DIY Control & Machine

[Chris D]

The machine shown in the videos is something I have been working on for about a year and a half. I may have posted a video of it here on the group a year or so ago but thought it was time for an update.

The machine's primary purpose is to be used as a platform for testing out motion control software and electronics (CNC control) that I wanted to create. The machine has changed a bit over time, but basically it is a PCB sized CNC router with about 10" X travel, 16" Y travel, and 4" Z travel. All 3 axes now use linear bearing ways whereas in an earlier version I used V-Rollers on Y and Z. X and Y are belt driven and the Z axis uses a belt driven ball screw. I only have a 35 volt power supply for the steppers, but even at that I can get 750 IPM rapid rates but I usually set it around 600 IPM.

The spnidle is shop made and runs at 24,000 RPM (although the video says 14,000). The spindle is a collet spindle and has an automatic actuator for the collet open/close.

The stepper drives are Gecko 250s.

The control is where I have spent the majority of my time on in the last year. I wanted to build a control that did NOT need a PC nor was PC based. Rather I wanted to use microcontrollers. I also wanted the control to operate in closed loop. The contoller is probably 1/3 done depending on how carried away I get with it. At present its performance is fairly decent as it is capable of 120Khz stepping frequency (give or take as I have not measured it in recent months). Closed loop feedback is accomplished through the use of linear scales made with US Digital linear strips and encoders which provides for .0005" resolution. It is capable of rapid and linear interpolation at present. Supports work offsets and tool length offsets. It also has canned cycles for hole drilling.

The control is made up from 4 micro controllers, 2 of which are multi-core controllers featuring 8 micros each (Parallax Propellers) and the other two are Atmel Atmega chips, 1 is the 2560 the other is the 644. Program and data storage is via an SD card and eventually there will be a serial interface to a PC.

I have posted 3 videos on Youtube.

1) overview of the machine
2) overview of the control
3) machine rapid demo, plotting demo, pcb milling & drilling demo









Thanks for taking a look at my project. This control is not a commercial venture, just a personal challenge to see if I could do it

Chris

[jaydawg]

HOLY COW!!!! What a great project. Very impressive. I especially like the self built controller.

[Jesse B]

Astounding! This is an absolutely awesome project! Keep up the good work!

[beliefdrive]

great work

[PaulRowntree]

I like the use of the prop chips here ... very appropriate.

Can you estimate to what degree the performance and/or accuracy improved when you went from the V roller bearings to the linear tracking?

cheers!

[mlabruyere]

Man I feel humble after watching these videos.....man and I had trouble getting the XML file setup correctly for my G540 interface to Mach.....

[Jesse B]

Just out of curiosity, you don't happen to have a website/blog where you've documented any of this do you?

[Chris D]

Thanks much for the kind words - very much appreciated.

Regarding the change from V-Rollers to linear bearings. I can't say there was any performance increase, either in velocity or precision. On the original machine, I didn't have room for purchased V-Rollers so I had to make my own using bearings and a pressed on sleeve. At some point I was checking things out and noticed side play on the rollers/bearings which is why I switched to the linear bearings. While V-Rollers are generally okay to use, the homemade V-Rollers were the weak link.

Regarding the Build-log - I sure had intentions of doing one for this machine as I enjoy reading through other people's blogs. Shortly after getting started on the machine I just was having too much fun building the machine and working on the control and lost interest in doing a blog. I do regret it though at this time as I have done so much with this project and I am sure it would have been an interesting read/guide for someone else trying to do something similar.

Regarding the Propeller chips (From Parallax)... I must admit I really was afraid to use them at the beginning. The native programming language, Spin, seemed very strange and hard to understand. Turns out it is very easy to program and the super bonus of that chip is the assembly language. The assembly language for this chip is very easy to work with as compared to other micros. What started out as a "oh heck, I know I won't like it" turned out to be "I am so glad I started working with those chips!". The most critical function of the control (motion timing routine) is written in assembler. The other advantage of this chip is the amount of available code that is available to use off of their website.

Thanks again for the kind words everyone, very much appreciated.

Chris