The present invention relates to a safety apparatus and to a safety method, and is concerned particularly, though not exclusively, with a safety cabinet and safety method for use with an additive manufacturing device, such as a three- dimensional printing apparatus.

Three-dimensional printing is a form of additive manufacturing in which three dimensional objects are created by the computer-controlled joining or solidifying of liquid, or powdered material according to a set of data. One example is known as fused filament fabrication, in which an object is built up, layer by layer, as a continuous filament of thermoplastic material is precisely deposited by a moving print head that defines the shape in two dimensions, before moving in the third dimension to begin the next layer.

Various polymer materials are used in the process, and examples of machines capable of three-dimensional printing are now available in desktop sizes and are widely used in laboratories, classrooms workplaces and homes.

However, concerns have been raised about the release into the surrounding atmosphere of particulates and volatile organic compounds (VOCs) as the filament is deposited.

Embodiments of the present invention aim to provide a safety apparatus and method for use with a three-dimensional printer, in which the abovementioned problems are addressed. The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto .

According to one aspect of the present invention, there is provided safety apparatus for use with an additive manufacturing device, such as a three-dimensional printer, the apparatus comprising an enclosure having at least one air inlet, at least one air outlet, a fan arranged in use to urge air into the enclosure through the inlet and out of the enclosure through the outlet, and a filter unit placed between the inlet and the outlet.

Preferably the filter unit comprises a particulate filter, more particularly a HEPA filter. The filter unit may include a volatile compound filter, more particularly an activated carbon filter.

The enclosure may comprise one or more walls, a floor and a top. The enclosure preferably has an openable door which may be hingedly mounted on the enclosure and is more preferably removably mounted on one or more hinges.

The enclosure may comprise a frame for supporting the or each wall and/or the floor and/or the top and/or the door/hinge .

One or more walls and/or the door and/or the roof may include a viewing panel, which may comprise transparent PETG or Polycarbonate material. Preferably the fan is located on the top. The filter unit may be located on the top. In a preferred arrangement the fan and the filter unit are located inside a housing which is preferably located on the top.

The apparatus may comprise a fire extinguisher located in the enclosure. The fire extinguisher may be arranged for automatic activation and may be controlled by a thermally sensitive device within the housing.

At least one, and preferably at least two side walls may include air inlet vents.

The apparatus preferably comprises an electronic controller for controlling/monitoring/communicating one or more operations of the apparatus in use. The apparatus also preferably includes a memory device for storing data and/or instructions .

The filter unit may be removable. The apparatus preferably includes a monitor device for monitoring the condition of the filter unit. The monitoring device may be arranged in use to detect/estimate a condition of the filter unit by one or more of: measurement of elapsed time, sensed current drawn by the fan and/or sensed pressure drop across the filter.

The apparatus preferably includes a data logger, which may comprise an electronic processing device, to log events such as, but not limited to: time/length of use, fan speed, sensed fan current, detected pressure drop and/or warning messages. The apparatus preferably comprises a display for displaying one or more of: warning messages, temperature, humidity, operational time, theoretical filter remaining time, fan current/ speed.

In a preferred arrangement, the apparatus is provided with an interface for connecting the device to an external device or network. The interface preferably comprises an RS232 serial output.

The apparatus may include a communication module for communicating wirelessly with an external device.

The invention also includes a method of operating an additive manufacturing device, such as a three-dimensional printer, the method comprising locating the device inside an enclosure of a safety apparatus according to any statement herein and activating the fan while the device is in use, so as to capture particulates and/or volatile compounds produced during operation of the device.

The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent .

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a front perspective view of an embodiment of safety apparatus in the form of a safety cabinet, in accordance with one embodiment of the present invention;

Figure 2 shows the safety cabinet of Figure 1 in a rear perspective view;

Figure 3 shows the safety cabinet of Figures 1 and 2 in a different configuration;

Figure 4 is a different view of the safety cabinet of Figures 1-3 ; and

Figure 5 shows schematically a filter unit for the cabinet of Figures 1-4.

Turning to Figure 1, this shows generally at 100 a safety cabinet, in accordance with an embodiment of the present invention, for use with a 3D printer (not shown) .

The cabinet 100 is generally cuboid in shape and comprises sidewalls 110 and 120, a top 130, a floor 140, a rear wall 150 and a hinged door 160, releasably mounted on hinges H. The sidewalls 110 and 120, and also the door 160 comprise transparent viewing panels of fire and impact resistant PETG (polyethylene tetraphthalate ) or Polycarbonate, whilst the floor 140, rear wall 150 and top are of steel. Steel frame portions F hold the cabinet together and it is supported on four adjustable feet 170 at its lower corners. Mounted on the top panel 130 is a combined fan and filter unit 180 which in use is arranged to draw air from around the cabinet 100, through inlet slots S located at lower edges of each of the sidewalls 110 and 120. An additional inlet slot (not shown) is located immediately below the door 160 above the floor/base 140. At a lower part of the rear wall is a cable aperture 190 with a rotatable cover (not shown) .

Figure 2 shows the safety cabinet of Figure 1 in a rear perspective view. The rotatable cover 192 is shown together with a power cable 194. At the rear of the combined fan/filter unit 180 is an air outlet vent O/L and a combined power supply P/S for the fan and interior lighting (described below)

In use, a 3D printer (not shown) is positioned inside the cabinet 100 to rest on the floor 140. The hinged door is then closed and locked using a key (or press-button) lockable latch L. Power and control signals are provided to the printer via cables that enter the cabinet through aperture 190. When the door is locked in the closed position the combined fan/filter unit 180 is turned on, and air is drawn through the slots S, across the printer, through the filter and is expelled at the outlet O/L. The printer can then be used safely, with substantially no particulates or VOCs being released into the environment outside the cabinet.

Turning to Figure 3, this shows the cabinet 100 with the door lifted from its hinges H and removed, to allow a printer (not shown) to be readily loaded into the cabinet. Inside the cabinet, mounted on the rear wall 150 is a built-in automatic, self-triggering independent fire extinguisher 200, which is triggered by a thermally sensitive device in the form of a glass bulb (not shown) containing a heat- sensitive liquid that expands when it becomes hot, the expansion causing the glass bulb to break and thus trigger the extinguisher. The fire extinguisher 200 can be of any suitable type, such as but not limited to a powder or oxygen suppression gas system.

In addition, an optional independent electronic sensor 210 emits a loud alarm sound when the temperature within the enclosure rises beyond a threshold level. The threshold temperature for sensor 210 is set to be lower than that which would trigger the extinguisher, to allow remedial action to be taken in the event of an unexpected rise in temperature, prior to the extinguisher automatically activating.

Figure 4 shows the cabinet 100 from below and to one side, with one side panel 110 removed for illustration purposes. The door has also been lifted off its hinges and removed in this drawing. Inside the cabinet, mounted on the top panel is a lighting system comprising LED lighting units 220. This view also shows an air inlet I/L to the fan/filter 180. Mounted on the rear wall 150 is a bracket 230 for supporting the fire extinguisher (omitted) .

Figure 5 shows the combined fan/filter unit 180, in exploded view. A an electrically powered rotor 240 is arranged to draw air from inside the cabinet through a two-stage filter 250, which includes a High Efficiency Particulate Air (HEPA) filter portion, for capturing particulates, and an activated carbon filter portion to capture fumes such as VOCs . The fan/filter unit 180 is mounted inside a housing 260, on a rear wall of which is the air outlet vent O/L.

Optionally, the safety cabinet 100 may be supplied as a kit of parts (not shown) with assembly instructions, which kit can be flat-packed for transportation and readily assembled for use. This helps to minimise storage and transportation costs, which in turn keeps the overall cost of the unit down. The simple frame-and-panel structure lends itself to this approach, as does the design of the ventilation. In particular, since fan is arranged to draw air from the environment outside the cabinet (through inlet slots S) and to expel it through the outlet vent O/L after the filter has extracted particulates and VOCs, there is no need for a close-fitting seal around the walls and door of the cabinet. Because the extraction fan system, operating through the filter system, creates a significant negative pressure within the enclosure when the door is locked shut, any small gaps in the enclosure structure will not allow particulates or VOCs to escape. Instead, they are directed towards the place where the pressure is most negative, which is the inlet to the filter. This means that the tolerances and assembly standards are not such that specialist skill and/or knowledge is required for assembly.

The safety cabinet 100 is designed to protect against potential hazards associated with the use of all types of desktop 3D printers which may be presented to users and bystanders or visitors to the area in which the 3D printer is being operated. Furthermore, in maintaining a negative pressure inside the cabinet, as compared with outside the cabinet, the air cleansing system employed by the safety cabinet 100 provides the secondary benefit of cleaning, and thereby improving, the air in the surrounding environment, such as a laboratory, classroom or office.

The filters are numbered uniquely and matched to uniquely numbered safety cabinets in a database log to ensure that the filters are replaced in a timely manner, in accordance with stored data about the installation location and usage levels of the printer.

An electronic display (not shown) includes a countdown timer indicating the necessary replacement schedule for the filter, as determined by the usage and environment. The electronic display is also arranged to indicate the internal humidity and temperature within the safety cabinet.

In the example described, the fan is a centrifugal-type extraction fan and is specifically designed for a consistent airflow within the cabinet, so as not to detrimentally affect the quality of any 3D printing models due to air movements.

An important integral safety feature of the apparatus is that in addition to the protection of users and bystanders from exposure to particulates and VOCs the lockable access door also keeps unwary, unauthorised and inquisitive persons from the potential hazards of burns and traps associated with the mechanical and electrical working operation of a desktop 3D printer.

Exposed movement of the various 3D printer mechanical mechanisms and drive belt systems (trap hazard) and the exposed high operating temperatures of the 3D printer extruder nozzle heater system and heated build plate, which can vary between 50 degrees C and 300 degrees C (burn hazard) are both protected with the key-locked enclosure. The controller is preferably a low voltage DC powered unit capable of driving a fan at varying speeds, and monitoring a number of environmental factors, which may be made available to a user via an LCD display and/or individual LED indications.

The fan/filter extraction unit is removable in its entirety and may therefore be returned to the manufacturer for the information to be downloaded from the log and the filter replaced .

The hardware provides the following features/ functions

• Input power - 12V dc, 500mA min current. Note power is only available when extraction is to be provided.

• PWM (pulse width modulation) drive for a dc fan - 12V 300mA dc, max (the fan speed being user selectable eg. 50% to 100% in 10% stages)

• Measurement of fan current, which may be used to

identify that the fan is operational, and possibly whether the filter is blocked.

• Digital Temp sensor - e.g. with an accuracy of 0.5°C, and e.g. with a resolution of 0.1°C.

• Digital Relative Humidity sensor with accuracy of 4%

• Non-Volatile memory to store log of all operation

criteria and settings of extraction. iO • Real Time Clock with battery back up to enable

date/time stamping of operation log

• 2 x 16 character back lit LCD module (direct or

indirect mounting to PCB if practical via PCB mounting technique inside Filter housing)

• 3 x LED outputs for connection of separate indicators - or one RGB LED (connection to main PCB via 5mm terminal blocks or direct connection to PCB if practical via PCB mounting technique inside filter housing)

• 2 x 12V 1A switched outputs (Open collector - switching down to 0V) for activation of external modules, eg. Buzzer, Fire extinguisher (and including 'factory selectable' on PCB board Piezo beeper c.

108db - similar to domestic battery-operated smoke detector beeper (ideally 'factory selectable volume output for various beep warning uses including HIGH temperature warning inside Safety Cabinet)

• Push switch input

• Integral WiFi module

• Expansion port - via two low profile connectors to

allow for an external WiFi module to be connected

• RS232 connection - for manufacturer commissioning

and/or download of log.

• Differential pressure sensor - to test measurement of airflow through the filter.

All inputs/outputs may be provided by 5mm terminal blocks.

The basic operation is to monitor the operation time of the extraction unit, and report to the user once the preset filter operation time is exceeded. Additional

i i environmental information is also to be displayed via the LCD character display.

The following features are provided:

• The unit is operational once power is applied

• RTC operation.

• Log of operation of the filter.

o The log has a resolution of e.g. 15-minute intervals as a minimum

o The time the extraction unit has been operational o Any warning message

o User fan speed setting - i.e. fan PWM setting o All log events may be time/date stamped where

possible

o The log may be stored in NVM

• Temperature and RH are to be read from a digital

Temp/RH sensor

• The display shows the unit serial number (e.g. max 8 digits) for 10s at Power on. (all resettable - including all log information - when electronic module is recycled into a customer exchange intelligent filter unit)

• The display is arranged to normally scroll between the following messages:

o Temperature

o RH

o Cumulative time the extraction has been

operational

o Theoretical time remaining before the filter

needs replacing - unless over-ridden by 'filter blocked' warning

1:2 o Fan drive - PWM level (displayed in % - 100% being full speed)

• Additional warning messages shall also be displayed as appropriate

o If humidity is >55% then a message informs the user to store the filament away from the machine o If the temperature exceeds the user-preset

temperature alert, then display indicates an over temp condition and activates the on-PCB beeper and auxiliary output.

o If the fan is not operational (based on the fan current measurement) then the display indicates a possible fan problem and activates the on-PCB beeper and auxiliary output.

• Under normal operation the fan operates with a 100%

PWM signal. However, if the push switch input is activated then the fan PWM reduces to a user choice between e.g. 50% and 100%, until such time that the push switch input is activated again. 100% PWM signal for the fan will be restored on next power down / power up cycle

• The fan current is monitored via an ADC. If the

current is outside a safe operational window, then an extraction WARNING message is generated with PCB beeper output.

• LED output to be capable of having a PWM signal.

o Under normal operation then the LED outputs e.g. green .

o If the time remaining for the filter is within 90% of the filter operation period, the output is e.g. yellow. o If the filter operation time is exceeded or there is a problem with the fan (based on the current measurement) the LED outputs e.g. Red.

• Output 1 is to activate if the temperature exceeds a user-selected preset high temp point. The active polarity of the output will also be preset.

• Output 2 is initially to follow output 1.

• There is a serial output (RS232) which is to connect to a PC via a FTDI cable and run a basic manufacturers "app". The app is to provide a mechanism to:

o Download the operation time log

o Clear the operation time log

o Read/Write the serial number

o Set the filter operation period

o Set the high temperature value (and/or user selectable )

o Configure the active condition for output 1 o Configure the active condition for output 2 o The fan PWM level for normal operation (expected to be 100%)

o The fan PWM level for reduced operation (expected to be 50%) - user selectable

o The correct operating fan current window (100% operation)

o The correct operating fan current window (50% operation)

In order to determine the effectiveness of the

filter/extraction unit, and in particular whether the filter is blocked, one or more methods may be used alone or in conjunction: • Monitoring the current drawn by the motor and

comparing between a clear filter and a blocked filter. The fan motor would be expected to draw a greater current as the filter becomes more blocked.

• Monitoring the differential pressure between the

extraction unit and the outside environment. The pressure differential would be expected to increase as the filter becomes more blocked.

• The fan current will be an ADC value

• The differential pressure will be a I ² C interface,

typically using a SM9541 type device

In some embodiments there may be a WiFi module provided (either directly connected, or via a separate daughter board) . Some features are:

• Set the controller WiFi module as a Network Access

Point to allow connection directly to a mobile device for configuration of network parameters, and any specific local user settings.

• Thereafter the controller will ping messages to a

server to indicate the operation time and other environmental factors - in effect the onboard log will also be stored on a server.

• Users have access to their server account to view

performance characteristics of their extraction unit ( s )

• All communications are to be encrypted, and transfer is to utilise https mode.

• Provision for the server to provide firmware updates to the controller. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.