How to CNC machine forms for candy production
20 Eurocent coin - to be eatenMatthijs in the Netherlands is a manufacturer of sweets (wine-gums, liquorice, gom). The company is in business since 1920 and produces a wide assortment of sweets, that needs to be continuously updated by adding new products.
For their new models Matthijs relies on DeskProto user Deltavorm, located the in the south-west of the Netherlands. Deltavorm specializes in producing models and molds for candy manufacturing. As one of the few players in this niche market Deltavorm is a global player, delivering to all major manufacturers worldwide.
A picture from the Matthijs archives, and some current products.
Manufacturing these types of candy is an intriguing process: the molds are produced and again destroyed "on the fly", as part of the manufacturing process. The molds are made of starch powder, by pressing a positive stamp into a bed of powder (or rather a series of stamps for a series of cavities). Each cavity then is filled by molten candy, and after solidifying the complete batch is sieved in order to separate sweets from powder. The powder can be re-used for a next batch, the sweets can be post-processed and sold.
Deltavorm supplies the series of stamps needed to create these "throw-away" type molds. Stamps that are perfectly adapted to the requirements of this unusual manufacturing process.
Manually carving in plaster, and next a part of Deltavorm's model archive.
The idea for a new model comes in as a sketch, a verbal description, an sample piece, etc
Deltavorm immediately starts working in full 3D, by manually carving a mother-model in plaster. This ability to carve is a important quality: the 3D model is produced far more quickly than we have even seen using any computer based technology. Also important is the vast archive of models, currently containing over 20.000 molds and 40.000 models that have been created over the past 30 years.
These models cannot just be copied and then supplied to the client. Typically small changes in size are needed, as the client will need the product to be exactly on a certain weight (volume). So often a scaling needs to be applied, either in full 3D or per axis. Such change can of course be done much more efficiently in CAD/CAM than by manually carving a new model. This means that the model needs to be scanned.
The 3D scanner, by 3Shape. The line of red laser light moves over the object when scanning.
Deltavorm has tested many 3D scanners in order to find the scanner best suited for this application. After evaluation the best solution proved to be the D700 laser scanner made by 3Shape in Denmark.
This 5-axis scanner has originally been designed for dental applications, and features two rotations of the part during scanning in order to eliminate accuracy problems when scanning steep walls. The scanner is fast (under 3 minutes for a scan) and comes with post-processing software to clean up point cloud and STL file. End-result of the scan is an STL file that describes the top side of the model.
The resulting STL file, in the 3Shape software and in DeskProto.
As the bottom of the model has not been scanned, the resulting STL file is not a perfect solid (from below you see a hollow shape). This is not a problem as for milling it is not needed to have a perfect solid.
Applying the scaling is easy: in DeskProto scaling is possible per axis or uniform, by just entering the scaling factor(s) needed. For most models two operations are used: first roughing and the finishing. DeskProto can easily handle even the largest STL file size, and very quickly calculates the toolpaths needed.
The Roland MDX-540 with ATC (Automatic Tool Changer).
Milling is done on a Roland CNC milling machine, type MDX-540. As you can see in the illustration above, this machine is equipped with an Automatic Tool Changer (ATC). The optional rotation axis is not needed for this application. Deltavorm typically uses two cutters: a ballnose cutter of 6 mm diameter for roughing, and a smaller ballnose (diameter 3, 2 or 1.5 mm) for finishing.
This Roland machine is very fast, and as no manual toolchange is needed all is done automatically. So milling can be completed during a cup of coffee: this 20 cent model only took about 15 minutes.
As the toolpaths can be sent to the MDX-540 directly from DeskProto, without even saving an NC file first, the process is very easy as well.
The coin model during roughing, and after finishing.
As can be seen in the illustrations, the ballnose cutter travels deeper than the model. This is needed to completely machine vertical and steep surfaces. So below the models an extra slab of material is present that may be damaged as it can easily be replaced (called the 'wasteboard'). The material used for the models is tooling board. For each model Deltavorm 'clamps' a small block on the wasteboard using double-sided tape.
Real coin, hand-carved plaster one, scaled copy, candy coin.
For mass production a series of stamps is needed, so machining just one model is not enough. Multiplication can be done using casting: either casting resin in a silicone rubber mold, or casting metal in a metal mold. The machined model is of course very well suited as prototype, for concept testing.
The resulting candy that is sold by Matthijs.
This project concerned a series of coin candy, to be produced in liquorice. Three different coins have been designed: 20 cent, 50 cent and one Euro. Of course the level of detail that can be achieved in liquorice is very limited: small details in the real coin cannot be reproduced. Still the resulting candy can clearly be recognized as Euro coins, so the design is OK. As the candy also tastes great and is currently being sold in large numbers the project is an absolute success !