Lean Analysis of the Molds Cleaning Inside Glass Manufacturing. Step C.
- Silvio Ruiu
- Jul 17, 2023
- 7 min read
Updated: Jan 24
Intro.
Inside the shop life where mold (or mulds) maintenance is a real thing. Molds have a stressful life while producing inside the IS machine, high temperatures bring strong thermomechanical stress, the use of swabbing compounds is important to maximize the operational speed of the IS.
Cleaning the molds after the run into the IS is mandatory to eventually repair the molds (fixing the cavity loss and the seams) and to anyway prepare the surface for the next run with the new layer of lubricant.
Who already own a wheel blaster, 👉others here.👈
Each case, so each plant is unique and it is common that different molds from the material point of view and complexity require different parameters on the cleaning cycle to avoid unwanted wear.
Wherever technology you are using today, you may already have a wheel blaster, CM only delivered more than 600 around the world, and so you are questioning why still having issues.
Long story short the blaster is not eternal, and the process may deviate as well, using these 2 simple criteria you can eventually understand your status:
1) 1-1 (1-2 in USA) rule: if you are consuming more than 1kg of media per blasting hour there is something to check; the hour is still the same, the weight in pounds and so the rule in US becomes 1 hour per 2lbs. of media. More details here.
2) 5-10 rule: If your process has not reviewed in the last 5 years, or your machine older than 10, you need to review the process in case of 5, both process and machine in case of 10 years. Learn more here.
If you need support on your current wheelblaster process you can contact here.
On purpose, there is no single world about CAPEX, OPEX and TCO, making them argument for the next article and focusing here by LEAN manufacturing on what really counts on the production floor: performances.
Summary of Results.
Full analysis is below the summary.
Technology | Process Stability & Quality | Risk Factor (Human/Safety/EPA) | Lead Time | Versatility vs. Volume | LEAN manufacturing lens |
Manual Air Blasting | Impossible to standardize. No quality detected. | High. Injury risks (sprains), "rolled seams". | Slow. One part at a time. | Excellent for small, eventual touch-ups. | High waste of human labor and efforts. |
Automated Air Blasting | Low due to uncontrollable wear. No quality. | Medium. Extreme noise, air leaks. | Too slow. Long cycles (15 min), workshop bottlenecks. | Good for a mix of small, complex batches. | Energy Inefficient: energy consumption. High maintenance. |
Wheel Blasting (Centrifugal) | Highest. Jidoka via Amp monitoring; Poka Yoke via media consumption. | Minimum. Closed process, ergonomic. | Fast. <5 min per batch. Can increase with tools. | The benchmark for massive production (e.g., 14 lines). | Low and efficient consumption, low and easy to dispose waste. |
Chemical & Ultrasonic | Good, limiting with materials and procedures. | Critical. Chemical hazards, EPA rules, waste disposal. | Very Slow. Long soaking and drying times. | Scalable only with a massive footprint. | Hazardous waste, chemical active environment. |
Laser Cleaning | High depending on shapes. | Low, but requires optical barriers and fume extraction. | Extremely Slow. Point-to-point; struggles with complex shapes. | Only for niche or ultra-tech applications. | Bottleneck: Cannot match the pace of massive glass production. |
Technology Choice: 5 Methods under the LEAN Manufacturing Lens.
To protect these assets, we must evaluate technology through Lean Manufacturing principles: eliminating waste (Muda) and ensuring process stability through Jidoka. .
👉(cup of coffee/tea suggested, it’s gonna be a long ride) 👈
Manual Air Blasting - High Flexibility but high Risk.
This method is inconsistent and extremely labor-intensive. It relies entirely on the operator's hand, making it the leading cause of "rolled seams" and inconsistent mold closure, not to mention the most important, among the leading factors in sprains and strains among the polisher- if not the whole plant.
Backing on the human factor, or the shop has dedicated personnel committed to the task, and still everything rely on their hands, mood, motivation – really no standardization possible; or some skilled mold’s repair members of the team need to shift into the cleaning, people that are relatively high paid and never grateful to spend their time into such boring task – still speaking about standards is just an illusion; so they may think to turnover somewhere else where their skills are much more appreciated for the same wage.
Is it necessary? Indeed, it is, because it is cheap by itself, extremely flexible and can be helpful for hundreds of small tasks on the molds and not on the molds, makes sense if used really few hours per week.
Automated Air Blasting - A move towards stability.
By automating many nozzles spraying simultaneously on a rotating table, you eliminate human variance. However, each nozzle has its own pattern of wear due to the air delivery line feeding it, in the “human powered” unit a committed operator can compensate this wear correcting the angle of impact and the distance between nozzle and blank, which is impossible to do in an automatic equipment. To standardize the process frequent stop for maintenance, with parts to replace indeed quite expensive, is a must.
Automatic air blasting makes the “magic” to add many fixed nozzles instead of one only human controlled, so instead of spraying 5kgs per minute by one nozzle they spray about 50kgs (ten times more) by adding many nozzles (about 10 usually), so compressed air consumptions follows increasing 10 times too, and here arrives the second part of this game:
A massive compressor that due to its noise needs to be allocated in another (silenced) room – otherwise the life inside the mold shop would near to a nightmare.
An air delivery line with its own storage tanks and dryer massive accordingly in terms of dimensions and potential air leak.
These machines usually blast the equipment in long cycles (around 10-15 minutes) and contribute to long wait time from IS machine to the mold maker’s vice. Where an automatic air blaster really wins is where tiny to average productions require parts treated in different ways with different impacts by the two sides for example.
Wheel Blasting - Leading in industrial standard and efficiency.
The wheel blasting method is currently the industry’s benchmark for quality and efficiency. It uses kinetic energy to provide the most consistent finish with the lowest cost-per-part, ideal for absolute repeatability – it means highly standardizable - no wait time reduced to less than 5 minutes per batch of molds and no “Reruns".
It also has the perfect KPI by media consumption in the mid-term timing (learn more here about 1 – 1 rule) and the perfect Jidoka in wheel Amps consumptions while the cleaning cycle is ongoing advising if anything is going out of the established path. Process can be extra stabilized using automatic media feeding systems to ensure the media operating mix is consistent with always the same percentage of new/middle/used shots to get maximum repeatability.
Carts, layouts, planetaries (indeed a Poka – Yoke if designed on purpose) with accordingly engineered layout can speed up the process time overall and perfectly integrate with highly automated mold shops. The centrifugal blasters utilize minimum air and rely on electricity as the main power to energize the turbine, separating it from the lines of all other pneumatic machines.
Shop Reference 1: In a 14 lines glass factory, molds cleaner operators has been reduced by 11 units and now doing processes with higher added value rather than clean the molds. If there is a need of standard and efficiency, the wheel blaster is simply unbeatable.
Shop Reference 2: this process has been validated by one of the biggest corporate worldwide by blasting the molds/blanks for continuosly 12 hours, without any loss in weitght measurable afterwards and abit of rounding on the seams, while the regular process is less than 5 minutes - usually 4.
Ultrasonic & Chemical Baths-Effective, Expensive and not a friend of EPA.
Effective for deep cleaning without abrasion; yet it often lacks the "mechanical action" needed to perfectly prepare the surface for the repair team. In practicality, this method requires a very long wait-time (which will determine your total mold/set qty); not to mention the significant waste disposal costs and the strict safety protocols required for the plant.
To increase the capacity the only possible way is to fulfill the requirements of a massive production, with equipment that has big footprint and other significant implications as the safety protocol for the workers in a chemical hazardous environment. Considering the glass plant as mid to long term investment, there is a huge question mark about the rules will be enforced in the future about the hazardous chemical waste and its own cost, it is a kind of “roulette” absolutely unpredictable.
Laser – the newcome in the game.
Promise of this technology is the no use of media or chemicals to get the task accomplished. However, laser is ray of light/energy that works punctually, risk is a localized overheating of the surface with the issue that a mold, especially the interesting part, is anything but straight or flat. In the end of the day it come with a huge footprint for the shop and incredibly low process speed, which does not match the needs of a massive glass production.
Wheel blaster, the industrial benchmark inside mold shops.
It is now clear while beside any other consideration and applying LEAN manufacturing the wheel blaster is the winner of the challenge, by technology that can reach the targets needed and even overcome them.
Summary of the analysis:
Step A: molds as primary asset of a glassmaker.
Clarifying importance of molds for glassmakers. Target: all people involved in glass industry from mold shop to corporate management.
Step B: Molds impact on EBITDA.
How cleaning of the molds impact on the P&L of a glass plant. Target: plant Managers and corporate management.
Step C: Professional standard inside the mold shop. this article
Technologies available and Lean manufacturing analysis. Target: mold shop Managers and Supervisors, plant Managers.
Step D: financial analysis of the options available.
Summarizing all the results under Lean manufacturing. Target: plant and corporate management.
