1.0 Product Description and Operation

1.1 The product is a desktop CNC drill, intended for printed circuit boards and drilling of other thin sheet materials. Drilling co-ordinate information is generated in a CAD package, and exported via HPGL (Hewlett Packard Graphics Language). The HPGL file is loaded into an parser application that controls the drill operation, and sends the appropriate data to the parallel port. The data is fed to an interface/driver PCB, and on to the drill, as in the diagram below.

 

Figure 3.1- Top level operation of CNC PCB drill

 

The blank PCB material is held by a gripping mechanism, and the drilling starts upon instruction from the user via the PC software.

2.0 Market

2.1 The target markets for the product are those of small scale PCB prototyping, sheet material prototyping, home workshop, hobbyist, small scale production of any drilled sheet material. Manual drilling of PCBs is an especially time consuming process. This makes automation of drilling very productive, and suited to computer control.

2.2 See the chapter on Market Research for more information.

 

3.0 Performance

3.1 General

Max. material Size

150mm x 150mm

Max. material thickness

3mm

Edge border required

5mm

3.2 Drive System

No of motors

2

Motor type

4 phase Permanent Magnet Stepper

Steps per revolution

200

Phase Excitation V

12V

Current per phase

0.7A Max.

Repeatability

0.1mm

Resolution

0.1mm

Running Torque

1.16kgf cm min

Static Torque

0.12 kgf cm

Load inertia

0.003kgf cm2

Excitation

2 phase, software controlled

Speed X direction

25mm/sec

Speed Y direction

25mm/sec

Running temperature

75 deg. max

Winding DC resistance

5ohm per winding

Pulse per second

TBD (half wave op)

3.3 Drill

No load speed

6000 rpm

Torque at stall

100g/cm min

Supply Voltage

12V

Drill bit size

0.5 - 3mm

 

3.4 Drilling Performance

Max No of Holes per minute, in 2mm x 2mm rectangular array

30

Time for 4 x 1mm holes in corners of 10mm square

5 sec

3.5 Power Drive Electronics

Control Connector

25 way sub D type

Step Mode

Half Step, software controlled

Motors and drill

12V DC 3A

TTL components

5V DC 1A regulated and smoothed

PSU Power Supply

240V 50Hz

 

3.6 Drive Software

Output port

Parallel Port, defaults to &378 address (user definable by software)

Input File Format

HPGL, (possibly Gerber)

Input File Length

Limited by RAM

Channel Data for Motors

4 bits O/P per motor

1 byte total

Channel Data for Drill

1 bit O/P for spindle, 1 bit I/P for drill depression and return sensor

Channel Data for Limit Switches

4 bits for limit switches

 

Figure 3.2 - The core software interface model

 

3.6.1 Minimum Computer Requirements (IBM AT/XT compatible)

CPU

386 - 16Mhz

RAM

1MB min. free

Hard Disk

1MB min. free

Monitor

VGA Mono or better

Operating System

MD-DOS v5.0 or later

3.7 Misc. Features

3.7.1 The product shall have a removable drill head and a plate with holes suitable for mouning customer designed heads.

 

3.7.2 The product shall have a swarf tray, to allow easy removal of debris. see 5.1 and 5.2

3.7.3 The product shall have a graphical user interface front end to software

4.0 Environment

      Operating Temperature Range

      0C to 60C Ambient

      Operating Humidity Range

      10%to 90% RH

 

4.2 The machines operation and performance should not be adversely affected by dust and dirt.

4.3 The machines operation and performance should not be adversely affected by being dropped from a height of 300mm onto a carpet tiled concrete surface. Test by pushing of a the edge of a desk and by being released by hand from the mentioned height.

5.0 Maintenance

5.1 The product should require minimum maintenance, but removal of swarf tray is required when it becomes full

5.2 The swarf tray shall capture all particles and not allow contamination of the drive mechanism or the material vice.

5.3 All bearings must be replaceable.

6.0 Target Product Cost

6.1 The product’s suggested retail price is £250 ex VAT

6.2 Total direct cost of product is to be less than £80

7.0 Competition

7.1 A company called Dolphin Systems sell a CAD/CAM/DNC mill, lathe, engraver for £595. This is aimed at model engineers, but could be used for PCB drilling.

7.2 CNC products with similar market positioning are EMCO lathes and milling machines, which retail at £2650 and £3500 respectively.

7.3 T-Tech produce a 'Quick Circuit System' costing £8200 ex VAT. It can mill tracks and drill holes. (no need for masking/etchant and so on) It also has an accessory for producing through-hole inserts on double sided boards.

7.4 See drill product benchmark in the Market Research Report.

8.0 Quantity

8.1 The estimated volume of sales/production is 1000 per year, selling within the EU.

9.0 Size

9.1 The product’s footprint shall fit inside a 300x300mm square.

10.0 Weight

10.1 The product's weight is to be 6kg max

11.0 Aesthetics, Appearance and Finish

11.1 The product shall have a painted finish to any sheet metal parts visible to the customer.

11.2 Harnessing/wiring shall not be visible wherever possible and shall be securely fastened to avoid catching on any moving parts.

11.3 Wiring shall be of a sufficient power rating and colour coded to show function.

11.4 Sheet metal parts shall not have any sharp edges or corners. All burrs to be removed on parts that customer can touch.

12.0 Materials

12.1 Materials used in the product shall not become stained discoloured or react with human sweat.

12.2 The chassis shall be made primarily of painted sheet steel parts, given the relatively low volume of units.

12.3 The shall be no custom injection moulded parts due to the high cost of tooling and low volumes estimated for this product.

13.0 Product Life Span

13.1 The product should last for 4 years given 1 hour continuous operation per day, i.e. 1460 hours operation, before servicing.

13.1.1 The product shall be capable of 6 hours continuous operation allowing drill bit replacement and raw material replacement.

13.2 Standard replaceable parts will include motors, bearings, driver/interfacing PCB, drill chuck

13.3 Consumable parts are drill bits and drilling substrate, e.g. blank PCB

14.0 Standards and Specifications

14.1 The product shall conform to the CE standard

14.2 The product shall confirm to EU standards on electromagnetic emission, i.e. Part 15 of FCC rules.

15.0 Ergonomics and Human Interface

15.1 The only human interaction with the machine shall be the insertion and removal of PCBs, and the removal and replacement of drill bits.

15.2 There will also be a hardware interrupt push button that cuts power to the motors and halts operation in an emergency.

 

16.0 Customer

16.1 The following are likely users of this type of drill:

16.2 See Market Research chapter for more information on the customer requirements (Figure 2.2)

17.0 Quality and Reliability

17.1 The drill shall be capable of 6 hours continuous operation at 23 deg. C and 50% relative humidity, with no loss of accuracy or repeatability, while drilling holes in a 2mm rectangular array

17.2 The drill shall have a software-based drill wear timer, and warn the user if the drill is becoming worn. (hardware solution a possibility...)

18.0 Testing

18.1 The product shall be tested to ensure that the performance specification is adhered to. Testing schedule to be defined at a future data.

19.0 Safety

19.1 The product shall have the case, chassis, or exposed metal parts grounded.

19.2 The PSU shall have a 1A slow blow fuse

20.0 Installation

20.1 The product shall be packaged/delivered/sold in a black printed cardboard box, adequately packaged with the following items

20.2 The product shall come with software on 3.5" HD floppy disk, and be installed automatically by running a file called setup.bat from DOS

20.3 The software shall have a self test routine, with software diagnosis of any problems, reporting to the user any corrective actions required.