Formlabs Castable Resin, First Melt Failure, Where to Go Next?


#1

When my company considered the purchase of the Form 2, I put forth as many justifications for the purchase as I could, including investment casting mold forms. In addition to our prototyping needs for injection molded parts, we have part designs we would like to cast, but are cost prohibitive to try due to up front tooling costs. As such once we were approved for the purchase, I plunged right in and bought the Formlabs Castable resin. I contacted a local investment casting foundry and printed a sample for them to try and burnout. For the test piece, I hollowed the part out, added an internal support structure and thoroughly washed and cured the resin piece. Unfortunately our part failed the melt test anyway…

I am now looking at next steps and am kind of concerned with what I am finding. First is that 99% of literature and forum posts that discuss FL Castable resin are strictly for jewelry. This is fine if investment casting was a technique used to serve only the jewelry industry, but is in fact only a portion of the investment casting market overall.

Second, the foundry is insisting that I use their supplier, which uses a FDM printer using PLA material. Which would be fine if we didn’t buy the printer and castable resin, I need what we have to work.

Lastly, further research into this I find someone else is in the same situation as I: Unsuccessful castable resin results using investment casting The difference here is that I bought the printer, the author of this post did not.

I want to try and continue to modify this design and make use of this resin (adjust wall thicknesses, cure time and the like), but my engineering instinct and findings here indicate that this resin is just not good for big parts and rapid high temp burnouts as is fairly standard in the investment casting industry.

Are there others here in the same situation and have you overcome the hurdle of using the Form 2 for investment casting of parts other then jewelry? Any tips on what foundry to try, what resin to use and design/burnout process would be appreciated!

Thanks,
Dan


#2

So we bought our form 2, two years ago, had a little trouble at the beginning, but after a little bit of tweaking we have been getting nothing but perfect castings. cure time is huge! and the formlabs recommended burnout works best. we do our own casting here so were able to change stuff if we have to. i would recommend looking for another casting house, some people just dont want to change their ways and will eventually be left in the dust. 3d printing has changed the jewelry industry.


#3

@antsaldana Thanks for your feedback however it sounds like you are also using the formlabs castable resin for jewelery as well. I am referencing larger parts with thick cross sections. The big issue I believe to be the burnout schedule. Most foundries for industrial parts use a 20-30 minute burn out at a single temp, not 10+ hours throughout a range of temps.

Since I am stuck I will bump this question again; Have any members here used the Form2 and the Castable resin to print larger parts using standard industrial investment casting techniques?? (Lets say 3"x3"x3" volume or really anything bigger then jewelry rings and pendants!)


#4

I’ve printed these with BlueCat resin and cast commercially

Unfortunately the BlueCat seem prone to warping and doesn’t like there to be too much time between printing and casting.

I have some Photocentric Castable resin that I’ll be trying in the next few weeks.


#5

Thanks for the reply! I was getting worried that no one else has been trying to use the formlabs printers for casting parts used in machinery. The warping is certainly visible in your pictures. Do you believe this deformation took place during transit to the foundry, during curing, washing etc?


#6

The warping is partly to do with the orientation and partly the curing.


#7

Dan:

We have cast prints that barely fit into the printing envelope.

When you say " failed the melt test", what do you mean? If you mean that the FL resin did not melt, all SLA resins decompose at temperature, they do not melt. This is why your foundry must use the FL burnout procedure especially the 300 degree dwell. Your foundry wants you to use PLA because it does melt and they can treat it like wax, but FDM prints cannot compare to SLA prints in precision or surface finish.

If your foundry will not use the FL procedure, you will never get good castings in my opinion. I suggest you look on the FL web site and find a foundry that does. Even so, you may find it necessary to use a modified procedure like staying at 1350 degrees for a longer time. We must do this for larger pieces. I assume you are are casting low melting alloys - not steel or Inconel. The pocedure is slightly different.

Bill Box


#8

Bill Box,

Thanks for the feedback. By melt test, I am referring to a sample piece I constructed for them to try and run through their casting operation to gauge if a larger run of the same part could be made. The purpose of the test as it was described to me was to see how the material melts out as they had concerns about ash/residue as well as the shell blowing out. The shell ended up blowing out and the feedback I got was less then enthusiastic.

We are looking to cast parts in 6061 Aluminum as well as various 300 series stainless steels. Would you be willing to recommend a foundry? I have not found a good list of foundries willing to work on the FL burnout schedule (again other than jewelry houses).

Dan


#9

Dan:
I am afraid that I can’t recommend a foundry, but one of the subjects on the forum page give some friendly foundries., I think.

As I stated in the previous message, SLA resins do not melt - they decompose in the burnout cycle. The resin is not completely removed until the maximum investment temperature is reached. Resin expansion seems to be maximized at around 300 to 350 degrees. This is why you must dwell at that temperature for a while. Probably the investment gets stronger, too so it can resist cracking better. It takes some time to get the temperature on the inside of the flask to become the same temperature as the outer parts of the flask. That means the bigger the flask, the longer the dwell time. This also holds for the time at maximum temperature.

We have instrumented 3"x5" flasks and it take hours for the temperatures to reach equilibrium.

Keep in mind that aluminum and stainless steels require different investment powder. Investment “for gold and silver” work for aluminum and investment “for platinum” are required for steel. Your 300 series stainless steels will probably be annealed. Most of the times we work in stainless steels they have been cold worked so they are harder/stronger, but that is not necessarily true for castings. If you need stronger stainless, you should look at 17-4. (I am sure that there may be exceptions for what I said, but I have not experienced any.)

Let’s face it - anything the melts can probably be cast, but most cast aluminum castings use 356 or it’s cousins. I do not know why, but maybe cast 6061 loses the properties you are looking for.

I have found the metals volume of The Manufacturing Engineer’s Handbook helpful. I am sure that there are other good texts out there (ASM come to mind). I would encourage you to look into the alloy choices you make.

Bill


#10

Hi dbarry87, as far as I know, the best thing that works for resin burning is the air flow inside the oven chamber it is know that some people have made modifications to their ovens by connecting those aquarium air compressors to pump air into the oven in the burning cycle. And what really is the problem is that the resin consumes a lot of oxygen to burn, so in the larger parts more oxygen is required for proper combustion, so if the resin does not have enough oxygen it will start to expand and break the investment. And also that’s why the resins burnings times are between 12 to 14 hours , the more slow the less probability that the casting fail. And also there is not really any resin that is like wax the only printers that really uses a wax type material are the solidscape 3z and the projet mjp 2500w but are super expensive printers and a lot of maintenance are required in those printers so hopefully in the near future would be a resin that really burns like wax.