Getting Ready for Your New Long Mill


Hi all. In preparation for my new Long Mill, I’ve been looking at gcode senders. There are quite a few, like Universal G-Code Sender, Source Rabbit, Candle, etc. I was reading the GRBL docs and read that the GRBL team highly recommends UCGS.
UGCS is an easy install, especially if you have Java already installed. It will start up and load a file, and you can make some config changes, but to simulate a machining operation you need to be connected to a machine. I found out it’s pretty easy to simulate a connected machine before your machine arrives, and I thought the process might be of interest to the other anxious waiters.
Since the controller for the Long Mill is an Arduino Uno, you can convince UCGS you have a machine connected by simply flashing GRBL onto an Uno, and connecting it via USB to your PC. Now you can watch UCGS send the G-Code commands as if it was routing for real. I think now is the better time to learn how it works than after your Long Mill is assembled!
You can buy an Uno for <$20 at or Amazon, and instructions for installing the Arduino IDE and flashing the Unu, and a ton of useful info about GRBL, are found at
If you add LEDs to pins 2, 3, 4, 5, 6, and 7 of the Uno you can see how direction and move signals are sent. Put a 470 ohm resister in line with the direction signals (5, 6, and 7) since they either on or off. The step signals are very short and if you put resistors on line the LEDs are hard to see.
And, if you put normally closed (NC) switches on pins 9, 10, and 12 you can simulate homing switches.
After I did all this I discovered that GRBL does not like some things, like the M6 command, that Fusion 360 adds to the standard GRBL post file. If you get this you can delete it from the file, but better yet is to tell UCGS to ignore it in the future when it asks. I understand the latest post configurations from AutoDesk eliminate this added command. Glad I caught it now.
I hope somebody finds this useful. Hve fun.

1 Like

@BillKorn: Knowing nothing about arduino, I searched locally for the uno. Can you pls tell me if this one will do what your are suggesting?

thanks much


The R3 version is the latest and has been out for a while so this one will work. But you can find it cheaper and probably faster elsewhere. I really like adafruit - They stock loads of parts, they ship right away, and they know their stuff. They also design things they sell, and have very good tutorials.
The Arduino is a fun device. It comes in several sizes and capabilities, and is programmable in C. It’s particularly good at interfacing with other hardware like motors, sensors, controllers, etc. It has digital and analog I/O that are easy to set up, and uses existing libraries so instead of writing a lot of repetitious code your program only has to include a library. There are newer single board computers - it’s really a controller - but it’s still very useful.


I would highly recommend looking a cncjs as well. It is updated regularly and the layout is easy to use.


I understood some of those words …

Fuck what have I gotten myself into haha


cncjs looks great from everything I’ve seen, but I haven’t been successful getting it loaded. It has too many cool features to pass up so I’ll keep trying.
Another one that I tried with the Arduino simulation board is bcnc. It has a lot of cool stuff like autoleveling, tracing, scanning. I seems a little finicky, but it gets such great reviews I must be doing something wrong there too.
The GRGL guys like UCGS and I’ve been feeding it files from Fusion 360 and it hasn’t hiccuped - as far as I can tell with the sim board - so at least at the beginning I’ll use that.


Hey, this wouldn’t be fun unless there was some head-scratching involved, so we’ll all be lost from time to time. That’s where an active forum community will be a big help.


@BillKorn: I’m in Canada. ADAFruit is in the US, as you likely know. I looked on their site and as usual, the shipping cost of the board is more than the cost of the board itself. By the time I add in shipping and convert the price to Candian dollars, the one that I linked to is much cheaper and the store is local.
Tks .


@gwilki another ‘local’ canadian retailer is also has Arduino stuff. I bought a bunch of Raspberry Pi stuff from them over the years.

I have also bought a bunch of stuff from Adafruit which is an excellent open source / hardware company. Shipping is always a killer, a couple of ways around it I have found over the years is using which is an electronics parts supplier our of the US with free shipping over $100 canadian including covering the import duties. Also buying from the UK is sometimes cheaper too with no duties on any of the orders I have placed, including stuff from Adafruit. (,, It all depends on which site has the all stuff I am looking for so it’s a single shipping fee.


@BillKorn this is exactly something I was hoping to do, thank you very much for this post.

This will help me play with a bunch of different gcode senders I have been looking at for performance on a Raspberry Pi 3 B+, wireless keyboard and a 4" HyperPixel display I purchased from

The ones I have been looking at are:

  • Universal Gcode Sender
  • CNCjs
  • bCNC

You dont need any of that stuff guys. G Code sender platform is good and after that figure out what program you want to use. I understand wanting to play around but you don’t really need grbl and stuff. Its already set up as far as I know.


@gnuthbie Thanks. This is an easy way to test out some software and even some designs before the machine arrives. You don’t need to connect the LEDs, but if you do it’s also interesting to see how direction and step commands are sent to the controller. BTW, when the direction pins are high and the LEDs are lit, that’s movement in the negative direction - seems backwards, but that’s an old CNC convention that has become standard.
The three senders you listed are the ones I’ve been looking at. UCGS seems pretty robust, and teh guys at Sienci and the GRBL maintainers recommend it, so that’s where I’ll start.
Let me know how you make out.


@GregsReinventions This certainly isn’t required. I did it because as I’ve researched software I’ve read several comments about how some gcode generators add commands, like the way they generate code for rounding and arc & circle generation, that either the senders I was looking at or GRBL itself do not handle well. I didn’t want to have a completed Long Mill and find out I was being held up by software head-butting, so I wanted to get ahead of it. Some of you guys have been CNC’ing for a while and know a lot more about it than I do, so I want to learn something while we’re waiting.
I’ve also found it useful for studying how different ways of milling a part yield faster results. Fusion 360 gives what I hear is a pretty accurate estimate of cycle time, but some of the others don’t. Once again, I think we’re all going to learn a lot from each other. I’m looking forward to it.


Yes I agree there is a lot to learn but its way easier to learn with the machine in front of you. For me I cant learn a lot just by messing around with the software. I need to design a project and learn say a program like easle or if you like fusion 360 and draw it out first. The gcode sender will make the machine do what you want it too to a certain extent. One thing I am learning is if you want to cut say a square ring out of mdf how do you make that happen without making the waste in the center sawdust. LOL. I figured that out and its in the commands you give the program in the cuts you want it to make. Once you figure out that you need the machine to create a groove inside 3/4" from the outside of the edge of the finished piece you click on that and make that a cut through. That eliminates the need to cut the whole center into sawdust. Wasting all that material. Can save the inner waste for another project. The pieces I was trying to cut yesterday for a client were 24" square mdf. He needed square rings 23.5" across 3/4" wide. I couldn’t think of how to do it in front of the machine and him. But I did just morning thinking about it in my head.


@GregsReinventions What I am hoping to learn with this is the performance of different gcode senders running on the Raspberry Pi with a 4" screen on it. From what I have read the web based gcode senders can have some performance issues, but are more customizable in the interface than Universal Gcode Sender. I also want to see how they all work with a wireless keyboard and possibly an XYZ homing plate.

I will have my LongMill in the garage and don’t want to bring out my laptop every time I am running a job for the full length of time. I used something similar for my 3D Printer having a Raspberry Pi running OctoPrint, but the start of a job on the CNC is a bit more involved than on the 3D Printer.

With some of this testing I can hit the ground running and hopefully run into less snags after I get it setup this summer.


Man that sounds really complicated. Way beyond me. I like raspberries but not in pie LOL


@gnuthbie That’s exactly why I set up the Arduino simulation. There’s a bunch of stuff you can iron out without a machine in front of you.
Another thing I’ve looked at is keeping an eye on the router from across the room. It’s probably bad practice to leave it unattended - There’s a really scary video on YouTube of a guy who left his machine unattended for several hours only to find that a clamp broke, the workpiece got jammed, and he had a fire. Anyway, I found a neat free Android program called DroidCam that uses an old cell phone that you can watch on any web browser, and it will take time lapse videos at a frame rate you choose. Cool stuff.
Now I’m looking at designed for a table/desk to house the Long Mill and provide some table and storage space. First design has desk on top, Long Mill on the shelf below, and storage at the bottom sort of like one of Winston Moy’s attempts. Should allow plenty of access to the machine and room to route dust collection hoses. Sound deadening and dust scatter prevention are two of my main goals so it has foam panels on the sides, bottom and top to seal it up. I’ll stick an F360 file here when I get it the joints assigned and the assembly done.
Have a good one.


Hey guys. I sketched up a very plain preliminary desk/machine workbench based on one Winston Moy did and others I’ve seen. I certainly don’t think anybody is going to build this, but if you’ve been thinking about where you’re going to put your Long Mill it may stir up some ideas. When you come up with a better design (should be easy) please let us have a look.

The desk on top is for the PC, monitor, drawings, etc. to help keep them out of the sawdust, and the space for below is for the Long Mill. I made it 48"x48" per the Sienci description with 4x4 legs. The sides and back are fitted PU foam for sound and sawdust containment that can be easily removed. The fron door is acrylic and swings or slides. There’s lots of room for dust collection hoses and wires.

I used WAY too many parameters but I’ve gotten in the habit of making designs that can be easily changed and parameters in Fusion 360 are very helpful. It also makes generating a BOM and cut list very easy. The parameters you probably want to change are the overall height (56" as shown), which determines the length of the legs, and the space between the top. The horizontal supports are 2x4s.

The forum doesn’t allow attaching F360 files and stls, but here’s a pic that shows the concept. I can email the files to anyone interested -

August is only two months away.


Hey guys.I’m sure there are a bunch of us trying to figure out what to put the machine on. Now that the machine specs are out, I did a Fusion 360 drawing of the machine sitting on a simple 32" high 48x48" table. The top is two pieces of 1/2" MDF, (or 4 x 24x48" pieces to fit in the car). All of the frame pieces are 2x4s and the supports are flush all around the edge of the table so there are places to attach doors, sound enclosure etc. I put the machine on 3/4" MDF spacers so there is room for a 35x40" spoil board without losing Z axis travel. And I put a Makita router in for good measure.
The F360 file includes the assembly joints for the router travel in all 3 directions. Let me know if you’re interested in the file, and please post your alternate ideas. Thanks.


That should work really well for you.