--- title: "How do burn mark defect risks affect injection molding supplier sourcing decisions?" description: "Tired of picking low-cost injection molding suppliers that hide unaddressed burn mark defect risks? Get clear defect classification criteria, side-by-side supplier evaluation metrics, and actionable cost calculation methods to eliminate hidden quality losses and lock stable mass production output." url: "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html" language: "en" type: "Q&A" category: "Injection Molding Q&A" datePublished: "2026-09-17" dateModified: "2026-09-17" brand: "OK TOOL" manufacturer: "OK TOOL" answerCount: 10 --- # How do burn mark defect risks affect injection molding supplier sourcing decisions? ## Question Last month I shortlisted 3 injection molding suppliers for our new line of power tool housing components, all quoting within 8% of each other on unit price and tooling cost. I received initial prototype batches from all three last week, and two of them have faint visible burn marks at the far end of the 2mm thick rib sections, while the third one delivered completely defect-free samples but quoted 7% higher than the lowest bid. My current dilemma is that the two lower-priced suppliers insist the burn marks are “purely cosmetic” and will not affect part function, but I know even faint burn marks can lead to hidden fatigue failure over 2 years of end use. I also can’t justify a 15% total price premium just based on prototype visual checks, especially when our annual order volume hits 120k units. I need a structured way to compare these suppliers’ actual burn mark control capability side by side, instead of just negotiating a per-unit discount for defective parts. ## Answers ### Answer 1 — Best Answer The first step to resolve this dilemma is to separate burn mark risks into 3 distinct categories before running any supplier comparison. Visible surface burn marks are easy to identify during incoming inspection, but 62% of unaddressed burn mark issues in 2024-2026 injection molding projects fall into the hidden category: localized polymer degradation inside thick ribs that shows no surface discoloration, but reduces the material’s impact resistance by 25% to 40% under long term cyclic load. Many low cost suppliers classify these as acceptable cosmetic defects because they have no formal test to validate internal material integrity, which is the core hidden risk that will generate far more cost downstream than any small per unit price saving. The first comparison metric you can use immediately is to ask every supplier to submit their formal burn mark validation report for the exact part design, not a generic quality document. **Require each supplier to run a 200 shot uninterrupted trial under their standard mass production parameters, then cut 5 sample parts from the 50th, 100th and 180th shot to do cross section inspection at the highest risk rib positions**. This test costs less than $150 per supplier and will eliminate all suppliers that only fix burn marks on 1 or 2 hand tuned prototype samples, but cannot maintain stable process windows for full mass production. Next, calculate the total cost of poor quality for each supplier instead of only comparing quoted unit price. For a 120k annual volume order, even a 2% burn mark related rejection rate at incoming inspection will add 120 man hours of rework time per year, plus 0.5% of total order value for scrap. If 1% of parts with hidden internal burn marks slip through inspection and reach end customers, the warranty claim and reverse logistics cost can be 7 to 12 times the original part unit cost. **Mark any supplier that refuses to provide a 12 month warranty against burn mark related functional failure as non compliant, regardless of their quoted price**. The last step is to add two specific clauses in the final purchasing agreement to lock consistent performance after sourcing. **Set a clear non-conformance threshold that classifies any burn mark deeper than 0.1mm on cross section as a full rejection, no exceptions for cosmetic concessions**. All suppliers that can consistently meet this threshold on the trial test will have a total cost of ownership 3% to 5% lower than suppliers that quote lower unit price but carry high hidden defect risks, even if their initial quoted unit price is slightly higher. This avoids the common mistake of sourcing based on prototype quality alone, and creates a measurable baseline that all production batches can be audited against. **status:** accepted **Author:** Amy Li **Date:** 2026-09-17 ### Answer 2 The total impact of burn mark control on overall production efficiency is often overlooked during supplier comparison. Suppliers that eliminate burn marks only by slowing down injection speed and extending cycle time by 15% to 20% will have lower output per mold every hour, which translates to higher unaccounted labor and machine hour costs that are not reflected in their initial quoted unit price. You can ask each supplier to submit their planned full mass production cycle time for this exact part, and cross check it against industry baseline for the same material and wall thickness. A supplier that uses proper venting optimization to remove trapped air instead of extending cycle time can run 12% more parts per shift on the same machine, reducing per part overhead significantly even if their base quote looks slightly higher. This also eliminates the risk of unexpected order delays during peak season, when suppliers will push cycle times to the limit to meet delivery deadlines, and burn mark defects will spike sharply if they do not have proper venting in place. **status:** suggested **Author:** Michael Wu **Date:** 2026-09-17 ### Answer 3 When comparing suppliers on burn mark control, it is critical to map this requirement to every stage of the project timeline instead of only adding it as a generic quality clause. For the prototype sign off stage, add burn mark cross section inspection as a mandatory gate that must be passed before tooling steel hardening, not after the tool is fully finished. If a supplier finds burn marks at the prototype stage and needs to adjust gate position or add extra venting, this change can be completed in less than 3 working days before final tool finishing, with almost zero extra cost. If the same issue is found after the tool is hardened during pre-production trial, modifying the venting will take 7 to 10 days and add unplanned delays to the whole product launch timeline. Suppliers that can lock burn mark performance at the early sample stage will have much lower risk of unplanned change orders that push your launch date back by weeks. **status:** suggested **Author:** Eric Zhao **Date:** 2026-09-17 ### Answer 4 Burn mark risk is directly tied to resin formulation and grade selection, which is a hidden comparison point most procurement teams miss during supplier evaluation. Some lower tier suppliers use 10% to 15% regrind mixed into virgin resin without formal disclosure, which lowers material cost but also reduces the material’s thermal stability, making it far more likely to generate degraded burn marks even under standard process parameters. You can ask each supplier to provide the exact resin lot number they plan to use for mass production, and run a 30 minute thermal stability test on a small sample of the same resin to check for degradation at the standard processing temperature. If two suppliers quote similar material cost, the one that uses a higher thermal stability grade of resin will have a far wider safe process window, and can resist burn mark formation even if minor process fluctuations happen during 24/7 mass production. This avoids the situation where suppliers cut material cost to offset their lower quoted price, and introduce hidden defect risks. **status:** suggested **Author:** Linda Xu **Date:** 2026-09-17 ### Answer 5 A clear defect classification system for burn marks will eliminate 90% of the argument and concession requests between you and the supplier after production starts. Most suppliers use a generic cosmetic standard that allows faint discoloration that is not visible at 30cm distance, but this does not account for different part use scenarios. You can work out 3 distinct burn mark grades for this specific part: grade 0 is no discoloration or material degradation, grade 1 is faint surface discoloration less than 0.05mm deep with no impact to structural performance, grade 2 is any burn mark deeper than 0.05mm or located on critical load bearing sections. Then map each grade to clear action items: grade 0 parts are 100% acceptable, grade 1 parts require formal notification before shipment and come with a 5% per unit discount, grade 2 parts are full rejection with no concession allowed. You can then audit each supplier’s existing IPQC records for similar parts to check if they already have a matching classification system in place, which tells you how consistent their quality control process is. **status:** suggested **Author:** Sophia Wang **Date:** 2026-09-17 ### Answer 6 Burn marks that look completely harmless on individual parts can create major fit and consistency issues during high volume automated assembly lines. Even faint surface discoloration from burnt volatile gas will leave a thin layer of residue on the part surface, which reduces the bonding strength for ultrasonic welding or adhesive assembly by 15% to 22%. If your assembly line runs 600 parts per hour, a 3% drop in welding yield from burn mark residue will generate hundreds of defective assembly units every week, most of which cannot be reworked and have to be scrapped completely. When comparing suppliers, you can take their prototype parts and run a small batch assembly test using your standard production process, to verify if burn marks on the parts create any drop in assembly yield. Many suppliers that claim burn marks are purely cosmetic have no data on how those defects impact downstream assembly steps, which is a major hidden cost that never shows up on their initial quotation sheet. **status:** suggested **Author:** Olivia Chen **Date:** 2026-09-17 ### Answer 7 The core root cause for 80% of burn mark defects in new part designs is poor venting design that traps air at the end of fill, rather than bad process tuning. When evaluating different suppliers, ask each one to share the venting layout they have designed for your specific part, including vent depth, location, and total vent cross section area. A properly designed venting layout for your 2mm thick rib sections will have vents placed exactly at the last fill position, with vent depth controlled between 0.02mm and 0.03mm for general ABS material, which allows trapped air to escape completely before the melt front reaches that position. Suppliers that do not pre-design dedicated vents for high risk sections will have to rely on manual process tuning to reduce burn marks, which cannot be maintained consistently across thousands of production cycles. This design choice made at the very beginning of the mold project determines 70% of the final burn mark control performance, long before any material is injected into the tool. **status:** suggested **Author:** Jason Zhou **Date:** 2026-09-17 ### Answer 8 Mold steel selection and surface finishing have a direct impact on long term burn mark control performance across the full mold service life. Lower cost P20 steel molds that are not properly stress relieved will develop micro cracks on the cavity surface after 50k to 60k shots, which trap accumulated volatile gas residue from melted resin, and create recurring burn mark defects that are impossible to eliminate via process adjustment. When comparing supplier tooling packages, confirm the exact steel grade they plan to use, their standard stress relief process, and their scheduled maintenance cycle for vent cleaning. A supplier that uses hardened H13 steel for the cavity inserts will have a much longer service life for the critical vent positions, and can run 300k+ shots without recurring burn mark issues, while a P20 steel mold will start generating consistent burn marks after 60k shots, requiring extra regular maintenance that adds unplanned downtime and cost. **status:** suggested **Author:** Daniel Yang **Date:** 2026-09-17 ### Answer 9 A wide stable process window for burn mark control is far more valuable than a single perfect prototype that is tuned with hand adjusted parameters. You can run a simple process window test for every supplier during the trial stage: increase injection speed by 15% and melt temperature by 10°C on the same part, then check if burn marks appear immediately. Suppliers that can absorb these minor process fluctuations without generating defects have a properly designed process window, which means even when night shift operators make minor adjustments, or resin batch properties have small normal variations, the defect rate will stay near zero. Suppliers that can only produce burn mark free parts on a very narrow parameter setting will have random defect spikes every few hundred shots, even if their initial prototype looks completely perfect. This test only takes 1 to 2 hours per supplier, but can filter out most suppliers that cannot maintain consistent quality at mass production scale. **status:** suggested **Author:** Emily Chen **Date:** 2026-09-17 ### Answer 10 The precision of vent machining on the mold cavity directly determines how well trapped air can escape during injection, and this is a factor very few procurement teams check during supplier comparison. Vents machined with standard 0.05mm depth on general molds will generate flash on the part, so many lower tier suppliers will manually polish the vent surface after machining to reduce depth, but this creates uneven vent depth across different vent positions, and some sections end up fully blocked. You can ask each supplier to show you their vent machining process record, confirming if they use 5 axis CNC machining to finish vent positions to exact depth tolerance, or manually finish vents by hand. Manually finished vents will have inconsistent depth, and some sections will be blocked completely after 10k shots, leading to sudden burn mark issues that appear without warning during mass production. Precision machined vents with consistent depth can maintain full functionality for the entire mold service life, with no extra process tuning required. **status:** suggested **Author:** David Zhang **Date:** 2026-09-17 ## Related Resources - [Injection Molding Q&A](https://www.ok-tool.com/qa/injection-molding/) - [Plastic Injection Molding](https://www.ok-tool.com/capabilities/plastic-injection-molding/) - [Injection Molding Guide](https://www.ok-tool.com/manufacturing/injection-molding/) - [Injection Molding Buying Guides](https://www.ok-tool.com/buying/injection-molding/) - [Products](https://www.ok-tool.com/products/) - [Custom Manufacturing](https://www.ok-tool.com/custom-manufacturing/) - [Manufacturing Knowledge Base](https://www.ok-tool.com/knowledge/) - [Injection Molding](https://www.ok-tool.com/knowledge/injection-molding/) ## Structured Data ```json [ { "@context": "https://schema.org", "@type": "QAPage", "mainEntity": { "@type": "Question", "name": "How do burn mark defect risks affect injection molding supplier sourcing decisions?", "text": "Last month I shortlisted 3 injection molding suppliers for our new line of power tool housing components, all quoting within 8% of each other on unit price and tooling cost. I received initial prototype batches from all three last week, and two of them have faint visible burn marks at the far end of the 2mm thick rib sections, while the third one delivered completely defect-free samples but quoted 7% higher than the lowest bid. My current dilemma is that the two lower-priced suppliers insist the burn marks are “purely cosmetic” and will not affect part function, but I know even faint burn marks can lead to hidden fatigue failure over 2 years of end use. I also can’t justify a 15% total price premium just based on prototype visual checks, especially when our annual order volume hits 120k units. I need a structured way to compare these suppliers’ actual burn mark control capability side by side, instead of just negotiating a per-unit discount for defective parts.", "answerCount": 10, "upvoteCount": 8, "datePublished": "2026-09-17T19:28:37Z", "dateModified": "2026-09-17T19:32:27Z", "author": { "@type": "Person", "name": "Anonymous", "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html" } ,"acceptedAnswer": { "@type": "Answer", "text": "The first step to resolve this dilemma is to separate burn mark risks into 3 distinct categories before running any supplier comparison. Visible surface burn marks are easy to identify during incoming inspection, but 62% of unaddressed burn mark issues in 2024-2026 injection molding projects fall into the hidden category: localized polymer degradation inside thick ribs that shows no surface discoloration, but reduces the material’s impact resistance by 25% to 40% under long term cyclic load. Many low cost suppliers classify these as acceptable cosmetic defects because they have no formal test to validate internal material integrity, which is the core hidden risk that will generate far more cost downstream than any small per unit price saving. The first comparison metric you can use immediately is to ask every supplier to submit their formal burn mark validation report for the exact part design, not a generic quality document. Require each supplier to run a 200 shot uninterrupted trial under their standard mass production parameters, then cut 5 sample parts from the 50th, 100th and 180th shot to do cross section inspection at the highest risk rib positions . This test costs less than $150 per supplier and will eliminate all suppliers that only fix burn marks on 1 or 2 hand tuned prototype samples, but cannot maintain stable process windows for full mass production. Next, calculate the total cost of poor quality for each supplier instead of only comparing quoted unit price. For a 120k annual volume order, even a 2% burn mark related rejection rate at incoming inspection will add 120 man hours of rework time per year, plus 0.5% of total order value for scrap. If 1% of parts with hidden internal burn marks slip through inspection and reach end customers, the warranty claim and reverse logistics cost can be 7 to 12 times the original part unit cost. Mark any supplier that refuses to provide a 12 month warranty against burn mark related functional failure as non compliant, regardless of their quoted price . The last step is to add two specific clauses in the final purchasing agreement to lock consistent performance after sourcing. Set a clear non-conformance threshold that classifies any burn mark deeper than 0.1mm on cross section as a full rejection, no exceptions for cosmetic concessions . All suppliers that can consistently meet this threshold on the trial test will have a total cost of ownership 3% to 5% lower than suppliers that quote lower unit price but carry high hidden defect risks, even if their initial quoted unit price is slightly higher. This avoids the common mistake of sourcing based on prototype quality alone, and creates a measurable baseline that all production batches can be audited against.", "upvoteCount": 8, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#acceptedAnswer", "datePublished": "2026-09-17T20:59:33Z", "author": {"@type": "Person","name": "Amy Li","url": "https://www.ok-tool.com/team/amy.html"} } ,"suggestedAnswer": [ { "@type": "Answer", "text": "The total impact of burn mark control on overall production efficiency is often overlooked during supplier comparison. Suppliers that eliminate burn marks only by slowing down injection speed and extending cycle time by 15% to 20% will have lower output per mold every hour, which translates to higher unaccounted labor and machine hour costs that are not reflected in their initial quoted unit price. You can ask each supplier to submit their planned full mass production cycle time for this exact part, and cross check it against industry baseline for the same material and wall thickness. A supplier that uses proper venting optimization to remove trapped air instead of extending cycle time can run 12% more parts per shift on the same machine, reducing per part overhead significantly even if their base quote looks slightly higher. This also eliminates the risk of unexpected order delays during peak season, when suppliers will push cycle times to the limit to meet delivery deadlines, and burn mark defects will spike sharply if they do not have proper venting in place.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-2", "datePublished": "2026-09-17T20:56:19Z", "author": {"@type": "Person","name": "Michael Wu","url": "https://www.ok-tool.com/team/michael.html"} } , { "@type": "Answer", "text": "When comparing suppliers on burn mark control, it is critical to map this requirement to every stage of the project timeline instead of only adding it as a generic quality clause. For the prototype sign off stage, add burn mark cross section inspection as a mandatory gate that must be passed before tooling steel hardening, not after the tool is fully finished. If a supplier finds burn marks at the prototype stage and needs to adjust gate position or add extra venting, this change can be completed in less than 3 working days before final tool finishing, with almost zero extra cost. If the same issue is found after the tool is hardened during pre-production trial, modifying the venting will take 7 to 10 days and add unplanned delays to the whole product launch timeline. Suppliers that can lock burn mark performance at the early sample stage will have much lower risk of unplanned change orders that push your launch date back by weeks.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-3", "datePublished": "2026-09-17T20:45:32Z", "author": {"@type": "Person","name": "Eric Zhao","url": "https://www.ok-tool.com/team/eric.html"} } , { "@type": "Answer", "text": "Burn mark risk is directly tied to resin formulation and grade selection, which is a hidden comparison point most procurement teams miss during supplier evaluation. Some lower tier suppliers use 10% to 15% regrind mixed into virgin resin without formal disclosure, which lowers material cost but also reduces the material’s thermal stability, making it far more likely to generate degraded burn marks even under standard process parameters. You can ask each supplier to provide the exact resin lot number they plan to use for mass production, and run a 30 minute thermal stability test on a small sample of the same resin to check for degradation at the standard processing temperature. If two suppliers quote similar material cost, the one that uses a higher thermal stability grade of resin will have a far wider safe process window, and can resist burn mark formation even if minor process fluctuations happen during 24/7 mass production. This avoids the situation where suppliers cut material cost to offset their lower quoted price, and introduce hidden defect risks.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-4", "datePublished": "2026-09-17T20:40:12Z", "author": {"@type": "Person","name": "Linda Xu","url": "https://www.ok-tool.com/team/linda.html"} } , { "@type": "Answer", "text": "A clear defect classification system for burn marks will eliminate 90% of the argument and concession requests between you and the supplier after production starts. Most suppliers use a generic cosmetic standard that allows faint discoloration that is not visible at 30cm distance, but this does not account for different part use scenarios. You can work out 3 distinct burn mark grades for this specific part: grade 0 is no discoloration or material degradation, grade 1 is faint surface discoloration less than 0.05mm deep with no impact to structural performance, grade 2 is any burn mark deeper than 0.05mm or located on critical load bearing sections. Then map each grade to clear action items: grade 0 parts are 100% acceptable, grade 1 parts require formal notification before shipment and come with a 5% per unit discount, grade 2 parts are full rejection with no concession allowed. You can then audit each supplier’s existing IPQC records for similar parts to check if they already have a matching classification system in place, which tells you how consistent their quality control process is.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-5", "datePublished": "2026-09-17T20:25:11Z", "author": {"@type": "Person","name": "Sophia Wang","url": "https://www.ok-tool.com/team/sophia.html"} } , { "@type": "Answer", "text": "Burn marks that look completely harmless on individual parts can create major fit and consistency issues during high volume automated assembly lines. Even faint surface discoloration from burnt volatile gas will leave a thin layer of residue on the part surface, which reduces the bonding strength for ultrasonic welding or adhesive assembly by 15% to 22%. If your assembly line runs 600 parts per hour, a 3% drop in welding yield from burn mark residue will generate hundreds of defective assembly units every week, most of which cannot be reworked and have to be scrapped completely. When comparing suppliers, you can take their prototype parts and run a small batch assembly test using your standard production process, to verify if burn marks on the parts create any drop in assembly yield. Many suppliers that claim burn marks are purely cosmetic have no data on how those defects impact downstream assembly steps, which is a major hidden cost that never shows up on their initial quotation sheet.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-6", "datePublished": "2026-09-17T20:24:08Z", "author": {"@type": "Person","name": "Olivia Chen","url": "https://www.ok-tool.com/team/olivia.html"} } , { "@type": "Answer", "text": "The core root cause for 80% of burn mark defects in new part designs is poor venting design that traps air at the end of fill, rather than bad process tuning. When evaluating different suppliers, ask each one to share the venting layout they have designed for your specific part, including vent depth, location, and total vent cross section area. A properly designed venting layout for your 2mm thick rib sections will have vents placed exactly at the last fill position, with vent depth controlled between 0.02mm and 0.03mm for general ABS material, which allows trapped air to escape completely before the melt front reaches that position. Suppliers that do not pre-design dedicated vents for high risk sections will have to rely on manual process tuning to reduce burn marks, which cannot be maintained consistently across thousands of production cycles. This design choice made at the very beginning of the mold project determines 70% of the final burn mark control performance, long before any material is injected into the tool.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-7", "datePublished": "2026-09-17T20:20:22Z", "author": {"@type": "Person","name": "Jason Zhou","url": "https://www.ok-tool.com/team/jason.html"} } , { "@type": "Answer", "text": "Mold steel selection and surface finishing have a direct impact on long term burn mark control performance across the full mold service life. Lower cost P20 steel molds that are not properly stress relieved will develop micro cracks on the cavity surface after 50k to 60k shots, which trap accumulated volatile gas residue from melted resin, and create recurring burn mark defects that are impossible to eliminate via process adjustment. When comparing supplier tooling packages, confirm the exact steel grade they plan to use, their standard stress relief process, and their scheduled maintenance cycle for vent cleaning. A supplier that uses hardened H13 steel for the cavity inserts will have a much longer service life for the critical vent positions, and can run 300k+ shots without recurring burn mark issues, while a P20 steel mold will start generating consistent burn marks after 60k shots, requiring extra regular maintenance that adds unplanned downtime and cost.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-8", "datePublished": "2026-09-17T20:14:04Z", "author": {"@type": "Person","name": "Daniel Yang","url": "https://www.ok-tool.com/team/daniel.html"} } , { "@type": "Answer", "text": "A wide stable process window for burn mark control is far more valuable than a single perfect prototype that is tuned with hand adjusted parameters. You can run a simple process window test for every supplier during the trial stage: increase injection speed by 15% and melt temperature by 10°C on the same part, then check if burn marks appear immediately. Suppliers that can absorb these minor process fluctuations without generating defects have a properly designed process window, which means even when night shift operators make minor adjustments, or resin batch properties have small normal variations, the defect rate will stay near zero. Suppliers that can only produce burn mark free parts on a very narrow parameter setting will have random defect spikes every few hundred shots, even if their initial prototype looks completely perfect. This test only takes 1 to 2 hours per supplier, but can filter out most suppliers that cannot maintain consistent quality at mass production scale.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-9", "datePublished": "2026-09-17T19:50:39Z", "author": {"@type": "Person","name": "Emily Chen","url": "https://www.ok-tool.com/team/emily.html"} } , { "@type": "Answer", "text": "The precision of vent machining on the mold cavity directly determines how well trapped air can escape during injection, and this is a factor very few procurement teams check during supplier comparison. Vents machined with standard 0.05mm depth on general molds will generate flash on the part, so many lower tier suppliers will manually polish the vent surface after machining to reduce depth, but this creates uneven vent depth across different vent positions, and some sections end up fully blocked. You can ask each supplier to show you their vent machining process record, confirming if they use 5 axis CNC machining to finish vent positions to exact depth tolerance, or manually finish vents by hand. Manually finished vents will have inconsistent depth, and some sections will be blocked completely after 10k shots, leading to sudden burn mark issues that appear without warning during mass production. Precision machined vents with consistent depth can maintain full functionality for the entire mold service life, with no extra process tuning required.", "upvoteCount": 0, "url": "https://www.ok-tool.com/qa/burn-mark-risk-impact-injection-molding-supplier-sourcing.html#suggestedAnswer-10", "datePublished": "2026-09-17T19:32:27Z", "author": {"@type": "Person","name": "David Zhang","url": "https://www.ok-tool.com/team/david.html"} } ] } }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ {"@type": "ListItem", "position": 1, "name": "Home", "item": "https://www.ok-tool.com/"},{"@type": "ListItem", "position": 2, "name": "Q&A", "item": "https://www.ok-tool.com/qa/"},{"@type": "ListItem", "position": 3, "name": "Injection Molding Q&A >", "item": "https://www.ok-tool.com/qa/injection-molding/>"} ,{"@type": "ListItem", "position": 4, "name": "How do burn mark defect risks affect injection molding supplier sourcing decisions?"} ] } ] ```