The ten step pointers, drafted by resin technology Adviser Mr H. Vaidyanathan in industry interest will help plywood manufacturers develop the quality product that is consistent with the BIS norms.
These pointers are applicable for the stakeholders applying for license under standardization IS:303 which consists of MR (Moisture Resistant) Grade, BWR (Boiling Water Resistant) Grade, & BWP (Boiling Water Proof) Grade of Plywood Boards.
Standard Operating/Operations ProcedureSOPs are the only way to consistency in Quality & Quantity (Q&Q), especially in manufacturing. Maintain the following (critical) SOPs, in order to remain care-free from IS: 303-2024 sample-rejection/failure probabilities.
Point 1 Think simple and consistent
Do not get carried away by multiple advises from multiple sources of “well-wishers” and experts. What works elsewhere need not work for you. Create your own SOPs. Adhere to Them and do not allow “tinkering” with SOPs for temporary “clearing” of production. Do not allow floor supervisors and managers to mislead you for their temporary escape from problem identification and accountability.
The only first question must be – Why SOP was not followed? And who is accountable for the deviation? This accountability must be for Owners also.
Point 2 P.P.C.
PPC stands for Production Planning & Control – It is the most critical aspect of Q&Q in manufacturing, especially manual/semi-automated manufacturing units.
Planning of Raw Material (RM) procurement & utilization without involving multiple brains Maintain well-delegated work mechanisms. Small factory also can have multi-tasked delegations among a few staff/ supervisors. Empower your staff & workers and Let-Go of delegation-fear.
Ensure well-planned & scheduled preventive maintenance of all machinery, equipment, tools & laboratory.
Point 3 Peeling & Drying
Check core veneer peeling thickness consistency. Maintain strictly implemented SOPs for core grading, sorting, and stacking.
Drying to an extent possible maintains uniformity in drying speed, for each species &thickness. Ensure appropriate ventilation & RH (Relative Humidity < 65%) in dried core Veneer storage area (even if shed is small, plan and create the layout space.). Use Mezzanine floor layout & space.
Ensure core veneer moisture-stabilization & temperature-stabilization for at least 48 hours.
Point 4 Core Veneer Assemblies
Maintain strict discipline in core veneer assembly. Plan assembly and strictly delegate implementation with accountability.
Avoid overlaps, parallel joint-lines across assemblylayers, and uneven joints in all directions of each assembly layer. Re-work and re-orient “assemblyhabits”in your factory to create consistency and discipline.
Some small factories can come together and “develop” simple equipment for manual stitching, manual patching etc. China developed by making their own tools & handy equipment for work-convenience and consistency of work. We have to start doing this, right now. Invest time and a little money in devising tools and equipment suiting your work style at the factory. Do not wait for Chinese to decide which working tool your factory wants. Let’s start working for our own factories. No investment is needed.
Point 5 Resin-making/Specification
Become well aware of resins & glue-mixing. Ensure proper, slow cooking of resin, if you have your own resin making kettle. Do not compromise on cooling efficiency & cooking time. Again, SOP is final. No one should change or have the authority to change it. Maintain strict precision in weights & measures of raw materials & chemicals. Ensure strict Specification if you are purchasing resins from suppliers.
Point 6 Glue-Mixing
Glue Mixing is the most crucial aspect of consistency. Maintain precise weights & measures. Consistently check accuracy and method of glue mixing. Create & maintain exact glue-mixing sequence. Understand that filled viscosity is different from swollen viscosity. Manufacturers should use well established, branded glue-line treatment (GLT) preservative chemicals at precise/recommended quantities.
Maintaining perfect glue PH in all-weather without deviating from established glue-mixing SOPs is utmost.
Point 7 Glue Spreading
Have high quality glue-spreader machine. Get the machine cleaned daily, & maintained perfectly, and avoid misuse/abuse of glue spreader. Glue spreader is an investment which will help you with reduced tensions. Continuously check for precise glue coverage and ensure workers/operators maintain the glue-spread SOPs. Check and record glue-spread data, at every 30 minutes intervals. Check glue-spread consistency on both surfaces of core veneer, as well as both half-portions of the core veneer.
Point 8 Prepressing & Hot-pressing
Try to introduce prepressing (cold-pressing) to have proper moisture balance in the matboard.
Though not really mandatory for excellent quality, introducing prepress helps with certain critical parameters like equilibrium moisture-balance of the glued board assembly, enables cutting/cleaning of overlap joints, enables surface patching and corrections, thus helping you to obtain higher levels of confidence with consistency & uniform surface. Small factories can also have cute/small-capacity prepress systems.
Ensure Hot-press preventive maintenance, checking of daylight temperatures, heating media (steam/oil) flow etc., regularly and on a daily basis. Make a routine for machine function check-ups daily. Takes 5 minutes. (Check & align with PPC) Always calibrate (comparison & measurementcorrection) dial gauge pressure with actual pressure, dial gauge temperature with actual daylight-platen temperature. Keep track of measures with precision. Keep ensuring precise steam/oil flow pressure and boiler firing parameters.
Learn, understand & standardize the PressureTemperature-Time balance in all species, glues, and core-veneer combinations you use in your factory. Never try to copy Quality & Quantity from another factory. Getting a direction is entirely different from copying everything.
Do not throw water on hot, freshly unloaded MR Grade Boards. Do you know that glue linecures only up to around 85% during hot-pressing? Remaining curing happens during stabilization period, and conditioning period. This is called as the post-curing period. Final quality & strength of the boards is gained during postcuring period.
Point 9 Calibration, Surface Repair & Face Overlay (FO)
Popularly & wrongly called as ‘re-facing’, face overlay is an area of many common mistakes. Use nonshrinking, non-cracking, medium-speed curing surface repair pastes/putties.
Do not undertake putty work on hot/warm boards. Allow putty work to cure fully before FO. Wet/damp/ moist/uncured putty during FO hot-pressing can create patches & splits on face veneers.
Do not overload the calibrator with higher thicknessremoval. Ensure no more than 0.4mm thickness planning per side of the boards (0.8mm both sides, single pass).
Ensure strict maintenance & preventive maintenance in calibrator-sander machines. Do not over-cure board during FO hot-pressing. Apply only 75-80% of mat-board pressure during FO hot-pressing. Excess pressure during FO can crack the brittle, cured gluelines under the face-line core veneer and lead to postdelivery, application-site face-line core delamination during cutting and processing of the boards.
Point 10 Conditioning of Boards
Every lot of production must be “conditioned” before stamping & dispatch. Conditioning is the time provided for boards to be fully “post-cured”. Conditioning helps attain full curing, peak strength, bonding consistency, moisture stability, and reduce warping/bending of manufactured plywood boards.
ADDITIONAL NOTE:
Earlier, Production Manuals (PM) were ‘cooked-up’ (open secret). You cannotafford to do this anymore. Mandatory BIS Quality Control (QC) requires mandatory entry of data from each hot-pressing cycle.
- Maintain 1 stack for real-time PM entry, lot-sampling, and lot-testing data.
- Ensure consistent, uniform, and well-tracked flow of production data from the floor of your factory to the QC section/laboratory department.
- Stick to SOPs and the PPC work-style & approaches to laboratory.
- Ensure installation, maintenance and functioning of all laboratory equipment, tools, fixtures, glassware, and chemicals.
- Ensure calibration of all required equipment & glassware as per BIS norms.
- Ensure proper entry, follow-up, and easy availability of all relevant records for BIS inspection & scrutiny.
- Ensure all chemicals/reagents are relevant, and well within their expiry dates.
- A Place For Everything, & Everything In Its Place.
Key Short-forms:
- SOP – Standard Operating/Operations Procedure
- PPC – Production Planning & Control
- Q&Q – Quality & Quantity
- BIS – Bureau of Indian Standards
- GLT – Glue Line Treatment
- PM – Production Manual
- FO – Face Overlay