Hi!
I am a industrial designer in need of a CNC machine. I have looked around for machines to buy but decided to build one myself. It seems feasible given the vast amount of resources available to do so nowadays. And also fun! I have operated several 3-axis CNC machines in the past and have assembled a Shapeoko for a friend but still consider myself a novice in the area, that is why I decided to post here. I want to share with you the results of my research and hopefully get some feedback on how to proceed.
Machine requirements:
- It will mostly carve 3D shapes, occasionally 2D shapes.
- 5-Axis: It will have to mill undercuts on parts sized 150x150x70mm approx.
- 3-Axis cutting volume: 450x450x200mm approx.
- It is meant for fine detail work so it must be very precise with an emphasis on high quality surface finish. Repeatability precision must be at least 0,01mm, hopefully better.
- I mostly want the machine to mill PU foams(like Prolab65, or this), plastics like Nylon, ABS or Acetal and hardwoods.
- Minimum tool size: 0,2 mm
- Small budget of course
My thoughts so far on how to solve this are:
- In order to achieve these requirements I think the best alternative would be to base the design on the Tweakie CNC and customize it so an AB platform can sit on the machine table. Looking around this one seems like a good candidate. Has any of you tried a platform like that? The platform will have to be removed for larger 3-Axis milling, of course. I can have the frame built locally by a professional metal shop for a decent price.
- I made a quick schematic model for the machine in Inventor. I used the measurements provided by the seller for modeling the AB platform:
- The quotes I got for the frame uses 25x25x2mm steel square pipe. The design considers the addition of a plate that will be milled completely straight in order to have a proper mounting surface for the square rails to sit on. Also, oversize holes to allow for fine tuning the alignment of the rails. Do you think I should provide other means in the frame for calibrating the alignment and squareness of the X,Y and Z axis?
- I am thinking of getting these rail+ballnut screw and supports kit. If possible, I would love to know your thoughts on this kit, do you think they will be precise enough for my needs?
- As you can see in the picture I am planning on making an outrunner brushless motor for the spindle. No other reason other than I thought it would be fun to build and maybe can make it lighter that a spindle from Aliexpress. I was thinking on building something like this one, with conical bearings and other improvements. I am aware that I will need high RPMs(higher that 20000RPM) for the toolsize I want.
- My thinking is that NEMA 23 stepper motors will do fine. I have these Wantai 57BYGH218 in mind, they are 2Amps per winding and 1,8º step angle. Will I need 0,9º stepper motors? Do you think 2Amps motors will do for my application? I have used Wantai motors before and the quality is good but I am not an expert.
- Might add epoxy granite slabs to the frame for harmonics damping. In these areas(red):
- My plan for building this is to buy the components first to make sure all measurements are correct and then have the frame built. That way I can minimize fit issues between components.
- Toolchain that I plan to use is:
- Toolpath and Gcode generation: Inventor HSM
- Machine controller: Arduino Due(running g2core)+BigEasy Driver
- Control Software: Chillipeppr
I would LOVE to get some feedback from you. Thanks!