Hi, I am thinking of getting a Mostly Printed CNC for my 15 yr old son to build and troubleshoot. I am trying to keep the cost down and was looking at using the Mini-Rambo but how can it control this CNC which has 5 steppers of the board is only capable of 4?
2 Likes
Series Wiring allows the Mini to control the CNC----It’s dual endstops that require 5 drivers.
Explained here: Dual Endstops - V1 Engineering Documentation
1 Like
So since there are 2 steppers per axis for the X & Y, are these two steppers run from one driver and therefore you only need 3 drivers for the axis and then another 2 for end stops of you add that option? I am trying to comprehend how 5 steppers can be run from the mini-Rambo.
1 Like
Exactly!
1 Like
Sounds like Paul has you squared away. I just want to add that it is awesome that you are doing this with a 15 yo. There are so many great ways your brain thinks when working on this machine that it will do so much to expand their brain. I was building RC cars and planes with my dad when I was 15 and it was a great experience, but this would have taught me a ton that I could have used.
If you hit any snags, drop a message here, there are a lot of people who are eager to help.
5 Likes
I couldn’t possibly agree any more strongly with this! 
In my (what’s beginning to seem ancient) youth an A C Gilbert Erector Set was IMO one of the great learning tools of the day and a great opportunity for spending time with my Dad. I can only see something like the MPCNC in the same light and it looks damn good! 
3 Likes
Guys,
Thanks for the info. My son has a 3D printer and has really gotten interested in expanding his CNC knowledge. My thought at this point is to buy a Rambo board, series wiring and one stepper and see if he can get the controller working. If this works, then I will order the kit and do the full build. Is there any thing else I will need to buy so he can try this? We are using Fusion 360 for design, what other software is needed to send to the controller? Where do I get the firmware?
Thanks in advance
You’ll need a power supply. The board comes flashed from Ryan. We keep the firmware on the MarlinBuilder releases.
Take a look at the software workflow.
For the right teenager, this is a fantastic gift. If you son needs plug and play, then the Rambo board with pre-flashed firmware is the way to go. But if he is willing to struggle a bit more and learn some things along the say, and alternate (cheaper) solution to test your son is to purchase a Ramps 1.4 kit from Amazon. The kit cost around $35 and includes a display with an SD card reader. A stepper will set you back another $10. And you don’t need a series wiring harness just to spin some stepper(s). The downside to Ramps 1.4 are: 1) the Ramps 1.4 boards are not forgiving if you make wiring mistakes, 2) it does not come with firmware pre-flashed, and 3) the cheap clone Arduino Mega boards tend to have the voltage regulators fail. On the other hand, you can replace a Mega for $15 or less. I believe he will also have to make a couple of firmware changes for the drivers that come with the kit since the firmware Jeff provides for the Ramps 1.4 defaults to different drivers. The Ramps 1.4 is more work, but he is going to learn a lot more. If you decided to go for a full build of the MPCNC, then purchase the more robust Rambo board.
You will also need to install a post processor in Fusion 360 to take the CAM setup and generate g-code that works with the Marlin controller. I use this one, and it is the one linked to on Ryan’s Milling Basics. page. Delivering the g-code to the controller can be done in a variety of ways. The display in the Ramps Kit (as well as the display Ryan sells) has an SD card slot, so the code can just be copied to and SD card and inserted in the controller. Based on forum comments, the most common way to send g-code to the controller is Repetier-Host which is free and sends the code to the controller over USB from a computer.
There is also something else your son can do with the setup. The g-code that drives the controller is a simple, text-based language that can be handwritten. So in terms of getting a stepper spinning, all he has to do is write line(s) of g-code in a text editor, put it on an SD card and execute it on the controller.
Ok, I have the Rambo, a stepper and the series wiring. Is there a link to how to hook everything up? Once connected what is the best way to test the single stepper to ensure he can controller from his PC?
-
You need to hookup power to both the steppers and to the control logic. Typically it is done by using “jumpers” between the two power connections like this.
-
Wiring up a single stepper will depend on what came with the stepper. If you purchased the stepper from Ryan, and if it is like the one he has pictured in his store, then you can plug the stepper directly into the control board using the provided wire (not the serial wiring harness). if the motor does not come with the wire, then I recommend you purchase one. It likely needs to have a four pin Dupont connector on one end and a six pin female plug on the other like these. You can use the series wiring harness you purchased to wire up the motor, but with a single stepper, you will have to install jumpers in the connections for the second motor. This is a bit ugly, and not knowledge needed to assemble the MPCNC. Here is a pinout for the Rambo board showing where things get plugged in including the steppers. Have him plug the stepper motor into the X socket. He can plug it in either way…it will just change the direction the stepper moves.
-
To move the motor, he can use Repetier-Host. It is free software, and the primary way Ryan documents to send g-code to the controller. There are several other methods he may want to explore long term. If/when you purchase a display, you can also control the machine from the display including running g-code files from an SD card. Ryan documents the Repetier-Host setup here. Under manual control in Repeiter-Host, you can click on the arrows to send movement commands that will cause the stepper to spin.
-
Taking it a step further, he could play/learn a bit about g-code. There is a field in manual control panel of Repetier-Host that sends g-code to the controller. Documentation for Marlin g-code can be found here. It is not necessary to learn g-code to use a CNC machine, but it is very helpful to have a basic understanding of the language and knowledge of a few of the codes.
P.S. If you did not purchase your Rambo board from Ryan, you will need to flash firmware. That is its own journey.
1 Like
Ok, not good… it only took him an hour to get it wired and running. Now, of course, he wants me to order the rest of the MPCNC. Lol. Thanks for all the help
1 Like
Am I correct in that the kit comes with enough belt to have a 24” x 24” x 3” working area machine? Does that result in 20 feet of rails?
You can use this calculator to figure out your material needs. A machine with a 24" x 24" working area will require aprox. 20.5 feet of tubing and require 4 meters of belt. The kit only comes with 3 meters of belt. If you order your extra belt at the time you order the kit, Ryan adds the extra belt to the end of the roll for the kit.
Is there info on how to connect the two ribbon cables from the display to the Rambo?
which display?
The one from Ryan… I bought the display and Rambo from him
I think all you have to do is use the 2 ribbon cables and plug them into EXP1 & EXP2 on both boards. make sure that you get PIN1 on both ends correct for each cable.
It only works one way, but the other ways are harmless. Sometimes the key is installed backwards and you have to cut it off or remove the shroud.