Topic: Film forming for in-mold decoration (IMD / IML / film insert molding)

IMD & IML Thermoforming Machines: Process, Film Forming, Die Cutting and Applications

Q: What temperature range do SANSEN machines cover?

From the published tables: AS201F Room temp. – 400 ℃; gas-liquid hybrid model Room temp. – 350 ℃; AS201F-G IR heater Room temp. – 500 ℃. The actual forming temperature depends on the film.

Published 2026-11-14 · Updated 2026-11-14 · Author: SANSEN Engineering Team

Using the published specifications of SANSEN machines, this guide walks through an IMD/IML film from printing to injection molding and shows exactly which step a hot press forming machine performs, which belongs to a high-pressure gas forming machine or a 3D die-cutting machine, and which must be done on an injection molding machine.

Key takeaways

A hot press forming machine is not an injection molding machine. It heats a printed film until it softens and presses it into a 3D shape; the resin is injected later on your injection molding machine.
A typical IML / film insert molding route is: print → punch locating holes → heat → form (hot press or high-pressure gas) → 3D die cut → load into the mold → inject. SANSEN machines cover heating, forming and die cutting.
“IMD” is used as an umbrella term in China, while many international sources use it only for roll-to-roll transfer, where the carrier film is peeled off after molding. When you request a quote, say whether the film stays on the finished part.
Key selection data: forming method (matched-die or high-pressure gas), press force, effective heating area, temperature range, table size, daylight and stroke.

1. IMD, IML and IMT: what the terms mean

In-mold decoration covers processes that bond a decorative layer to a plastic part during injection molding. An article by CMF设计军团 published on Puxiang notes that the Chinese industry often uses IMD as the umbrella term, covering IML, IMF, IMR, INS and others, and splits them into transfer processes (IMR) and processes in which the film stays on the part (IML/IMF/INS/IME) ^[1].

International usage differs. In Nissha’s documentation and in Plastics Decorating, IMD usually means roll-to-roll transfer: a printed foil is fed through the mold, only the ink layers transfer to the part and the carrier film is peeled away. IML means a printed film that is pre-formed and trimmed, then placed in the cavity, where it stays as the part’s outer skin ^[2]^[5]. Niebling adds that film insert molding (FIM) has no registered name, so IML, IMF and INS often describe the same process, while IMD is a generic term for decoration ^[4]. The safest question to ask a customer is therefore: “Does the film remain on the finished part?”

Table 1 – In-mold decoration processes and where forming and trimming equipment fits
Process	Film stays on the part?	Separate forming and trimming?	Where SANSEN machines fit
IML / IMF / FIM (film insert molding)	Yes, the film becomes the outer layer ^[2]^[5]	Yes: print, form, trim, then insert into the mold ^[2]^[4]	Hot press or high-pressure gas forming machine for forming; 3D die-cutting machine for trimming
INS (insert film molding)	Yes; usually thicker ABS or PMMA+ABS film ^[1]	Yes: pre-heat, form, trim, insert. The source says INS generally needs only medium-pressure forming, while IML needs high-pressure forming ^[1]	Choose hot press or high-pressure gas forming by film thickness and draw depth
IMR (in-mold roller / transfer)	No: the carrier is peeled off, leaving the protective and graphic layers ^[1]	Normally no; a foil feeder brings the transfer foil into the injection mold ^[1]	Mainly an injection machine plus foil feeder – not a core application for SANSEN hot presses
IMT	No: the carrier is peeled off and the graphic layer transfers to the part ^[1]	Yes: the source describes IMT film being heat-formed and trimmed before injection ^[1]	Forming and trimming steps
IME (in-mold electronics)	Yes, with printed conductive traces and components such as LEDs ^[1]^[5]	Yes: print circuits, form, trim, mold ^[4]	Forming and trimming; tighter registration requirements

Layer diagram comparing IML, where the film stays on the part, with IMR/IMT transfer, where the carrier film is peeled off after molding — Figure: layer build-up of IML vs transfer (IMR/IMT) (original SANSEN schematic) View vector (SVG)

In short: any process that turns the film into a 3D shape before it goes into the injection mold (IML, IMF, INS, IMT, IME) needs dedicated film-forming and trimming equipment. Pure roll-to-roll transfer relies mainly on the foil feeder of the injection molding machine.

2. How a hot press forming machine works

A hot press forming machine is a press with a heating system. It heats a printed film sheet until it softens, then the main cylinder closes the dies at a set force and holds them so the film takes the shape of the tool. After it sets, the press opens and the formed film is removed. The machine does not melt plastic or inject resin, which is the basic difference from an injection molding machine.

One cycle on a SANSEN hot press forming machine

Loading and locating: the printed film is placed on the lower die using locating holes or a fixture.
Heating: the heater plate heats the sheet. SANSEN’s hydraulic IMD hot press page describes uniform far-infrared radiant heating, a constant-temperature stage, then instant forming by the hydraulic cylinder, with carbon-fiber heating tubes ^[S]. The AS201F table lists the heater plate drive as “Inverter + synchronous motor” ^[S].
Closing under force: depending on the tonnage, the AS201F series uses a hydraulic HOB cylinder or a fast master-slave cylinder ^[S]. The gas-liquid hybrid model uses air-oil boosting with a preset fast-to-slow change-over ^[S].
Setting and opening: after the hold time the press opens and the formed film goes to trimming.

Temperature, time and force can be set and stored. The AS201F uses “Touch screen + PLC” control ^[S], and the advanced configuration of the gas-liquid hybrid model stores forming hold time, heating time and heating temperature as numbered recipes ^[S].

Schematic comparing a hot press forming machine (upper and lower dies close under force) with a high-pressure gas forming machine (no upper die, gas presses the softened film onto the lower mold) — Figure: hot press forming vs high-pressure gas forming (original SANSEN schematic) View vector (SVG)

SANSEN IMD hot presses running in a customer workshop — Photo: IMD hot presses on site (SANSEN original photo)

3. Process flow: printing, heating, forming, trimming and injection molding

IML film insert molding process flow: printing, locating holes, heating, forming, 3D die cutting, loading and injection molding, with the steps done by SANSEN machines highlighted — Figure: IML process flow and who does each step (original SANSEN schematic) View vector (SVG)

Table 2 – Who does what in IML / film insert molding
Step	What happens	Equipment	Watch out for
1 Printing	Graphics, ink and adhesive layers are printed on the film, typically by screen or gravure/four-colour printing ^[1]^[2]	Screen printing machine from partner LICHAO: automatic sheet screen printing machine with CCD or LC-FZSYJFG-6060 roll-to-roll screen printer (sp.catekvo.com, not SANSEN equipment); UV texture transfer: LICHAO LC-500UVZY / LC-600RLUV	Inks must survive forming stretch and molding heat ^[5]
2 Locating holes	Holes are punched relative to the print so the graphic lands in the right place after 3D forming ^[4]	2D punch	Hole-to-print registration
3 Heating	The sheet is heated into its softening range ^[3]^[4]	Heater plate of a hot press / IR panel of a high-pressure gas former	Too cold can crack the hard coat; too hot can blur the graphic ^[6]
4 Forming	Matched-die pressing or high-pressure gas presses the film onto the tool	SANSEN hot press forming or high-pressure gas forming machine	Draw depth, radii, graphic registration ^[6]
5 3D die cutting	Excess film is trimmed so the insert fits the injection cavity ^[2]^[4]	SANSEN 3D die-cutting machine	Locate on formed features, not on the graphic ^[6]
6 Loading	The insert is placed in the cavity by hand or robot ^[1]	Molding shop	Coverage must keep the film out of the parting line and avoid edge light leaks ^[5]
7 Injection molding	Resin is injected behind the film and bonds to it	Injection molding machine (not SANSEN)	A poorly placed gate can wash out the ink ^[5]^[6]

Printing & UV texture transfer partner: LICHAO

SANSEN builds hot press forming machines, high-pressure gas forming machines and 3D die-cutting machines – the heating, forming and trimming steps of IMD/IML film. Screen printing and UV texture transfer come before forming and use equipment that is not made by SANSEN. For these steps, see the screen printing and UV transfer machines of our partner LICHAO PrintTech (力超):

Screen printing

UV texture transfer

These machines are LICHAO products, not SANSEN products; see the LICHAO website for specifications and enquiries. LICHAO website: sp.catekvo.com

4. Materials and how to choose them

Common films in the public sources: Nissha lists PET, PC and PMMA+ABS (laminated) as IML surface films ^[2]; Plastics Decorating lists polyester, polycarbonate, acrylic and acrylic-capped PC ^[5]; INS films are usually ABS or PMMA+ABS ^[1].

Materials named on SANSEN product pages: the high-pressure gas forming machine is intended for PC, PC+PMMA and ABS+PMMA ^[S]; the hydraulic IMD hot press targets PET, PVC and similar film sheets ^[S]; the 3D die-cutting machine is used for PET, PC, PVC and other plastics ^[S].

Start from the surface requirements. Scratch, chemical and environmental resistance decide the film and hard coat, because the film is often the first surface the user touches ^[5].
Check the draw depth. Excessive stretch can thin inks until they turn translucent and can reduce hard-coat chemical resistance ^[5]; PET suits flat or shallow parts ^[6].
Check the bond to the molding resin. In service the film-to-resin interface fails most often, so match the tie layer to the resin and run adhesion tests ^[6].
Matte or textured films: conventional thermoforming can make matte films look glossy and damage textures; high-pressure forming (HPF) handles them better ^[3]^[4].
Sample with your real film. Forming windows differ by brand and thickness, so this article does not quote generic temperatures or pressures detached from a specific material.

5. Key factors: tooling, temperature, pressure and time

Table 3 – Process factors and the related SANSEN machine settings
Factor	What it affects	Adjustable on SANSEN machines (published data)
Tooling	Surface accuracy, radii and locating method decide the formed shape and graphic position; IML injection molds also need dedicated changes ^[5]	Upper and lower molds preheated with independent control on the high-pressure gas former ^[S]; T-slot tool clamping ^[S]
Temperature	How far the film softens, hard-coat cracking, graphic sharpness ^[6]	AS201F adjustable temperature Room temp. – 400 ℃ ^[S]; AS201F-G IR heater Room temp. – 500 ℃, upper/lower mold plates Room temp. – 150 ℃ ^[S]
Pressure	How fully the film follows the tool and how sharp the radii are	AS201F force 5 / 10 / 30 / 40 / 80 t ^[S]; AS201F-G two-stage high/low gas inlet with independently adjustable flow and hold time ^[S]
Time	Heating and hold times affect forming completeness and cycle time	Numbered recipes for hold time, heating time and temperature on the gas-liquid hybrid model ^[S]
Parallelism and accuracy	Consistency of forming and cutting	AS201F-Z platen parallelism (any point) within 0.05 mm ^[S]

For orientation only: Sabreen quotes typical film pre-heat values of about 160–190 °C for thermoforming PC and about 120–150 °C for high-pressure forming, a useful starting point for discussion with your film supplier ^[6]. The real process window comes from the film data sheet and sampling.

6. Hot press forming vs high-pressure gas forming

Table 4 – Matched-die hot press forming compared with high-pressure gas forming
Item	Hot press forming (SANSEN IMD/IML hot press)	High-pressure gas forming (SANSEN AS201F-G)
Forming force	Main cylinder closes upper and lower dies ^[S]	High-pressure gas presses the softened sheet directly onto the lower mold ^[S]
Tooling	Upper die + lower die	Lower mold only, no upper mold ^[S]
Heating	Heater plate with carbon-fiber heating tubes ^[S]	IR ceramic heater panels with multi-point PID control; upper and lower molds preheated independently ^[S]
Published pressure data	Force 5 / 10 / 30 / 40 / 80 t (AS201F)	Gas source 0-4MPa (80T), 0-8MPa (250T) ^[S]
Graphic registration	—	Sources report that HPF keeps printed symbols more precisely positioned, and forming distortion can be compensated by distortion printing ^[3]^[4]
Applications listed by SANSEN	Appliance panels ^[S], smart-lock panels ^[S], phone cases ^[S], 2.5D protective film (roll feed) ^[S]	Automotive clusters and IMD/IME interior and exterior trim, appliance control panels, phone and electronics housings, irregular deep-drawn parts ^[S]

How to choose: for flat or shallow panels with moderate registration needs, where investment and cycle time must be balanced, evaluate hot press forming first. For deeper draws, symbols that must land precisely, composite sheets or matte/textured films, evaluate high-pressure gas forming first ^[3]^[4]. Confirm with samples.

7. Common defects and troubleshooting

Table 5 – Common film forming and trimming problems
Symptom	Typical causes	What to check
Graphic out of register with the shape	Forming distortion not compensated; trimming located on the graphic instead of formed features; different shrinkage between film lots ^[6]	Use distortion printing ^[3]; locate trimming on formed features; control film lots and storage ^[6]
Wrinkles	Uneven heating, loose clamping, draw too deep for the radius ^[6]	Re-balance heating, tension the film, open up the radius or switch to high-pressure forming ^[6]
Bubbles or delamination	Moisture in the film, contamination, wrong tie layer, cold mold ^[6]	Dry and clean the film, match the tie layer to the resin, raise mold temperature ^[6]
Hard-coat cracking	Coating fully cured before forming, radius too tight, film too cold ^[6]	Use a formable hard coat cured after forming, larger radii, higher pre-heat ^[6]
Ink thinning / translucency	Excessive draw ^[5]	Reduce draw depth or move graphics away from corners ^[6]
Matte film turns glossy, texture damaged	Heat of conventional thermoforming ^[3]^[4]	Evaluate high-pressure forming ^[3]^[4]
Whitening or delamination at corners of composite sheets	High stretch at corners of composite sheet	SANSEN’s high-pressure gas forming page states that composite corners formed on it do not whiten or delaminate; compare by sampling ^[S]
Film caught in the parting line, edge light leaks	Insert coverage and trim size not designed for the cavity ^[5]	Check the trimmed outline against the cavity and correct the cutting die ^[5]
Ink washed out near the gate	Injection-molding issue: gate too close, fill too fast, melt too hot ^[5]^[6]	Move the gate and profile the fill speed on the injection machine ^[6]

8. Industries and typical products

Home appliances: air-conditioner panels and control panels — SANSEN builds a dedicated IMD/IML air-conditioner panel hot press ^[S].
Smart door-lock panels — IML smart-lock panel hot press forming machine ^[S].
Automotive: instrument clusters and IMD/IME interior and exterior trim ^[S]; INS is widely used for interior trim ^[1].
Consumer electronics: phone cases and housings ^[S]^[S], plus IMD samples such as earphone housings, mouse shells and eyeglass frames shown in the SANSEN factory gallery.
Protective film: automatic hot pressing and slitting of 2.5D screen protectors on the roll-feed hot press ^[S].
Smart surfaces: IME builds touch and lighting functions into the decorative film ^[1]^[5].

IMD decorative film parts formed on a SANSEN hot press — Photo: IMD hot-pressed film parts (SANSEN original photo)

Sheet of IMD phone-case films after hot press forming, several cavities on one sheet — Photo: hot-formed IMD phone-case sheet, ready for 3D die cutting (SANSEN original photo)

9. Parameters to check when selecting a machine

Forming method: matched-die hot press or high-pressure gas (see section 6).
Press force and cylinder type: they set the formable area and pressure stability.
Effective heating area and table size: they must cover the film blank or multi-cavity layout.
Temperature range and control: matched to the softening temperature your film needs.
Maximum daylight, stroke and minimum closed height: they limit tool height.
Feeding: manual sheet loading or automatic roll feeding (e.g. AS201F-Z).
Die cutting: a cutting press whose table and force match the forming machine.

The main published data from SANSEN’s original specification tables: