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Prevention of webbing

admin — Wed, 13 Jul 2011 15:21:13 +0000

Webbing is prevented just by setting on the machine:

- reduce compression speed,

- prevent too fast cooling down of material.

Webbing is prevented by screens in the clambing frame:

- limit forming area, so that geometrical compression conditions will be more favourable, … so that the “initial tent” will be smaller.

Webbing is prevented by design change:

- apply larger radii on the upper side of the mould so that geometrical compression conditions will be more favourable,

- change mould is such a way that webbing looks like purposely implemented reinforcement rib,

- create more surface in the lower section on that the webbing area can be used up.

Webbing is prevented by changing the mould in the waste area:

- build up mould higher so that webbing will form in the waste area ( this is only possible if the coresponding section will be severed),

- tear webs apart.

This can be effected with 2 artificial elevations ( e.g. hemispheres ), one right and left each of the web.

Similarly successful might be a wide recess below the web.

Webbing is prevented by means of the pre-stretching plug:

- according to the basic principle: ” you may press small webs, you have to pull large webs”,

- the pre-streching plug must be propably used in combination with negative moulds, especially for long, negatively formed groove-like recesses.

Webbing is prevented due to heavy sagging:

- if the surface of a heated material is larger than the surface of the forming tool, there will be surface webbing. This is the case, when sagging is severe and the mould is flat,

- the solution is to mounth the mould at an increased height so that there will be a larger forming surface ( mould + increased height). It should be at least the size of the material surface generated by sagging.

Positive and negative forming

admin — Mon, 30 Aug 2010 09:13:37 +0000

During thermoforming process only one side of the processed material contacts the mould. Its shape and texture are therefore reproduced on the surface of formed sheet or foil.
Depending on the side of material that contacts the mould we deal with positive or negative thermoforming.
During positive forming the inside of the blister becomes an exact mapping of the mould shape because this side contacts the mould. In case of negative forming it is the opposite and the outside of the blister is reproduced on the surface of the sheet – foil.
Following issues should be taken into consideration when positive thermoforming is taken into action:
• Creation of shrinking effects in case of rectangular moulds, especially if distance between clamping frame and the mould is significant
• Development of chill marks on the edges
• Uneven thickness of the walls on blister rims
• Uneasy detaching of the blister out of the mould caused by small angle of the wall
• Too shallow areas (not completely formed) between the areas of multi-cavity blisters, whose reduction is possible only through employment of additional clamping frame
• Positive forms are usually cheaper to make than the negative ones
Following issues should be taken into consideration when negative thermoforming is applied:
• Development of thick rims
• Eden thickness of the walls aroung the rim
• Development of thin edges
• Easy detaching of the moulds with single forming areas
• Łatwy demontaż form o pojedynczych obszarach formowania
• Negative forms are usually more expensive to make than the negative ones
Most of the setbacks can be reduced or eliminated through application of appropriate mould production techniques as well as control of the thermoforming process.

Table for the Thermoformer

admin — Mon, 12 Jul 2010 14:30:10 +0000

					OPTIMUM TOOL TEMPERATURE °C
LETTER SYMBOL	THERMOPLASTIC	DENSITY [g/cm3]	TENSILE STRENGTH [N/mm2]	ELASTICITY MODULUS [N/mm2]	ILLIG UA/SB	ILLIG RV	ILLIG RDKP	ILLIG RDM	ILLIG HSA/FS	PROCESSING SHRINKAGE [%]
PS	Polystyrene, standard	1,05	55	3200	70	-	-	15	-	0,5
OPS	Biaxally orientated crystal PS film	1,05	57	3200	65	-	65	40	-	0,5
ABS	Acrylonitrilre-butadene-styrene	1,05	39	2300	85	35	25	15	-/15	0,6-0,7
ASA	Acrylonitrilre-styrene-acrylester	1,04	32	1800	75	30	25	15	-/15	0,3-0,7
PVC U	Polivinyl chloride (hard)	1,39	58	2400	85	25	25	15	35/15	0,4-0,5
PVC P	Polivinyl cloride (soft)	1,2	14		50
HDPE	Polyethylene high density	0,95	28	1000	80	30	25	15	-/15	1,2-7,0
PP	Polipropylene	0,91	30	1200	90	(25)	25	15	-/15	0,8-0,4
PMMA extr.	Polymethyl- methacrylate extruded	1,18	72	3300	80	35	25	15	-/15	0,6-0,8
PMMA wylewany	Polymethyl- methacrylate casted	1,18	80	3300	85	-	-	-	-	0,6-0,8
POM	Polyacetal	1,41	66	3000	100		100	40		1,5-1,2
PC	Polycarbonate	1,2	61	2250	130	(125)	125	40	/120	0,9-1,1
PA (6) (66) (11)	Polyamide (6), (11)	1,13	78	1400	100	-	-	-	-	0,8
APET (G)	Polyethylene terephthalate amorphous	1,33	30	2200	65	35	20	15	35/20	0,4-0,5
CPET	Polyethylene terephthalate crystalised	1,37	47	3000	-	-	170/160	-	-	0,3-2,0

What is thermoforming?

admin — Mon, 23 Nov 2009 09:08:19 +0000

Thermoforming technology basics

Thermoforming is a process, in which the plastic film or plates are pre-heated to a certain temperature that softens them in order to be formed into products of specific shapes. Due to relatively simple and cheap processing this technology is commonly used in large-scale production. Depending on the technical solutions required and the scope of processing one can conduct both single unit manufacturing and mass production.

Thermoforming of large products is done in two stages: heating of the material and forming of the final product. Processed material is fixed on the edges of the forming area. Heating is executed through electrical infrared heaters located at a distance of ca. 125 mm (5 inches), on both sides of the plastic sheet. Heating softens material and its time depends on the type of material, its thickness and color. White boards absorb infrared radiation much slower than dark-colored items. The darker the plate, the shorter the heating cycle gets.

There are 3 basic types of thermoforming process:
● Vacuum forming
● Pressure forming
● Mechanical forming

Usually a combination of methods is used as it improves productivity and quality of the products.

Stretching of the plate during thermoforming changes the thickness of the material, usually reduces it deeply formed areas. The process is fully controlled and deviations are determined already at the stage of product design, tooling and selecting the forming technology.

During the vacuum forming we apply:
● negative tools (representation of the shape and dimensions of the product takes place on the outer side of the sheet)
● positive tools (representation of the shape and dimensions of the product takes place on the inner side of the sheet).

What is a blister?

admin — Mon, 23 Nov 2009 09:03:30 +0000

There are products that do not require fancy packaging. A blister makes a perfect solution in such case. Blisters are formed in accordance with products dimensions. They display the products inside in a clear and appealing way. All details of the product are visible without removing the packaging.

Take a look at our gallery we present packagings made of hard plastic foil. Material in use is usually PVC or PET, colored or transparent. Its thickness usually varies between 0.2 – 0.5 mm. Construction of the blister enables sattaching it to cardboard by sealing it or inserting into slots in foil.

Blisters have numerous forms, they can be sealed, closed, snaped, inserted or glued. Packaging of such kind are: sealed with the cardboard, blisters with folded edges, capsules, little boxes with separate or joined lids, and bottoms.

Blisters make a simple yet common type of packaging. They lack the charm that is provided by the carton packaging, various colored bags or sophisticalyy printed packages with labels and graphics.

Yet they are a very good solution when the most important detail is the product displayed inside.