I've seen too many projects start with PP to save money, then the customer complains "this looks so cheap." I've also seen projects start with PC, then switch back to ABS after production because they couldn't justify the cost. Six months of back and forth that could've been avoided by thinking it through upfront.

On Grade Selection

I need to spend some time on this because this is where I see procurement waste the most money.

ABS isn't one material. It's a family. General purpose, high impact, heat resistant, flame retardant, plating grade, medical grade... Price spread can be 80%.

Last month I quoted a job. Spec said "flame retardant ABS, UL94 V-0." I quoted FR grade at around $3.20/kg. Customer said too expensive, find a way to cut it.

So I asked what the part was for. Decorative trim inside an equipment cabinet. I asked if the cabinet itself was UL listed. He said yes. I said then why does the decorative trim inside need flame rating? The cabinet enclosure already passed.

Switched to GP grade at $2.10. Annual volume maybe 50-something tons. Saved them over fifty grand a year.

But there's the opposite too. Had a customer last year making EV charger housings, insisted on GP to save money. I told them this thing sits outdoors, at least use UV stabilized grade. He said let's try it first.

Eight or nine months later they came back. Housings had yellowed and started cracking. I didn't say anything, just requoted UV stabilized. Could've saved a lot of headache if they'd listened earlier.

Rough price ranges for different grades, so you have a sense:

This is current North American market. China pricing runs twenty to thirty percent lower. Also varies by supplier and brand. SABIC CYCOLAC versus Chi Mei POLYLAC, similar specs but price can differ by ten to twenty cents. Doesn't matter on small orders but adds up on volume.

Oh right, one more thing. A lot of people don't realize that even within the same grade there's extrusion grade versus injection grade, different melt flow index. Extrusion needs lower MFI material, if flow is too good the profile can't hold its shape coming out of the die. I've seen someone try to extrude with injection grade ABS. Surface came out all wavy. Not a material problem, wrong grade selection.

Processing Pitfalls

Honestly ABS is one of the easier plastics to process. Way less hassle than PC. PC has those strict drying requirements and narrow temperature window, slight deviation and you get stress cracking and silver streaks everywhere. ABS is much more forgiving.

But "more forgiving" doesn't mean "anything goes."

Drying is mandatory. ABS absorbs moisture. Not as bad as nylon but can't be ignored. Our standard is 80-85°C for 2 to 4 hours, moisture target below 0.1%. If material sat in warehouse too long or you're in humid season, 4 hours might not be enough.

Here's something most people don't know: black and dark colored ABS absorbs moisture faster than natural. It's not the ABS itself, it's the carrier in the color masterbatch that's hygroscopic. Black material we usually dry 4 to 6 hours. One time we were rushing an order, black material only dried 2 hours before running. Surface came out covered in silver streaks. Entire batch scrapped.

Temperature wise, we typically set barrel zones in progressive steps. Something like 150→160→170→180°C, die zone around 190. Too high and material degrades, turns yellow. Too low and flow isn't good enough. Specific settings depend on the resin, each supplier's formulation is a bit different. New material always needs a temperature run to dial in.

Had a customer before who was getting parts from another supplier, complained about dimensional instability. I looked at their incoming inspection data, same batch varied by point-two or point-three mm front to back. I asked how their supplier controlled temperature. He didn't know. They switched to us, problem went away. Not rocket science, just better temperature controller precision and tighter zone control.

Extrusion speed matters too. Theoretically faster means more output means lower cost per meter, but too fast builds internal stress. Profile looks fine coming off the line, passes your incoming inspection, goes into assembly. Three months later customer calls because parts are warping. We quote based on moderate conservative speeds. Some competitors quote really low, I'm not going to comment on how they do it, but cheap usually has a reason.

How to Actually Calculate Cost

Purchasing obviously cares most about price. But for plastic parts, looking only at price per kilo isn't enough.

Let me give you a few real cases I handled. Numbers might not be perfectly precise, some projects were two or three years ago, but the general picture is right.

When NOT to Use ABS

I said a lot of good things about ABS above. But honestly there are scenarios where it really doesn't fit, and forcing it will cause problems.

What to Watch When Picking Suppliers

Few observations from my experience. Not guaranteed correct, just my take.

Very low quotes deserve questions. ABS profile pricing, material cost is what it is, processing cost has a floor. Quotes more than 20% below market rate, either they're using a cheaper grade than specified (swapping high impact for GP but not telling you), or cutting corners on process (skipping dry time, running too fast). Not saying low price definitely means problems, but worth asking more questions.

Traceability. Proper operations should be able to trace each batch of product back to which lot of resin, when it was produced, what parameters were used. In case issues come up you can investigate. Can't do this, management level is questionable.

How they handle samples. Some factories send you cherry-picked samples during quoting, actual production is another story. Better to ask for random pulls from normal production line, not "specially made for you."

Ask about changeovers. Multi-material facilities need to purge between material changes, otherwise cross-contamination. Some places shortcut this to save time, finished product has impurities. White specks in black material, black specks in clear material. Usually this is why.

Alright this is getting long enough. Actually there's a lot more that could be covered, coextrusion, die design, surface treatments, but at some point you have to stop.

Pricing data reflects 2024-2025 market. Raw material prices fluctuate with petrochemical markets. Actual quotes depend on current conditions.