This is the first post in the series.
Let's start by saying that we understand that there are clear engineering considerations in choosing a raw material for a machined part. And yet, in cases where there's design flexibility, we will be happy to tell you what our favorite plastic materials are for us as manufacturers.
The materials listed in this post are the "most popular" for us. There are less common materials with which sometimes we work with them, depending on the needs of the client. Over the years there have been significant changes in the supply of materials, their quality, and also in the demands of the customers.
For convenience, we will divide the materials into three categories (of course, this is our internal division):
1. "The bread and butter"
2. The materials are less sympathetic for machining
3. The exotic materials
and by extension:
1. "The bread and butter"
This group is characterized by:
low cost
Easy to process (well machined)
Available in stock (extremely important since the Covid-19)
Natural materials without special classification of food, medical, military standards, etc., and without the addition of fibers of any kind.
There are several materials that are characterized by all of the above parameters. With most suppliers, these raw materials will come in a large number of dimensions and configurations (rods, plates, blocks). As manufacturers, we have the flexibility to buy the dimensions of the raw material that are most convenient for us to manufacture the product, and this flexibility lowers the final price for the customer.
These materials will usually be sold in a price range of up to NIS 100 per kilo (since the covid19 and problems in the global supply chain - the price of some of the materials has doubled and even more), and as I noted, they can be machined relatively easily. What it means? They have a relatively high dimensional stability and the wear of the tools in their processing is not particularly high, which can save thousands of shekels and more in serial batches performed on the same material.
Examples of materials from this family:
PVC
POM (known as delrin/acetal)
ABS
PET- (known as Ertalyte)
· Nylon 6 (known as Okolon)
POLYCARBONATE (known as Lexan)
PMMA (known as acrylic/perspex)
· Nylon 12
2. Materials that are less sympathetic for machining
These materials are characterized by one or more of the following parameters:
·Soft materials
Fiber-reinforced materials - armored (glass fibers, carbon, etc.)
Materials without a large supply of raw material configurations
The difference in the processing of soft materials to the processing of fiber-reinforced materials is very substantial, but in both cases the processing is not trivial and with the complexity the price also increases.
Soft materials require working with dedicated tools, different processing speeds and suitable finishing tools, but mainly what is needed when working with these materials is experience and familiarity with its behavior in front of the tool, such as the tendency of the material to spread during processing. When the work with the above materials is not correct, we will see suboptimal results that are manifested in low surface quality, wall collapse, crushing in particularly thin areas, and more.
Examples of materials from this family:
PE-Polyethylene
PP-polypropylene
PTFE-Teflon
Polyurethane
COC- Cyclic olefin copolymer (generally combines Teflon and polyethylene in its properties)
In the armored sector, there are two main problems and they are:
Tool wear and danger of damage to the machines themselves. The machines are sensitive to fibers because the chips of the reinforced material tend to find their way to the axes of the machine and they cause wear in the long run. On the other hand, many times it is precisely the dimensional stability created by the fibers that will facilitate the processing and laying of the parts. This is a consideration of the geometry of the part.
The most common armored materials we process are:
PEEK-GF 10-30
POM-C-GF
Nylon 66/12-GF 30
GRIVORY NYLON 6 -GF 60***
GLASS EPOXY
·POLYPROPYLENE GF
3. Exotic materials
Materials belonging to this category meet one or more of the following criteria:
Price per KG that crosses the threshold of 400 NIS
Compatible grade
Low stock in the world
There are two materials that we work with very frequently and we have a great fondness for them as manufacturers and they are:
Peak and Ultem.
These two materials are characterized by excellent dimensional stability, are strong and usually fit most of the features required by the final customer. The main problem with them is their high price. The price of Peek ranges from NIS 700-1200 per kilo. The range is quite wide, and the actual price will depend on the supplier of the raw materials, the country of origin (production), how long the supplier has in stock, in what configuration it comes and many other factors. Ultem's price will be about 200 NIS cheaper on average than Peek, but even here this is only a rough estimate that changes due to the reasons I mentioned in the previous line. In the production of miniature parts, the choice of raw material will not have a significant weight on the price.
When there is a demand for medically approved material, the prices will increase to a price that is several times the price of their natural grade. This statement is true for the Peek and Ultem we mentioned, but also for polycarbonate, Delrin, PVC and more.
Beyond the high price of the medical materials there is another problem and it is stock. Sometimes the supplier does not have stock for these materials, or the stock is missing, for example the raw material is available in plates but not in rods, etc.
In addition, there are biocompatible materials, such as those approved for permanent implants - their price is much higher than the price of the medical material. For example - biocompatible peek for transplant price is about NIS 15,000 per kg and sometimes more. We note that these materials cannot be purchased by us as manufacturers, but only by the final customer who receives approval for this.