Mass balance
Record part mass by cavity, active cavity count and runner/sprue mass. Keep purge, startup scrap and normal per-cycle shot in separate fields.
G8
SIZE / INJECTION UNIT
Plasticizing capacity and shot weight answer different machine-fit questions.
Shot mass and volume describe the material required each cycle. Plasticizing capacity describes how quickly the configured screw can prepare material under stated conditions. Connect both to the exact resin, recovery window, residence behavior and acceptance trial.
ANSWER FIRST
Check volume, rate and material history as separate gates.
An injection unit can have enough nominal shot volume and still be unsuitable for the required plasticizing time, pressure/flow or resin behavior. A high catalogue rate can also be irrelevant when its material and measurement basis do not match the project.
Define the resin and plasticizing hardware questionsScreening sequence
- Total injected mass and volume per cycle
- Average demand from the target production cycle
- Recovery demand from the actual available time
- Exact resin, screw and supplier test basis
- Project margin confirmed by process/material owners
DIFFERENT CHECKS
Do not collapse six injection-unit questions into one gram value.
Each field needs its own source and condition. Mark the status as measured, calculated, supplier-confirmed or estimated.
| Decision field | Question | Collect | Boundary |
|---|---|---|---|
| Total injected shot | How much material enters the mold each cycle? | All cavity parts plus applicable cold runner/sprue, with weight and volume source | Not the same as machine catalogue capacity or saleable part weight |
| Material basis | Which exact resin and condition are used? | Grade, density basis, filler/additive, moisture condition, color and regrind/recycled share | A reference-resin shot weight cannot be treated as the actual-resin result |
| Shot volume / screw stroke | Where does the shot sit in the proposed injection unit? | Calculated or measured volume, screw diameter/configuration and supplier working guidance | Capacity fit does not prove pressure, flow, melt quality or residence fit |
| Plasticizing demand | How much melt must be prepared per unit time? | Total shot per cycle, target cycle and production interruptions included/excluded | Average throughput alone can hide a short recovery window |
| Available recovery time | When may the screw recover inside the real sequence? | Cooling, holding, mold/robot motions, permitted overlap and control sequence | Do not automatically use the full cycle time |
| Plasticizing evidence | On what material and method is supplier capacity stated? | Reference material, screw, settings, test method, units and applicable conditions | EUROMAP or supplier values need the same basis before comparison |
PLANNING CHECKLIST
Six reviews connect the shot to a repeatable recovery plan.
The responsible material and process teams must approve conversion, residence and margin assumptions before a configuration is released.
Volume conversion
Use the intended material and a controlled conversion basis. Mark whether density is solid, melt, supplier-provided or estimated.
Cycle demand
Convert the total shot and target cycle into a required average material rate with explicit units and availability assumptions.
Recovery-window demand
Compare shot mass with the actual time available for plasticizing after required non-overlapping motions and process constraints.
Residence and melt review
Check the proposed shot use, barrel inventory, thermal history, shear, screw design and material-supplier guidance together.
Common-basis trial
Confirm the proposed screw and injection unit using the intended resin, mold, cycle sequence and agreed melt/part-quality evidence.
RFQ EVIDENCE PACK
Put each calculation beside the file that supports it.
A controlled pack lets the buyer and supplier revise the same calculation when resin, cavities, runner or target cycle changes.
| Record | Required fields | Evidence state |
|---|---|---|
| Part and runner record | Mass/volume by cavity, active cavities and cold-runner contribution | Measured sample, controlled CAD/mold record or marked estimate |
| Resin record | Exact grade, additives/filler, density basis, moisture and regrind/recycled content | Current material TDS/processing guide and buyer specification |
| Cycle sequence | Holding, cooling, plasticizing, mold, ejector and robot timing plus allowed overlap | Current stable process or reviewed target sequence |
| Proposed injection unit | Screw, volume, pressure/flow, torque and plasticizing basis | Current configured supplier data—not a family-level headline |
| Rate comparison | Required average rate and recovery-window rate with units and assumptions | Reviewed calculation plus supplier test basis |
| Acceptance evidence | Recovery time, melt/part quality, process stability and recorded deviations | Agreed mold/material trial and measurement plan |
BUYER QUESTIONS
Plasticizing and shot-weight FAQ
The answers separate capacity, rate, recovery and material behavior so one catalogue field does not decide the injection unit.
01Is shot capacity the same as plasticizing capacity?+
No. Shot capacity describes a mass or volume associated with the injection unit, often on a stated reference-material basis. Plasticizing capacity is a rate under stated screw, material and test conditions. Both checks are needed.
02How should required plasticizing rate be screened?+
Start with total material injected per cycle and the intended cycle to calculate average demand. Then check the more restrictive recovery window in the actual motion sequence. Preserve units, material basis and all assumptions for supplier review.
03Can a catalogue polystyrene shot weight be used for every resin?+
No. Reference-resin mass cannot be copied directly to another grade. Compare volume and the intended material using an approved conversion and confirm the configured injection unit with the machine and material teams.
04Should plasticizing demand use the full cycle time?+
Not automatically. The available recovery window depends on holding, cooling, screw delay, mold movements, robot actions and which motions the configured machine permits to overlap. Map the real sequence.
05What belongs in a plasticizing and shot-weight RFQ?+
Include part and runner mass/volume, cavity count, exact resin grade and condition, target cycle sequence, available recovery window, pressure/flow need, screw and residence constraints, supplier capacity test basis and the planned trial evidence.
SHOT + RATE / NEXT STEP
Send the resin, shot and cycle basis together.
Attach the total shot record, exact material, recovery sequence, supplier capacity basis, screw questions and trial criteria so the injection unit can be reviewed.
Build the machine brief