Any studies on the accuracy of 3D printing

[Photon713]

First Post. I have been using 3D printing since 2008. I started with a ZCorp printing service, moved to Statasys 1200 and now testing various desktop printers. I design professional pitching horseshoes that are cast from ductile iron. It is imperative that the output is accurate to generate a horseshoe that will weigh 2 pounds 8 ounces. First, I have no way of knowing how slicing software deals with the last pass printed. Some slicers round up, some down. After printing, I spray the output with Acrylic Lacquer Primer and after drying fill any voids with Super Red Putty. I finish by sanding to a very smooth finish. My question...have there been any studies on the accuracy of 3D printed output? My input files are always .STL and software calculates the cubic volume. So far, I'm not having much luck finding a 3D printer that gives me accurate results. Why not stay with the Stratasys? They cost too much and I need two copies. BTW: PLA is warping in transit to the foundry in hot weather. ABS warps during printing. Which create other problems. Any pertinent information appreciated. Thank You

[Sebastian Finke]

Define accurate...

[Photon713]

Define accurate...

Accuracy that is close to the initial volume provided in the .STL file. My output is 9.1400 cubic inches of material. In this case, for ductile iron casting. 9.0 to 9.20 would be acceptable. My difficulty is knowing whether the slicer(s) are rounding down or up. So, I don't know if I should be sanding to the top of the hills or down to the valleys or something in between. The only solution I've come up with thus far is to develop some sort of volume gauge that measures the output against the calculated input. However, I've not seen any information that provides a measure of the volume accuracy of printed output. Hope that answers your question.

[awerby]

If you're not happy with the accuracy of 3D printing, and the materials aren't working for you either, why not go with CNC milling for your horseshoes? It doesn't seem that you really need the ability of 3D printing to produce undercuts and interior volumes, which is the major reason for using it on a prototype. With CNC you could cut it out of steel and just weigh it if you needed to know the mass, or measure the volume with Archimedes' method.

[richardphat]

Just by converting your CAD files to STL your files could be off tolerancing already. I have seen customers with piss poor meshing STL, instead of having a smooth circular shape you end up with octo/deca or whatever you call those straight face.

If you expect plastic printer to be accurate, you should not trust them. Any plastic would shrink going from syrup-amorph to solid.

[Nicos.s]

Actually, it is hard for the 3D printer to achieve very high accuracy in the current industry. It is limited by the technology and materials.
Even the EOS printer for metal, they also need many postprocessing to get the ideal result.
As I know, if printing the wax, some industrial printer can get very high accuracy, but it is hard for ABS and PLA.

[Photon713]

Actually, it is hard for the 3D printer to achieve very high accuracy in the current industry. It is limited by the technology and materials.
Even the EOS printer for metal, they also need many postprocessing to get the ideal result.
As I know, if printing the wax, some industrial printer can get very high accuracy, but it is hard for ABS and PLA.

Good Morning, Nicos.s...thank you for your response. I just received my 3D print from Shapeways. I requested their "White, Strong, Flexible". Volume wise I don't know yet until I get the results cast at the foundry. However, I include 1/4" dowels on the underside of each split (I split my designs for patternplate mounting using the dowel pin locations). I can normally determine the shrinkage by checking the alignment of the dowels to a master template. The dowel pin locations were perfectly located against the master template on the received print. However, that only implies correct horizontal alignment. The real challenge is consistency. If I know the shrinkage factor (percentage) of the 3D print, then I can allow for that in the design as I already do with the shrinkage factor of ductile iron. One pleasant surprise was the reduction of post processing the print. Normally, I spray the output with Acrylic Lacquer Primer which bonds to the plastic. I then followup with Super Red Putty to fill the voids (steps) and sand to a smooth surface. The surface results from the EOS printer reduced significantly the filling necessary as their layer thickness was very thin. The powder left behind after cleaning was as fine as talcum powder. The real bonus was the ability to send only a single file for both splits separated by 5/8" and connected with the dowels included. Normally, it is necessary to send two files for FDM printers, so everything is printed at the same time. In the past, this need to print splits at two different times resulted in misalignment between them when measured against the template. Finally, I have to have all of my prints as two copies. If the output is satisfactory at the foundry, then I order a second print. This also creates problems for compatibility between copies. The key is both copies must end up weighing the same when cast in ductile iron for production molds. Sorry to be so long winded, but, this have been a problem since I lost access to a Stratasys 1200. I'm confident that desktop printers will improve over time, but, right now I have to use high end printers. Thanks for your input. (Hilfling Horseshoes)