Daily Archives: July 19, 2017

The Basics of High Speed EDM Hole Drilling

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This article discusses how EDM hold drilling – designed for fast, accurate small- and deep-hole drilling applications – has become a whole new method of manufacturing molds and parts.

 

High speed EDM hole drilling was designed especially for fast, accurate small- and deep-hole drilling applications. Small holes that were once almost impossible to drill by conventional machine tools are now being performed with ease. With the capability of drilling through virtually any conductive material, the use of this technology is continually expanding.

 

Initially shops were using this technology specifically for start holes in wire EDM jobs. Because of this technology, workpiece materials are being sent out for heat treating prior to drilling the start hole. This removed two problems: (1) having to program, locate and drill the start hole by conventional machine methods in the “soft” workpiece prior to heat treat and (2) by sending the workpiece for heat treat before drilling the start hole, all the stresses were being removed from the workpiece prior to the EDM process being applied. As this process became more widely known, test burns were being done in more than just hardened tool steel; tungsten carbide, aluminum, brass and inconel were being tested. High-speed EDM hole drilling applications began to expand to mold and part manufacturing-injection nozzles, oil drain holes, hydraulic cylinders and dowel pins, as well as turbine blades, ball bearings and safety wire holes in hex nuts, to name a few.

 

Basic Features of the EDM Hole Driller Machine

  • Stainless steel work table
  • Rotating spindle
  • Drill chuck or collet system for holding electrodes
  • Ceramic or diamond guides
  • Power supply with control panel
  • Capacitor box
  • Dielectric fluid pump

 

The EDM Drilling Process

The process consists of using a precision tubular electrode (generally brass or copper) mounted into the drill chuck located on the “Z” axis and held in location on top of the workpiece by the ceramic guide. The top of the workpiece is located and the drilling depth is set. The electrode rotation is turned on and the deionized water solution, which is pressurized between 50 and 100 kg/cm2, is sent through the tubular electrode as a flushing agent. The power supply parameters are set-which normally consist of on-time, off-time, peak current and amount of capacitance. At this point, the discharge is turned on to begin the drilling cycle. At the end of the drilling cycle, the discharge is turned off and the “Z” axis is retracted above the workpiece.

 

Drilling Times

Drilling times are based on the hole size and type of material. Chart I lists a few samples for reference.

 

Chart I

Material Electrode Dia. Drill Depth Machining Time
Alloy Tool Steel .020″ 0.50″ 25 to 35 seconds
1.00″ 50 to 60 seconds
.040″ 1.00″ 55 to 65 seconds
Tungsten Carbide .020″ 0.50″ 4 to 5 minutes
1.00″ 8 to 9 minutes
Aluminum .020″ 0.50″ 40 to 50 seconds
1.00″ 90 to 100 seconds
.040″ 2.75″ 3 minutes

 

Observing the aforementioned times explains why high-speed EDM hole drilling has become an alternate method to conventional machining in mold manufacturing. In addition, this method of drilling produces burr-free holes, which results in the elimination of secondary deburring processes. Larger power supplies and drill/collet chucks have expanded the diameter range of standard drilled hole sizes from .010″ to .118″ to .010″ to .236″. EDM hole drilling can now be done on a manual, ZNC or CNC machine.

 

Today, many of the machines use distilled water as the flushing agent, which opens up new application possibilities in the medical field. With continued improvement in this technology, more and more applications are being seen on the horizon – EDM hole drilling has become a whole new method of manufacturing molds and parts.

 

If you need more information about drilling machine manufacturers or hole drilling, try to visit the website of EXCETEK, you’ll find what you need.

 

Article Source: http://www.moldmakingtechnology.com/articles/the-basics-of-high-speed-edm-hole-drilling

What Are CNC Rotary Tables And How Are They Used?

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CNC rotary tables are a key to automated machining. Before getting into the specifics of CNC rotary tables though, a brief discourse in the development and terminology of CNC machining will help from this point forward.

 

CNC is an acronym for Computer Numerical Control. It is the direct descendant of numerical control (NC) technology; think punch cards and magnetic tape. In turn, NC technology was invented to improve upon cam and tracer machine control in use at that time. Cam and tracer machining required construction of a template to trace and that interposed a costly, time-consuming step that had significant potential for human error.

 

Rotary Tables Defined

 

A rotary table is, as its name suggests, a table that rotates very accurately in concentric fashion around its center axis. In the high-accuracy, high-cost category of rotary tables, accuracy can mean radial runout – the amount of deviation from perfectly centered while rotating on the center axis – of 0.00004 of an inch and angular accuracy – degrees of rotation about the center axis – of 0.0002 of an inch. For the purpose of dampening vibration, the body of a rotary table is normally made of one of the “gray” iron grades. The rotating table plate is typically hardened, alloyed steel that is machined and rotary ground.

 

Purpose of CNC Rotary Tables

 

For automated machining, the entire purpose of CNC rotary tables is to provide a fourth axis. In addition to the normal axes of X, Y and Z, a CNC rotary table adds a rotational axis, known as the “W” axis, to increase machine accuracy and reduce costs. For example, using a CNC milling machine alone to make a stop sign-shaped piece would require moving the cutting tool around the piece to cut the vertical and horizontal sides and then cutting the angled sides by moving the cutting tool on a 45 degree angle as it is removing material. This requires eight machining passes. Each operation introduces a cumulative dimensional error for the sides parallel each other. Using a CNC rotary table for the same part means positioning the cutter in X or Y one time while rotating the part in 45 degree increments for each horizontal or vertical pass. Because it is cutting on only one side of the cutter in either X or Y, any machine tolerance error, tool wear and normal tool deflection from the forces of machining are reduce by half.

 

Spintop Machinery Co., Ltd. and Tanshing Accurate Industrial Co., Ltd. are professional manufacturers of rotary table, index table, and tailstock. If you are interested in learning more information about CNC rotary table or other related products, welcome to visit the website of TOPSDISK or Tanshing to obtain further details you need.

 

 

Article Source: http://www.cnc-rotarytables.com/