Thermoformer's forming area and speed overview

Choosing a thermoforming machine is challenging, especially if you are new to the industry. Suppliers publish an array of parameters on their websites and brochures, but comparing those parameters and their roles might be shady. In this article, we will try to give a short introduction to the basic parameters and how they affect your production.  

Through most of my meetings with fresh thermoformers since 2014, confusion and misunderstanding of parameters are one of the biggest problems. A skilled engineer with a rich background can discuss with suppliers for hours specific parameters and details. Still, when a company has just decided to jump into the thermoforming industry, there are things to start with, and they are not about aspects but general understanding. 

In this article, we will try to reveal essential parameters of vacuum- and plug-assisted pressure formers for the packaging industry and common mistakes with an understanding of parameters.

Thermoformer size. 

As you can guess, it is not about how big the machine is, but how many products you can produce in 1 cycle. 

Once you get the machine parameters, this is the first set of parameters presented by a supplier. 

Pay attention to the words: 

1. Max mould size (tool block size) – is how big can be the external dims of the tool
2. Max forming area (functional forming area) – is the space used to place products. 

As you can guess, those parameters are not the same. The Mould size is more extensive than the forming area, which is obvious. If you want to compare machines for the size, you should be careful with reading parameters. 

Thermoforming parts height. 

Another aspect is the depth of draw or your product’s height. 

Pay attention here to the names of the parameters:

3. Mould height – how high can the mould be? Precisely as it was with mould size, it refers to the tooling dims and not to your product. 
4. Max table opening – another technical parameter that doesn’t help you – shows the max distance between the top and bottom beams in the opened position. 
5. Depth of draw (max product height) – is the parameter you are looking for, and it tells you how high your product can be. 

There is no standard in the industry, and suppliers choose which parameter they put on brochures. Those figure and number games are not helping the supplier or the customer, but some equipment producers are still playing those games.

You are wrong if you think those two parameters are sufficient for placing products in forming area; there is one more group of parameters. 

Cutting capacity. 

This group of parameters is based on the closing of the top and bottom beams. Machine closing power is limited, and different material thicknesses and densities require various machine tonnage to cut. 

6. Cutting tonnage – The force in tons that the machine can release when closing beams. It is usually measured in Newtons or tons. The higher tonnage allows you to place more cavities on a tool but doesn’t tell you precisely the length of the linear knife. It is clear that 75 tons are better than 60, but how many extra cavities do you get with those 15 additional tons?
7. Max linear knife length -is the sum of cavities perimeters. Usually given in meters, but it doesn’t specify material and thickness. Tricky, isn’t it? 
8. The cut graph – the actual parameter you need to compare machines and clarify how many products you place on your forming area. You can never find it in a brochure, but you can get it by request from a supplier. 
9. Dies heating option – If you can heat the cutting dies to 130-180 Celsius, you increase your cutting capacity. 

The number of cavities placed on a tool.

With all parameters above, we finally clarify how many cavities we can place on our tool and get the answer to the question: “How big is the forming area of this machine.” 

When a thermoforming company says I need the most significant forming area – they don’t mean it. They say that they want to have max possible # of cavities. Usually, the bigger forming area gives you a bigger tool with more cavities, but only to a specific limit. If your product is big and you can place 2-12 cavities on a mould, it is all about the forming area. But once you work with small products and you can place 20+ cavities on a tool, the cutting capacity becomes the constraint. There is always one constraint in any system; the focus should be not on a particular parameter but a limiting factor. 

If a supplier tells you that his machine has an 800×600 forming area while their competitor’s forming area is 760×530 (19% higher forming area), it doesn’t mean that you will be able to place an extra 19% of products on a forming area. If an 800×600 machine has less tonnage or linear knife length than 760×530, then for small products, the cutting capacity of the first machine will be the same or even less. 

Remember, when you compare thermoforming machines, your goal is to get as many products on a tool as possible; this is the focus, not the forming area. 

Thermoformer’s speed. 

The speed is measured in cycles. One cycle includes heating, forming, cooling, cutting, and stacking products. Once you have clarified how many products can be placed on a tool, you want to know how many cycles the machine can reach. It is usually measured in cycles per minute. Once you start to explore machine parameters, you can find a parameter called “dry cycle.”

10. Dry cycle – shows how many cycles the machine can reach without a mould. The higher the dry cycle is, the higher your speed is. What is wrong with the dry cycle? It tells nothing about the actual speed of the machine. 

As mentioned above, the speed depends on many aspects of the thermoforming process, and most don’t rely on machine parameters. Depending on the type of material and its thickness, the time you spend on heating changes. So to get an idea about cycle speed, you need to consider additional parameters: 

11. # of shots in the oven – tells you how many indexes material stays in the oven to heat up before it gets to the mould? If you can index material in the oven four times, you get better heating and reach a higher CPM than three shots. 
12. Oven length – how long is the heating oven, and how many shots are heated before the material gets to the tool? If you can index material four times before it gets to the mould, you heat material more than if you can index it only two times. 

But every tool has its length in the material direction, and your oven is 2,5 meters; you can index material six times for a 400mm tool and four times for a 600mm tool. 

Usually, we calculate # of shots with the max possible mold length. But if you know your products, it is much better to get the tool layout and calculate precisely # of shots for your case. 

Once we have clarified heating, we must consider the material’s cooling. The mold is cooled with water supplied by the chiller, and depending on water flow and tool design, you get cooling capacity. 

13. Machine water flow, measured in liters/minute. The higher water flow allows you to reach higher CPM. No matter how long the oven is. If your water flow is 50 liters/minute, you will get a lower CPM than the machine with 100 l/minute. 
14. Tool water flow. Same parameter but for the mold. Remember that the tool’s design must keep up with the machine’s water flow. If your tool’s cooling channels can process less than the machine, it becomes a limitation. 

We should remember that it relies on the material when discussing cooling and heating. 

15. Material thermal conductivity – is how fast your material can heat up and cool down. You don’t need to go deep in material physics. Just remember that speed of processing for PP is much lower than for other materials, and PP requires additional heating that is provided by a preheater. So for PS and PET, your speed can easily reach 40 CPM, while for PP, speed is between 15 and 30 CPM. 

One more thing that affects your speed is your machine and tool configuration. Here is some basic information: 

16. FCS machines – the forming and the cutting process are in separate stations. It allows you to cool material on the way to the cutting station and get a speed increase. It is straightforward to heat the dies and increase the cutting capacity of FCS machines.
17. IMC machines form and cut in one station, and their speed is usually slightly lower as some processes can’t happen simultaneously. Another thing with IMC is that heating the dies is not always possible – heat from the dies transfers to the tool, and the mould starts to expand, losing parallelism and cutting.  
18. Upstacker – the classic stacking option doesn’t have a speed limitation, but for some products is not appliable. 
19. Robotic stacker – robotic arm picks the products and places them on a conveyor belt, sometimes with rotation. The robotic stacker has a speed limitation (30-40 CPM, depending on the technology). Running at max CPM for a robotic stacker can cause extensive wear out. 

To sum up the ideas about machine speed, here are some conclusions:

• Don’t chase the dry cycle – it is a marketing parameter, that tells you nothing
• Check your product, material, machine, and stacking requirements first. Some products require IMC configuration for precise cutting, and others need FCS type due to product design. Those might set the limitation for your speed, and in this case, the machine’s speed is something that you don’t care much. 
• Check the heating oven size and calculate the number of shots for your tools and products, don’t rely on general info.
• Check the machine’s water flow and your toolmaker’s awareness of these parameters. 

Now, when you know basic concepts for thermoformers’ size and speed, the choice process should beclearer and more straightforward for you.