Thermoforming Workshop

Alan McKinley: Hi, everyone. My name is Alan McKinley and I am a product manager at aPriori with a focus on developing our manufacturing process models. Today, I am excited to talk to you about sheet plastic thermoforming with the focus on our recent improvements to the aPriori manufacturing model. The agenda will focus on a quick overview of thermoforming, a review of the challenges we face with the existing cost model. A summary of the enhancements we have made before a detailed look and demo of the enhancements. Before we look at thermoforming in aPriori, I want to give a brief overview of the applications and benefits of thermoforming. As you can see from the pictures on the left-hand side of the slide, thermoforming is applicable across multiple industries and a common manufacturing method in our customer base.

Cost Effectiveness

AM: Example parts from different industrial sectors include agricultural, vehicle panels, and bulk containers. Automotive with dashboards and bumper covers. Aerospace with the likes of seat panels. Medical with equipment enclosures and equipment trays. Consumer durables with suitcases, home appliances, and toys. Thermoforming is typically used for mid to low-volume production volumes and has a number of benefits. So it is cost effective at low volumes compared to injection molding due to significantly cheaper tooling. It has typically fast lead times to production readiness. It is lightweight and a great corrosion resistant alternative to some sheet metal parts. It supports complex shapes and deep draws. It can produce large parts.

AM: It has a wide range of materials available to fill required design, aesthetic, and mechanical properties. And it has excellent reproducibility. So the Sheet Plastic Process Group was introduced to aPriori in 2012, so over 10 years ago. We can see that a quarter of our customers are licensed for the process group, but our actual usage of it is much lower than expected. When we reviewed our current customers, we found a common theme of high configuration of the model required to be successful and these configurations were primarily working around usability and accuracy issues of the model. And we decided to do a full overhaul of the cost model so that it better represents the industry as it stands today.

Types of Forming Machines

AM: With improved and intuitive user inputs resulting in more precise simulations, providing our customers with decreased time to value, and reducing the amount of configuration required in the model. To achieve this, we have the following five areas of enhancements that we introduced in 2023R1. So we updated our out-of-the-box materials to be in line with industry expectations. We improved how we are accounting for material costs. We have improved and added more types of forming machines in the baseline digital factories to better represent the manufacturing standards of today. We have improved and added more post-processing and finishing processes to the model. And finally, we have updated our tooling model to be mechanistic and in line with all their cost models, such as injection molding.

AM: Looking across these five areas of improvement, all of them contribute massively to the usability of the model and accuracy. I would now like to deep dive into each of these areas in more detail before a quick demo of our new model. We have three primary areas of improvement in our material stock and material utilization. The first area is a notable change in supported stocks. Our previous model had resin pellet stock types, where aPriori simulated the melting and extrusion off the pellet stock to create a sheet stock for forming. The new model now just uses sheet stocks directly, which better represents our customer use cases and is much easier to configure. We have also improved our material coverage by adding four new material types to the digital factory.

Nesting Algorithm

AM: The second area of improvement is our stock selection. Previously, the model considered the part size and finished part thickness to assign a stock. We now have enhanced logic that importantly accounts for the material thinning during the forming process, hence, we select a thicker stock size that will thin down to the finished part thickness during forming. And finally, we have added the ability to nest parts on a single sheet. Previously, the nesting ability was defined by routing logic, which is hard to use and had hard-coded nesting computation. We have improved this now so the end user can simply specify the number of parts to be nested together, aPriori will then use the nesting algorithm to determine the best orientation and to maximize the utilization of the sheet.

AM: We also produced an output of the nesting diagram for the end user to consume. One important new feature with nesting is dynamic spacing of the parts based on the part size. This really helps us represent reality and ensures that the part is manufactured without issues, such as webbing, which can be seen in the image on this slide on the top right. Just pointing to it now with my cursor, you can see webbing happening in between these parts as they are spaced too closely together to form the material. I would now like to review the general manufacturing process before getting into the specific changes made in the aPriori cost model. The general process for thermoforming is shown in the top image.

Thermoforming Machines

AM: So a sheet plastic stock of appropriate size and thickness is loaded into the thermoforming machine. This sheet is positioned under an infrared heater until the temperature is high enough to form it. The sheet is then moved into a forming station and a vacuum is applied through the mold forming the plastic after which it is allowed to cool. The formed sheet is then unloaded from the thermoforming machine. After the thermoforming machine, the next step is an optional vertical bandsaw process to separate the sheet into individual parts. This is used when multiple parts are nested in one single sheet, as shown in the middle image. Note, this is a brand-new process added to the thermoforming process group to better simulate the industry standards.

AM: Finally, a CNC router builds the final trimming process, removing any excess material and creating holes in the part. Again, this process has been significantly improved with an added perimeter GCD extracted during our geometric extraction process. This results in an improved cycle time computation for our CNC router. And I will show and talk more about this during the demo. Previously, aPriori supported single station forming only. We now support four different forming stations as alternative routings. And out of the box we select the forming machine, which results in the lowest fully burdened costs. The four forming machine types are shown on this slide and are as follows.

Machine Configuration

AM: On the top left, we see a single station where the sheet is loaded and transferred between the stations in series as it is heated, formed, and then cooled. This machine configuration can only process one sheet at a time. Below that, we see a shuttle station where a single oven station is located between two forming stations. This configuration, which is also referred to as a double ender, allows the heating of one sheet to occur in parallel with the loading, forming, cooling, and unloading off of the previous sheet. This machine configuration requires at least two tools and can process multiple sheets in parallel.

AM: The diagram on the top right depicts a three-station rotary machine, where the sheet material is loaded in station one, automatically rotated to station two, where it is heated, rotated further to station three where it is formed and cooled, and then rotated back to station one for unloading. And then finally below that we have a four-station rotary, which is similar to the three-station, except it has a dedicated loading and unloading station. At this point, I just want to reinforce that previously aPriori only had a single station forming machine, and now we support all four machines depicted in this slide. The final piece of detail I want to cover is our new mechanistic tooling model.

Tooling Costs

AM: So the cost to manufacture, assemble, and inspect the tool and individual tooling components is now calculated in a mechanistic model that considers the following factors: the design costs, the programming costs, material costs, labor costs, SGNA and markup costs. aPriori’s default assumption is that a positive tool will be used to form the part, and this can be seen in the bottom left-hand image. However, the end user can make a series of overrides to inform the cost model of the tool type being used, which in turn drives the tooling cost, but also, our part spacing assumptions, which we will see whenever we come to our live demo. The main user overrides for tooling are as follows. The end user can specify to use a negative tool to manufacture the part, as seen in the large picture in the middle.

AM: The end user can specify that the part will require a pressure box to assist with the forming, as can be seen in the left-hand images where a box is placed over the mold and air pressure used to help push the material into place. The end user can also specify the need for a plug assist when using a negative tool. This can be seen on the right-hand image and its common practice when parts require deep draw and need some assistance to help the material start getting down into the tool. Finally, the geometry recognition and the process group has been improved to identify the sides of the part and contacts with the positive tool versus a negative tool. This intelligence, coupled with the recognition of undercuts, allows our geometry extraction to identify when core pulls are required in the tool.

AM: Just for reference, this bottom right-hand picture is just showing a negative tool with core pulls retracting to allow an undercut feature and the part to be removed from the mold. Again, just to reflect on this slide, our tooling model accounts for all the tooling configurations shown on this slide. So that is positive tool with pressure box, negative tool, negative tool with pressure box, negative tool with plug assist, and negative tool with core pull. At this point, we are now going to move on to a short demo reviewing the key features in the slide deck. So in this demo we have a relatively simplistic sheet plastic, bucket-type part. And I have a ready cost of this part using our out-of-the-box settings. So aPriori USA is the digital factory.

AM: We have our default material and default volume and batch size. The first thing to review is our process writing selection window. In here you can see that aPriori has evaluated four different writings, one for each thermoforming machine type, and you can see that we have selected the cheapest option, which in this case is the three-station rotary thermoforming machine. You can see in the window that the vertical bandsaw has not been included automatically. That is because in this simulation we only have a single part nested on our sheet. You can also see that we have included automatically our CNC routing operation for finishing the part and manufacturing the holes in the part.

Perimeter GCD

AM: With that in mind, I want to stick with the routing process and move to our first new GCD, which is the perimeter GCD that is being selected on screen now. You can see when this GCD is selected that we have a purple line around the outside of the part depicting the perimeter that requires routing post performing process. The GCD has the length property, which the cost model then uses to calculate the cycle time of the routing process. In the manufacturing process pin, you can see router has been assigned to perimeter one, but also all the simple holes within this part. The next new GCD that we have introduced is the side GCD, highlighted on screen now is side one, which represents the outside of the part, and now side two, which represents the inside.

AM: So this side two with the inside will actually be representing all the surfaces in contact with the positive molds. Side one is the inverse of that. The final new GCD that we have is our core bundles, which are extracted whenever we have undercut features. You can see in this model we have a single undercut feature and that one feature results in two core bundles being extracted. And the reason we do that is to represent when a tool is required in either the positive or negative mold pipe. So in this simulation we have a positive mold and you can see that we have assigned a core pull to this core bundle. As core bundle one is on the inside of the part, which is in contact with the positive mold.

AM: In this simulation core bundle two, which is on the outside of the part, is assigned the as formed operation effectively, meaning it does not need a tool to be formed, it is just going to be formed automatically during the forming process. And we will see how those two operations switch whenever we change to a negative tool later in the demonstration. The next feature that we are going to introduce that is brand new to this process group is our material nesting diagram. You can see now in the bottom-right of our viewer, the material nesting diagram has been displayed. In the material nesting diagram, the blue line represents the outline of our sheet stock that is being selected for this given part, and the red line represents the outline of the part that will be nested before the forming process occurs.

Sheet Thermoforming

AM: We are now going to look at our main user inputs through our process setup options. So on our sheet thermoforming node, you see a number of process setup options. And starting from the top we have our number of parts per sheet, which is default at one, and in a second, we will change that. Below that, we have three options for changing the material stock that we select, so the sheet length, width, and thickness. You now see in the middle of the screen, the user can specify the mold type to be used, by default we have positive, again, we will change that to negative. Followed by three options to change the settings within nesting. We will not go into that detail today. And then towards the bottom, we see a PSO for pressure forming being required and plug assist tooling being required, which we will review slightly later in the demo.

AM: The first change we are going to make then is changing our number of parts to three and recasting this part. So what you will notice straight away is that our nesting diagram has been updated and also that our vertical bandsaw process has now been automatically included, where the vertical bandsaw will do the minimum number of cuts required to separate this nested sheet into its individual parts. You can see in our nesting diagram we have three parts shown in red and one in grey. What this is showing us is that this given sheet stock can actually fit four parts into it, but because the user has specified three, we are actually under-utilizing this sheet and that will drive a higher material cost.

Pressure-Forming

AM: So the first thing that I am going to change just for the purpose of the demonstration is moving this to four parts per sheet and re-costing. And we will see once this is finished costing that the nesting diagram is updated to show that all four parts are nested on the sheet, which is great. And in our cost summary, we can see that we have a significant reduction in material costs with our increased utilization of material. The next user override I want to look at is the need for having a pressure-forming box in the process. So this is currently simulated with a positive mold. I have just set the pressure forming required to be true, and we will see that once this is finished costing, that our total capital investments have increased.

AM: That is because our tooling calculation is now accounting for the cost of having a pressure-forming box as part of our manufacturing process. Now getting into a little bit more detail, we are removing this override and setting our mold type to be the negative mold type and we will see a couple of main changes in the UI. The first is our material nesting. You can see that the part spacing has reduced significantly, and that is because, with a negative mold type, we will not have an issue with webbing as shown in the presentation as material is getting drawn down into the mold. This allows us to nest the parts a little bit closer together. The other change that you will notice is the designation of process for our core bundles.

Plug-Assist Tool

AM: Core bundle one that was on the inside of the part is now on the air side of the molding process, which is assigned as formed. Core bundle two, that was on the outside of the part, the other side of the part that has the negative mold is now assigned the core pull operation. So we are dynamically deciding how to manufacture these core bundles that we have extracted. And finally, for today’s quick demo, I want to look at the addition of a plug assist tool. So this is quite a deep drawn part, so it is most likely with a negative tool, it will need plug assist to help push that material down into the mold during the forming process. The result of this is, again, that you can see we have a significant increase in total capital investment costs of the simulation.

AM: And again, this is due to aPriori simulating the cost for that plug assist tool in our tooling model. So that is a very quick review of all our user overrides and some key overrides for expert users that know exactly how the model will be manufactured in real life to try and get their simulation as accurate as possible. For anyone who has been interested in availing of the enhancements in our sheet plastic thermoforming in this presentation, please reach out to your customer success manager. They can help with upgrading your software to the required version if needed, and they can help organize the sheet plastic thermoforming license again if you do not already have it. I would just like to thank everyone who has made it this far for listening.

Thanks, everyone, and bye for now.