Automating Machines

Basic information relating to the upgrading and automation of propietary mills, profilers and lathes etc.

Section 1, Engineers Mills, Section 2, Auto-Routers etc.

The following information is provided for engineers and developers to review aspects of conversion of existing machinery in broad terms. There is additional information available for designers and technical developers of new devices.

Assesment of the machine you want to automate.

The machine should be in a serviceable condition.

Quill, this must have no slop or lateral movement.

The axial thrust and nose bearing must be 100%.

The alignment must be truly vertical.

The spindle should not run out.

Motor, This must be adequately rated and balanced ie. not vibrating.

Must have a no-volt controller.

Controller must generate a motor fail signal.

Slides, should be set, free running and true.

Leadscrews, good quality ball-screws with adequate shielding.

Axial bearings shielded and 100%.

Preparing the machine and installing the electro-mechanicals.

Quill, this has to have a "Z" control fitted so the ICAM system can set down the quill to the correct depth for maching. The "Z" unit is commonly in two parts, on an entry level machine the end stop is pre set manually with the set down or plunge effected by an ICAM controlled air ram. A regulator will allow the plunge rate to be adjusted. On a fully programmable system the end stop for layered or 2.5D work is also controlled via ICAM often in 0.01mm steps. A number of files can be sequenced to make complex shapes or components.

The "X" and "Y" table displacement is controlled by the ICAM system using two integrated motor encoder units one on each axis. The motors move the table and the encoder units feed positional data back to the controlling system. The motor units may need "gearing" to achieve smooth performance. A "Transdev" toothed belt drive is preferred as this will not present with backlash. The motor-encoder units have to be attached solidly to the table. On small mills a high reduction transmission might be required and 20:1 is not uncommon.

Encoders tell the ICAM system where the cutting or milling head is, its direction of travel and velocity. Most installations have encoders mounted on to the Leadscrew/ballscrew shaft but alternatively they may be mounted as linear devices on the body of the machine with mechanical connections to the table. The encoders used on small mills can have 2000 or more lines per rev. TrueMotion ICAM units work on "change of state" and this doubles the resolving power. Our works engineer's mill uses 500 windows or lines but 100 can be tolerated. It is worth noting that auto-routers often use 50 or 100 lines per rev. The ICAM system will normally resolve to within +/- 1 line at mill cutting speeds! It is unlikely that the mechanics can ever match that! the accuracy of machining is therefore dependent on the ability of the mechanics to hold things true.

Notes:-

It is recommended to use 20mm or larger ball-screws on engineers mills because of the accuracy required.
It is sometimes better to use shaft mounted encoders than linear types as the latter can miss-read due to vibration.
Anti-backlash techniques including "bunging" should be considered on older machines.
Pneumatic "Z" set down is superior to electric actuation for most operations.
Pneumatic "Z" set down is recommended for auto-drilling or multiple sinks as faster and less prone to wear.
ICAM automation systems are much more cost effective on large mills than small ones.
ICAM "Draw and Go" systems enables you to automatically or manually control a mill using touch screens.

In Conclusion

ICAM systems are used on engineers mills but they tend to be installed on larger machines devoted to high production or prototyping. ICAM is better suited to bridge mills and particularly for prototyping as the "Draw and GO" facility makes for very cost effective operation. TrueMotion is not recommended for driving small mills.

If you are going to automate a small engineering mill as a hobby machine and can spend time entering number strings with codes and be content to make the same machine pass several times to get depth, tolerate the ocasional wobble and run out, then a stepper drive will be fun! Use the line shafts supplied on the machine as re-fitting with expensive ball-screws will be uneconomic.

Should you want a small machine with tool autochanging for continious production then there are some very good machines on the market for as little as £25k +VAT. The "Draw and Go" is extra!

TrueMotion ICAM is a closed loop device (as are servo systems), the controlling computer gets feedback from encoders. Stepper systems have no feedback so no error correction is possible, messing up happens!

If you have a bridge mill and a lathe in your workshop a single ICAM device can be switched to drive either unit. (Cannot drive both at the same time but does give the workshop user additional diversity for the cost of a few hardware components).

Finally it is worth noting that a TrueMotion ICAM unit can turn a mill into a very good server for a face plate lathe as it can cut and produce a tolerably good blank from sheet stock ready for turning.

Assesment of the machine you want to automate

The machine should be in good condition, presenting without wear or backlash with good bearings and smooth slides. There may be issues with imperial or metric measure and this will need to be resolved before conversion.

Because of the diversity of machine types and drives attention should be given to:-

Parts that may be serviceable but cannot be replaced without major work.

Non standard components or imperial calibration.

Unsafe fittings.

Parts designed to operate only manually.

Stock hold down mechanisms.

Components using high air or hydraulic pressures.

High voltage control gear.

This list is only a guide, it is likely there will be other important matters that need to be addressed.

Preparing the machine and installing the electro-mechanicals.

the "Z" control will need to be fitted so the ICAM system can set down the spindle or router to the correct depth for the maching. The "Z" unit is commonly in two parts, on an entry level machine the end stop is pre set manually with the set down or plunge effected by an ICAM controlled air ram. On a fully programable system the end stop for layered or 2.5D work is also controlled via ICAM.

The "X" and "Y" table displacement is controlled by the ICAM system using two integrated motor encoder units one on each axis. The existing motors will most likely need to be changed to move head gear. The encoder units feeding positional data back to the controlling system will need to be changed or re-mounted. Both "X" and "Y" motor units may need new gearing to achieve the required traverse rates. when re-gearing use a "Transdev" toothed belt drive as this will not present with backlash.

Bridge type mills can suffer from "racking" under load so check for this, the work bed should be checked for creep or dish, this is not so important with auto routers where the sole plate is positively loaded and not flying.

Notes:-

It is recommended to use ball-screws when very accurate machining is required.
Ball screw units should be sealed or clean air, positive pressure fed to ensure they do not choke.
Avoid the use of ball screws for stone machines. (See designing stone machines).
Use 100% sealed ball screws for MDF/HDF machining.
It is sometimes better to use shaft mounted encoders rather than linear types as the latter can miss-read due to vibration.
Pneumatic "Z" set down is softer and superior to electric actuation for most operations.
The accuracy of ICAM can be considerd to be absolute for most purposes, unlike mechanics.
Machines with large mechanical spans tend to become very expensive if accuracy is to be maintained.
ICAM automation systems are much more cost effective on large machines than small ones.

In Conclusion

ICAM systems tend to be installed on medium sized machines and are particularly good at prototyping because of the systems agility. ICAM is a boon for prototyping as the "Draw and GO" facility enables modifications to the parts being made to be carried out almost instantly.

TrueMotion ICAM is available in several formats enabling you to carry out multiple sequential operations without operator intervention.