication by oil pump - Extraction connection diameter: 4 x 120 mm - Dimensions (LxWxH): 3200 x 1370 x 1830 mm DBCA – Tenoner Infeed Conveyor - Max. feed speed: 40 m/min - Max. workpiece width: 150 mm - Motor: 0.55 kW - Overall dimensions (LxWxH): 2320 x 600 x 1150 mm DBGA – Strip Infeed Conveyor - Strip length: 200–600 mm - Strip width: 30–120 mm - Strip thickness: 10–40 mm - Infinitely variable feed speed: 10–40 m/min - Motor: 0.75 kW - Overall dimensions (LxWxH): 1500 x 500 x 980 mm - Total weight: approx. 4900 kg – Made in Poland – Technical Documentation (DTR included) – 5 spindles – Not painted – Very good condition Hedpfxsxwytie Aazopa – Used machine Net price: 63,900 PLN Net price: 15,200 EUR (based on an exchange rate of 4.2) (Prices may vary due to exchange rate fluctuations) * MAR-MASZ guarantees the quality of your purchase, but is not an authorized representative of the manufacturer. All trademarks and names are used for informational purposes only for product identification. We resell only goods previously put on the market by the manufacturer. We have no business relationship with the manufacturer.

Kondisi: diremaj di bengkel (bekas), Tahun pembuatan: 2013, Leadermac Speedmac 631 Lebar kerja: 310 mm, tinggi: 150 mm. Spindel: 6 x 50mm (4x spindel dengan kontrol kecepatan inverter) Hodpfx Ajxzthbsazspa Bawah (22 kW) – 6000 rpm, bantalan luar Kanan (15 kW) – (4000 sampai 9000 rpm) jointer lurus Kiri (15 kW) – (4000 sampai 9000 rpm) jointer lurus Atas (22 kW) – 6000 rpm, bantalan luar Atas (22 kW) – (4000 sampai 9000 rpm), bantalan luar, jointer lurus Bawah (22 kW) – (4000 sampai 9000 rpm), bantalan luar, jointer lurus Kecepatan pengumpanan 60 m/menit (dapat ditingkatkan). Roller pengumpan atas 200 mm (2 pertama) dan lainnya 140 mm Koneksi: 380 V // 50 Hz Dokumentasi lengkap disertakan.

Kondisi: bekas, Tahun pembuatan: 2009, 1 Hedpfsxxtlbex Aazjpa

Kondisi: bekas, Tahun pembuatan: 1984, nomor mesin/kendaraan: 241-502, Mesin planer empat sisi untuk dijual Hodpfx Asx Aryxeazepa

Kondisi: bekas, Tahun pembuatan: 1981, Weinig U22N Jumlah spindle: 7 buah Lebar penyerutan: 220 mm Tinggi penyerutan: 120 mm Panjang meja masuk: 2.500 mm Rol penggerak pada meja: 2 buah Rol pada meja (tidak digerakkan): 3 buah Motor penggerak umpan: 5,5 kW Bantalan lawan: spindle 6 dan 7 Jointer: spindle 6 Susunan spindle Hodpfjx Da Rbox Aazepa Bawah 5,5 kW Kanan 3 kW Kiri 5,5 kW Kanan 7,5 kW Atas 5,5 kW Atas 4 kW Bawah 4 kW

Kondisi: sangat baik (bekas), Fungsionalitas: berfungsi sepenuhnya, panjang pemakanan sumbu X: 230 mm, panjang umpan sumbu Y: 140 mm, kecepatan spindel (min.): 6.000 rpm, diameter nosel ekstraksi: 140 mm, diameter poros mesin serut: 40 mm, tinggi benda kerja (maks.): 140 mm, sambungan udara terkompresi: 120 batang, lebar benda kerja (maks.): 230 mm, tegangan masuk: 400 V, masa garansi: 2 bulan, jumlah spindel: 5, diameter rol pengumpan: 140 mm, lebar meja: 230 mm, diameter poros pisau: 40 mm, Perlengkapan: kabin, rem mesin, Four-side planer Weinig Unimat 500 Working width: 230 mm Working height: 140 mm Number of spindles: 5 Spindle arrangement: Bottom: 5.5 kW Right Left: 7.5 kW Top: 11 kW Hpodpfx Aswv Slkoazoa Bottom: 5.5 kW Feed speed adjustable by inverter up to 30 m/min Feed motor: 4 kW Drive via cardan shafts Pneumatic pressure rollers 3 axes controlled from the control panel (width, height, pressure position) Air pads in the worktable Infeed table length: 2470 mm CE certificate Technical documentation (DTR)

Kondisi: sangat baik (bekas), Four-Sided Planer SCM P64 Technical Data: Hjdpfx Aajvafdpozepa Max. planing width: 190 mm Max. planing height: 120 mm Spindle diameter: 35 mm Number of spindles: 4 Spindle arrangement: bottom 5.5 kW right + left 5.5 kW top 5.5 kW Number of powered, toothed feed rollers: 3 Dust extraction port diameter: 150 mm Cardan shaft feed Worktable lubrication pump Electric height adjustment of the machine body Power supply: 400 V Overall dimensions: Length: 3500 mm Width: 1230 mm Height: 1730 mm

Kondisi: sangat baik (bekas), CATALOGUE NUMBER 7679 TECHNICAL DATA - Maximum planing width: 610 mm - Maximum planing height (double-sided): 200 mm - Electric adjustment of the table up/down - Maximum planing height (four-sided): 100 mm – Top section: - Feed-in shaft, toothed - Kickback protection - Pressure device - 2 toothed feed rollers - Pressure device - Planing shaft 610 mm, 4-knife, 7.5 kW - Pressure device - Outlet feed shaft, smooth – Bottom section: - Guide bar - Toothed feed roller - Planing shaft 610 mm, 4-knife, 5.5 kW - 2 smooth feed rollers – Rear section: - 2 vertical side spindles + pressure device 1) Right vertical spindle 100 mm, 4 kW 2) Left vertical spindle 100 mm, 4 kW - Spindle diameter: 35 mm - Spindles adjustable up/down, left/right - Manual adjustment of planing width - 6 feed speeds: 7/9/11.5/14/18/23 m/min - Feed motor: 3.1 kW - Dimensions (LxWxH): 2500 x 1800 x 600 mm - Weight: approx. 3000 kg ADVANTAGES - Ideal for processing beams, flooring, etc. - German-made by KUPFERMUHLE Hedpfx Aewtp U Rjazspa - 2 horizontal planing shafts + 2 vertical spindles - Used planer, very good condition Net price: 56,900 PLN Net price: 13,550 EUR (based on exchange rate 4.2 EUR) (Prices may change with significant exchange rate fluctuations)

Kondisi: sangat baik (bekas), Tahun pembuatan: 2010, Fungsionalitas: berfungsi sepenuhnya, lebar kerja: 230 mm, tinggi penyerutan: 120 mm, diameter spindel: 50 mm, lebar perataan: 230 mm, tinggi kerja: 120 mm, daya motor pengumpan: 37.000 W, kecepatan spindel (maks.): 6.000 rpm, kecepatan spindel (min.): 3.000 rpm, jenis penyesuaian ketinggian: listrik, diameter poros mesin serut: 50 mm, jenis arus masuk: tiga fasa, jumlah spindel: 10, daya: 574 kW (780,42 hp), frekuensi input: 50 Hz, Perlengkapan: kabin, kecepatan rotasi dapat diubah tanpa batas, rem mesin, Weinig Powermat 2500 10 spindles, Working width: 230 mm, Working height: 120 mm, Spindle diameter: 50 mm, Feed: 37 kW / 12–120 m/min, Spindle arrangement: 1– Bottom (22 kW) – with hydraulic clamping and fully automatic straight jointer 2– Right (11 kW) 3– Left (11 kW) 4– Top (37 kW) – with fully automatic straight jointer 5– Bottom (18.5 kW) with hydraulic clamping and fully automatic straight jointer 6– Top (18.5 kW) – with hydraulic clamping and fully automatic straight jointer 7– Top (53 kW) – with hydraulic clamping, speed 3,000–6,000 rpm 8– Bottom (53 kW) – with hydraulic clamping, speed 3,000–6,000 rpm 9– Top (53 kW) – with hydraulic clamping, speed 3,000–6,000 rpm 10– Bottom (53 kW) – with hydraulic clamping, speed 3,000–6,000 rpm Short infeed table 1.3 metres (4 rollers) with 2 driven rollers above the table, and 2 driven rollers in the table. Both table rollers can be lifted. Table height adjustment with electronic digital display. Incl. 2 heavy-duty lateral pressure rollers, diameter 140 mm, pneumatic. Support feet, height 320 mm for table height 1190 mm Marathon POWER Coating for machine table, fences and guide rails (excluding infeed table and special table plates). Special coating to protect table plates, fences and guide rails against excessive wear. Recommended Hpedpfxsxz Thbe Aazsa for processing abrasive materials (e.g. tropical woods, MDF, chipboard, plastics, metals). Automatic lubricant pump for table resin removal. Driven rollers in the machine table, hardened. Heavy-duty steel pressure rollers from above with diameter 120 mm. In the area of the right and left spindle.

Kondisi: siap digunakan (bekas), Tahun pembuatan: 2010, Fungsionalitas: berfungsi sepenuhnya, kecepatan pemakanan sumbu X: 12 m/menit, tinggi benda kerja (maks.): 120 mm, lebar benda kerja (maks.): 230 mm, model controller: Siemens Simatic Panel Touch, panjang benda kerja (maks.): 8.483 mm, No reserve price - guaranteed sale to the highest bidder! TECHNICAL DETAILS Minimum workable height: 6 mm Maximum processing height: 120 mm Minimum processing length: 370 mm Maximum processing length: 8,483 mm Minimum processing width: 25 mm Maximum processing width: 230 mm Maximum feed speed: 12 m/min Drive rollers Number of rubber wheels: 1 Number of gear wheels: 4 Number of rollers: 5 UNITS Hedpfx Aasxw U Syezopa Unit 1 Saw spindle: bottom Spindle diameter: 40 mm Spindle length: 240 mm Motor output: 4 kW Unit 2 Saw spindle: right Spindle diameter: 40 mm Spindle length: 240 mm Maximum tool diameter: 4 mm Motor output: 4 kW Unit 3 Saw spindle: left Spindle diameter: 40 mm Spindle length: 240 mm Motor output: 4 kW Unit 4 Saw spindle: top Spindle diameter: 40 mm Spindle length: 240 mm Motor output: 5.5 kW MACHINE DETAILS Control model: Siemens Simatic Panel Touch Installed total power: 24 kW EQUIPMENT CE marking

Kondisi: hampir baru (bekas), lebar kerja 630 mm pengaturan umpan variabel Hodpfxexztfys Aazopa poros dengan 4 pisau ketinggian maksimum elemen 240 mm pengaturan ketinggian elektrik motor 7,5 kW start bintang/segitiga tegangan 380V

Kondisi: sangat baik (bekas), Tahun pembuatan: 2002, Fungsionalitas: berfungsi sepenuhnya, diameter nosel ekstraksi: 140 mm, diameter poros mesin serut: 40 mm, tinggi benda kerja (maks.): 230 mm, jenis arus masuk: tiga fasa, jumlah spindel: 7, jangkauan kerja: 230 mm, diameter poros pisau: 50 mm, Perlengkapan: kabin, rem mesin, Mesin ketam empat sisi Weinig Hydromat 23, 80m/menit Lebar kerja: 230 mm Tinggi kerja: 160 mm Jumlah spindle: 7 Susunan spindle: 1. Bawah 15 kW 2. Kanan 11 kW 3. Kiri 11 kW 4. Atas 15 kW 5. Atas 7,5 kW (dengan penyangga hidrolik) 6. Bawah 11 kW (dengan penyangga hidrolik) 7. Universal 11 kW (kecepatan rotasi variabel melalui inverter) Pengaturan dimensi ketam dari panel ATS Kecepatan putaran spindle: 6000 rpm Diameter spindle: 50 mm 5 rol penggerak pada meja kerja Kecepatan maju dapat diatur dengan inverter hingga 80 m/menit Penggerak makan didorong oleh poros kopel Hedpfx Aaoxww Hmozspa Tekanan penekan pneumatik Dokumentasi teknis tersedia Dimensi mesin: 460x230x200 cm Berat: 6000 kg

Kondisi: sangat baik (bekas), Four-Sided Planer PAOLONI SAC RD 230 15/24 Technical data: Maximum planing width: 230 mm Maximum planing height: 120 mm Spindle diameter: 40 mm Number of spindles: 4 Spindle arrangement: bottom right left top Number of upper steel feed rollers: 2 Number of upper rubber feed rollers: 1 Number of smooth table rollers: 1 Extraction port diameter: 3 x 120 mm Table lubrication pump Manual body lifting Power supply: 400 V Total power: 21 kW Overall dimensions: Length: 3280 mm Width: 1290 mm Hodpfx Aaeuy H Nwjzjpa Height: 1500 mm

Kondisi: sangat baik (bekas), Mesin serut empat sisi Leadermac Smartmac 423 Lebar serut maksimum: 230 mm, Tinggi serut: 120 mm, 4 spindel, Pengaturan dimensi serut secara elektrik, Konfigurasi spindel: bawah 5,5KW; kiri dan kanan 7,5KW; atas 7,5KW Hpsdpfjxzqwysx Aazsa Motor dengan rem, Diameter spindel 40 mm, Spindel sepenuhnya dapat diatur, Mesin dilengkapi 2 rol pendorong di meja, cocok untuk kayu basah, Feed menggunakan poros kopel dengan pengaturan, Mesin ditawarkan dengan kepala pemotong yang terpasang pada spindel, Kopel dalam kondisi baik, mesin berjalan lancar tanpa getaran, Mesin serut kokoh dan orisinal, berat sekitar 3 ton. Kondisi sangat baik.

Kondisi: baik (bekas), Tahun pembuatan: 1998, Fungsionalitas: berfungsi sepenuhnya, Four-side planer Weinig Hydromat 23 strip laminating machine 8 spindles, Working width: 230 mm, Working height: 160 mm, Spindle diameter: 50 mm, Feed system: 7.5 kW / 6 – 36 m/min, Spindle arrangement: 1- Bottom (7.5 kW) 2- Right (7.5 kW) 3- Left (7.5 kW) with profile jointer 4- Right (7.5 kW) with profile jointer 5- Top (7.5 kW) with hydraulic clamping 6- Bottom (30 kW) with hydraulic clamping 7- Top (7.5 kW) with hydraulic clamping and straight jointer 8- Bottom (7.5 kW) with hydraulic clamping and straight jointer. Hard coating. Two driven rollers in the table. Hjdpfjxqh E Hex Aazopa

Kondisi: bekas, Tahun pembuatan: 2000, Number of spindles: 6 units Working width: 230 mm Planing height: 120 mm Infeed table length: 2500 + 500 mm Feed motor: 3 kW Feed speed: 6–36 m/min 1 WEINIG Planing and Profiling Machine Unimat 23 E 6 spindles (including 2 on the right), powerful motors, EM 11 infeed magazine optional Working width: 20–230 mm Working height: 8–120 mm 1st spindle bottom 7.5 kW ----- Diameter: 40 mm Speed: 6000 rpm Tool diameter: 125–180 mm Rabbet facility incl. tool Hardened table insert in front of 1st bottom spindle 2nd spindle right 11.0 kW ----- Shared motor with left vertical spindle Diameter: 40 mm Speed: 6000 rpm Tool diameter: 112–250 mm Max. tool diameter behind fence plane: 203 mm Max. profiling depth: 35 mm Axial adjustment: 80 mm 3rd spindle left ----- Shared motor with 2nd spindle Diameter: 40 mm Speed: 6000 rpm Tool diameter: 112–200 mm Max. profiling depth: 35 mm Axial adjustment: 80 mm Pressure shoe before left spindle, incl. side pressure roller, spring-loaded 4th spindle right 7.5 kW ----- Diameter: 40 mm Speed: 6000 rpm Tool diameter: 112–250 mm Max. tool diameter behind fence plane: 203 mm Max. profiling depth: 35 mm Axial adjustment: 80 mm 5th spindle top 11.0 kW ----- Diameter: 40 mm Speed: 6000 rpm Tool diameter: 112–200 mm Max. profiling depth: 35 mm Axial adjustment: 45 mm Segmented pressure shoe before top spindle, adjustable to tool diameter and can be swung clear of tool, spring-loaded. 6th spindle bottom 7.5 kW ----- Diameter: 40 mm Speed: 6000 rpm Tool diameter: 112–250 mm Max. profiling depth: 15 mm Axial adjustment: 45 mm Spindles general ----- All profiling spindles feature high concentricity. Lubrication points for axial spindle adjustment. Vertical spindle length: 170 mm Feed system ----- Motor with mechanical brake, 3 kW Steplessly adjustable mechanical feed 6–36 m/min. Infeed roller before 1st bottom tool pneumatically controlled (high/low) Durofer pointed tooth rollers (Weinig patented) with depth limiter and self-cleaning Axial adjustment of feed rollers in relation to the left spindle: 35 mm Extension of the floating axis in relation to left spindles to 150 mm Machine electrics ----- Operating voltage: 380–400–415 volts, 50 Hz. Machine frame, tables and fences ----- Infeed table 2.5 m long (incl. jointer bar) Aluminum table extension 0.5 m for infeed table, incl. jointer bar extension Manual Waxilit pump for table resin removal One driven rubber roller (spring-mounted in outfeed table) Pressure elements and guides ----- Top pressure rollers, pneumatically actuated Top pressure rollers can be swung away opposite right spindles for easy tool change Machine operation ----- Hodpjwqr Rvefx Aazspa Pressure shoe before top spindle with mechanical digital readout Discharge after top spindle with mechanical digital readout ATS/E system, automatic 2-axis positioning for spindle No. 3 and 4 Min. working height: 12 mm Electric height adjustment for top spindles and feed Centralized lubrication points at machine front Safety and sound...

Kondisi: sangat baik (bekas), Fungsionalitas: berfungsi sepenuhnya, 11 Hpjdpfx Aajxz E Dnszsa

Kondisi: sangat baik (bekas), Tahun pembuatan: 2013, Fungsionalitas: berfungsi sepenuhnya, Tahun pembuatan: 2013 Kepala milling Area kerja X: 3000 Area kerja Y: 900 Hpodpfsw Npyqex Aazja Area kerja Z: 50 Unit terpisah: 1 Bor vertikal: 12 Bor horizontal X: 4 Bor horizontal Y: 2 Gergaji alur: Ya Mesin stasioner: Ya Sistem penjepit: Jangkar Pengaman: Fotocell Kontrol dan perangkat lunak SCM XILOG Luas minimum: 3920x1170x2150

Kondisi: baik (bekas), Planing width: 20–230 mm Planing height: 8–160 mm Number of cutter heads: 6 Cutter head arrangement: Bottom Right Left Right Top Bottom Number of feed rollers in the worktable: 4 Hpjdpfxjvbwzve Aazea Pneumatic hold-downs Hydraulic infeed

Kondisi: sangat baik (bekas), Tahun pembuatan: 2015, de-DE: Weinig Powermat 2400 Vierseitenhobelmaschine mit 7 Spindeln. (Baujahr 2015) 50 mm Spindeln, 6.000 U/min (kein Powerlock) Untere Spindel 15 kW + Außenlager Rechte Spindel 11 kW + Geradeausrichtgerät Linke Spindel 11 kW + Geradeausrichtgerät Obere Spindel 15 kW + Geradeausrichtgerät + Außenlager Hjdjxyik Aopfx Aazspa Untere Spindel 18,5 kW + Profilierlineal Obere Spindel 18,5 kW + Geradeaus- und Profilierlineal Untere Spindel 18,5 kW Geradeausrichtgerät + Außenlager 11 kW Vorschubmotor Automatisches Schmiersystem Elektrisches digitales Anzeigespeichersystem Optional lieferbar mit WEINIG Einzug und Auszug.

Kondisi: baik (bekas), Tahun pembuatan: 1993, Fungsionalitas: berfungsi sepenuhnya, lebar kerja: 230 mm, tinggi penyerutan: 170 mm, diameter spindel: 50 mm, lebar perataan: 230 mm, tinggi kerja: 170 mm, daya motor pengumpan: 7.500 W, jenis penyesuaian ketinggian: listrik, diameter poros mesin serut: 50 mm, jumlah spindel: 8, frekuensi input: 50 Hz, Perlengkapan: kabin, rem mesin, 8 spindles, Working width: 230 mm, Working height: 180 mm, Spindle diameter: 50 mm, Feed: 7.5 kW / 6 – 36 m/min, Spindle arrangement: 1-Bottom (7.5 kW) - scoring spindle 2-Bottom (7.5 kW) 3-Right (11 kW) 4-Left (11 kW) 5-Top (11.0 kW) 6-Bottom (22.0 kW) 7-Bottom (7.5 kW) Hsdpfxsr Axwne Aazepa 8-Top (7.5 kW) 8 powered rollers in table

Kondisi: bekas, Tahun pembuatan: 2010, 001 Hpodpfxewmggke Aazsa