Low-cost Metal Parts Production by 3D printing

Jack Lie CNC machining expert

Specialize in CNC milling , CNC turning, 3D printing, urethane casting, rapid tooling, injection molding, metal casting,


Introduction

Metal parts are always produced by investment casting technology, however, there is an issue of molding cost. In order to produce large metal parts with very low cost, we apply FDM technology to create castable patterns, which cannot be created by traditional manufacturing techniques with various features. In this article, we will explain the benefits of FDM patterns, and when to apply this process over alternative technologies like DMLS or CNC.

Metal Parts Manufacturing

In low volume metal parts production, investment casting, CNC machining and DMLS are all viable technologies. We summarize the advantages of each manufacturing method as following. It is critical to notice that final parts geometries determine which method is the most suitable way, this is a general guideline for decision making.

3D Printing Technologies for Metal Parts

DMLS

DMLS is a powder bed fusion technology, it is widely applied to produce metal parts with high dimensional accuracy. This technology is able to create parts with very complex geometries design. Its design freedom encourage it to be adopted by many industries like automotive and aerospace, where weight optimization and excellent performance are critical. DMLS can produce part from a wide range of metals like aluminium and stainless steel, as well as biocompatible metal in density and medical industries like titanium. The main limitations of DMLS are the high cost, small build size and long leading time. DMLS parts also need support structures to reduce the likelihood of distortion and warping, and must be removed after printing.

Investment Casting

Investment casting apply wax patterns to create molds for casting, it has a clean burn-out without any residues. It including the following process:

  1. 3D printed pattern
  2. Mold assembly
  3. Shell building
  4. Burnout
  5. Pouring
  6. Knock off
  7. Cut off
  8. Finished parts

For low volume investment casting, normal pattern are machined form wax blocks by CNC machining. For larger series, the die molds is machined by casting wax by the die. Molding is a very expensive investment as this production will take a very long time.

3D printing is regularly applied in conjunction with investment casting applications, in order to produce patterns form casting materials. Castable 3D printing is common in dental and jewelry industries, the normal process are SLA. This vat-photo-polymerization technology can produce parts with very smooth surface and extremely fine details. The main limitation of SLA are build size, high cost for large patterns. For larger metal parts, castable FDM provide a cost-effective and rapid solution.

Castable FDM

For lager metal parts, SLA is not feasible to create patterns,  in reason of it high cost of resin and limited build size of SLA machines. Castable FDM provide a low-cost solution for rapid parts printing. FDM is a material extrusion technology, which can provide a smooth surface by micro-droplet polishing. In order to satisfy high quality investment casting requirement.

There are several many advantages to apply FDM for investment casting patterns.

  1. Low-cost: FDM is the lowest method of 3D printing, which eliminates the cost of tooling.
  2. Large build size: FDM printers have large build size than DMLS and SLA machines. In addition, FDM materials are cheap, it have more competition than other technology once parts size increase.