I had the demand for some more serious aluminum milling. I did that with the MPCNC before and it was kind of okay but I wouldn´t like to mill higher part counts with it. The spindle gets hot after some time and leads to more flex in the toolhead. It´s not made for aluminum so I looked around for a more suitable platform.
I found the openbuilds C-beam machine to be nicely designed and versatile enough to be worth adding to my machinepark. I looked around for a europe based shop and found openbuilds poland , v slot europe and ooznest .
I decided to go with the ooznest version as they had the best full kit. I didn´t wanted to source all the parts from here and there. Sometimes it´s nice to have a complete package 🙂
The sipment was fast after the payment went trough and so I had a first look at the package today. All was nicely packed and labeled according to the build section like X, Y and Z Axis. The printed parts for the power supply and the controller board looked pretty nice and felt solid.
Can´t say much yet but a real manual would be more comfortable than a build video. It´s way faster to look at a drawing than to forward, play, stop, rewind, play, the buildvideo 😀
I currently got some problems with drilling holes again. It seems there is something odd in the Z- axis. I didn´t assembled it carefully enough. I suppose that the spindle isn´t lowered in a straight line, instead it is tilted on the way down pushing the endmill into the material sideways and ripping a hole into my plywood.
I´m using this as a reason to reprint the tool- and steppermount.
When I originally build the MPCNC I had no drillpress and the terrible idea to tap a M4 thread into the stainless. This is a bad idea as it clearly makes the alignment of the screws in the tool mount to the conduit almost impossible.
I redrilled the holes and I am now using the original path with the nut traps inside the conduit. Along with the adjustment of the leadscrew this hopefully improves the precision and rigidity of my z-axis.
Finished toolmount replacement. The one on the left was printed with an pre R17 BCN3D Sigma and the right one printed with my DIY printer.
Now everything is assembled again. The tubes are now „perfectly“ straight and parallel. I used a glass plate to verify the alignment.
I did a short test run and I had the same result as before. A nice circular vibration and a not very pretty drill hole. I´m using a diamond cut endmill at the moment and went successfully through two sets of printer frames. I´ve been told in ryans formum (viscious1.com) that diamond cut bits are everything but ideal to dive 12mm into beech plywood. They are very robust so they were the only ones that survived when it came to an error. They are compressing the shavings within the hole and that leads to more and more pressure hence the heat rises and the endmill escapes in the circular movement.
In the past I ordered a endmill from sorotec which broke after some drilling operations. That left me confused what the error might be. I also tried a shorter endmill originally for aluminum which transported the shavings quiete nicely but was too short.
I ordered new endmills again and hopefully all the possible errors caused by the machine are gone and I get my drill patterns and contours out of one endmill.
Inspired by one of my readers I had a look at the dust shoe for the Kress again. I redesigned it completely and got rid of the additional tubes and clamps. I thought that it would be a good idea to have a highly flexible part between vaccum and CNC. If I had ordered the 20mm silicon tubes it may have worked as well but reducing parts is allways priority.
So in the end we got a pretty classic dust shoe here. It doesn´t have a brush at the bottom as it seems to work pretty good at the moment and I really like to see the endmill. However I included three holes at the bottom for a later brush design.
It works pretty good with lighter materials but GFK, aluminum or similar are not fully sucked up.
It has been printed in 0,3mm draft quality for testing purposes.
In order to find a suitable endmill I had to understand the principles involved first. That led me to feeds and speeds. The difficult part was to determine the limits of my cnc. I already had a look on that topic when I chose my Spindle. It has a minimum RPM of 10000 and a maimum of 29000 RPM so I decided to go for a 2 flute endmill with a diameter of 3 mm from cnc-plus.de. More on the calculation later..
After testing the gcode and finding out if the steps/mm of the steppers are dialed in correctly I used a simple ruler to check. Josef Prusas stepcalculator gave me 160 steps/mm and that resulted in the correct distance of movement with my 20 tooth pulleys. As I couldn´t set the parameters from the graphic display I had to reflash the Marlin firmware.
I used a M8 threaded rod like suggested in the original plans. It is not meant for machine operations and so It loves to do what it is designed for. It binds pretty often, resetting the z axis position and making sudden, unexpected deep cuts as shown in the video below. It is the straightest rod I could find and it is well greased but it was necessary to lower the acceleration and speed. I only had this one piece of hardwood and I wanted this to suceed. I´m trying to get the speed back up again because the milling took ages (1h15min) because of the adaptive clearing and the many retractions of the tool head.
The 3D printed rigid couplers didn´t worked to well for me so I ordered a jaw coupler also from http://cnc-plus.de to make it more reliable.
In conclusion : I liked the results of the cuts and they were somehow thrilling. The accidentially super deep cuts showed that I can go much deeper than 3mm in one pass with hardwood. The method used here was also a test for the ultimate goal for cutting alumium sheet and composites.