Centroid Community CNC Support Forum

After the relative ease at which i had success in retrofitting the hercus mill and some of the apparent shortcomings in the design and construction of the mill hardware it was based on i decided i would have a crack at designing my own mill from scratch. I wanted to take full advantage of the 4th axis capabilities of the acorn board but rather than design a 3 axis vertical machine and put a 4th axis trunnion on it it decided i would have a go at designing a horizontal milling machine. I dont know of any desktop horizontal milling machines and it makes more sense to me for a desktop milling machine which is likely to end up running minimal coolant.

I thought i would start up a build thread where i can update as i slowly chip away at it. this isnt going to be a rapid build by any stretch of the imagination but hoping to make small milestones semi regularly.

I had some hardware saved up i pulled out of some other desktop milling machines i was planning on using which has somewhat governed the work envelope of the machine. I have linear rails for the X and Z axis. i have double nut ball screws for X, Y & Z but they are an odd design and have quotes for replacements including end supports which are pretty well priced which i also have all the cad models for.

I have a BT30 spindle shaft and bearings i pulled from a machine however it had a long bolt acting as the pull stud retention and i want to have a pull stud retention mechanism for eventual ATC so i have designed up my desired spindle and will modify this one to suit.

I plan on using a relatively cheap rotary table coupled to a servo for the B axis to start with with plans to pull the worm drive mechanism and table out to then house in my own one machined up to be all integrated.

I have designed the frame to fit a 0.55kW 3PH motor but i would really like to have the ability to index the spindle for eventual tool change mechanism. ive done a little bit of research but not found an ideal solution. i have a 0.75kW 180V DC motor so i am wondering if the dc motor may have more options to achieve a spindle orient function. possibly running 2 contactors and swapping between a spindle drive and a servo drive when comes time to orient. i was thinking of gearing the spindle 2:1 to get increased rpm and just slave the the encoder of spindle shaft via a gear drive.

Here is a screenshot of the computer model so far: here is a photo of the spindle design (i forgot to transfer SW licence and this is all i have at the moment): I made my first part for the project this afternoon; the collet which houses the ball bearings to pull on the retention knob. i programmed it up last week. i just loaded the tools in the lathe this arvo and knocked one out. i drilled the 6mm holes just deep enough to leave a tiny lip to stop the balls from falling it but they fall in deep enough to engage on the pull stud and the whole assembly slips perfectly into the existing hole in the spindle shaft. i have the material for the spindle housing, i just need to whip up a program for that and knock it out one arvo.

i also need to modify the spindle to add the groove for the ball to pop into to release the pull stud. that i can do on any one of the lathes at work but i need to modify some soft jaws to hold the spindle in out big lathe to try and drill out the cavity for the 20mm belleville springs. its the only one with a spindle bore large enough to house the flanged bit so i can grip the part where the bearings mount in order to ensure it runs true when drilling.

my plan is to finish the y axis way covers before ordering any laser cutting as I ended up tweaking the structure when designing the x and z covers and will likely have to do some tweaking to get the Y covers to all work.

I was planning on pulling the leadshine drives out of the vertical mill to power this but i am thinking depending on how long the build takes and how much money it costs i would love to put some decent servos like delta or yaskawa. if i did that i would use a braked servo on the y axis to avoid having to put a counterbalance cylinder. Maybe a servo that would work with the acorn but also work with full closed loop oak board down the track.

The machine will end up being quite small. with a 150mm table, 150mm x 220mm x 150mm(x,y,z) travels and with hopefully some decent spindle speed, direct coupled 400w AC servos, it should be quite a rapid little machine.

i will try keep the thread updated with progress.

The cool thing about Acorn and CNC12 is the cost. Opens up all sorts of possibilities for someone to invent.
You can automate things too! Think of a back gauge on a shear, single axis, punch in the desired dimension desired in MDI and the back gauge moves stomp done....just an example

THINK OUTSIDE THE BOX! Its just G code and axis motors
Post the cool stuff in the Success Stories Section.

Good luck with your horizontal machine build. Have fun with it. Build a cool tombstone for it, think about work holding, the whole process before you commit to building the machine. I'm sure you are looking at other machining centers. Depending on the part size you want to build, what about finding a horizontal mill and starting from there? There used to be some neat little benchtop units. Use the knee to raise and lower the part. OR start from scratch. Have fun and yes, share the journey, it will inspire others to try something different or to Acorn for a specific application.

Marty