Sophomore Build - Starting the Joe CNC

[Sbthomas13]

Hey everyone,

My friend, Tyler, and I are starting to gather materials and resources to build a Joe CNC. My school has a CNC so I should be able to cut out all of the parts using it.

They use MasterCam software, and I have all the parts CADed in .dwg format (Thanks to Joe!), but how do I convert them to tool paths (g-code) set the depth, and find what bit to use??

And can the bit be set so it cuts to the outside of the line.....because if I use a 1/4" bit and it cuts on the line.....wouldn't the part be 1/8" (the radius) shorter on all edges??

I am assuming that the bit cuts to the outside of the line...and that this is preprogrammed.

Just wondering if someone could clear that up for me and help me with the software aspect.

[BobF]

A good Cam program should do that for you. I would think MasterCam can do it, but I can't tell you how. Never seen MasterCam. There is a MasterCam forum here though.

[Sbthomas13]

So I am waiting for approval from my teacher to start to cut out the CNC.......I'm hoping he does in fact approve, he must be thinking "these kids are planning on building a CNC machine, they must be insane!"

After asking around I am comfortable on all the software aspects, and hope that all the parts will be cut out 2 weeks (being optimistic, it will most likely be 3 but lets shoot for 2) after approval. Seeing that we (Tyler, my group member, friend, and fellow CNCer..and I) are limited to one Marking Period to build a working CNC, time and accuracy are vital. We plan to first cut out the X-axis Torsion Box....and while one of us continues to cut out parts, the other will work on assembly.

So until approval of the project, I can only cross my fingers. Between now and then we will be gathering supplies (yay capital!.....looks like I'll be getting a job) But hopefully I will be able to get some pictures of the start of the build process up here in no time.

I CAN'T WAIT TO START THE JOE!

[Sbthomas13]

Work has begun!

[Sbthomas13]

Our build of the Joe CNC Model 2006 has begun after months of research, multiple failures of other CNC machines, and gathering of resources.

After the project was approved by the teacher, plans were made showing an actual picture of each part, a CAD picture with dimensions, and a picture of that part in the total build of the machine.

The first step was to cut the 4' x 8' sheets of MDF into 30" x 35" blanks that will fit on the school's CNC machine.

Next CAD files were uploaded to school computers. Using Mastercam, parts were laid out on blanks to provide the most efficiency. Toolpaths were generated. NC file was Posted.

Then we had to wait for our bit to arrive:
Brand: Antrax (from Use-Enco.com)
Type: Square-End End Mill
Diameter: 1/4"
Shank Diameter: 1/4"
Length: 2-3/4"
Cut Length: 3/4"
Material: Carbide
Coating: Titanium Nitride

The collet on the router was changed to a 1/4" collet and then the bit was chucked in. After some initial tests the cutting began. We decided to cut the X Axis Torsion Box first. First we cut out the X Axis Torsion Box Pipe Supports.

(4) X Axis Torsion Box Pipe Supports were cut out the first day of cutting. The bit failed to completely cut through the blank, most likely due to improper Zeroing of the Z, or a warp in the sacrificial board. The depth of cut was 1/2", the speed was 50 IPM, and the router was set to 21,000 RPM. The machine made an extremely high pitched sound. The parts were cut out, but rough edges had to be filed and lightly sanded (not on critical parts of the piece, just the inside contours).

(1) X Axis Torsion Box Pipe Support was cut out the second day of cutting. Cut depth was decreased to .18" with 3 passes and the RPM was decreased to 16,000. This allowed for faster cut speeds...80+ IPM.

(3) X Axis Torsion Box Pipe Supports were cut the third day of cutting. The bit went entirely through the blank resulting in clean cut parts. Using a shop-vac, dust particles were removed from the channels which allowed for a more quiet cut.

All of the X Axis Torsion Box Pipe Supports were completed. Tomorrow X Axis Long Run Braces will be cut. Then CNC End Support Pieces will be cut. I am hoping all parts for the X Axis Torsion Box will be completed by the end of the week.


(Student shown in photo is Tyler. He is my partner for this project)

[joecnc2006]

Looking very good guys, you are very well organized and know exactly what you want to accomplish, A fine example of students taking charge and not just getting by in school.

For the areas that did not cut all the way through, you can use a trim router with a flush bit to go around the edge, will be allot faster than a knife. Thats how i remove all my tabs.

Can you e-mail me your plans (your binder looks good) I would love to take a look at them, and maybe i can post in the yahoo files to help others out also.

So what does your teacher think of your little project?

Joe

[Sbthomas13]

The plans have currently only been created for the X Axis Torsion Box. I will finish the plans and have them to you sometime tomorrow night, they should be quite helpful for all who wish to use them.

And the trim router with flush bit! is an excellent idea! As of our cut today, we no longer have the problem of excess material on the edges of parts, but maybe we just got lucky... Should the problem arise again, this will definitely be our course of action.

Our teacher seems to be interested in our grand "little project", however, as of now he is just sitting back and letting us do the project. Every now and then he will shoot us some advice, but other than that he doesn't say much. Whether this is because he doubts our project will be completed, he doubts it will work when completed, or some other reason... I do not know.

But everything is going as planned as of now, and we are meeting all of our goals and self-set deadlines. I will definitely send you the plans as soon as I finish them up.

[calgrdnr]

Looking good Spencer and Tyler. I am bettting your teacher is proud. you guys pick a great project . Take your time make sure you keep everything square, and you will have a great machinne to fight over Have you picked out your motors and controller ?

Another thing I was born to late for. first was Big Wheel. Dang how much fun are those things and CNC when I was in school O'well I will just have to be happy I have it in my Mid life crisis range ( can't afford Porche) .

Keep up the good work you have lots of fun and learning ahead

Kent

[tybrenis]

Thanks Kent,

If everyone didn't all ready know, I'm Tyler, Spencer's partner in crime in this crazy hobby of building CNC machines.

Believe it or not, its been over a year since we first started designing and building our first machine, so a year later, we're three test machines down and plenty of parts UP. I have a 3 axis Hobby CNC driver with power supply and 304 oz./in. Keling steppers. I also have 1/2" - 10 ACME single start Dumpster leadnuts that will be used on our Joe. I also have acme threaded rod as well as 1/2" and 3/4" drill rod, however, the drill rod is only long enough for the gantry and the Z, and we will most likely need to purchase more ACME rod and gas pipe for the X axis.

[Sbthomas13]

Today we started to cut out the X Axis Torsion Box Long Run Supports.

Preperation: First we ripped a piece of MDF to a blank that would fit two of the supports on it. We then cross cut it to the desired length on the radial arm saw. The blank was then placed on the CNC table and placed against a fence in the sacraficial board. This fence was made by lowering the bit into the sacraficial board and then moving the bit along the X and Y, allowing for a channel that was 1/4" wide and that was parallel with the movement of the router on the X and Y. We then cut 1/4" pieces of wood to fit into the channel to make the fence. The blank was then attached to the sacrificial board using screws.

Geometry: Using the CAD provided by Joe, I combined the X Axis Torsion Box Long Run Brace (1) with the X Axis Torsion Box Long Run Brace (2) creating one long part. I then split the geometry at the half point. The geometry was then divided into two files. The first file places the part that will be cut first 1" from the bottom of the blank. The second file places the second part that will be cut directly on the X-axis (our shorter axis that runs across the table..we did call it the Y until our teacher told us it was the X). This would allow us to align our pieces to the fence, zero the machine on the bottom left hand corner of the blank, cut the first part, mark a line at the end of the first cut, slide the blank down until the mark lines up with the origin, make the second cut.


We cut out the first part, but now we are not quite sure how to cut out the second part. Should I just draw a line at the end of the first cut (Look at picture) and then line that up with the origin? Or should I draw a line at the end of the first cut, measure down 1/8" to account for the radius of the bit, and then line that up with the origin? Or should I use a different method?

I just don't want the part to be too short....It can't be too long, because if it is there will be a gap of mdf between the two halfs and I will know. But if the tool paths run into eachother, then it could shorten the part.. Ideas?


Picture 1: Layout of Blank on sheet of MDF
Picture 2: Cross cutting MDF Blank to length
Picture 3: Blank placed on CNC table
Picture 4: Fence Channel
Picture 5: Fence Channel (2)
Picture 6: Fence Channel (3)
Picture 7: Cut Begins
Picture 8: Inside contours being cut
Picture 9: Inside contours being cut (2)
Picture 10: Outside contours being cut
Picture 11: Outside contours being cut (2)
Picture 12: Origin
Picture 13: Finished cut
Picture 14: Finished cut (2)
Picture 15: First half cut
Pitcure 16: Line drawn at end of cut
Picture 17: Geometry Split

[aolshove]

Draw a line at the end of the first part and align that with the origin for the second program. The toolpaths are relative to the center point of the bit such that the center of the bit is in line with mark at the end of the first program and the center of the bit is at the line when it's moved to the origin for the second program. No need to compensate for the diameter of the bit.

[Sbthomas13]

Excellent! I will put it to the test tomorrow morning! You really don't get much sleep when CNCing...its too much fun!