The most frequently asked question when investing in an injection molding machine is: "Should I buy servo, hydraulic or all-electric?" There are scenarios in which each of the three is right. In this article we compare the technologies on the axes of energy, precision, speed and cost.
Conventional Hydraulic: Why Is Its Era Ending?
In a conventional hydraulic machine a fixed-speed asynchronous motor turns the pump continuously. Even when the machine is not injecting — while waiting for cooling, while the mold is open — the motor runs at full speed and consumes energy. In addition:
- The oil heats up as it circulates continuously, creating additional cooling water consumption
- Control by proportional valves responds more slowly than servo systems
- Energy efficiency is around 30–50%
Today the conventional hydraulic machine has remained almost exclusively on the second-hand market; it is not recommended for new investment.
Servo Hydraulic: Today's Standard
In a servo hydraulic machine the pump is driven by a servo motor. The difference is fundamental: the motor turns only when movement is needed, and at the speed needed. Consumption during waiting phases is close to zero.
Advantages:
- 30–60% energy savings compared with conventional hydraulics
- Pressure and speed are controlled in closed loop — repeatability is high
- The advantage of hydraulic power is retained: at high tonnages (over 1000 tons) it is the most economical solution
- The investment cost is markedly lower than all-electric
The DKM SV Servo Series uses this technology from 130 to 3350 tons; the DH series, meanwhile, combines servo hydraulics with high injection speed.
All-Electric: The Peak of Precision
In all-electric machines the hydraulic circuit has been removed entirely: each of the injection, clamping, metering and ejector movements is driven directly by a separate servo motor.
Advantages:
- Energy efficiency above 95% — 20–40% less consumption even compared with servo hydraulics
- 0.01 mm positioning precision, 10 ms response time
- No hydraulic oil: no risk of leaks, no oil changes, no oil cooling water
- Quiet operation (~65 dB) and clean room compatibility — ideal for medical, optical and electronics
- Parallel movements: metering and mold opening can be done at the same time, shortening the cycle
Limits: The investment cost is high, and at very large tonnages (1000+ tons) servo hydraulics retain their economic advantage.
Comparison Table
- Energy (kWh/kg): conventional hydraulic 0.55–0.90 · servo hydraulic 0.35–0.55 · all-electric 0.25–0.40
- Repeatability: conventional ± moderate · servo good · all-electric best
- Maintenance: oil and filter maintenance on hydraulics · periodic greasing on all-electric, no oil
- Noise: conventional 75–85 dB · servo 65–75 dB · all-electric 60–68 dB
- Investment: conventional lowest · servo medium · all-electric highest
Which for Which Production?
- General-purpose technical parts, automotive, household appliances: Servo hydraulic SV — price/performance balance
- Thin-walled packaging, high speed: DFS or the HH series — 400–600 mm/s injection
- Medical, optical, connectors, precision gears: All-electric FE or the EH hybrid
- Large-volume parts (pallets, crates, bumpers): TP two-platen or high-tonnage SV
- PET preforms: PET series · PVC fittings: PVC series
When Deciding
Calculate the total cost of ownership (TCO) over an 8–10 year window: electricity consumption, scrap rate per mold, maintenance and downtime cost. On a line running 6000+ hours a year, the energy savings of an all-electric machine pay back the price difference within 3–5 years in most scenarios. At low utilization rates, servo hydraulics make more sense.
For a model and tonnage recommendation based on your production profile, contact us — we carry out a free selection study based on your part drawing.
Once the drive type has been decided, the next step is choosing the tonnage and series. A list of the servo, hybrid and all-electric options in the DKM range with their tonnage ranges: plastic injection molding machine models and tonnages.