What "20–35 Moulds Per Minute" Actually Means — And How to Check It Before You Wire a Deposit

Every quotation you receive this quarter will contain a cycle rate. Almost none of them will be comparable.

One supplier writes 35 per minute. Another writes 30. A third writes "up to 40" and puts an asterisk at the bottom that says nothing. The numbers look like they describe the same thing. They do not, because a cycle rate without three other numbers attached is not a specification — it is a marketing figure.

This note explains what sits behind a cycle rate, using our own HX-6575 line as the worked example, including the part of the range where the machine does not reach the top of it.

Output per hour = cycles per minute × 60 × cavities per cycle

Three variables. A quotation that gives you one of them has given you a third of an answer.

Note where cavities sit in that formula. A machine running at 30 cycles per minute into a 4-cavity mould produces 7,200 pieces an hour. The same machine at 20 cycles per minute into a 12-cavity mould produces 14,400. The slower machine makes twice as much. This is why cycle rate arguments between suppliers are usually arguments about two different moulds.

A forming cycle is: clamp, heat, form, cool, release. The cooling step is the one that decides the clock, and cooling time scales with wall thickness — roughly with the square of it. Double the sheet thickness and the cycle does not double, it lengthens by more than that.

So four conditions move the number:

1. Sheet thickness and material. 0.15 mm PP and 1.2 mm PET do not run at the same speed on the same machine, and no honest supplier will tell you they do. Amorphous materials such as PS and PET form and cool differently from semi-crystalline PP. The cycle rate printed on a brochure is only meaningful next to a thickness and a resin.

2. Heating capacity per unit area. Faster cycles need more heat delivered in less time. Ovens with more independently controlled zones recover faster and hold a flatter temperature profile across the sheet. On the HX-6575 the upper and lower ovens each carry four separately controlled zones — that is what makes the short end of the cycle range reachable at all, not the number of stations.

3. Forming method. Pressure-assisted forming with vacuum on the reverse side pulls a part against the mould faster and more evenly than vacuum alone, which shortens the form-and-set portion of the cycle and lets you hold a deeper draw without webbing.

4. Cutting arrangement. In-line forming and cutting removes a separate handling step, but the cutting stroke itself takes time. A 60-ton cutting force on a 650 × 750 mm area is sized for multi-cavity tools; the stroke time is part of every cycle and has to be counted.

We publish 20–35 moulds per minute for the HX-6575. Here is what that range means in practice:

The 35 end is not universal. It belongs to thin sheet — the lower half of the 0.15–2.0 mm range — with a mould sized to suit it. Run 1.5 mm PET with a deep draw and a heavy multi-cavity tool, and 20 is the honest figure. A supplier who quotes you 35 without asking what you are forming has either not understood the question or does not want you to ask it.

We would rather you arrive at the factory expecting 20 and watch it run at 32 than arrive expecting 35 and spend the first week explaining the gap to your own production manager.

Question one — "At what wall thickness, in what material, with how many cavities?" If the answer arrives without all three, the cycle rate is not a specification yet. Ask again.

Question two — "What is the cooling time in that cycle, and is it water or air?" Any engineer who has actually run the tool will answer this immediately. Anyone quoting from a brochure will change the subject.

Question three — "Can I watch my own part run before I pay the balance?" This is the only question that cannot be answered with a number. Send your drawing or your sample. A witnessed run on your own tool, at your own thickness, settles in twenty minutes what a month of email cannot.

Buyers in Europe are now working under packaging rules that push toward less material per unit — thinner walls, less void, fewer grams per tray. Thinner sheet is generally faster to form, which sounds like good news for cycle rates. It also narrows the process window: at 0.2 mm there is very little material to distribute, and a line that was tuned for 1.0 mm will not simply run twice as fast without re-tuning heat, pressure and cooling.

The practical consequence is that the cycle rate you should plan your business case around is the one for the thinnest and the thickest gauge you will actually run — not the best number in the brochure.

If you send us your part drawing, your resin and your target output, we will return a cycle estimate with the assumptions written down, and tell you where the estimate is weak.

HengXing Blister Machinery (Shenzhen) Co., Ltd. hxblistermachine.com · WhatsApp +86 180 3814 9443 · hxmachinery@outlook.com