PET is tough to trim. (Thermoforming Troubleshooter).
Ironically, the toughness of PET also poses the biggest challenge to its success in replacing other transparent amorphous polymers, namely, high efficiency and trouble.
Free parts trimming.
The muscles of the formed PET package are visible from its convenient packaging in Hinge egg cartons, fruit and vegetable flap, separated and edible food trays, and hardware products such as nails, nuts, etc. bolts
The toughness of PET is the key to replacing PVC, hips and OPS, as PET is the best choice when the package has hinges or snap
Suitable function or must meet extended durability and shelf-
Requirements of life.
Prospects for pet
The lower oven temperature required to form the PET sheet further increases the PVC (450 F vs. 600 F)
And into a shorter cycle of formation that reduces energy use.
The processing advantage of PET comes from its lower glass
Conversion temperature than PVC (158 F vs. 170 F)
The thermal conductivity is higher.
In addition, recycled PET is ideal for reuse in transparent packaging.
Finally, the PET board runs on thermoforming equipment for PVC, HIPS and OPS, with only minor modifications to the hardware and processing parameters.
However, its toughness also makes the pet a bear that needs to be trimmed.
When PVC, hips and OPS are crushed-
When cutting, 50% of the mold penetration thickness is usually enough to get clean particles-
In contrast, the mold has to go through almost 100% of the PET thickness to have a clean break (Fig. 1).
Due to the greater force and strain applied to the mold, the trimming behavior of the pet will have adverse consequences
This means that mold damage and wear rate are usually higher than other materials.
The trim cycle is usually longer for pets.
Pet Trim should be assigned to the well-Well-trained workers
Because the mold has to touch the cutting or forward plate evenly to ensure that the pet is cut clean and avoid damage, accurate \"make\"
The \"preparation\" of die-cutting boards is crucial.
Prepared procedures are essential for efficient pet trimming.
Improper pruning produces particles in the form of Blur, angel hair and dust that pollute the trimming waste and reduce the quality of the final part.
Imperfect trimming also often results in edge defects, so the edges or perimeter of the part is damaged, resulting in a higher scrap rate.
Therefore, it is essential to systematically solve the pet trimming problem.
Only when the user selects the right mold, this promising material will maintain momentum in the thermoforming packaging market
Cutting method and perform proper dressing procedure.
Choosing a trimming method the three most commonly used methods for trimming PET include the use of steel
Regular mold, forging mold and matching moldmetal dies.
The first two ways are to kiss\"cut\" or \"clamp-cut\" action--i. e.
, Force the mold through the paper to contact the precise point of the cutting plate at the tip of the mold.
This board is usually heated for PET, and the PVC rarely needs to be heated. Kiss-
Cutting is usually the best for low
To intermediate levelVolume program. Steel-
Regular trimming uses a sharp knife that is usually installed on a laminated wood template.
Cutting is usually done in the appropriate place (in the mold)or in line.
This method usually requires moderate skills, low cost, and best suited to a lower level
Batch Application. A central-or double-
It is recommended to use an umbrella steel mold with a hardness of 50 to 55 °c.
Thin sheet (under 0. 01 in. )
Or complex parts, only 45-
The hardness of 50c will reduce the chance of mold fracture.
Another choice for Kiss
Cutting is fake. steel die.
This is usually a cut. in-
Using the heating substrate placement method, the intermediate function is bestvolume uses.
Forged metal molds are commonly used for \"hot-assisted\" die-cutting mode--i. e.
, The mold initially touches the PET sheet at low pressure and waits while heating from the base plate to the cutting point.
Heating softens the plate and makes it easier to cut.
After a short delay, high
Pressure cut finish trimming.
It is critical to keep the substrate temperature slightly lower than about 160 F the PET sheet is attached to the plate.
The preferred material for the cutting board is 58 C Rockwell (or higher)tool steel (
Short Life of aluminum, easy to split).
The hardness of the cutting plate should always exceed the hardness of the mold, because this minimizes the damage of the plate and the depression of the die slope.
The insulation of the substrate is recommended to improve the control of the heat level (i. e.
, Avoid PET sticking to the board)
Optimize energy use.
Ideally, the death force of a kiss
The cutting will push the mold through the part continuously and completely, but will not exceed the part.
Extra force to bend or darken the cutting edge or mold quickly.
A common rule of thumb is that the die length per line inch uses a force of 400.
Although it is difficult to accurately measure shrinkage, it is important to compensate for the part shrinkage that occurs between forming and trimming.
A common practice is to assume 0. 3% to 0. 6% shrinkage (or 0. 005 in. /in. )in PET sheet. Matched-
The third choice in metal molds
The PET parts that are cut and formed are matchedmetal die (MMD)
Method, also known as punch-and-die cutting.
MMD is usually the most reliable and fastest way to trim PET parts.
But it needs a separate cutting machine that continuously shapes the paper through it.
This is more capital.
Dense than other pruning methods, making it the most suitable for higher pruning
The most popular method in MMD is to combine harder blows (i. e. Rockwell C)with a softer (43 C)die.
The key need is to keep the minimum mold gap at all times.
This includes a process called impact that allows to restore the minimum gap by spreading the edge of the mold back to its original size using airOperate the hammer.
MMD cutting is sometimes done using equal punch and die (62 C)
Hardness, maintaining a minimum clearance through the continuous re-surface of the mold and punch.
Coining is a technique for reducing the required cutting force and extended matchingmetal die life.
It takes place during the forming process, including by designing the ridges into the pressure box, thinning the area to be cut up to 50%.
When the pressure box is clamped onto the mold, the part is wound.
Other simple but easily overlooked rules in pet trimming are to always keep the mold sharp and use properly protected cutting equipment to maximize mold life.
Effective trimming of pet parts is inevitably an attemptand-error process.
Larry Coster is v. p.
Marketing and Sales at Lavergne group in d\'Anjou, Queville.
The company compounded the thermoplastic and extracted the original and recycled-
Content PET table.
Lkoester @ please contact the author. ca.