A 3D printed boat hull pattern, from which fiberglass boat hull molds are made, has been completed using a near net shape additive manufacturing process and then successfully used to produce a production capable fiberglass mold in a proof of concept joint evaluation program. The completed pattern was recently displayed at the AM2017 Additive Manufacturing Conference in Knoxville, Tennessee. 

Video 

Finished boat hull pattern - shown with Thermwood LSAM® 10'x20' machine

A Collaborative Effort

This achievement was the result of a collaborative effort between Thermwood Corporation,Techmer PM and Marine Concepts. The tool was printed slightly oversized and then trimmed to final net size and shape using a Thermwood’s large scale additive manufacturing (LSAM®) system.

It was made from Techmer’s Electrafil© ABS LT1 3DP, which has proven ideal for marine tooling applications when processed using LSAM print technology. The entire print, assembly and trim process required less than ten working days to complete. After the printed and trimmed tool was coated and finished, a fiberglass mold was produced using the printed pattern. This effort clearly demonstrates the feasibility, practicality, economics and advantages of using additive manufacturing in the production of boat tooling. 

The Details

Thermwood LSAM® 10'x20' machine printing two of the six sections

The final tool was printed in six sections, four major center sections with walls approximately an inch and a half thick and a solid printed transom and bow, which were pinned and bonded together using Lord plural component urethane adhesive before being machined as a single piece on the Thermwood system.

Bonding the boat hull pattern pieces together

Bringing the two sections together

Boat hull pattern after bonding together and before machining

Thermwood LSAM® 10'x20' machining boat hull pattern

The final trimmed pattern weighs approximately three thousand pounds. It required approximately thirty hours to print and fifty hours to machine.

Final trimmed pattern before coating

Thermwood’s demonstration machine, used for this program, has a 10 foot by 20 foot worktable and features both print and trim capability on the same machine. The print head used for this project can print at rates approaching 200 pounds an hour when running this particular Techmer material. Thermwood also offers larger machines and higher throughput print heads as part of its LSAM product line. 

Pulling the Mold

Building frame on boat hull pattern to pull mold

Finished frame on boat hull pattern after casting the fiberglass mold

Removing fiberglass mold from boat hull pattern

Finished boat hull mold in red

Additive Manufacturing Could Change Marine Tooling Process

Additive manufacturing offers the promise of even more advances in marine tooling such as printing the hull and deck pattern as a single piece, allowing a production mold to be taken from the hull and then flipping the pattern over and taking a deck mold from the other side of the same pattern. All of these possibilities result in dramatically lower tooling cost and substantially faster build time. 

For large boats and yachts, Thermwood is evaluating the feasibility of printing molds directly, rather than printing a pattern from which the mold is taken. Because of their large size, these tools will need to be printed and machined in sections, even with very large LSAM® printers. It may also be possible to print integrated cooling channels for air or liquid into these large tools as part of the print process. 

With this initial success and some radical new ideas that appear to be possible with current materials and technology, it is becoming apparent that additive manufacturing may very well represent a disruptive force for the marine tooling industry.

Thermwood has taken a major step toward its goal of 3D printing autoclave capable tooling from high temperature carbon fiber filled thermoplastic materials.

As an added benefit, Thermwood believes it will soon produce molds and tooling that function properly under vacuum in a heated, pressurized autoclave without the use of any type of coating to seal the printed tools. 

50% Carbon Fiber filled PPS Panels Tested by Fleet Readiness Center

50% Carbon Fiber Filled PPS Panel Printed and Machined on LSAM

Working toward this goal, Thermwood engineers have printed 50% Carbon Fiber filled PPS panels on its LSAM additive manufacturing machine that held vacuum to an industry acceptable level in independent testing. The test was conducted by the Fleet Readiness Center, FRC-East, located at MCAS Cherry Point, NC under a previously announced Cooperative Research and Development Agreement (CRADA) partnership, and the results met FRC-East acceptance criterion that the bag must not lose more than 2 in Hg over 5 minutes.  

View of LSAM PPS Sample with Vacuum Bag

Previously, other unaffiliated companies have tested actual tools printed by Thermwood from 20% Carbon Fiber filled ABS and have also found that those tools held vacuum to an acceptable level without the use of any sealer or coating; however, the ABS material is not suitable for high temperature applications. 

LSAM ABS Demonstration Part showing as printed (rough cut and finished surfaces) 

Vacuum Bagging Test on LSAM ABS Demonstration Part at Fleet Readiness 

Despite that, several parts have been made from those tools under vacuum at room temperature and at slightly elevated temperatures. Thermwood has also already printed a 50% Carbon Fiber filled three dimensional PPS mold which has not yet been tested. Thermwood’s goal is to produce molds that will be used in a production autoclave, molding finished parts suitable for actual end use. 

Thermwood's Additive Printing Process 

Thermwood’s additive printing process differs fundamentally from conventional Fused Deposition Modeling (FDM) printing. Most FDM processes print parts by melting and extruding a relatively small bead of thermoplastic material onto a heated build platin that is contained within a heated chamber. The heated chamber keeps the extruded material from cooling too much before the next layer is added.

Thermwood machines print a large bead at such a high rate that a heated environment is not needed. It is basically an exercise in controlled cooling. Print speed is adjusted so that each layer cools to the proper temperature just as the next layer starts to print resulting in a continuous printing process that produces high quality parts. Thermwood believes this fundamentally different approach produces superior parts. 

Thermwood's Patent Pending Compression Roller 

One other feature that Thermwood engineers believe helps produce solid, void free parts, is a patent pending compression roller that follows directly behind the print nozzle, flattening the bead while fusing it tightly to the previous layer. 

More About LSAM

Thermwood’s large scale dual gantry LSAM machines both print and trim parts on the same machine. They are programmed with Thermwood’s LSAM Print ^3D slicing software, which is rapidly becoming the most capable additive manufacturing software in the industry.

The LSAM and its software operate within Mastercam and are specifically designed for near-net-shape, rather than net-shape printing.

It works with most major CAD file formats including virtually all solid, surface and mesh formats. Thermwood maintains a continuing software development effort to continuously improve, enhance and expand its features and capabilities.

New Print Head Design for LSAM

Thermwood Corporation has unveiled a new design for the print head on its large scale additive manufacturing machines which it calls LSAM, (pronounced L-Sam). This new “Universal” design print head can be equipped with any of three interchangeable “Melt Cores”.

The print head is large by industry standards, being over 10 feet long and weighing one and a half tons, but despite the size and weight it moves at speeds up to five feet per second. The print head is designed so that the “Melt Core”, which consists of a feed housing, extruder and polymer melt pump, can be changed should higher or lower print rates be required.

Universal Print Head Installed on LSAM Development Machine

Thermwood has installed a universal print head on its current 10’ x 10’ LSAM development machine with a 40mm Melt Core and has successfully printed composite tooling masters from 20% Carbon Fiber filled ABS, and has printed actual autoclave tooling from both 50% Carbon fiber filled PPS and 20% Carbon Fiber filled Ultem using this print head. 

LSAM is DIfferent Than Other Thermoplastic 3D Printers

The print head is a critical element in Thermwood’s additive manufacturing process which functions differently than other FDM thermoplastic 3D printers. Most thermoplastic additive manufacturing systems print with a relatively small print bead onto a heated table in a heated environment. The heated environment is needed to keep newly printed layers from getting too cool to properly fuse with subsequent layers.

In Thermwood’s approach, the only heat source is the print head itself. A heated environment isn’t required. The process prints a large bead at such high output rates that the printed layer must be cooled rather than heated to achieve the proper layer to layer fusing temperature. The entire process is essentially an exercise in controlled cooling and produces large size, high quality, virtually void free printed structures.

Each layer is printed at a rate that allows it to cool to the ideal temperature before the next layer is applied. If the layer becomes too hot, print speed is reduced to allow more cooling time. If it becomes too cool, print speed is increased to reduce cooling time. 

Real-Time Thermographic Image Display

A built-in thermographic imaging system displays a real time thermal image on the CNC control screen which aides the operator in achieving and maintaining the ideal print temperature during the print process.

Temperature Control Module Integrated into LSAM

The LSAM Universal Print Head can process material at temperatures up to 450^oC. It uses an electronic temperature control module integrated within the print gantry CNC control, allowing full integration of temperature and pressure control with exclusive features of Thermwood’s print gantry CNC control, better supporting processes unique to 3D printing.

Three Melt Core Choices for LSAM

Thermwood offers three melt cores for its print head, each with a different maximum print rate. The maximum print rate determines the longest bead that can be printed during the available cooling time between layers.  This cooling time varies depending on material, amount of fan cooling and geometric shape of the layer, but the faster the print rate the more material that can be laid down within the cooling time between layers, so faster print heads allow larger parts to be printed, but don’t really print parts faster.

Fastest Printing With LSAM

Even the standard 40mm LSAM melt core is generally so fast that it must be slowed on most parts to keep from printing a layer so fast that it doesn’t have sufficient time to cool properly between layers. In this case, often multiple parts can be printed in the same time it takes to print just one.

The LSAM machine is equipped with a standard 40mm Melt Core which includes a patented 40mm high speed extrusion screw coupled to a corresponding melt pump and deposition head. This standard configuration processes over 200 pounds of material an hour, depending on the specific material and is suitable for parts that have a print layer lap length of up to 200 feet while printing a standard bead that is .200 inch thick and .830 inch wide. This configuration has proven more than adequate for virtually all large parts today.

If even longer layer bead lengths are required, higher output Melt Cores are available. A 60mm Melt Core can process 50% more and a 70mm Melt Core has operated at rates of over 500 pounds per hour, which Thermwood expects to increase.

The fastest speed at which a part can be printed is determined by the cooling time required to reach the proper bonding temperature between layers and not by the output of the print head. Larger print head outputs simply allow larger parts to be printed within the cooling time between layers.

High output melt cores do, however, have a minimum operating speed so may not be suitable for smaller parts. If both small and really large parts are required on the same machine, the melt core can be changed from one size to another in less than a shift. 

New 10'x20' Demonstration LSAM Under Construction

This print head will be installed on a new 10’ x 20’ demonstration machine currently under construction at Thermwood. Production machines come standard with the 40mm Melt Core.

Thermwood’s LSAM machines both print and trim on the same machine using separate gantries. The new approach to print head design adds even more flexibility.

LSAM Produces Solid, Void-free Parts

Using this technology, Thermwood has been able to produce large tools that are solid and void free enough to maintain vacuum without sealing or surface coating. This simplifies production of the tool, allowing accurate machining of the surface without having to deal with distortions that might be caused by variations in the thickness of a coating. 

Print and Trim on the Same Machine

Thermwood offers a line of dual gantry additive manufacturing machines which both print and trim parts on the same machine. These machines can be up to 100 feet long with print head output rates from 150 to 500 pounds per hour.  

The Thermwood LSAM is used to produce large to very large sized components from reinforced thermoplastic composite materials.

Although suitable for producing a wide variety of components, Thermwood is focusing on producing industrial tooling, masters, patterns, molds and production fixtures for a variety of industries including aerospace, automotive, foundry and boating.