A Quality Inspector's 4-Step Checklist for Verifying Festo Plastic Tubing & Polyurethane Moldings

A practical, step-by-step guide for procurement and engineering professionals on how to verify the quality of Festo plastic tubing and polyurethane moldings, based on real-world inspection experience.

Who This Checklist Is For

This checklist is for anyone responsible for signing off on deliveries of plastic tubing, polyurethane moldings, or polycarbonate vs. thermoplastic polyurethane (TPU) components—especially if you're sourcing from or alongside Festo's catalog. It's for the person who has the spec sheet in one hand and a caliper in the other, and needs to make a yes/no decision before the shipment goes to the production floor.

I wrote this after reviewing roughly 200+ unique items annually for a mid-sized automation integrator. We use a lot of Festo pneumatic cylinders and fittings, but we also source custom polyurethane moldings and compare materials like polycarbonate and TPU for specific guard and seal applications. Over 4 years, I've rejected about 8% of first deliveries due to issues that could have been caught with this checklist. Here are the 4 steps I follow.

Step 1: Verify the Core Material Specs (Don't Assume 'Festo' = Correct)

This sounds basic, but it's the most common failure point I see. You order a Festo air hose, and it arrives with the right label but the wrong durometer or the wrong wall thickness. Or you spec a polyurethane molding in a certain shore hardness, and the delivered part feels noticeably different.

My first check is always against the spec sheet —not the product name, but the specific datasheet parameters. For Festo tubing, I look for the outer diameter (OD) and inner diameter (ID) tolerances. For polyurethane moldings, I check the shore hardness (e.g., Shore A 70 vs. A 85) and the tensile modulus.

If I remember correctly, we once received a batch of Festo nylon tubing that was spec'd for higher pressure resistance than the TPU version we actually needed. The vendor had substituted a 'comparable' product. It was within the industry standard for nylon, but it was the wrong material for our application because it didn't have the same chemical resistance. We rejected the batch.

What to check:

Confirm Shore hardness for polyurethane/polycarbonate parts
Verify OD/ID tolerances for all plastic tubing
Cross-reference the material (PP vs. nylon vs. TPU) with the application environment (heat, chemicals, UV)

Bottom line: A 'Festo' brand label doesn't guarantee the material variant is correct. You have to verify the spec line.

Step 2: Run a Simple Dimensional Check on a Sample

I don't inspect every single piece in a 1,000-unit order. But I do pull 5-10 items from the batch and run a quick dimensional check. For hose assemblies, I measure the cut length. For molded parts, I check critical fit dimensions.

Here's where I see a lot of people skip a step: they measure the part but don't zero their caliper correctly, or they don't account for the temperature of the part (polyurethane can expand slightly). I've caught dimensional drift that was within the 'acceptable' range on paper but would have caused binding in a tight assembly.

I wish I had tracked this more carefully from the start, but anecdotally, about 3% of our first deliveries have a dimensional deviation that's technically within spec but consistently on the high side of the tolerance—which leads to fit issues. We now ask our vendors to target the middle of the tolerance range, not the max or min.

What to check:

Cut length of hose assemblies (don't just eyeball it)
Critical fit diameters for moldings
Repeat the measurement on 3+ samples to spot variability

Step 3: Do a Visual + Tactile Inspection for Surface Quality

This step is subjective, but it matters for brand perception—especially if the part is visible. I ran a blind test with our engineering team a few years ago: we showed them the same polycarbonate guard part from two different batches. One batch had minor surface dullness from a worn mold; the other was glossy. Without knowing the difference, 70% identified the glossy part as 'more professional.' The cost difference between the two batches was about $0.12 per piece. On a 5,000-unit run, that's $600 for measurably better perception.

For TPU and polyurethane moldings, I look for flash (thin lines of excess material), sink marks, or uneven texture. For Festo air hoses, I look for surface scratches or deformation from poor coiling during packaging. This isn't about rejecting good parts—it's about catching the ones that will degrade the user's experience or fail prematurely.

What to check:

Surface dullness or gloss mismatch
Flash or rough edges on moldings
Scratches, cuts, or deformation on tubing

Step 4: Pressure or Load Test a Single Unit (If Applicable)

This is the step people are most likely to skip because it takes time. But for hydraulic hose assemblies or pneumatic tubing that will carry pressure, you need to verify the burst pressure and working pressure are as spec'd. You're not testing every unit—just one or two from the batch at your standard test pressure (not the max, just 110-120% of the working pressure).

I had a situation in Q3 2024 where a batch of Festo-compatible PU tubing passed all the visual checks and dimensional checks, but when we pressure-tested it, 2 out of 10 samples failed at 150 psi (our standard test pressure was 145 psi). The vendor claimed the material was 'within industry standard' at 140 psi. We rejected the batch. That decision cost us a 2-week delay, but it saved us from a potential failure on the production floor—which would have been a much bigger problem.

What to check:

Perform a burst test on a sample at working pressure +20%
Look for weeping or swelling at fittings and joints
Document the test pressure and result (photographic evidence helps if you need to reject)

Final Notes & Common Mistakes

Mistake #1: Trusting the certificate of compliance (CoC) blindly. A CoC is a document, not a guarantee. I've received CoCs for batches that later failed dimensional checks. Use the CoC as a starting point, not a substitute for your own inspection.

Mistake #2: Only checking one unit. Variability in production (especially for molded parts) can be significant. A sample of one might be perfect while the rest of the batch isn't.

Mistake #3: Not photographing the issue. If you need to reject a delivery, a picture of the failed part with a date stamp and measurement overlay is worth more than a written description. We include this in our contracts now.

Mistake #4: Forgetting to account for the 'time certainty' premium. On a tight deadline, you might be tempted to accept a 'close enough' batch to keep the line running. In our experience, paying for expedited delivery of a verified-good batch is cheaper than accepting a suspect one and dealing with a production halt. In March 2024, we paid $400 extra for rush delivery of a verified polyurethane molding instead of waiting for a redo. The alternative was missing a $15,000 production run. It was a no-brainer.

Pricing references as of January 2025. Verify current specs at Festo's official support portal.