Is Resin Going Missing? Reconcile Granules Issued vs Parts Made in a Moulding Shop (₹)
Is resin going missing between your store and your presses? Check it monthly: kilos issued against good parts, material sent out and floor stock. As of 15 Oct 2026, an IOCL distributor list puts injection-moulding PP at ₹1,57,952 a tonne in Thane, before GST. At that price, an unexplained 2% gap in our 20-press example costs about ₹3.1 lakh a month.
Last checked: 17 Oct 2026
By the Mama Editorial Team. This piece is for owners of Indian injection-moulding shops making closures, containers, housings and technical parts. Every figure from a published source carries its date and link. Our own inputs are marked "assume". This is a reconciliation, not an accusation: a gap can come from measurement as easily as from loss.
Key takeaways
- The test is a simple mass balance. Granules and masterbatch issued, plus opening floor stock, should equal good parts, plus material that left the shop floor, plus closing floor stock. Whatever is left over is the gap.
- Regrind that goes back into the hopper is not an output. It is the same plastic going round again. Count it only as floor stock at month-end, or you will count it twice.
- Explain the gap before you blame anyone. A stale standard part weight, a blocked cavity, unweighed purge or a drifting scale can each explain a gap on their own.
- Price the gap at your real resin cost. IOCL's distributor list of 15 Oct 2026 puts its injection-moulding PP grade 1110MG at ₹1,57,952/MT in Thane, basic and cash, GST additional. That is about ₹158 a kilo.
- A written-off loss can cost you tax credit too. Section 17(5)(h) of the CGST Act blocks input tax credit on goods "lost, stolen, destroyed, written off" (CBIC consolidated text as on 30.09.2020).
- A camera can't weigh granules. It can show when bags left the store and where scrap piled up. The scale and the register do the weighing.
How this differs from a scrap-cost calculation
Our guide to regrind and scrap costs in a moulding plant and the regrind, runner and scrap calculator price the plastic you know about: runners, purge, start-up shots and rejects.
This page asks a different question. Does every kilo issued from the store end up somewhere you can weigh? Scrap is a known loss. A reconciliation gap is material you can't place at all.
The same logic works in other trades. Garment owners can follow it in our piece on fabric and trims issued vs consumed.
The mass balance on one page
Treat the moulding floor as a box with one door from the store and one door to finished goods. Over a month, weight goes in and weight comes out. What comes out includes what is still sitting inside at the end.
In:
- Virgin granules issued from the store, by issue slip.
- Masterbatch and additives issued.
- Opening floor stock: regrind bags, granules in hoppers and dryers, part-used bags at the presses, weighed on the 1st.
Out:
- Good parts: count of good parts × standard part weight, for each mould.
- Material that left the floor: regrind and lumps sent to the scrap store or sold, purge, sweepings, and rejects held in quarantine, all weighed.
- Closing floor stock, weighed on the last day the same way as opening.
Gap = In − Out. Express it as a percentage of granules and masterbatch issued in the month.
Two rules keep the balance honest. First, never add reground runners and rejects as an output if they went back into the hopper; they appear later as parts or as closing regrind stock. Second, the opening and closing floor counts must be done the same way, at the same time of day, by the same person.
A worked example: a 20-press PP shop
Assumptions (illustrative, replace with your own):
- 20 presses on a homopolymer PP injection grade, one month of production.
- Granules in 25 kg bags; 3,840 bags issued, so 96,000 kg of virgin PP.
- Masterbatch issued: an assumed 1,900 kg.
- Resin and masterbatch priced at ₹158/kg, rounded from IOCL's 1110MG list price of ₹1,57,952/MT basic in Thane on 15 Oct 2026.
- Assume you claim GST input credit, so the basic price, not the GST-inclusive price, is your cost.
| Line | Kilos (kg) | Where the number comes from |
|---|---|---|
| Virgin PP issued | 96,000 | Store issue slips |
| Masterbatch issued | 1,900 | Store issue slips |
| Opening floor stock (regrind 2,100 + hoppers, dryers, part bags 600) | 2,700 | Weighed on the 1st |
| Total in | 1,00,600 | |
| Good parts (count × standard weight, all moulds) | 91,442 | FG receipts × part weight card |
| Regrind and lumps sent to scrap store | 2,900 | Weighed at scrap store |
| Purge and sweepings | 650 | Weighed per shift |
| Rejects in quarantine | 350 | Weighed |
| Closing floor stock (regrind 2,600 + hoppers, dryers, part bags 700) | 3,300 | Weighed on the last day |
| Total out | 98,642 | |
| Gap | 1,958 (2.0% of 97,900 kg issued) |
At ₹158/kg, 1,958 kg is ₹3,09,364 a month, or about ₹37 lakh a year. Spread over 20 presses, that is about ₹15,500 a press a month.
The same shop at other gap levels:
| Gap (% of issued) | Kilos per month (kg) | ₹ per month at ₹158/kg |
|---|---|---|
| 0.5% | 490 | 77,341 |
| 1.0% | 979 | 1,54,682 |
| 1.5% | 1,468 | 2,32,023 |
| 2.0% | 1,958 | 3,09,364 |
| 3.0% | 2,937 | 4,64,046 |
Prices move. IOCL rolled PP prices over unchanged with effect from 15 October 2026 (Plastemart price news, checked 17 Oct 2026). Reliance's PP circular of 1 Oct 2026 (ref. 2026-27/PP/DTA/026) lists its grade H110MA at ₹1,60,035/MT delivered in Pune, GST extra, with a cash discount of ₹1,100/MT. Use your own landed price from last month's invoice.
Tolerance bands: when a gap is noise and when it is a question
We found no published Indian norm for a permitted resin reconciliation gap in a moulding shop on the CIPET or AIPMA websites (checked 17 Oct 2026). The bands below are our assumption, set so that measurement error stays inside the first band. Tighten them once you have six months of your own data.
| Gap (% of issued) | Assumed reading | What to do |
|---|---|---|
| Under 0.75% | Measurement noise | Record it, change nothing |
| 0.75% to 1.5% | A standard or a count is off | Run the six checks below |
| Over 1.5% | Material is leaving unrecorded, or a big count error | Checks, plus a review of how material leaves the store and the floor |
| Negative (more out than in) | Parts are overcounted or issues are under-recorded | Check cavity counts and issue slips first |
A negative gap is as useful as a positive one. It means parts are overcounted or issues went unrecorded, and either can hide a real gap.
Six checks that explain a gap before anyone is blamed
1. The standard part weight is stale. The weight on the part card was set when the mould was new. A worn tool, a changed packing pressure or a heavier wall can make parts heavier without anyone noticing. In the example, parts 1% heavier than standard would explain 914 kg, almost half the gap. Weigh 20 parts per mould each week and update the card.
2. Cavities are counted wrong. If good parts are counted as shots × cavities, a blocked cavity breaks the count. On an 8-cavity mould with one cavity blocked, the count overstates output by one part in eight. That makes the gap look smaller than it is, or even negative.
3. Purge and sweepings are not weighed. Night-shift purge often goes into a bag that nobody weighs. Every unweighed kilo lands in the gap. Weigh it per shift, even roughly.
4. The scales disagree. The store issues on one scale and the floor weighs on another. Check both against the same known weight once a month, and check-weigh ten 25 kg bags from each lot.
5. Moisture leaves as steam. Hygroscopic grades lose weight in the dryer. One ABS injection grade lists 0.22% moisture at 23 °C and 50% relative humidity (ISO 62), dried to below 0.05% at 80 °C for 2 to 4 hours (Bada BADALAC ABS 20 datasheet, issue date 16.01.2019). That is up to about 0.17% of weight if granules arrive at that moisture. It matters for ABS, nylon or PC, not much for PP. For an assumed 20 tonnes of ABS a month it is about 34 kg.
6. Floor stock is guessed, not weighed. If the closing count is "about ten bags", the gap moves with the guess. Weigh it.
Only when these six are clean does the remaining gap point at the store and the gate. The raw material store CCTV specification shows how to set up the issue counter so each slip can be checked against what physically left.
Why the money is bigger than the kilos
The gap costs more than resin.
- Tax credit. Under section 17(5)(h) of the CGST Act, input tax credit is not available on goods "lost, stolen, destroyed, written off or disposed of by way of gift or free samples" (CBIC consolidated text as on 30.09.2020). Ask your CA how this applies to a stock difference written off in your books.
- Costing. If your quotations use the standard part weight and real consumption runs 2% higher, every price you quoted is 2% light on its biggest cost line.
What a camera can and cannot tell you here
A camera cannot:
- weigh a bag, a hopper or a gunny sack of purge;
- tell PP from ABS, or virgin from regrind;
- read the weight on a part card or the count on a shot counter;
- prove that a gap is theft; a counting error leaves the same gap.
A camera can show:
- when material left the store, to check against the issue slips;
- whether bags are carried out after hours, through a door with no register;
- how often presses are purged, and on which shift purge piles up;
- whether regrind and scrap bins are filled and emptied as the register says;
- when the scrap vehicle left, to match against the weighment slip.
The pairing that works is a scale for the kilos, a register for the slips and video for the times. Our camera guide for injection-moulding units covers the press-side views.
On people: this is about material flow, not about watching operators. Review footage of doors and counters, not of individuals at work. Footage of recognisable workers is personal data under s.2(t) of the DPDP Act, 2023; tell workers in writing what is recorded and why (see the worker CCTV notice under DPDP).
Running the reconciliation every month
A routine that takes about two hours a month:
- On the last working day, weigh all floor stock: regrind bags, part bags at presses, hoppers and dryers (or estimate those from the level mark, the same way every month).
- Total the month's store issue slips for granules and masterbatch.
- Pull good-part quantities from FG receipts, not from shot counters, and multiply by this month's checked part weights.
- Total the weighed scrap, purge, sweepings and quarantine.
- Work out the gap and its percentage, and write it on one line in a register with the date.
- If it is above your band, run the six checks in order before anything else.
Where Mama fits
Mama reads the cameras a factory already has and sends the owner a short plain-language note each morning about where press-hours went the day before. It covers presses that stood idle, long purges and colour changes, and stoppages that clustered on one shift. It watches machines and material flow, not individual workers. It doesn't weigh resin or replace the store register. If you'd like Mama to look at your floor and suggest where cameras would earn their keep, leave an email or phone in the form below.
FAQ
How do I calculate resin consumption against parts produced? Multiply good parts by the checked part weight for each mould, add weighed scrap, purge, quarantine and closing floor stock, and compare that with granules issued plus opening floor stock. The difference is the gap. Express it as a percentage of the month's issues.
What reconciliation gap is acceptable in an injection-moulding shop? We found no published Indian norm on the CIPET or AIPMA websites (checked 17 Oct 2026). As a working assumption, treat under 0.75% as measurement noise, 0.75% to 1.5% as a count or standard to check, and over 1.5% as a question about how material leaves the floor. Tighten the bands once you have your own history.
Should regrind be counted as an output? Only the regrind that left the floor (sold, sent to the scrap store) or sits on the floor at month-end. Regrind that went back into the hopper turns up later as parts, so counting it as output double-counts it.
Why is my gap negative? Either good parts are overcounted, for example shot counter × cavities on a mould with a blocked cavity, or some issues were made without a slip. A negative gap can hide a positive one.
What does a 2% resin gap cost? In our 20-press example, 2% of 97,900 kg issued is 1,958 kg. At ₹158/kg, based on IOCL's PP list price of 15 Oct 2026, that is about ₹3.1 lakh a month, before any lost GST credit.