JGRO in progress... Very Simple Questions

[dustin1706]

Hey all, been lurking on here for a long time, finally got started building a machine.

Eventually I would like to convert a big mill to CNC to be able to do some serious steel milling to make one off auto parts, but I decided that I would start with a basic machine to learn how to use the software and such.

I'm making a JGRO basically exactly like the free plans. I am using all 3/4" MDF.

I have a gecko 540, 3x 380oz Nema 23, 48v PS, dumpstercnc anti backlash nuts with 1/2-10 acme single start. Planning on a Hitachi 2 1/4 HP router.

I am planning on running mach 3. I will probably build myself a new PC and use my current one for the CNC. (QuadCore OC@2.8GHz, 4GBrDDR2, SSD HDs, SLI 8800GTXs, Vista)

Pics to come, I have the Base nearly finished. I am gluing everything and using counter sunk "deck" screws as well. Very tedious to make the torsion boxes for the base and bed

I would like to do some basic woodwork kind of stuff in hardwood and MDF. Signs, coasters all that jazz, some pexiglass and delrin. Those Lithophane things look cool, I want to give them a try. and maybe even give it a shot in some aluminum once I see how the machine handles the lighter stuff.

So, i have some VERY basic questions that I have been searching for, but I just keep finding threads on how to do very advanced things, but nobodyy actually mentions how to do the basic stuff.

I would like to know what I am going to need for "bits" to do this kind of stuff. I see that there are ball nose, flat, V and others, and that ther are different numbers of flutes and different feedrates, But I cant seem to find out what kind of bit is best for what kind of work. Looking for decent quality ones too.

Also, What is the best way to zero the tool on the workpiece? I keep thinking about using a piece of paper as a feeler gauge, but Im sure theres a better way...

And, when you are cutting right through something, what do you do to keep from ruining your cutting table? I am assuming that you put an expendable piece under your workpiece, but what is the best material to use for that?

[MrWild]

Still early enough to make some changes I wish I had. The X rails are unsupported. This lets the wobble even though they seem stout. A modification to the base and gantry that gives real benefits is to change the gantry/rails into a one rail likeness of a Joes2006. If you don't do it now, you will be adding sides and supports for the rails (pipes) as an afterthought like I and quite a few others have done. Everything else works out fairly well.

[sports.racer]

Second the x rails thought! Also do not make the pipe supports from MDF unless you need practice drilling and tapping! Z and Y are ok from MDF but not the X, the gantry and pipes are too heavy.

[dustin1706]

Originally Posted by MrWild change the gantry/rails into a one rail likeness of a Joes2006..

By a "one rail likeness" do you mean that I should use a solid rail rather than gas pipe, or that I should use 2 pieces of gas pipe per side like the joe 2006?

And Sports.racer, by pipe supports I assume you mean the "adjustment blcoks", what is a recomended material? I was thinking that I would do MDF for now, then cut some replacements out of delrin or similar plastic once the machine is going.

[sports.racer]

Yeah, brain lock and couldn't remember what to call them. Not sure what I'm going to make them from yet but I do need to remake the big ones.

[dustin1706]

Another Question:

Is there any tips or tricks to getting the gantry parallel with the table?

I am thinking that I can just lower a bit so that it is just barely dragging on the table, then move it around and adjust the rails until it drags on every area of the table?

[nearbeer]

Does any one have drawings (.pdf or .dwg) of the x-axis modifications mentioned above? I am in the process of gathering materials too and don't want to have to spend time correcting design flaws. Thanks!

[Agro]

Originally Posted by dustin1706 Another Question: Is there any tips or tricks to getting the gantry parallel with the table? I am thinking that I can just lower a bit so that it is just barely dragging on the table, then move it around and adjust the rails until it drags on every area of the table?

I thought the usual practice was to essentially 'mill' the top of the table to match the gantry. A reasonable practice given the MDF sheeting may not be as flat as you think it is.

[MrWild]

Look at the Joes2006 build. The rails are on the inside and supported very well, with the gantry hugging them. A good mod for the JGRO is to change it from the pipes on the outside, to pipes on the inside. Because the gantry has to be wider to accommodate this change, you end up with a stiffer X AND a little more Y travel. I didn't see it until I had cut my parts out, and decided to just drill the needed clearance holes to run threaded rod across the bed so I could solidly support added exterior planks to hold the pipe braces. My JGRO will probably last just long enough to cut out all the parts for a Joes2006. Don't feel bad if you seem to be making slow progress. I've got four years, a double bypass, and pace maker all tied up in my build. :-) Hopefully this weekend the gantry will finally be bedded home on the table for the last time. I'm making a cable support for the Y axis now and when done, on it goes.

[dustin1706]

Hey all,

I finally got to the point where I am starting to assemble this thing and I have some questions!. I just have it sitting on the table saw for now. I need to find it a better home and give it a paint job once I've mocked it up and have it ready for final assembly. Plus I got dust all over it after sanding the gas pipe and then touching the thing.

It has all been assembled with wood screws, drilled and counter sunk. The only thing glued is the torsion boxes, and the only tapped MDF are the adjustment blocks. I plan on using the machine to cut out some plastic adjustment blocks once it is working. For rail stiffness, I have a few pieces of 3/4" (I think) Gas pipe laying around and it fits tightly inside the 1", so I will give that a try.

I find that on my Y and X there is always one bearing not touching the pipe... What is the best way to correct that? Should I shim between the wood and the angle alum of the bearing carrier? Or should I shim the bearing out away from the angle aluminum?

Also, I have seen mentioned that the best way to ensure that your cutting bed is parallel to the movement of your router is to simply cut the top of your cutting table with the router?

Thing is, looking at a lot of other peoples JGRO pictures, it doesn't appear that they have done this. And, what happens when you want to do something to a piece of material that is larger than your cutting table? Won't you have a bit of a "lip" around your cutting table where the router could not reach?

And, I would like to buy some carbide bits. Which are the most common ones I would need to work with wood and plastic, to do engraving, signmaking, and just for cutting all the way through? I am thinking just a few different V-bits, Flat 2 flute upspiral endmills, and ballnose 2 flute upspiral endmills?

What size and type of bit would be best suited for just cutting straight through 1/2 to 3/4" MDF or plywood? 1/4"?

Excuse the poor iPhone pic and messy garage, I will take real pics one day.

Thanks!

[dustin1706]

Alrighty then...

I have this thing put together, basically as per the original JGRO plans.

I am having a bit of trouble trying to adjust the x axis so that all the bearings touch, but it is pretty close.

I have a few more questions for you guys.

Limit switches: I have them installed for all 3 axis'. They are wired in series. Thing is, I have no clue what to do with the wires... Obviously the X and Z switches will move with the gantry so there needs to be enough wire to make it from one end of the table to the other. I am thinking about making a deal where there is basically a spring with a piece of dowel to hold the wires all up to keep them from going slack and getting caught in the router. I have been trying to find pics of what others have done, but the search button is not being my friend tonight. Same goes for the X and Y motor cables. Any suggestions?

Motors: My motors seem to make a very quiet "staticy" noise while idle. Is this normal for steppers? Also, I had my power supply set at 48V, but after being jogged a bit and sitting idle for maybe 20 mins, the motors got Very warm. Too warm to touch actually. So, I dialed down my power supply to 32v.

I have a craftsman 2HP router installed and everything Jogs nicely.

I have the X and Y set at 60 IPM and the Z at 30 with my 1/2-10 acme. I see no whipping. Is this reasonable? what speed has everyone else found to be comfortable?

Almost time to cut!

[MrWild]

look up cable carriers. They can be silly expensive or a great deal. There are a few threads on home made cable carriers. Some folks even use flexible plastic wire conduit from home improvement stores.