Engraving Stone on a CNC milling machine
Stone engraving – Demands on the CNC machine
Deep machining of stone
Beside milling metal, the machining of stone makes the highest demands in the CNC manufacturing. When it comes to deep machining of granite, marble and slate, it turns out if the machine construction is stable enough in all axes, that there is no bending of the components during the machining process. An unstable built CNC router cannot process the milling paths precisely and produces inaccurate results. You can visualise this by imagining a machine which is supposed to mill a straight line into stone, but due to the bending of the Z-axis, the milling cutter shifts left and right which makes it impossible for the machine create a straight line.
Engraving stone with a stable machine design
Trying to engrave fonts as a 3D relief in solid stone, many homemade CNC routers fail because of low-quality components or non-professional mounting. How to design a stable machine with steel components and a high-frequency spindle which is sturdy enough to mill stone accurately in the low-price segment? Asking this question is crucial before buying a CNC machine. A standard milling motor is sufficient for machining wood, brass or plastic. But milling solid stone like granite you need the performance of a high-frequency spindle for getting good results. In the following pictures you the quality of stone engravings made by the RaptorX milling machine and an HF-spindle:
Tips for buying an appropriate CNC machine to do 2D and 3D stonework
Before purchasing a machine, you should know that milling marble or granite requires a much more robust CNC router and a high-frequency spindle than milling Softwood or plastic. Of course, you need to spend more money on such a machine due to the high-quality component used for building the machine. The following tips will help you to buy an appropriate CNC router for machining stone:
- You should better expect to spend more money. Usually, cheap CNC routers cannot mill resistant stone in the deep.
- We recommend only to buy a machine you have seen in action before. A demonstration with your desired material helps you to decide if the CNC router can mill stone precisely.
3D stone engraving in marble plates
Engraving a 3D relief in stone looks quite impressive. A wall decorated with marble plates and 3D reliefs is a real eye-catcher. The fine contours of the angel figures we milled in a marble plate, a sculptor could not have worked out better, especially not at the same time as the machine accomplished the engraving. It took only 4 hours for the RaptorX-SL milling machine to finish this masterpiece. Considering that the stone is solid Carrara marble, the CNC machine has accomplished the 3D stone engraving in a little while.
The machine processes the data of the CAD software ConstruCAM 3D line by line with a misalignment of 0,3mm in the 20mm thick marble plate and removes only the necessary material for 3D relief to arise. We used a spray cooling to keep the wearing of the milling tool as little as possible. Apart from that, we vacuumed the dust directly at the milling cutter to avoid any health risks. Doing so you can keep standing beside the CNC Mill without wearing a dust mask.
Engraving photos on stone
Beside stone engravings done by milling, we provide suitable CNC equipment for engraving photos on stone. The engraving module GranitoGrav grinds the picture with a rotating diamond tool into the rock surface using different grey shades. The engraved photo is put together by the contrast of light and dark tones of grey. The contrast becomes most visible on dark materials with a flat surface. This is the reason why headstones, tomb slabs and memorial stones made of granite are perfectly suitable for grinding photo engravings on them.
Compared to milling granite you don’t need a CNC mill with maximum stability for grinding the photos on the stone surface, but anyway, a machine with high accuracy is necessary. The basic version of the GranitoGrav includes a High-Z router with ball screw spindles which ensures the necessary precision for engraving photos. If you want to mill deep into the rock as well as engraving photos on the stone surface you can also use the GanitoGrav with a RaptorX-SL milling machine