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WOODEN ENGRAVING MACHINE VejenHlebarov 2006 Introduction This part does not contain technical information. It starts from the next chapter. How the ideas come out? One day I wanted to buy wooden toys for my daughter. I remember my grand dad made wooden toys for me when I was little boy. I remember being very happy playing with cars, trains and constructors made from wood. I went to my local shop and in 5 minutes discovered that my child will play with plastic stuff. The wood toys were either very expensive either not for her age. Going back home I was thinking can I copy some of my grand dad ideas. He is not alive from many years, but I remember his toys. Grate stuff. At least this is my remembering from my childhood. I decided to browse on the internet and see for some ideas. I will be happy if one day my children remember my toys the same way I remember my grand dad. I wanted something unique. After almost a week I decided that Majosoft’s hobby site is the best solution to my problem. In the age of the computer CNC engraver is very cool idea I can make engraving machine and at the same time I can help myself preparing my PCBs with the same engraver. I was very enthusiastic. Main construction and kinematicsI wanted to copy the idea because I am not very experienced with building machines. Also I did not have the right tools so I had to by some. I couldn’t find in the local shop special nuts for MDF.(the small cylinders with perpendicular screw shown on Majosoft’s site). I have used combination between wood and MDF ( not very good because the wood is not as precise as MDF but at least I can screw with no problems) For axe Y and Z I decided to change the construction of the sliders rather then position two sliders one next to another (see the original Majosoft’s hobby wooden engraving machine). In My construction axe Z is made square for bigger stability. The machine finally looks almost identical as the original CNC Engraving machine in Majosoft’s site. Building the machineI am writing this saga to protect you from mistakes which I made. I am not saying that I built this machine without any challenges and I am not pretending it is the best. I would like simply to benefit the community by presenting pictures and materials for my effort to build CNC engraver. Please take some suggestions just before the pure technical part. 1) My machine is not expensive. My budget was 100GBP. This includes even the bench grinder to prepare my instruments. 2) If you intend to copy this idea do not plan to do it for one night. It is not possible. It took weeks to me. 3) Ask friends! I found elements and electronic parts just by asking friends. 4) Before building the machine please sit and draw simple plan. Sometimes this will save days of tinkering to avoid some problem. Technical part – main construction and shopping list My machine is very simple and does not have many elements. I have started with half MDF sheet. (half of size: 2.4 X 1.2m X 18mm). I have asked in the shop to cut the sheet in the pieces calculated in advance. I took one beam ( wood) 2.4m 47mm x 74 mm. Bolts for wood 3mm x30, 4mm x 40, four long screws for wood 10mm x 80 and 8 bolts 100mm (metal) . Also you need glue and 4 metallic angles. You will need sliders depending on your construction. In my machine I have used for Y axe old sliders 52cm x 40mm , 4 sliders for X axe 25mm X 28cm and 4 sliders for Z axe ( same as X axe). Leading screws Y axe – 55cm (M12), X axe -50cm(M12) and Z axe 22cm ( M12) I hope I didn’t forget anything. Main constructionThe main construction is made on top of a stable MDF sheet 550x480mm. First you have to cut measure glue and connect with bolts two vertical wooden beams to the horizontal once. Please measure the right angle correct! This is very important. On top of the two wooden beams you have to construct axe X. I have done this the same way as in Majosoft’s site using 4 sliders. Axe Y uses simple trick. I have decided that in order to stabilise the table I will use not 4 sliders but just two. This allows reducing the overall size of my machine. In order to do this I have opened the sliders from one side and took out the metallic inserts with the bearing. I have cut these inserts in two peaces then assembled the hall construction again. Now looking at the slider- you have two peaces with bearings inside. I have put small metallic inserts (copping the original shape) in between the original and finally end up with the following construction. (see the picture) SHAPE \* MERGEFORMAT
 Of course you have to calculate how long this inserts have to be. Also I have decided that the cutting force have to be always in between the bearings. This is very important since this is Y table and has to support the material been drilled. Axe Z is required also opening the sliders. I have decided that I should make table Z square. This will allow better stability because the sliders will be on bigger distance then in Majosoft’s design. I didn’t want to make axe Z long 2 sliders. The trick here is to use the inserts with the bearing from one slider and to put it into another. Finally you have slider with doubled size of the bearings inside. Please not that this will restrict the movement of the slider more then 50%. This approach is OK for Z axe because the movement here is only 12cm( not 28 as usual). Electronics and controlMy motors are 5V (stepper) and 24V drilling motor. I must say that the voltage of the steppers is perfect to supply from computer power supply, but the main motor 24V?!! I have measured the current of the main motor – 0.7Amp. Later I have decided to use +12 and -12V from a computer power supply in order to start this 24V motor. After several disappointments I have figured out that I can drive it only if I restrict the current with resistor and use of one diode. This way the motor turns with 18000rpm instead 20000 but the current is 0.6 which is OK for my computer power supply. Driving the steppers was not easy also. I have measured each coil is around 4 homs. This makes around 1A per coil- which means no way to use ULN2803 to drive it. Instead I have constructed similar circuit using 4069 inverter and TIP 120 transistors. You can see them on the pictures in the small black box ( 12 X TIP122 transistors + 2 X 4069 chips inside) I have done my first experiments with simple VB program. You can see the result on small wooden peace. I don’t have software at the moment to test properly the machine, but I am exited even from this small peace of wood made today. Finally I have the machine ready. Pictures Bellow each picture will be small comment.
 This is the machine with the control box. Looking at the picture I still have to tide up the cables. This nut is my discovery from my junk box. I was lucky to find this size M12 nut.
 This is the control box. You can see the red cables are coming from standard computer power supply. The connectors are for the steppers. I am cooling the box because TIP120 transistors inside are getting hot. (They don’t have radiators. I wanted it this way to reduce the size of the box)
 This is the back of the machine. You can see X axe. The nut is plastic. It is connected to the table with 2 aluminium profiles. You can see the wooden beams and the horizontal wooden piece. This makes the connection between the MDF parts very easy.
 This is the machine from the left side. You can see the main MDF sheet at the bottom, the Y axe (on top of the horizontal wooden beam) and Y and Z axe on the vertical wooden beam.
 This is how I connected the motor for X axe. It is on separate MDF platform which is screwed to the vertical wooded beam.
 This is the nut ( plastic). I have made the same tool as in Majosoft’s site to make a screw in the plastic. It was very tricky. After several trials I discovered that if you heat the tool on the cooker it is easy to make the screw. Otherwise you have to press to much.
 This is the drilling motor. The end of the motor was only 6mm cylinder and I had to prepare the connector. It is copped from Majosoft’s site ideas. The drilling bit is also from 2mm drill I broke recently. I had to buy grinder in order to produce the right configuration.
 Final prove. The wood on which I tested the machine. The zigzag canal is 1.5mm | 
