Cutting 3/4" Acrylic

[Photon713]

Good Morning, All...

First post. Some advice please. I design, prototype and produce professional pitching horseshoes. For the past 3 years I have been using a ZCorp 3D printer for prototypes destined for the foundry. Sometimes they are singles and others are splits (sliced horizontally). The ZCorp printer is no longer operating. Consequently, I am forced to find another method.

Recently, I found that a community college in Maryland offers access to the public of their Fabrication Lab that has a variety of equipment including a UPrint 3D printer, ShopBot, laser cutter, etc. I'll be taking advantage of their ShopBot.

Here is my problem -- when I began the process in 2007 I fabricated my horseshoes out of beechwood, mahogany and polymer clay. Unfortunately, wood proved to be unstable and warped in shipment. I would like information about using the ShopBot for cutting my prototypes from acrylic. It would require cutting each slice from <=3/4" acrylic 8" x 8".

The output from my 3D design software will be a .STL file. PartWorks3D indicates it takes in .STL files. Does anyone have experience with cutting from acrylic. No vertical sides are permitted, including engraved and raised text. I do have 4 locations requiring 1/8" vertical holes cut straight through for pin alignment at the foundry. Any help appreciated.

Thanks...Bob (Hilfling Horseshoes)

[SomeSailor]

I cut it almost every day (mostly thinner... .25") but the ShopBot does very well with it.

Have you ever thought of using foam?

[Brady Watson]

Bob,
PW3D is a basic 3D CAM program & to take advantage of advanced toolpathing, you will want to use something like Aspire or ArtCAM. Due to the compound curvature of the shoes, a simple raster finishing toolpath (such as PW3D offers) is not going to give you the quality that you want for a master part.

Also, the tooling you use is very important in order to eliminate a lot of post finishing to clean up tool marks on the finished part. Typically tooling leaves a lot of white lines and marks on the finished part when doing 3D machining such as this project would entail. I've got the technique dialed in pretty well...

There are many other materials out there that would be easier to machine and dimensionally stable. Teak believe it or not, works very well, as does any type of tooling board (like RenShape and others), you can cast your own material using polyurethane resin or buy it already layed up like Precision Board 40# density HDU. Acrylic isn't the material that I would recommend. Even MDF that is epoxy hardened can be a cheap durable master.

-B

[Photon713]

Thanks for both responses,

It is essential that the output is an exact copy of my .STL file by volume and smoothness. Every horseshoe must occupy 9.80 cubic inches of material to become a horseshoe that weighs 2 pounds 8 ounces when cast in ductile iron. The material chosen must be able to withstand a fair amount of pressure during the molding process when cast from my singles or splits. I really don't know what to expect when I begin to take classes on the ShopBot. If I were using investment casting I would consider tight cell foam. The method used by my foundry is green sand or airset casting. The reason I had considered acrylic is to eliminate warping during shipping and be able to withstand the pressures of molding. I downloaded and evaluated MeshCam to use for CNCing when providing a .STL file, but, without knowing the target equipment and tooling available, it was of no value to me.

I will take the advice given and investigate the material mentioned. Thanks to everyone. Best Regards...Bob (Hilfling Horseshoes)

[Photon713]

Brady...

I've checked a couple of your suggestions, i.e., RenShape and Precision Board. If you had to tackle my project what material would you choose. Both RenShape and Precision Board have a variety of choices. PB has two HDU choices and RenShape a couple of dozen. They both seem to fill the bill depending on the tooling available. I defer to your expertise. Regards Bob

[Brady Watson]

Bob,
I would call both Freeman Supply & Coastal Enterprises and ask one of their application engineers what they would suggest. I would include your intentions with the material, including CNC routing and the fact that you want to use it as a durable master pattern. I think that 40# or more density PB would be fine for your master parts & I think that you won't see a lot of difference between physical characteristics between the two after the part is machined - and I am pretty sure that PB is way cheaper to buy than RenShape.

Just to elaborate a little on what I mentioned before - ShopBot hardware is completely up to the task of machining your parts. However, an experienced operator, well versed in 3D machining and high-end CAM software are required to pull it off with the level of quality that you are expecting a master part to be. You don't want this to be the first part you machine by yourself if you are completely new to CNC - so keep that in mind.

Feel free to contact me off list if you are considering having this machined, or if I can help you to make a decision.

-B

www.IBILD.com

[Photon713]

Thanks, Brady...appreciate the information. Frankly, I don't know what I'll find when I take the initial introductory class for the Fabrication Lab. Sounds like this will be a real challenge and I may defer the task to a professional. It's relatively easy to create the design with 3D NURBS software and fire off a .STL file for a 3D printer. Unfortunately, ZCorp was bought out and many of the offices were closed down. I preferred SLA output over FDM ABS M30 plastic. Trying to clean up ABS was painful. SLA on the other hand, sanded smoothly and proved strong enough for 2-3 copies, which was enough for prototype casting and testing by NHPA professional pitchers. I was paying $85 per single or split and some service bureaus were quoting in excess of $1,000 for the same. So, I need another way. Hopefully, I can get something meaningful from the ShopBot, which will be free for use except for any material needed. Best Regards...Bob (Hilfling Horseshoes)

[robtown]

When ordering your acrylic you want to make sure you order cast as opposed to extruded. They cut differently and extruded is a challenge to cut.

[SomeSailor]

Another thought might be to farm the work out. I have a friend with a Z-printer. I'm sure he could print your files for you. Send me your email address and I will forward his to you.