how to use injection molding machine

Have you ever thought about how so many plastic parts look the same every time? When I use an injection molding machine, I know small mistakes can be very dangerous. You could get burned, shocked, or hurt by moving parts. Here are some places where accidents happen a lot:

I always get ready with care. I load materials the right way. I set up the machine step by step. In this post, you will see how I make good parts every time. I also show how I stay safe at every step.

Key Takeaways

• Always check the machine and mold before you use them. This helps keep you safe and makes the machine work well.

• Pick the right plastic for your part. Think about how strong it needs to be, if it must handle heat, and how much it costs.

• Dry the plastic pellets the right way. This stops bubbles or weak spots from forming in your parts.

• Set the machine’s temperature, pressure, and cycle time correctly. This helps you make good parts.

• Follow all safety rules when you open the mold. Be careful with moving parts so you do not get hurt.

• Look at the parts for problems. Change the machine settings fast to fix any issues.

• Keep the machine clean and put oil on it often. This helps it work well and last longer.

• Get good training on how to use the machine. Learn about safety and how to fix problems so you can work safely and feel sure of yourself.

Machine Preparation

Getting my injection molding machine ready always starts with a careful inspection. I never skip this step because it keeps me safe and helps the machine run smoothly. I follow industry standards from OSHA and ANSI, which require me to check for damage, monitor temperature and pressure, and make sure all guards are in place. I also make sure I have my gloves, safety glasses, and hearing protection on before I begin.

Inspection Checklist

Mold Condition

I always start by looking at the mold. I check for cracks, wear, or leftover plastic from the last run. If I see any damage, I tag the mold and report it. I also make sure the mold is clean and dry. If I find any rust or residue, I clean it right away. I use a flashlight to look inside small cavities and corners.

Safety Features

Next, I check all the safety features. I test the emergency stop button and make sure the guards cover moving parts. I look at the interlocks and make sure they work. I check the area around the machine for anything that could cause a trip or fall. I also make sure the fire extinguisher is nearby and easy to reach.

Tip: I keep a checklist on a clipboard so I never miss a step.

Here’s a quick table I use to track my inspection:

Cleaning Steps

I always clean the injection molding machine before I start. I wipe down the mold, barrel, and hopper to remove dust and old plastic. I use special cleaning agents for the mold and a purging compound for the barrel. I check the nozzle for clogs and clean it if needed. Sometimes, I use dry ice blasting for tough residue. I also inspect the hydraulic system for leaks and check fluid levels. If I see any oil on the floor, I clean it up right away.

• I run out the screw by closing the hopper slide gate.

• I perform a purge to clear out old resin.

• I apply rust protection if the machine will sit for a while.

• I remove any rust preventive coatings before starting a new job.

Calibration

Calibration is my last step before I start production. I set the machine’s distance, speed, pressure, and temperature. I use certified measuring tools to check the sensors. I log the results and adjust the settings if needed. I use special software to compare the machine’s readings with my tools. If I see any big differences, I call a technician. Regular calibration helps me catch problems early and keeps my parts consistent.

• I check clamp and eject positions.

• I verify power supply and heater bands.

• I test temperature controllers for accuracy.

• I record all calibration data for future reference.

By following these steps, I make sure my injection molding machine is safe, clean, and ready for a smooth production run.

Material Handling

Material Selection

When I choose plastic for my injection molding machine, I always start by thinking about what the part needs to do. I look at how strong it must be, how much heat it will face, and if it needs to resist chemicals. I also check if it must be safe for food or meet other rules. I want the part to look good, so I consider color and finish. Cost matters, too. I balance price with how long the part will last.

Here are the plastics I use most often:

• Polypropylene (PP): I use this for many jobs. It leads the market because it works well for automotive, packaging, and household items.

• Acrylonitrile Butadiene Styrene (ABS): I pick ABS for medical, automotive, and electronics parts. It gives a nice finish.

• High-Density Polyethylene (HDPE): I use HDPE for strong, chemical-resistant parts.

• Polystyrene (PS): I choose PS for lightweight, rigid products.

• Polycarbonate, Polyamide (Nylon), and PVC: I use these for special needs like high impact or chemical resistance.

Tip: I always match the plastic to the job. For example, I use polypropylene for heat resistance and ABS for a glossy look.

I follow a step-by-step method:

1. I define what the part must do.

2. I screen plastics by type: commodity, engineering, or high-performance.

3. I compare properties like strength, flow, and resistance.

4. I check if the plastic molds well for my part’s shape.

5. I factor in cost and how many parts I need.

6. I make sure the plastic meets safety rules.

Drying and Pre-Treatment

Before I load plastic into the machine, I dry it to remove moisture. Wet pellets can cause bubbles or weak spots. I check the technical sheet for each plastic. For example, I dry ABS at 80-90°C for 2-3 hours. Polypropylene needs 40-80°C for 2-3 hours. Nylon takes longer—up to 6 hours at 75-90°C.

Here’s a table I use for quick reference:

I use a hopper dryer or desiccant dryer. I avoid drying below the recommended temperature. I never go above the max temperature to prevent discoloration. I keep pellets sealed until use to stop moisture from getting in.

Loading the Hopper

I always clean the hopper before loading new material. I check for leftover pellets, dust, or oil. I use a funnel to pour pellets in. I measure the amount with a gravimetric device for accuracy. I keep the area clean to avoid contamination. I store pellets in sealed containers. I train my team to handle pellets with care.

• I purge the machine between different plastics or colors.

• I use purging compounds to clear out old material.

• I check the nozzle and barrel for clogs.

• I keep the work area oil-free and dust-free.

Note: Clean equipment and careful handling keep my parts free of defects.

I follow these steps every time. It helps me make strong, clean, and reliable parts with my injection molding machine.

Injection Molding Machine Setup

Mold Installation

When I install a mold on my injection molding machine, I always follow a strict routine. This keeps me safe and protects the equipment. Here’s how I do it:

1. I check the mold size. It must cover at least 70% of the space between the tiebars. This prevents damage to the platens.

2. I inspect safety straps and make sure they are strong and in the right place.

3. I secure the mold eyebolts. I use shouldered or swivel-type hoist rings at the mold’s center of gravity.

4. I check the nozzle seat for wear or damage.

5. I position the carriage and screw. I watch for any resin drool.

6. I make sure the resin in the barrel is not degrading.

7. I clean the platens and clamp faces. I look for scratches or dents.

8. I inspect clamp bolt threads. I apply a light lubricant to help with tightening.

9. I use a crane to lift the mold over the tiebars. I check for anything overhead.

10. I lower the mold into the machine. I guide it so the locating ring fits into the alignment hole.

11. I advance the moving platen until it just touches the mold back.

12. I attach clamps on the fixed-platen side. I do not fully tighten them yet.

13. I install ejector bars and knockout rods. I check their length and straightness.

14. I torque all clamp bolts evenly. I use a torque wrench for accuracy.

15. I remove safety straps and eyebolts. I move the hoist away.

16. I open the mold and test the ejector plate. I make sure it moves smoothly.

Tip: I always clean up my work area and put away my tools after installing the mold.

Connecting Cooling System

Proper cooling is key for good parts and long mold life. I set up the cooling system like this:

1. I connect the cooling circuits. For simple molds, I use a series connection. For complex molds, I use parallel circuits with flow meters.

2. I label water inlets and outlets. I use red for "IN" and blue for "OUT." I mark these on the mold plates.

3. I place water connections on the non-operational side of the mold.

4. I check for dual straight-through paths in the cooling circuit. I avoid extra sealing rings to make maintenance easier.

5. I test coolant flow. I use a flow meter to check for blockages or low flow.

6. I use demineralized water if possible. This helps prevent scale buildup.

7. I run a quick flow test before starting production. I look for leaks or weak spots.

I perform chemical descaling on a schedule to keep the system clean.

Process Documents

I keep detailed records for every setup. This helps me repeat good results and fix problems fast. My process documents include:

• Mold preparation: I record cleaning, inspection, and any repairs. I note the mold temperature and if I used a release agent.

• Material preparation: I list the resin type, drying time, and how I loaded it.

• Machine setup: I write down mold alignment, temperature, pressure, and speed settings. I check all safety features.

• Injection process: I track injection pressure, clamp force, cooling time, and ejection steps.

• Post-injection: I inspect parts for defects. I record trimming, finishing, and quality checks.

I use a setup sheet for each job. I document six key variables: fill time, plastic pressure at transfer, cushion, recovery time, cycle time, and part temperature. I also keep records of the resin grade, mold design, machine model, and inspection results.

Keeping good records helps me make the same high-quality parts every time I use my injection molding machine.

Control Interface

Main Controls

When I stand in front of my injection molding machine, I see a touchscreen panel. This is the brain of the machine. I use it to start and stop cycles, adjust settings, and check the status. The interface feels easy to use. I tap icons to move between screens. I can set up new jobs quickly. The dashboard shows me everything I need—temperature, pressure, cycle time, and alarms.

Here are the main features I use every day:

• Touchscreen navigation lets me change settings fast.

• Quick setup tools help me switch molds and materials without wasting time.

• Real-time monitoring shows me if something goes wrong.

• Remote access lets me check the machine from my phone or computer.

• Custom dashboards display the most important data for each job.

• Training guides built into the interface help new operators learn quickly.

Tip: I always check the dashboard before starting a new cycle. It helps me spot problems early.

Setting Parameters

Before I run a cycle, I set key parameters. These control how the machine melts, injects, and cools the plastic. I know that each setting affects the final part’s quality. I use the touchscreen to enter numbers and watch the sensors update in real time.

Temperature

I set two main temperatures: melt temperature and mold temperature. Melt temperature controls how hot the plastic gets in the barrel. For ABS, I set it between 210°C and 270°C. Mold temperature keeps the mold at the right heat. For polycarbonate, I use 80°C to 120°C. I check the sensors to make sure the readings match my settings. If the temperature is too low, the plastic won’t flow. If it’s too high, the part may warp.

Pressure

I set injection pressure to push the molten plastic into the mold. I use values from 500 to 1500 bar, depending on the material. Holding pressure packs the plastic after filling. I set it to about 60% of the injection pressure. Nozzle pressure helps fill the mold evenly. I watch the pressure graphs on the screen. If the pressure drops, I check for leaks or clogs.

Cycle Time

Cycle time is the total time for one part. It includes injection, cooling, mold opening, and ejection. For small parts, I set it around 30 seconds. I adjust cycle time to balance speed and quality. If I go too fast, parts may not cool enough. If I go too slow, I waste time. I watch the timer on the dashboard and tweak it as needed.

Note: I always test a few cycles and check the parts before running full production.

Monitoring Status

I use real-time monitoring to keep my machine running smoothly. The interface shows live data from sensors inside the mold and machine. I see cycle times, temperatures, pressures, and even vibration levels. If something changes, I get an alert right away.

• I use dashboards to compare performance across shifts.

• Automated alerts tell me if a parameter goes out of range.

• I track historical data to spot trends and plan maintenance.

• Predictive maintenance tools help me fix problems before they cause downtime.

• I use Pareto charts to find the biggest sources of defects.

I rely on these tools to keep my injection molding machine efficient and my parts consistent. If I see a warning, I act fast to keep production on track.

Injection Molding Process Steps

Clamping

I always start the cycle by clamping the mold. The two halves of the mold must close tightly before I inject any plastic. If the mold does not close with enough force, molten plastic can leak out. This creates a defect called flash. I calculate the clamping force using a simple formula. I multiply the cavity pressure by the projected area of the part, then add a safety factor. For example, if my cavity pressure is 300 kg/cm² and the projected area is 500 cm², I need about 200 tons of force. I check the machine’s display to make sure it matches my calculation. I never use an injection molding machine with less force than I need. This keeps my parts clean and my equipment safe.

Tip: I always inspect the mold faces before clamping. Even a small piece of debris can damage the mold or cause leaks.

Injection

Once the mold is clamped, I move to the injection step. I heat the plastic pellets in the barrel until they melt. The screw pushes the molten plastic into the mold cavity. I set the injection pressure based on the type of plastic I use. Different plastics need different pressures. I use a table to help me choose the right settings:

I watch the pressure graph on the control panel. If the pressure drops or spikes, I stop the cycle and check for problems. I also pay attention to the speed of injection. Fast speeds fill the mold quickly, but can trap air. Slow speeds reduce defects, but may not fill complex shapes. I adjust the speed and pressure until I see smooth, complete parts.

• I always purge the barrel before a new run.

• I check the nozzle for clogs.

• I monitor the temperature to keep the plastic flowing well.

Dwelling

After injection, I hold the pressure for a short time. This is the dwelling phase. I keep the screw forward so the plastic stays packed in the mold. This helps the plastic fill every corner and prevents sink marks or voids. I set the holding pressure to about 60% of the injection pressure. I watch the timer on the control panel. If I release the pressure too soon, the part may shrink or warp. If I hold too long, I waste time and energy. I test a few cycles to find the best dwell time for each job.

Note: I always check the finished part for sink marks or short shots. These signs tell me if I need to adjust the dwelling time or pressure.

Cooling

After the dwelling phase, I let the plastic cool inside the mold. Cooling is one of the most important steps in the injection molding process. If I rush this part, the plastic may warp or crack. I always set the cooling time based on the material and part thickness. Thin parts cool faster. Thick parts need more time.

I use the cooling system to keep the mold at a steady temperature. Water flows through channels in the mold plates. I check the flow rate and temperature on the control panel. If the water gets too hot, I adjust the chiller. I watch for leaks or slow flow. These problems can cause uneven cooling.

Here is a table I use to track cooling times for common plastics:

Tip: I always check the part after cooling. If I see warping or sink marks, I adjust the cooling time or water flow.

I never open the mold before the part is fully solid. This keeps my parts strong and prevents damage.

Mold Opening

When the cooling phase ends, I open the mold. I always follow strict safety steps before I reach into the mold area. I make sure the safety door is open. I check that the oil pump is off. I never put my hands near moving parts while the injection molding machine is running.

Here is my safety checklist for mold opening:

1. I turn off the oil pump before inspecting or repairing the mold.

2. I disconnect the power if I need to enter between the mold plates.

3. I check that all safety devices work. I never operate the machine if any device is damaged.

4. I open the safety door before reaching into the mold area.

5. I notify my team before I approach the machine. I switch to manual mode.

6. I confirm any unusual actions with my team.

7. I test the emergency stop button. It must cut off power and oil pump.

8. I report any leaks or damaged wires right away.

Note: I always use operator safety gates and interlocks. These keep me safe from moving parts.

I open the mold slowly. I watch for sticking or resistance. If the part does not release, I check for mold damage or cooling issues.

Ejection

Once the mold is open, I eject the finished part. I use different ejection methods depending on the part shape and material. Ejector pins are the most common. I place them in areas that will not show marks. For delicate parts, I use air ejection or stripper plates. These methods help prevent damage and keep the surface smooth.

Here are the main ejection techniques I use:

• Ejector pins: I use these for standard parts. I place them to avoid stress marks or cracks.

• Ejector sleeves: I use these for cylindrical features. They apply even force around the part.

• Stripper plates: I use these for thin walls or large cavities. They push the part out gently.

• Air ejection: I use compressed air for flexible or clear parts. This avoids contact marks.

• Robotic handling: I use robots for complex shapes or delicate features. Robots remove parts without force.

I control the ejection speed and force. If I go too fast, the part may break. If I go too slow, the cycle time increases. I always check the part for marks or deformation after ejection.

Tip: I use automation for high-volume runs. Robots help me keep parts consistent and reduce defects.

I inspect every part after ejection. If I see damage, I adjust the ejection method or force. I keep my injection molding machine clean and well-maintained to prevent problems.

Quality Assurance

Mold Inspection

I always start my quality checks by inspecting the mold. This step helps me avoid problems before they start. I follow a set routine every time I prepare for a new production run. Here’s how I do it:

1. I review the mold design drawings and talk with the mold technician about any special features.

2. I check the mold on the workbench for scratches, missing parts, or loose pieces. I move all sliding parts to make sure they work smoothly.

3. I look for leaks in the water-cooling lines and air pipes. I mark any limits for how far the mold can open.

4. I select the right injection molding machine for the job. I check the injection volume and make sure the mold fits between the tie bars.

5. I install the mold carefully. I lock the clamp plates before I remove the lifting rings.

6. I test the mold’s moving parts, like the ejector pins and sliding plates. I check the nozzle alignment with the mold gate.

7. I run the mold at low pressure and speed first. I listen for strange noises and watch for smooth movement.

8. I heat the mold to the right temperature for the plastic I plan to use. I check again for any sticking or expansion problems.

9. I adjust one test condition at a time. This helps me see how each change affects the part.

10. I dry the raw material and use the same resin for all test shots.

11. I avoid using low-quality resin for trials. If I need to test color, I do it now.

12. I close the mold slowly and check the pressure. I repeat this to make sure the pressure is even.

13. I set safety limits for manual and ejector strokes. I adjust the mold opening and ejector timing to prevent damage.

During and after production, I keep checking the mold. I look for scratches, bubbles, or other defects. If I find a problem, I repair it before I keep running the machine. I write down all repairs and inspection results for future jobs.

Part Inspection

After I run the first shot, I inspect the part closely. I use a process called First Article Inspection (FAI). This means I check the first part from a new mold or setup to make sure it matches the design. I measure the part with calipers and micrometers. I check the weight and look for any visual defects. I test the part’s function if needed.

I take samples from each batch and test them. I look for material or tooling defects. If I find a problem, I fix it before making more parts. I record all my findings. This helps me track quality over time.

I always do a final inspection before packaging. I make sure every part is clean and free of defects. I use strong packaging and include instructions for safe use.

Common Defects

Even with careful setup, defects can happen. I watch for these common problems in injection molded parts:

I check every part for these issues. If I see a defect, I adjust the machine or fix the mold right away. This helps me keep quality high and waste low.

Troubleshooting

When I run an injection molding machine, I know problems can pop up at any time. I always keep a troubleshooting checklist nearby. This helps me fix issues fast and keep production moving. Here are the steps I follow when I see defects like short shots or flash.

How I Fix Short Shots

Short shots happen when the mold does not fill all the way. I see incomplete parts or missing details. To solve this, I use a step-by-step approach:

1. I increase the injection pressure. This helps the molten plastic reach every corner of the mold.

2. I adjust the injection speed. If the plastic moves too slowly, it can cool down and stop flowing.

3. I check and raise the temperature settings. Warmer plastic flows better, but I avoid overheating to prevent burning.

4. I make sure the mold has proper ventilation. Air trapped inside can block the plastic from filling the cavity.

5. I review the wall thickness of the part. Thin walls can make it hard for plastic to flow. Sometimes, I suggest making the walls thicker.

6. I look at the gate size and location. A bigger or better-placed gate lets more plastic enter the mold.

Tip: I always check for flash before raising hold pressure. Flash can limit how much pressure I can use, which may cause short shots.

How I Handle Flash

Flash shows up as extra plastic on the edges of the part. It means the mold is not sealing tight enough. Here is what I do:

• I check the clamping force. If it is too low, I increase it so the mold closes tightly.

• I inspect the mold faces for wear or damage. Even a small gap can let plastic leak out.

• I lower the injection pressure if it is too high. Too much pressure can force plastic out of the mold.

• I make sure the mold is aligned. Misalignment can create gaps.

• I clean the mold surfaces. Dirt or debris can stop the mold from closing all the way.

Balancing the Process

Sometimes, fixing one problem can cause another. For example, if I raise the hold pressure to fix a short shot, I might get flash. I always try to find a balance. I develop a process window that keeps both defects away. I adjust one setting at a time and watch the results.

I keep detailed notes on every change. This helps me remember what worked and what did not.

When I troubleshoot, I stay calm and work step by step. I know that careful adjustments and good records help me solve problems and keep my injection molding machine running smoothly.

Maintenance and Best Practices

Routine Cleaning

I always make sure to clean the injection molding machine often. A clean machine works better and lasts longer. I clean it after every time I change the material. If I see strange colors or things inside the parts, I stop and clean right away. When the machine slows down, I know it needs a deep clean.

I follow a cleaning schedule to keep things simple. Here is how I do it: I do basic cleaning every day, sometimes even twice. I check the ejection pins and moving parts after 10,000 cycles. I look at other parts that do not move after 50,000 to 100,000 cycles. I clean and add oil to all parts during these checks.

I use a table to help me remember when to clean and what to do:

Tip: I always clean the machine before and after long runs. This stops dirt from building up and keeps my parts looking good.

Lubrication

Lubrication helps my injection molding machine work smoothly. I use the right oil or grease for each part. For hydraulic parts, I use anti-wear hydraulic oil with a thickness of 68 CST at 40°C. I like brands such as Mobil DTE26 and SHELL TELLUS Oil 68. For big moving platens and sliding plates, I use the same oil. For injection and clamping parts, I use special greases like extreme pressure lithium-base grease.

Here is a table I use to remember what to use:

My machine has an automatic lubrication system. It sends oil and grease to important spots like toggles and guides. The system uses electric pumps, so I do not have to stop to add oil. It also checks for problems and makes sure each part gets enough oil.

I always check the lubrication system when I do my regular checks. If I see a warning or hear a weird sound, I fix it right away.

Record Keeping

Good records help me keep my injection molding machine in great shape. I write down everything during shift changes. I track how much I use each mold, how many parts I make, and any problems I see. When I take out a mold, I write down which machine it was on, how many parts it made, and what shape it is in now.

Here is what I put in my records: Mold use and notes for each shift. Mold details when I remove it, including machine number and part counts. Notes about problems, plus repair or improvement requests. Samples of bad parts to help with repairs. A mold library with files for each mold. Computer tracking if I can. Storage rules for molds—low humidity, good air, anti-rust, and dust covers.

I mark molds that need fixing clearly. I keep them in a safe, dry place until they are ready to use again.

Keeping good records helps me see patterns, plan for fixes, and stop big problems before they start.

Operator Training

When I started using an injection molding machine, I saw training was very important. Every operator needs strong training, no matter how much experience they have. My training covers all the basics and more, so I am ready for anything at work.

I always start with safety. I learn about the machine’s guards and emergency stops. I use personal protective equipment like safety glasses, gloves, and hearing protection. My trainers teach me to spot dangers and avoid injuries. They show me lockout/tagout steps, so I know how to shut down the machine safely for cleaning or fixing.

Tip: I always do safety drills. Practicing emergency stops and lockout/tagout keeps everyone safe.

Training is not just about safety. I get to use the injection molding machine myself. I learn to start and stop cycles and change settings. I watch the control panel and learn to load materials. I set temperatures and check for defects. I also learn how to fix problems fast if something goes wrong.

I like that my training uses different ways to teach. Sometimes I learn in a classroom or join online lessons. Other times, I use e-learning modules at my own speed. The best part is working on real machines at a training center or on the shop floor. This mix helps me learn quickly and remember things better.

Here’s what I want in a good operator training program:

• Safety training for machine risks and PPE

• Lockout/tagout lessons

• Step-by-step operation and maintenance

• Troubleshooting and emergency drills

• Courses for beginners and advanced users

• Flexible learning: classroom, online, and hands-on

• Custom lessons for my company

• Regular refresher sessions to keep skills sharp

• Certification after passing a test

I always ask questions during training. If I do not get something, I speak up. My trainers want me to understand and do well. I keep my training current. Refresher courses help me remember steps and learn new safety tips.

Note: A well-trained operator makes the whole line safer and better. Training does not happen just once. It keeps going and helps me grow at work.

I always use a simple process to stay safe with my machine. I get ready, set things up right, and keep the machine clean. This helps me avoid mistakes. When I follow good habits, I get many benefits:

• Guardrails and special platforms protect me from harm.

• Automation and live monitoring help me find problems quickly.

• Predictive maintenance stops long breaks and keeps work going.

• Smart tools help me use less material and make better parts.

I keep learning new things and follow these steps each time. This lets me make good parts over and over.

FAQ

What safety gear do I need when using an injection molding machine?

I always wear safety glasses, heat-resistant gloves, and hearing protection. I use steel-toed shoes and long sleeves. I never skip personal protective equipment. It keeps me safe from burns, pinches, and loud noises.

How do I know which plastic material to use?

I look at the part’s purpose. I check if it needs strength, flexibility, or heat resistance. I compare common plastics like ABS, PP, and nylon. I ask my supplier for advice if I am unsure.

Why does my part have bubbles or voids?

Bubbles or voids usually mean moisture in the plastic. I dry the pellets before loading them. Sometimes, I need to raise the mold temperature or slow the injection speed. I always check the drying instructions for each material.

How often should I clean the injection molding machine?

I clean the machine after every material change. I do a deep clean every week. I follow a schedule for checking and cleaning moving parts. Clean machines make better parts and last longer.

What should I do if the mold sticks and won’t open?

I stop the machine right away. I check for leftover plastic or debris. I inspect the mold for damage. I never force it open. If I cannot fix it, I call a technician for help.

Can I reuse leftover plastic from the process?

Yes, I can reuse leftover plastic, called regrind, in many cases. I mix it with new pellets. I check the part’s quality after using regrind. Some jobs need only new material for best results.

How do I prevent color streaks in my molded parts?

I clean the hopper and barrel before changing colors. I use purging compounds to clear old material. I run a few test shots to make sure the new color is even. Clean equipment helps me avoid streaks.

What is the best way to learn to operate an injection molding machine?

I start with hands-on training. I read the machine manual. I watch experienced operators. I take safety courses and practice emergency stops. I ask questions and keep learning new tips from my team.