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CNC + PLC Retrofit of Poreba Lathe/Deep Hole Borer

Machine Description:

The machine is primarily used for the deep-hole boring and surface-finishing of naval prop-shafts. It is approximately 60m in length, and consists of:

  • Main Spindle
  • Boring Spindle
  • Boring Feed
  • 1x Axis carriage with Phillips 3000 V200 CNC control without integrated PLC
  • 1x Axis carriage without CNC control
  • Motorised tailstock (removable)
  • Motorised Pressure-Head unit
  • Three main machine control stations situated at boring carriage and both axis carriages.
  • Three minor machine control stations situated at the Headstock, Tailstock, Pressure-Head plus two remote handsets.


  • To replace electrical cabinets and associated unreliable electromagnetics in entirety.
  • To replace current CNC controlled carriage with new CNC with IPLC
  • To upgrade second carriage to CNC.
  • To retain all pre-existing motors and newer Control Techniques Drives.
  • To allow Main Spindle to be controlled from any of the main control stations depending on which one is active.
  • To allow machine errors/messages to be viewed at both CNC stations and at HMI device mounted on main electrical cabinet.

Additionally, as all the electrical drawings were in a state of disarray, and written in a combination of German and Czech, then these also had to be translated and organised beforehand.


The image to the left shows the machine viewed from the headstock end. The removable tailstock and pressure head are visible in the middle distance, with the boring carriage at the far end of the factory.

CNC carriage 1 (after retrofit) can be seen to the left of the headstock.

Initially the customer wanted the CNC upgrading on axis carriage 1, as the old CNC was proving to be very unreliable.

As the machine was already fitted with Phillips optical scale for position feedback, it was decided that a newer Phillips 3000 V500 CNC control would be the most economic solution.

The image to the right shows the headstock of the lathe with the old electrical control cabinets mounted up on a mezzanine level to the rear. These can also be seen in the image below.

The customer was initially reluctant to fully upgrade the electrical system on the machine as they'd been told 6 months downtime by other companies who had previosly quoted for the work.

Robtec felt confident that with careful planning beforehand, the machine downtime could be limited to 4 weeks.

After deciphering the original electrical drawings, the planning of the new control system could begin.

Both CNC carriages were required to behave independently of each other, but share control of the spindle. Carriage 1 was to be given master control, with Carriage 2 able to control when Carriage 1 was either switched off or disabled.

When neither of the CNC carriages were in use, then the boring carriage would also be allowed to control spindle speed.

A PLC system within the main electrical cabinets would control the interlocks between the 3 main control stations, as well as all the secondary machine functions (hydraulics, lubrication, tailstock motor..etc).

A Mitsubishi Q Series PLC system was selected as the most appropriate solution.

New electrical drawings were completed, and the original wiring numbers were all carefully noted and reallocated.

As much assembly as possible of the new electrical cabinets were completed in Robtec's workshop beforehand, in order to save time when on site.

Once ready, the disassembly of the old electrical cabinets could begin.

All incoming wires were carefully labeled and bundled according to their location to save time when wiring into the new cabinets later on.


The old electrical cabinets were removed with the use of a crane, and the new ones mounted on the mezzanine level in their place.

The new cabinets only take up half the space of the original ones as a great deal of the old relay logic is replaced by the PLC. In addition, the drives for the axis carriages were being moved down into smaller electrical cabinets on the carriages themselves.

During the installation, Robtec was able to provide multiple engineers on-site to assist with the wiring. This allowed the cabinets on the CNC carriages and the main electrical cabinets to be wired simultaneously.

Towards the end of the second week, the most of the reassembly within the main electrical cabinets had been completed, and the incoming power cables could be reconnected.

Carriage 1 (which had already had the CNC fitted) had been re-wired for the new system configuration.

Carriage 2 had been fitted out with reader-heads, a reference switch and new optical scale along its X axis. The new cabinet and pendant unit had been installed, and wiring was continuing in preparation for the start of commissioning during week 3.


The machine was ready for commissioning mid-way through the third week.

The commissioning process took 1 week before Robtec engineers were happy to allow the operators to start to use the machine.

Full training on the new system was provided, and the project completed within the allocated time-frame.