Vacuum Former

Description

The Formech 450 is a manually operated vacuum-forming machine that is capable of producing high quality plastic mouldings from material up to 18” x 18” with a maximum draw height of 9”.  Materials up to 3/16” thick can be specified.

The Formech 450 Vacuum Forming Machine in the SOA has a dedicated electrical outlet located under the desk in the Wood Shop near the East wall of the shop. When not in use, it is stored in the compressor room (Room 008C) to keep it clean but can be requested for use at any time during open Fab Lab hours.

The 450 incorporates powerful infrared ceramic heaters, which are thermostatically controlled in concentric zones. A powerful reverse-blow facility to release the moulding from the tool is integrated into the 450.

Incorporating the latest technology, the Formech 450 is ready to use in minutes, quickly producing prototype or production runs of components in a variety of plastics. A timer is fitted as standard.

The machine has been designed to be highly adaptable and functions such as changing a mould, or fitting reducing windows (which allow smaller sheets to be used) can be carried out in the minimum amount of time.

Safety

• Do not operate the machine until you have been trained and are fully competent with it. Seek the assistance of a shop technician if you are in any doubt.
• The heater and pump on this model are not intended to be left running indefinitely.
• Only use the machine for vacuum forming plastic. It is not intended for any other purpose.
• Ensure that the area you are working in is properly ventilated and that you are aware of the potential hazards from the materials you are forming.
• Always let the machine cool down before attempting to work on it. Some parts of the heater and heat shield become extremely hot during operation.
• Ensure that the area surrounding the machine is clean and frequently cleared of finished product and any scrap. Do NOT put any materials on top of the heater housing…this is a FIRE HAZARD!
• This machine is fitted with a dry running vacuum pump. Do not allow any liquid to enter the vacuum system. Ensure that molds are properly sealed to prevent ingress of dust into the vacuum circuit. Severe damage may be caused if the above is not observed.
• Turn off the machine and disconnect the power supply when the machine is not in use.

Operating Procedure

1. Turn the isolator / power switch (1) situated at the rear of the machine to the ON position.
2. Using the heater controls turn the zones on to provide power to the heaters. It usually takes about 20 minutes before the heaters have reached their operating temperature.
3. Place your mould onto the drape table. See the section dealing with mould design to ensure that your mould is suitable.
4. Place the table into the lower position by pushing the table lever (13) away from you.
5. Open the materials clamps (4) and raise the clamp frame.
6. Position a sheet of plastic over the aperture. See the section dealing with plastics to ensure that your material is suitable.
7. Pull the clamp frame down and close the material clamps. The plastic should completely cover the white seals around the aperture. Use the adjusting screws at the front and rear of the material clamps to properly grip the plastic.
8. After the heater has reached operating temperature, pull it forward over the plastic. (As the plastic heats up it will begin to rise slightly. It will then soften and begin to drop back.) If the heating cycle time is known then the timer can be set. Our machine is typically adjusted for the most commonly used materials…23-30 thousandths of an inch thick Styrene and PETG. The settings are optimal at 450 degrees on all 3 temperature zones, and 22 seconds on the timer.
   (If not using the timer push the heater back slightly to test the softness of the plastic. Continue heating until it is soft enough to form.)
9. At this point, push back the heater all the way. Turn on the vacuum pump (7) and raise the table (9) until you can feel it lock into place.
10. Let the finished moulding cool down a little, then pull the Vacuum/Pressure valve (6) downwards. This will blow air between the mould and the moulding and assist in removing the moulding. If the plastic is still too soft some distortion may occur. In this instance then reverse the pump to apply vacuum and wait till plastic has cooled sufficiently.
11. Finally, lower the table and release the material clamps to remove the finished moulding.

General Layout Image

Reducing “Windows” (Shrouds)

(I need to add photos and description of procedure here…)

Operating Techniques

Heaters

The powerful infrared ceramic heaters are designed to heat the plastic rapidly without burning the surface. The time required to heat the plastic sheet remains fairly constant once the heaters have reached their operating temperature. When using the full forming area it is advisable to keep the central zones 1 and 2 turned down slightly. These areas retain the heat the most and the outer zones lose the heat the fastest. When using reducing frames the zones not in use should be turned down. Always push heaters over rear heat shield when not heating plastic. Heating cycle times vary according to a number of factors. With a little experience, timings may be easily estimated. Some plastics such as styrene have a wide tolerance to heating times giving consistently good mouldings. Care must be taken with materials, which are Hygroscopic (retain moisture) such as ABS, as the surface will blister if the material has not been pre-dried. The moulding should be formed when the plastic is sufficiently ‘relaxed’ or at its ‘plastic transition’ temperature. A properly heated sheet will give an excellently defined moulding. If the sheet is not hot enough while forming, the moulding will not pick up all the detail from the tool.

Various factors will affect the heating time including the color and surface finish of the material. Operating the switch to the left of the timer panel turns on the timer. The timing value is set by pushing the ‘+’ or ‘-‘ buttons above and below the respective display digits. The value displayed represents the number of seconds elapsed between the heater being pulled forward and the sounding of a buzzer. The buzzer indicates that the heating cycle is complete and the heater may be pushed back. Timing value may be changed at any time although the new value will not be recognized until the start of a new cycle. When the heater is brought forward it strikes a micro switch, which starts the countdown. Do Not pull the heater forcefully or lift it upwards…it could damage the timer’s micro switch or de-rail the heater! Pushing the heater backwards or forwards will not interrupt the countdown.

Bubble moulding

With the 450 it is possible to produce bubble mouldings without using a tool. To form a bubble the plastic sheet should be heated with the drape table in the lowered position. When the plastic sheet has heated right through, raise the table, push back the heater, pull down the pressure lever and hold. Turn on the pump. The plastic will start to inflate.

Tools

Tools (Items to be formed, known as “tools” or “mould positives”) for vacuum forming should always be solidly constructed as the operating air pressure

reaches approximately 100 kg over an area 100mm x 100mm (one ton per square foot)

Hollow tools will collapse or “implode” under this pressure.

All tools should ideally be mounted on a baseboard. They cannot have undercuts and must be produced with slightly angular sides ('draft angle') to aid release. Vent holes are needed to allow the air to be evacuated from pockets and sharp angles on the tool.  Vent holes can be made with a drill. (See a shop tech for assistance.)

Providing these holes are kept small they will not leave marks on the surface of the finished moulding.

Tools made from wood or medium density fiberboard (MDF) are easily constructed and can give short runs of good quality mouldings at a low cost. (See note below)

The use of close-grained wood will avoid grain patterns appearing on the mouldings.

Insulation foam is often used for mould positives, but do not lend themselves to multiple castings, as the foam surface tends to melt during the first casting session. One way to avoid this is to coat the foam with Gesso and/or to use styrene as the first casting layer, and to leave this layer on the mould as a heat barrier, trimming the perimeter for subsequent castings. Vent holes will need to be re-drilled.

Plaster of Paris or other masonry products may be used for one-offs but the material must be allowed to properly dry out.

(See note below)

Metal tools have the advantages of carrying fine detail and being more resistant to both distortion and surface damage. Metal tools should be pre-heated before use. A cool metal mould will absorb some of the heat from the plastic sheet before it can take up the full definition.

Resin tools combine most of the advantages of metal moulds with relative ease of manufacture. Various resinous materials are commercially available especially for vacuum forming tool production.

NOTE: Porous mould materials such as wood and plaster should be properly sealed to prevent the vacuum pump from sucking out any moisture or sawdust, loose plaster etc. The vacuum circuit may quickly become choked with dust or slurry if moulds are not properly sealed. Repairs to the vacuum circuit can be costly.

As the plastic cools after forming it will contract, gripping the tool tightly. If the tool has been made with sloping sides and has a good surface finish it will release more easily. Where the draft angle must be kept to a minimum a release agent may be used to assist release.

Sealed moulds will usually release more easily. Silicon based release agents may be used on more difficult moulds. Silicon based release agents are rapidly absorbed by porous (unsealed) moulds, rendering them ineffective.

Plastics

Plastic sheet is commercially available in a wide variety of grades, thickness and colors. Materials such as styrene and PVC are most suited to vacuum forming. Other materials such as acrylic, polypropylene and polycarbonate will mould but difficulties may be encountered. The supply store in the SOA sells Styrene and Polyethylene sheets (PETG), which are ideal for vacuum forming.  (The Vacuum Forming machine’s heat zones and time settings are typically set for these materials.) The supply store also sells thin sheets of Acrylic, which work well, but settings of temperature and heating time will need to be adjusted accordingly.

It is not within the scope of this manual to attempt to list all the potential problems and their solutions. It is recommended that the newcomer to vacuum forming gains experience and confidence with easily formed materials before moving onto the more difficult materials.

Post Forming Operations

After forming, most plastics can be subsequently heat formed to add such details as folds or clips. Although many plastics can be printed, and in some cases painted, the presence of release agent used to help free a tight moulding may make the surface resistant to further decoration.

Trimming

An ideal moulding will be ready for use when removed from the machine and requires no finishing. However, most mouldings do require trimming before they can be used. There are numerous methods available for this process.

Thin materials can be trimmed with a sharp knife or scissors. Thicker materials can be trimmed using metal cutting shears, a coping saw or the Scroll saw, all of which are available in the Wood Shop. (See a shop tech for assistance.)

Heating elements

The infrared heating elements supplied with this machine are manufactured from a ceramic material and are very brittle. A shock to the machine may break an element.

Therefore, do NOT use this machine (or any machine in the Wood Shop) as a worktable!

Vacuum system

The vacuum system on this machine is fairly simple but uses high quality components throughout. The life expectancy of the vacuum system will be compromised by the ingress of dirt, shavings, dust, liquid etc.

Therefore, do NOT introduce any powdery or granulated materials, which could clog or damage the vacuum system!

Clean-up

When you are finished working at the Vacuum Former and surrounding areas, please clean up your mess.

Please be aware that there are 4 Trash barrels in this room, and that each one has a broom, bench brush and dust pan attached. You must use these items to clean up your work areas at each machine, when you are finished working there. Also, there are scrap barrels at each workstation to deposit scraps of material, which may be useful for someone else. Please do not put materials with stray hardware or glue on them, or food/drink items, only re-useable materials.