Formech answers the more frequently asked questions (FAQ's) encountered during the forming process

FAQ's

For those new to vacuum forming or existing customers experiencing problems, this section provides an invaluable and fast reference for questions relating to Formech machines, the vacuum forming process, general enquiries and after sales service. We have tried to be as comprehensive as possible, however, there are no doubt questions raised for which the answers are not provided.

We would, in this instance, request you call us on +44 (0)1582 469 797 or click here to contact us.

Although in this section we cover the more frequently asked questions encountered during the forming process you can find a more comprehensive trouble shooting guide contained within the vacuum forming manual which can be requested by clicking here.

If your question is specifically related to a machine or service query, then please refer to the relevant machine manual which is available by clicking here. The manuals provide general, electrical and pneumatic fault diagnostics for each model.

Please select one of the areas below to view answers to some of the more frequently asked questions:

Forming

Q How long does it take to heat the plastic sheet?
A	This depends on which material and thickness is specified. A general guide to different materials and their approximate heating times with single heating are included in the Plastic section 4 of the training manual. Please contact us to gain access to it.
Q How do I know when the plastic is ready to form?
A	Generally speaking it is necessary with any new material to establish the correct heating cycle. Plastic is ready to form when it becomes soft and pliable. This is known as its Tg (Glass Transition Temperature). Once you have established the time you can set the heater timer for accurate and repeated heating cycles. You can find further information on this in the Plastic section 4 of our training manual. Contact us for access to it.
Q Why is the plastic webbing on the mould?
A	Material is too hot. Insufficient vacuum. Excess of material. Poor mould design. See the Trouble Shooting Guide in section 7 of our training manual. Contact us for access to it.
Q Why can't I achieve good definition on the finished part?
A	Material too cold Mould too cold. Insufficient vacuum. See the Trouble Shooting Guide in section 7 of our training manual. Contact us for access to it. Back to top
Q Why is the plastic thinning over the mould when formed?
A	Sheet cooled whilst forming. Mould design. Insufficient draft angles. Too thin gauge. No pre-stretch used. No plug assist used. See the Trouble Shooting Guide in section 7 of our training manual. Contact us for access to it.
Q Why does the plastic bubble and pit when heated?
A	Material is Hygroscopic which needs to be pre-dried prior to forming. Overheating.
Q Why does the plastic stick to the mould when I try to release?
A	Mould not fixed on baseboard. Mould not fixed to table. Insufficient draft. Mould undercuts. Poor mould quality. See the Trouble Shooting Guide in section 7 of our training manual. Contact us for access to it.
Q How easy is it to change the mould?
A	Moulds can be changed in a matter of seconds. If screwed to the table then a few minutes are required to make the change. Back to top

Plastics

Q What plastics can I use?
A	Any thermoformable grade of plastic. Ideally amorphous but also semi crystalline materials can be formed. See Plastic in section 4 of our training manual. Contact us for access to it.
Q What thickness can I use?
A	Up to 6mm with single heater machines and 10mm with twin heaters. Click here to refer to our full product range.
Q What is the thinnest material suitable for use on your machines?
A	We normally recommend a minimum thickness of 0.25mm for plastic. If skin packing then as thin as 100 micron can be used Back to top
Q Who supplies the plastic?
A	There are numerous material extruders and stockists offering a wide variety of thermoformable materials and grades. Stockists offer a wide variety of materials in smaller quantities. Extruders offer large quantities for production requirements. See the list of Suppliers in section 8 of our training manual. Contact us for access to it.
Q Why do I need to pre-dry the plastic before forming?
A	Some plastics are known as Hygroscopic and retain moisture which can surface as blisters on the material during heating. If so then pre-drying is required. Please consult the relevant supplier or contact us to access our training manual where more information can be obtained.
Q How much material should I allow for clamping?
A	We recommend approx. 20-25mm on each side. With thicker materials this may need to be increased to prevent the plastic pulling out of the clamping area. Back to top

Moulds

Q What material do I make the moulds from?
A	Moulds can be made from plaster, wood, resin and aluminium. See section 5 of our training manual for further information. Contact us for access to it.
Q What should I make the mould from? How many parts can it produce?
A	The application and quantity required determines which type of mould material needs to be used. Wood is ideal for prototype applications and small series up to 500 pieces. Resin or aluminium are ideal for larger quantities and production runs.
Q Should I use a male or female mould?
A	Male moulds are cheaper to produce than female moulds and are more suited to a single deep draw object. Female moulds would typically be used when multiple cavities are required. Both have different thinning characteristics. See section 5 of our training manual for further information. Contact us for access to it.
Q What is plug assist?
A	Plug assist is a male tool plug situated over the forming area of the machine, to force the material into a female cavity within the moulding area. Plug moulds are generally made from wood.
Q When should I use a plug assist?
A	Plug assist enables complicated and deep draw moulds to be produced without webbing and with even wall thickness distribution. The idea behind the process is to feed as much material into the cavity prior to the vacuum being applied in order to avoid thinning in that area. Back to top

Machines

Q Why am I losing vacuum?
A	Check seals. Check mould is vented. Check vacuum is at full strength. Check clamp frame is tight and both front/rear clamps are correctly adjusted.
Q Why does the plastic pull from out of the clamp frame?
A	Check clamp frame is tight and both front/rear clamps are correctly adjusted. Check material being used is extruded NOT cast. Cast material is not suitable for vacuum forming with single heater machines. Check the sheet size is large enough and has sufficient clamping area. Insufficient heat time.
Q Why do I need a timer?
A	The timer is incorporated into most models as a standard feature. The timer ensures accurate heating cycles on a repetitive basis, ideal for production runs. The timing cycle is set by pushing the + or - buttons above and below the respective display digits. A buzzer indicates when the heating cycle is complete.
Q What does the Auto Level do?
A	The Auto-level detects sheet droop during the heating cycle and injects a positive pressure into the chamber to hold the sheet level whilst heating. Useful when forming thicker materials which tend to sag when heat is applied. Essential when forming semi-crystalline materials like PP which are very heat sensitive and can sag in different areas during the heat cycle. Back to top
Q What is the advantage gained by having the Pre-stretch/bubble facility?
A	Pre-stretch enables the operator to blow the plastic prior to forming eliminating side wall thinning and chill marks. An essential feature when using deep draw moulds and those with deep draw ratios.
Q What are the reducing windows for?
A	Reducing windows are used to reduce the size of the forming area, in order to eliminate material wastage and also to help alleviate the problems associated with an excess of plastic, such as webbing. There are two parts to each set of reducing windows. The base plate is located on the machine forming area and the top plate is located on the clamp frame. Formech supplies a range of standard and custom reducing windows for each machine. Please contact us for further details
Q How long does the machine heater take to warm up?
A	From cold - 15-20 minutes / ceramic elements 5-10 minutes (quartz elements)
Q What are the heating zones for and why do some machines have more zones than others?
A	Most vacuum forming machines in the Formech range incorporate heating zones. They are used to give greater heating control. The heater unit is divided into independent zones, each containing a number of infra-red ceramic heating elements. Adjusting the zones controls the heating output to each zone.The number of zones depends on the size of the machine forming area. Heating zones are particularly useful when forming plastics with uneven heat characteristics, e.g. polypropylene. When using a reducing window the redundant zones can be switched off, conserving energy. Back to top