Selecting a CNC Machine

Working envelope

What is the maximum job size you will need to manufacture? Tt's worth trying to plan ahead and decide what type of work you will be doing in the future?

Will you want to do multiple jobs?

As a rule of thumb, the larger the cutting area or bed size the more expensive the machine.

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Maximum

Job size

X

Y

Z

Multiples

What materials will be cut?

This question seems very straightforward but often catches people out because they purchase based on the work they do today and not what they could be doing next month or year.

Cutting soft materials such as wood, plastic is normally fine for most machines, but cutting steel usually requires a heavy duty machine.

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Materials

Wood

Foam

Plastic

Aluminum

Steel

Positional accuracy

For very fine engraving the resolution of the motors that position the cutter is crucial to the final product quality, and a precision on 0.0002" (0.005mm) might be required.

Where as, cutting wooden panels may only need an accuracy of 0.005" (0.1mm).

Typically the more precise the more costly the machine will be.

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Accuracy

0.005"

0.001"

0.0001"

0.1mm

0.01mm

0.002mm

Control system

Most new CNC machines have PC based control systems that run from industry standard file formats such as ISO G-Code or HPGL. Making them very easy to use and compatible with most software solutions.

If the control system is proprietary (unique to the manufacturer) it's worth asking whether it will work with 3^rd party software solutions.

Another consideration is whether the controller can be networked to your PC, to enable quick and easy file transfer directly from the design software. Or does there need to be a DNC (Direct Numerical Control) link from the PC to the controller?

Data processing Speed is also a factor, especially for high speed / volume product or complex 3D work, where large toolpath files are commonly used.

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G-Code

HPGL

DXF

Stepper

Servo

Speed

Accuracy

Quality

PC based

DNC link

Data

processing

speed

Spindle speed & power

When cutting finely detailed products the engraving has to be done with very pointed conical / D-bit tools. This type of engraving has to be done using very high spindle speeds, typically over 20,000 rpm and up to 60,000 rpm depending upon the material being machined.

The power rating for the spindle is also crucial. For high volume material removal rates the spindle needs to be very powerful, but not necessarily very fast (rpm).

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10,000 rpm

25,000 rpm

60,000 rpm

1 Kw

15 Kw

Tooling / Cutters

How many different tools will be needed to produce your typical jobs?

For example, a furniture maker may need an Ogee form tool plus various drill sizes and cut-out tools, which need to be loaded automatically. But an industrial engraver cutting Brass may only need roughing and finishing tools and can simply change the tools manually.

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Automatic

ATC

Carousel

Rack

Manual

Table type

How will jobs be held on the table?

Will you require a vacuum table, vice or special fixturing?

Vacuum tables are often used in the Sign and Wood industries because they are very powerful and easy to use. But you will need to decide how powerful the vacuum pump needs to be and for how long it will be continuously used.

Most engravers will simply use a vice or a chuck to hold the work.

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Vacuum

Table

Vice

Chuck

Fixtures

Magnetic

2 Sided

Tape

Technical support

This is possibly the most important, but often overlooked factor to consider when deciding what machine to purchase.

If the machine breaks down, which it inevitably will because at the end of the day it's constructed from moving parts. How long will it take to fix?

Is there a Support Team in your region? How soon can a Service Engineer be on-site? How long do spare parts take to deliver?

Lost business due to machine failure or down-time can be very costly and may never return!

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Spare

parts

Support

Advice

Time = $'s