Contents
1. What a Food Grade PP Yogurt Cup Thermoforming Machine Does and Who Buys One
Forming, trimming and stacking in one cycle
A food grade PP yogurt cup thermoforming machine heats a sheet of polypropylene until it softens, presses it into a water cooled mold cavity with a plug assist, and pulls vacuum so the plastic takes the shape of the cup wall. The same machine then trims the rim, rolls or flattens the lip, and stacks the finished cup for a filling line, all inside one cycle that lasts between three and six seconds depending on cup depth and wall thickness.
Three buyer profiles and what each one actually needs
The first buyer is a dairy filling its own yogurt and wanting a dedicated cup shape, and that plant cares about rim consistency and stack height far more than raw output. The second is a contract packager running several brands on one line, which needs fast changeover between cup sizes and a tooling set that can be swapped in under an hour.
The third is a converter selling printed cups to dairies, and that buyer is the only one that also needs in line printing, because a cup sold as a blank loses most of its margin to a printer down the road. Each profile leads to a different machine width, a different number of cavities and a different level of automation.
2. Why PP for Yogurt Cups: Taste, Temperature and Regulation
Taste, odor and fat resistance
Yogurt carries lactic acid, live cultures and between 0.5 and 10 percent milk fat, and the cup has to hold all three without transferring anything back into the product. Polypropylene contains no plasticizer to migrate and has a very low odor threshold after correct drying, which is why it dominates single serve dairy packaging in most markets.
Fat resistance is the reason PP outperforms coated paper for full fat products. A coated paper cup will wick butterfat into the seam within a few weeks at ambient temperature, whereas a 0.6 millimeter PP wall shows no swelling and no delamination after twelve months of shelf testing.
Service temperature and the hot fill question
Homopolymer PP holds its shape to roughly 100 degrees Celsius, and a random copolymer grade with 5 to 12 percent ethylene reaches 120 degrees, which covers pasteurized desserts and microwave reheating. A cup drawn from homopolymer alone will soften and distort near 105 degrees, so a dairy running hot fill must specify copolymer sheet rather than accept whatever grade the sheet supplier ships that week.
What food grade actually means in practice
Food grade is not a single certificate. It is a chain of declarations covering the resin, the additives, the colorants, the processing aids and the sheet converting step, and a cup is only compliant when every link carries a food contact statement for the intended use.
The machine matters in that chain because it must not introduce contamination of its own. A thermoformer with exposed gearboxes, dry running chain drives and open vacuum lines will fail a dairy audit even when the sheet is perfect, which is why buyers now request a documented cleanroom class and a lubrication schedule before signing.
3. Cup Formats, Wall Thickness and Stack Height
Standard sizes and the draw ratio that limits them
A single serve yogurt cup runs 75 to 150 milliliters with a top diameter of 55 to 75 millimeters, and a family cup holding 400 grams runs 95 to 110 millimeters across and 60 to 75 millimeters deep. Draw ratio, defined as cup depth divided by the narrowest cavity dimension, stays between 1.0 and 1.6 for a dependable PP part and climbs above 1.8 only with a plug assist and a heated mold.
Wall thickness and the rigidity it buys
Wall thickness for a 100 milliliter cup sits between 0.5 and 0.8 millimeters, and the base runs 0.1 to 0.15 millimeters thicker than the side wall because the corner thins during drawing. A cup below 0.45 millimeters in the side wall will flex when a consumer squeezes it and will buckle in a six high shrink wrapped tray.
Rigidity rises with the cube of thickness, so moving from 0.5 to 0.65 millimeters increases bending stiffness by roughly 2.2 times and lets a dairy cut sheet weight elsewhere. That trade is the biggest single lever on cup cost, because sheet accounts for 55 to 65 percent of the price of a finished cup.
Rim geometry, stack height and denesting
The rim does three jobs at once, since it gives the lid something to seal against, it sets the stack pitch and it controls how the cup behaves in a denester. A rolled rim of 1.2 to 1.6 millimeters outer curl is the dairy standard, while a flat rim with a raised sealing bead suits foil lids heat sealed at high speed.
Stack height must be specified as a tolerance rather than a target, because 0.1 millimeter of drift per cup becomes 6 millimeters across a stack of sixty and jams the denester. Most dairies accept plus or minus 0.15 millimeters on stack height and reject any cup that nests too tightly to separate under its own weight.
The table below sets out the four cup formats that cover most dairy contracts, with the sheet weight each one consumes and the stack height it produces. A buyer moving from a 100 milliliter to a 150 milliliter cup should expect the sheet weight to rise by nearly half while the cycle time barely changes.
| Cup format | Volume and top diameter | Side wall and sheet weight | Draw ratio and stack height |
|---|---|---|---|
| Single serve yogurt | 100 milliliters at 62 millimeters | 0.55 millimeters at 4.8 grams | 1.25 ratio at 38 millimeters |
| Drinking yogurt | 200 milliliters at 68 millimeters | 0.60 millimeters at 7.2 grams | 1.45 ratio at 42 millimeters |
| Family tub | 400 grams at 105 millimeters | 0.75 millimeters at 14.5 grams | 0.68 ratio at 34 millimeters |
| Deep dessert pot | 150 milliliters at 60 millimeters | 0.65 millimeters at 6.1 grams | 1.60 ratio at 52 millimeters |
4. Food Grade PP Sheet: Resin Grades, Thickness and Cost
Homopolymer, copolymer and clarified grades
Homopolymer PP with a melt flow rate of 2 to 4 grams per ten minutes gives the stiffest cup and the clearest wall, and it is the default for cold fill yogurt in white or lightly tinted colors. Random copolymer with 3 to 6 percent ethylene softens the impact behavior and lifts the heat deflection point, which matters when the cup is filled at 60 degrees or above.
A clarified homopolymer costs 0.10 to 0.22 US dollars per kilogram more than the standard grade and raises transparency from roughly 60 percent to 88 percent, which lets a dairy show the product through the wall. That clarity is worth paying for on a dessert cup and is wasted on a cup that will be sleeve wrapped or printed over the whole surface.
Sheet thickness, tolerance and width
Dairy sheet is supplied from 0.5 to 1.2 millimeters thick, and the tolerance that matters is not the nominal figure but the cross web variation, which should stay inside plus or minus 3 percent. A sheet running 4 percent heavy at the center will form cups that are 0.03 millimeters thicker in the middle of the web and will produce a stack height mismatch across the mold that no machine setting can fix.
Sheet width follows the mold layout, so a four across tool on 62 millimeter cups needs a web of about 280 millimeters plus trim allowance. Buying sheet 30 millimeters wider than necessary wastes 3 to 5 percent of every roll, which on a 400 kilogram per hour line is 12 to 20 kilograms of resin an hour.
What the sheet contributes to cup cost
Food grade PP sheet trades at 1.55 to 2.10 US dollars per kilogram depending on grade, color and order volume, and a 100 milliliter cup at 4.8 grams therefore carries 0.0074 to 0.0101 US dollars of material. On a cup selling to a dairy at 0.028 to 0.045 US dollars, that material share of 20 to 30 percent is the largest single line in the costing sheet before conversion.
5. Machine Architecture: Inline Extrusion or Roll Fed
Inline extrusion and forming on one frame
An inline line extrudes sheet through a flat die, cools it on a three roll stack, and feeds it directly into the oven without winding, which removes a handling step and saves 0.04 to 0.09 US dollars per kilogram in energy and labor. It also removes the sheet inventory a converter would otherwise carry, and it lets the same resin lot run from pellet to cup with one traceability record.
Roll fed forming for converters and short runs
A roll fed machine buys sheet on rolls and forms from a dereeler, which suits a converter running four cup sizes for six dairies in the same week. Changeover becomes a matter of splicing a new roll and swapping the tool, and the machine can run at 25 to 40 cycles per minute on a 0.6 millimeter web without any extrusion upsets.
The trade is 0.06 to 0.14 US dollars per kilogram more in purchased sheet against 0.03 to 0.07 US dollars per kilogram in extra labor and scrap, so roll fed wins below about 250,000 cups a day and loses above it. A buyer should model the crossover rather than assume that inline is always cheaper.
Heating stations, mold and plug assist
Radiant ceramic heaters run at 320 to 420 degrees Celsius and are set in zones across the web so the sheet arrives at 145 to 165 degrees, which is the forming window for PP. Zone control matters because a 10 degree imbalance between the edges and the center produces cups that are 0.05 millimeters thinner on one side and fail a stack height gauge.
The mold is water cooled to 20 to 30 degrees and carries the vacuum channels and the plug assist travel, so it decides both cycle time and wall distribution. A plug assist in a matched polymer or a felted composite costs 2,000 to 6,000 US dollars per cavity set and is what makes a 1.6 draw ratio cup possible without a paper thin base.
6. Complete Equipment Price List and Line Layout
Package price and what drives the total
Wanplas quotes a four cavity inline line forming 100 milliliter cups at 0.9 to 1.3 million US dollars and a six cavity line at 1.2 to 1.6 million, with tooling, cleanroom enclosure and printing priced separately. The table below breaks the package into line items so a buyer can see which elements drive the total and which can wait for a second phase.
| Item | Typical specification | Price in US dollars |
|---|---|---|
| Sheet extruder with three roll stack | 90 millimeter screw, 400 to 600 kilograms per hour | 180,000 to 320,000 |
| Inline thermoformer, four cavity | 730 by 500 millimeter forming area, 35 cycles per minute | 220,000 to 420,000 |
| Inline thermoformer, six cavity | 1,050 by 560 millimeter forming area, 32 cycles per minute | 320,000 to 560,000 |
| Cup mold, four cavity | Aluminum cavity with vacuum ports and water circuit | 45,000 to 85,000 |
| Cup mold, six cavity | Aluminum cavity with independent cooling zones | 68,000 to 130,000 |
| Trim tool and plug assist set | Hardened steel punch, felted composite plug | 26,000 to 51,000 |
| Rim rolling unit | Heat and roll station for 1.2 to 1.6 millimeter curl | 35,000 to 65,000 |
| Counter stacker and orienter | Sixty cup stacks, antistatic bar, reject gate | 20,000 to 40,000 |
| Chiller and vacuum system | 30 kilowatt chiller, 250 cubic meter per hour vacuum pump | 34,000 to 60,000 |
| Granulator and regrind handling | Edge trim and reject grinder, 150 kilograms per hour | 15,000 to 28,000 |
| In line six color printer | Dry offset, 300 cups per minute, ultraviolet cure | 180,000 to 320,000 |
| Cleanroom enclosure | Class 100,000 panel build with air lock | 60,000 to 120,000 |
| Controls and data logging | Recipe management, batch record, alarm history | 25,000 to 50,000 |
| Installation and commissioning | Erection, alignment, trial run, operator training | 25,000 to 45,000 |
| First year spare parts | Heater elements, seals, punches, vacuum pads | 15,000 to 30,000 |
Layout, utilities and lead time
An inline line needs 28 to 45 meters of straight run, and the extruder end must sit close to the resin silo because pneumatic conveying over more than 60 meters starts to break down pellets. The forming end needs 800 millimeters of clear access on both sides of the mold for tool changes and 2.2 meters of headroom for the oven hood.
Utilities are modest but not negligible, and a buyer who forgets them delays the start up by weeks. Budget 90 to 140 kilowatts of connected load, 6 to 10 cubic meters per hour of chilled water at 18 degrees, 0.6 cubic meters per minute of compressed air at 7 bar, and a 12 to 20 week lead time from order to commissioning.
7. Heating, Drape and Vacuum Forming
Radiant heating and the forming window
PP has a narrow forming window between 145 and 165 degrees Celsius, and it has no sharp softening point, so the heater has to deliver a flat profile rather than a hot spot. A sheet at 140 degrees will draw without tearing but will spring back at the rim, while a sheet at 175 degrees sags in the oven and thins the base before the plug ever touches it.
Plug assist and where the material goes
The plug pushes sheet into the cavity ahead of the vacuum and drags material down the wall, which is the only way to keep a 1.6 draw ratio cup from thinning at the base corner. Plug diameter runs 60 to 75 percent of the cavity diameter, and the clearance between plug and cavity wall of 1.5 to 3 millimeters controls how much material stays at the rim.
Vacuum, air pressure and venting
Cavity vacuum of 0.4 to 0.7 bar is enough for a PP cup, and the vacuum must arrive before the plug bottoms out or the cup traps a bubble at the base. Vent holes of 0.5 to 0.8 millimeters in the cavity, backed by a 12 millimeter channel, keep the draw fast without leaving a witness mark on the visible surface.
Some tools use 2 to 4 bar of positive air pressure on the plug side to supplement vacuum, which shortens the draw by 0.2 to 0.4 seconds and improves sharpness at the base fillet. Pressure forming needs a sealed pressure box and a heavier frame, and it adds 30,000 to 70,000 US dollars to the machine price for a benefit that only matters on tight radius designs.
8. Cutting, Rim Rolling and Lid Fit
Trim in place versus a separate trim station
A trim in place tool cuts the cup while it is still in the cavity, which holds the part rigid and leaves a burr free edge, and it is the standard choice for cups above 0.6 millimeters. A separate trim station downstream allows a simpler mold and a cheaper tool change, but it needs a transfer system and adds 0.3 to 0.6 seconds to every cycle.
Rim rolling and the sealing bead
Rim rolling takes a flat trimmed edge and curls it into a 1.2 to 1.6 millimeter outer roll, which stiffens the opening and gives the lid a defined contact band. The roll is formed hot at 110 to 130 degrees with a rolling wheel, and the wheel pressure has to be consistent or the curl will vary around the circumference.
A cup intended for a foil lid usually gets a flat rim with a raised bead of 0.15 to 0.25 millimeters instead of a full roll. The bead concentrates sealing pressure from the filler’s platen, and it lets the dairy seal at 140 to 160 degrees for 0.8 to 1.5 seconds without cutting through the foil.
Lid fit and leak integrity
Lid fit is a system property, not a cup property, so the cup rim tolerance has to be agreed with the lid supplier before either part is ordered. A rim diameter held to plus or minus 0.1 millimeters and a bead height held to plus or minus 0.05 millimeters will seal on a standard aluminum foil lid; a rim held to plus or minus 0.3 millimeters will leak on one cup in two hundred.
9. Printing, Labeling and Shelf Presence
Dry offset printing on the formed cup
Dry offset printing applies six colors to the finished cup at 250 to 350 cups per minute, using a blanket that transfers ink from plate to cup surface without a solvent carrier. It needs a cup that is round and rigid enough to hold registration, which is why a printed cup is normally specified at 0.6 millimeters or above.
In mold labeling and shrink sleeve alternatives
In mold labeling places a printed film in the cavity so the label fuses into the cup wall during forming, which gives full wrap coverage and a photo quality finish without a second operation. The label adds 0.006 to 0.014 US dollars per cup and needs a robot or a pick and place unit at 12,000 to 30,000 US dollars per cavity, so it only pays on a premium product.
A shrink sleeve applied after forming costs 0.004 to 0.009 US dollars per cup and gives a 360 degree print, but the sleeve hides the cup and defeats the point of transparent PP. A dairy choosing between the three routes should decide on the shelf first and on the equipment second.
10. Sixteen Process Parameters and the Cost of Deviation
Why the setting sheet matters more than the machine rating
Two lines with the same hardware will produce different cups if one runs the oven 8 degrees hotter and holds the mold 4 degrees colder, and the difference shows up as 4 percent scrap rather than as a visible fault. The setting sheet is therefore part of the purchase, and a buyer should insist on a documented window for every parameter rather than a single nominal value.
The table below lists the sixteen settings that decide cup quality on a 0.6 millimeter PP web, with the window that produces a stable part and the cost of drifting outside it. These figures assume a four cavity tool forming a 100 milliliter cup at 35 cycles per minute.
| Parameter | Working window | What drifting outside costs |
|---|---|---|
| Sheet temperature at oven exit | 152 to 160 degrees Celsius | 0.03 millimeter wall loss and rim spring back |
| Oven zone spread | Within 5 degrees across the web | 0.15 millimeter stack height scatter |
| Web speed through the oven | 12 to 18 meters per minute | Short dwell and 6 percent output loss |
| Mold cooling water temperature | 22 to 26 degrees Celsius | 0.3 seconds added cycle and 5 percent output |
| Cavity vacuum level | 0.5 to 0.7 bar | Base bubbles at 1.5 percent reject |
| Vacuum delay after plug contact | 0.05 to 0.10 seconds | Witness marks and 2 percent print rejects |
| Plug penetration depth | 88 to 94 percent of cup depth | Base thinning to 0.28 millimeters |
| Plug temperature | 60 to 90 degrees Celsius | Surface marking or tearing at 3 percent scrap |
| Dwell under forming pressure | 0.6 to 0.9 seconds | Rim distortion and denesting faults |
| Punch and die clearance | 0.03 to 0.05 millimeters | Feathered rim and lid seal failures |
| Rim rolling temperature | 110 to 130 degrees Celsius | 0.2 millimeter curl variation around the rim |
| Rolling wheel pressure | 2.5 to 3.5 bar | Oval rim and denester jams on the filler |
| Stacker count per sleeve | 60 cups with count verification | Filler line stoppage at 4,000 US dollars an hour |
| Antistatic bar voltage | Below 2 kilovolts on the stack | Double cups in the denester and line stops |
| Regrind ratio in the core layer | 0 to 15 percent of total weight | Color drift and 0.1 millimeter stack change |
| Line rate against filler demand | Plus 5 percent buffer | 3,000 cups of frozen inventory per stop |
11. Hygiene, Cleanroom and Food Contact Compliance
Cleanroom class and air handling
A cup that will touch yogurt is a food contact article, and most dairies now require the forming and stacking area to run at class 100,000 with positive pressure and a documented air change rate. A panel build enclosure with an air lock costs 60,000 to 120,000 US dollars and adds 8 to 15 kilowatts of fan and cooling load.
Lubrication, metal detection and foreign body control
Every lubricant that can reach the product zone has to be food grade and registered for incidental contact, and the machine should carry a lubrication map that names each point and its interval. A single mineral oil grease point above the forming station is enough to fail an audit, because a drip travels straight onto the sheet.
Metal detection belongs on the cup line rather than only on the filling line, since a worn punch or a broken plug can shed a fragment into the stack. A tunnel detector sized for a 400 millimeter stack costs 12,000 to 25,000 US dollars and rejects to a locked bin that is emptied and logged every shift.
Documentation a dairy will ask for
The audit pack normally contains a resin food contact declaration, a declaration for each additive and colorant, a migration test report from an accredited laboratory, a cleaning procedure and a traceability record linking each pallet to a resin lot. A converter who cannot produce all five within a week will not be approved, regardless of cup quality.
Wanplas supplies the machine side of that pack, covering the material certificates of the food contact surfaces, the lubrication schedule and the cleaning instructions for the forming and stacking area. The resin and migration documents remain the converter’s responsibility, and the two sets have to match before a dairy signs off.
12. Quality Control Tests and the Cost of Failure
Dimensional tests on every shift
Four measurements carry most of the quality load: top diameter, rim height, stack height over sixty cups and base thickness at the center. A go and no go gauge set costs 1,500 to 4,000 US dollars and lets an operator check a cavity in under a minute without a coordinate measuring machine.
Physical and leak tests
A compression test loads the empty cup axially to 200 newtons and measures deflection, which predicts how the cup behaves in a six high shrink wrapped tray. A top load of 180 to 250 newtons is normal for a 100 milliliter cup at 0.55 millimeters, and a cup below 150 newtons will crush in the pallet stack.
Leak integrity is tested by filling ten cups per shift with water plus dye, sealing them with the production lid and inverting them for thirty minutes. Any weeping at the rim fails the lot, and the usual cause is a rim roll that has drifted 0.15 millimeters rather than a bad foil.
What a reject actually costs
A reject caught at the thermoformer costs the sheet weight, which is 0.007 to 0.010 US dollars per cup. The same defect caught at the filler costs 0.03 to 0.06 US dollars because it also consumes yogurt, a lid and labor, and one caught at retail costs 0.60 to 1.20 US dollars plus the claim handling.
13. Output, Energy, Labor and Overall Equipment Effectiveness
Cups per hour from cavity count and cycle time
Output is cavity count multiplied by cycles per minute and by sixty, less scrap, so a four cavity tool at 35 cycles per minute yields 8,400 cups an hour before losses. A six cavity tool at 32 cycles yields 11,520, and the difference of 3,120 cups an hour is what justifies the 100,000 to 140,000 US dollar step in machine price.
Energy per thousand cups
Extrusion and thermoforming together consume 0.8 to 1.1 kilowatt hours per kilogram of sheet, which at 4.8 grams per cup is 0.004 to 0.005 kilowatt hours per cup. At 0.09 to 0.13 US dollars per kilowatt hour that works out to 0.38 to 0.68 US dollars per thousand cups, a small number that becomes visible only when the chiller and the vacuum pump are left running between shifts.
Labor, changeover and overall equipment effectiveness
A four cavity line needs one operator and one packer per shift, and a six cavity line adds a second packer rather than a second operator. At a fully loaded rate of 18 to 26 US dollars an hour, direct labor lands between 2.10 and 3.40 US dollars per thousand cups at realistic output.
Changeover to a new cup size takes two to four hours including heater stabilization, mold swap, punch alignment and first article approval, and consumes 40 to 90 kilograms of sheet. Overall equipment effectiveness for a well run line sits at 82 to 90 percent, with unplanned stops for trim jams and stacker faults taking most of the loss.
14. Cost per Cup, Market Price and Investment Payback
What a cup actually costs to make
The costing sheet below is built for a printed 100 milliliter cup at 4.8 grams, forming from food grade homopolymer sheet with 12 percent regrind in the core layer. It shows why volume matters so much: the same cup costs 0.0210 US dollars at 100,000 cups a day and 0.0147 at 600,000, a fall of 30 percent driven almost entirely by labor, depreciation and overhead spreading over more cups.
Sheet remains the largest single line at every scale, holding 36 to 51 percent of the total, which is why a resin contract and a sheet yield target matter more than a saving on spare parts. A converter who cuts sheet waste from 8 percent to 4 percent saves more than one who negotiates 20 percent off the maintenance budget.
| Cost element | 100,000 cups per day | 300,000 cups per day | 600,000 cups per day |
|---|---|---|---|
| Sheet at 4.8 grams per cup | 8.06 | 7.68 | 7.44 |
| Regrind credit | minus 0.45 | minus 0.52 | minus 0.58 |
| Energy for extrusion and forming | 0.85 | 0.72 | 0.65 |
| Direct labor | 2.60 | 1.70 | 1.30 |
| Tools and molds amortized over three years | 1.10 | 0.55 | 0.37 |
| Machine depreciation over seven years | 3.20 | 2.10 | 1.60 |
| Maintenance and spares | 0.75 | 0.55 | 0.45 |
| Printing ink and plates | 2.50 | 2.20 | 2.10 |
| Packaging, sleeves and handling | 0.90 | 0.70 | 0.60 |
| Overhead, quality and cleanroom | 1.45 | 0.95 | 0.75 |
| Total per thousand cups | 21.0 | 16.6 | 14.7 |
Market price and the margin a converter keeps
A printed 100 milliliter PP cup sells to a dairy at 0.030 to 0.048 US dollars in most markets, and an unprinted blank at 0.019 to 0.028 depending on volume and payment terms. Against a cost of 0.0166 at 300,000 cups a day, that leaves a gross margin of 0.013 to 0.031 per cup, or 45 to 65 percent, before freight and financing.
Payback and the configuration we recommend
A six cavity inline line at 1.2 to 1.6 million US dollars producing 75 million cups a year earns 1.0 to 1.2 million in contribution at a 0.014 per cup margin, which pays back the equipment in 14 to 19 months before tax. A four cavity line at 0.9 to 1.3 million pays back more slowly because labor and depreciation per cup are 40 percent higher.
Wanplas recommends a six cavity inline line with a 90 millimeter extruder, a three layer feed block for regrind in the core, a trim in place tool, a rim roller and a counter stacker with an antistatic bar. Adding the cleanroom and the printer in the first phase costs 240,000 to 440,000 US dollars more but avoids the far larger cost of rebuilding a validated line later.
Frequently Asked Questions
What does a food grade PP yogurt cup thermoforming line cost?
A four cavity inline line forming 100 milliliter cups runs 0.9 to 1.3 million US dollars including the extruder, former, trim tool, rim roller and stacker. A six cavity line runs 1.2 to 1.6 million, and adding a cleanroom enclosure and a six color printer takes the funded project to 1.6 to 2.1 million.
How many cups per hour does the machine actually produce?
A four cavity tool at 35 cycles per minute yields 8,400 cups an hour in theory and 7,300 to 7,700 in practice, and a six cavity tool at 32 cycles yields 11,520 in theory and 10,000 to 10,600 in practice. Always ask for a demonstrated shift rate rather than a cycle time figure.
Can the same machine also run PS, PLA or paper cups?
Polystyrene runs on the same machine with a different heater profile and a colder mold, and PLA runs with a much tighter window because it crystallizes and stays soft when hot. Paper needs a completely different forming principle, so a dairy planning a fiber cup should not expect a PP thermoformer to cover it later.
What wall thickness should I specify for a 100 milliliter cup?
Specify 0.55 to 0.65 millimeters for cold fill yogurt and 0.65 to 0.80 for hot fill or for a cup that will be stacked six high in a shrink wrapped tray. Anything below 0.45 millimeters will flex in the consumer’s hand and will buckle under normal pallet load.
Why do my cups leak at the lid even though the rim looks perfect?
Three causes cover almost every leak: a rim roll that has drifted 0.1 millimeters or more, a sealing platen that is not parallel to the rim, and a foil lid whose lacquer does not match the PP surface. Check the rim gauge first, because it is the cheapest measurement and the most frequent fault.
Do I need a cleanroom around the machine?
Most large dairies now require class 100,000 with positive pressure for the forming and stacking area, and the enclosure costs 60,000 to 120,000 US dollars. It only delivers the class if the machine itself uses sealed bearings, food grade lubricants and smooth washable guards.
Is inline extrusion or roll fed better for a dairy?
Inline wins above roughly 250,000 cups a day because it removes sheet handling and saves 0.04 to 0.09 US dollars per kilogram. Roll fed wins below that figure and for a converter running several cup sizes in the same week, since changeover becomes a splice and a tool swap.
What should the acceptance test cover before final payment?
Insist on a four hour run at the contracted rate with scrap below 2 percent, a stack height within plus or minus 0.15 millimeters over sixty cups, base thickness within tolerance at all four cavities, and a dye leak test on twenty cups. Hold 10 percent of the price until the first production lot passes the dairy’s own incoming inspection.
Conclusion
A food grade PP yogurt cup line is decided by four choices that are all made before the purchase order: the sheet grade and its thickness tolerance, the cavity count against the filler’s real demand, the plug assist and vacuum arrangement that makes the draw ratio work, and the trim and rim geometry that the lid supplier will accept. Get those four right and the machine settings become routine; get any one wrong and no amount of tuning recovers the cup.
The economics reward volume far more than negotiation, since the same cup costs 0.0210 US dollars at 100,000 a day and 0.0147 at 600,000, and sheet holds 36 to 51 percent of that total at every scale, so a yield target and a resin contract are worth more than a discount on spares. That is also why a line bought for half the capacity the dairy will need in three years rarely survives the second year.
Wanplas recommends fixing the cup drawing, the rim tolerance and the leak test in writing, then specifying a six cavity inline line with a three layer feed block, a carbide punch and the cleanroom in the first phase. A line bought that way passes its acceptance run on the first attempt and is still holding stack height in the fourth year, which is the only measure that matters to a dairy that has already printed its packaging.
