[T_Brown]

This is quite the new hobby I have just stumbled upon, and I can’t wait to dive in. After looking at some different plans that are available, I have decided to build the JGRO. I think I understand the plans for the most part, but will see once I get into it a bit more. I feel very confident in machining the parts as I have a fairly well stocked wood shop, however the electronics are a mystery to me. I don’t really want to buy a kit off the shelf as this would teach me nothing about what I am creating. Therefore I think I am going to go with the HobbyCNC EZ Board and learn and do the soldering myself. My wife is asking me for Christmas present ideas and I would like to try and get most the necessary electronics for this build. However, I don’t fully know what I need at this point. Can someone please point me in a good direction for a list of necessary components. My thoughts thus far are: HobbyCNC EZ Board, 205 oz/in steppers…then I am lost. Also any guidance that can be given regarding lead screws would be helpful. I don’t fully graps the 3/8-10 5 start vs 10 start vs 3/8-8 etc. I don’t need .0001 in accuracy and this wont be a production type machine, what is my best bet for the absolute beginner? Thanks a lot and I look forward to learning a lot.

[ger21]

Just my opinion, but I don't think soldering the board together is going to teach you anything you need to now. When you move on to the inevitable bigger, faster machine , the higher performance drives won't require any soldering. It's just a matter of connecting wires.

Having said that, the HobbyCNC will give you the best bang for the buck, and is a good starter board. Spend the extra $5/motor and get the bigger ones, and use a 36V power supply.

As for screws, here's the basics. Say you have two screws, both 10 threads per inch. One single start and one two start. The single start takes 10 turns to move 1 inch. But the two start screw actually has two separate threads, each 5 turns per inch. So a two start screw only needs 5 turns to move 1 inch. Stepper motors torque decreases as rpm's increase, so to get the most speed, you need to keep the motor spinning slower. That's where multi start screws come in. You want to have between 2 and 5 turns per inch. 1/2" screws are probably better than 3/8", as they'll whip less at higher speeds. Best mix of price/performance is probably 1/2-8 2 start.

[TOTALLYRC]

You will have so much stuff to learn that doing the driver building is superfluous.:drowning:
As a suggestion, build the machine with a ready to go driver and save the electronics projects for something that is less mission critical.

G540 and matching motors would be great if a bit pricier than the hobby CNC kit you are looking at. G540, Biggest bang for the buck in my opinion.

The real nice thing is that once the router is up and running, you will be able to do simple circuit board milling on it.:banana:

Mike

[T_Brown]

Gerry, thanks for the explanation on the screws. Where is the best place to pick up some 1/2-8 2 start? It also seems like my best bet is going to be to make delrin nuts? Is it difficult making the tap or is that pretty easily accomplished. i am sure there is probably a how to thread somewhere out there. I think i had seen somewhere that 5/16" rod fits very well in skate bearings, so i would need to get other bearings for the 1/2" rods. Looking at McMaster theses look to be around $8-$10 each, does this benefit outweigh the additional price?
As for the driver board, i was looking at the Gecko, but the $500 price tag for the board, 3 steppers and the PS hurts the budget. I would like to try and do this first build as economical as possible. It will be easier to justify the cost if i can at least have made something that works and shows itself as useful. I know it is inevitable that i will use the first one to build the second, i would like to try and do the first one on a tight budget though.
That being said, if i get the HobbyCNC board, i also need to get the transformer, a 36V PS and the steppers and thats it for the electronics right?
Thanks a lot guys, you have already taught me something.

[ger21]

You can get the screws from McMaster Carr, MSC, or Roton. I highly recommend going with the Dumpster CNC nuts. money well spent. I had intended on making my own nuts, and after the first one was done, I ordered the Dumpster nuts for the rest. www.dumpstercnc.com

Here's how I mounted my screws in cheap roller blade bearings.
http://www.cnczone.com/forums/showthread.php?t=86180


If you buy the package from HobbyCNC, all you need is the transformer. The other parts to build the power supply are included in the kit. The HobbyCNC will be fine for a first machine.

[radcliffe]

I agree with Gerry, If you do go with the Hobbycnc package I recommend the Pro with 4 305 steppers. This way when you build your second and larger router you will already have the fourth axis and stepper to run dual axis on the x axis.

You can buy the transformer from MJPA, INC. After it has been bridge and filter you will have 33-34 volts at 10 amps.
http://www.mpja.com/category/Transfo...ER_7846_TR.asp

I brought the Pro Package with four 305 steppers and had no problem in the assembly, just follow the great instruction supplied.

Harold

[T_Brown]

Thanks for the responses. I think i am going to go with the HobbyCNC Pro Board with 3 305 steppers. The only additional electrical compnenet i need then is the transformer, correct? I should be fine to just mount it all in an old computer tower right?
Perhaps you can shed a little light on computer software now. I have quite a bit of knowledge of AutoCad, but only 2D. Is there a program with an easy learning curve to move to 3D obects? I am currently planning on just cutting out parts and doing some sign carving but i dont want to limit myself.
Once i have created my part in AutoCad or said other program, then i need to send it to a program to convert it to g-code right? I have heard some good things about LinuxCNC, do you have any experience with this? Once i have it covnerted to g-code than it goes to a CAM software which talks to the router and starts the cutting. Thoughts on this program?
I dont want to break the bank on software at this point, but also don't want to be continually fighting with the program.
Last question (of this post, i am sure there will be many many more) is there some sort of assembly manual created for the JGRO plans? Something that talks about alignment and order of assembly and such?
Thanks guys!

[MrWild]

There are quite a few hidden costs that jump up also. Many go with Mach 2 or Mach 3 as the interface program so the computer controls the motors ($160). Linux EMC2 is free and has a near turn key set up for stepper control. It also has a near plug and play for the Gecko G540. The G540 does away with wiring confusion and lets you concentrate on learning CAD/CAM which will be a challenge in itself. You can spend a lot to a little for CAD/CAM. A lot is over $10k to a little of free. The money you save with EMC2 would allow more funds elsewhere.

[ger21]

The CAM software is what creates the g-code. Control software is what runs the machine.


I create my g-code in AutoCAD with a macro I wrote. Works with 2002 and newer versions. Link in the last post. http://cnczone.com/forums/showthread.php?t=8226

Basically, you just draw where you want the tool to go. In a lot of cases, you can just offset the part outline by the tool's radius.Feel free to ask for any help in that thread.

I think you'll find that most parts do not require 3D modeling. Just a simple 2D drawing.

There are many inexpensive CAM packages out there. SheetCAM and Vectric's Cut2D are probably the most popular.

Sign carving is a vague description, but you might also want to look at V-Carve Pro It's a bit more money, though.

All these programs can use .dxf files from AutoCAD, and will automate a lot of the process of creating toolpaths from your drawings.

By far the most popular control software is Mach3, but if you don't mind Linux, then EMC is pretty poular, and it's free.

[T_Brown]

Can someone please enlighten me on this?
10-24 UNC (Down Arrow) 2B 1.500
The down arrow with top didn't copy. I think it means tap a 10-24 thread down 1.5 inches. If this is the case, what does the 2B stand for? Thanks

[iwantone]

It is the class of the thread , this link should help explain:
http://www.newmantools.com/taps/taptech.htm

[TommieK]

First, I would like to welcome you to the community. Second, some of these guys and gals on here are way smart. As far as the tap type and thread class goes, whatever tap or die that you can purchase at your local hardware store is going to be just fine for anything on the JGRO with the exception perhaps of any ACME thread you might decide to go with on your lead screws. Some of the members have made their own (Glidergider is one and he shows pictures of it). I got my 1/2inch 8-2 lead screw material and backlash nuts through Dumpster. I did try 1/4-20 stainless for leadscrew first because I didn't know any better and because I thought I did, but the 8-2 makes you feel like your running an honest to god real CNC. So much smoother and faster. Good luck with your build, oh and post pictures. Tom

[T_Brown]

I have the specs of my machine figured, now the part buying begins. JGRO design with extended X Axis to just over 48". Gecko G540 w/ (3) KL23H2100-35-4B 381oz Steppers with the Keiling 48v Power supply. Probably running Mach3 with Lazycam, however this is where i need some direction.
I have been using AutoCad off and on for the last 5 years, however strictly 2D stuff. (I am in the construction business and use it for floor plans and through sections and such). I am having trouble wrapping my head around CNC worthy drawings. If i want to cut out a simple 4"x4" rectangle how do i draw this to be imported into LazyCam? can i draw it from a top view and then do the rest of the work in LazyCam? What about if i want to cut out a 4"x4" rectangle out of 3/4" stock that has a 1/4"x1/4" dado around the perimeter? would this need to be drawn isometric? Or something more?
I guess what i am asking is if someone can point me in the direction of a good tutorial or beginners guide to drawing CNC appropriate parts. Thanks a ton!

[ger21]

Use the top view in AutCAD, and save as V12 .dxf.

Basically, you draw lines where you want the tool to go.
If using the free version of LazyCAM, you'll need to account for the tool size. So if using a 1/4" diameter tool, you offset the 4x4 by the tool radius, so you draw a 4.25" x 4.25" square. The simple way to do it is to draw your part, and then use the offset command to offset by the tool radius. For best cutting performance, set the OFFSETGAPTYPE variable in AutoCAD to 1.

Do you mean a dado, or a rabit? Either way, again, you just draw lines where you want the tool to cut.

You set the depth of cut in LazyCAM. It's a good idea for different cutting operations to be drawn on different layers, as it's easier to keep everything organized.

It's probably a good idea to thoroughly read the LazyCAM manual.

http://www.machsupport.com/forum/ind...c,12078.0.html

If you have AutoCAD 2002 or newer, I wrote a macro that can export g-code directly from AutoCAD. http://www.cnczone.com/forums/showthread.php?t=8226

[T_Brown]

Thank you for the explanation. I think i need to just but the Mach license and start playing around with it. As long as LazyCam is free with it and there seems to be nothing better than Mach3, it is a win win situation.

I have a question regarding the mounting of bearings for my leadscrews. How should i go about this? I know i have read in a couple of places that i want to isolate my leadscrews from the motors as much as possible so that the shaft of the motor doesnt support the leadscrew in anyway. I also read somewhere that to accomplish this i should mount my leadscrew in a bearing (possibly 2, one on each side of the support?)and then tighten a nut on each side to hold the lead screw in place. It appears that the original Jgro plans don't have this detail? is that correct? can someone point me in a direction of some pictures how others have done this? is the hole to mount the bearing in just slightly undersized for pressure fit? i have searched and searched and am not having any luck finding a source for the best and proper way to mount lead screws in Jgro. Thanks a lot!

[zeeway]

I have a question regarding the mounting of bearings for my leadscrews. How should i go about this? I know i have read in a couple of places that i want to isolate my leadscrews from the motors as much as possible so that the shaft of the motor doesnt support the leadscrew in anyway. I also read somewhere that to accomplish this i should mount my leadscrew in a bearing (possibly 2, one on each side of the support?)and then tighten a nut on each side to hold the lead screw in place. It appears that the original Jgro plans don't have this detail? is that correct? can someone point me in a direction of some pictures how others have done this? is the hole to mount the bearing in just slightly undersized for pressure fit? i have searched and searched and am not having any luck finding a source for the best and proper way to mount lead screws in Jgro. Thanks a lot!

You'll get several versions of answers to this question - here is mine. And just a warning - my machine is still in process.


Please excuse the strange colors...but maybe I can explain...

The long green thing is the feed screw. At the left end (motor end), going from left to right you see the stepper motor, attached to the end of the machine with gray posts (there are many versions of motor mounts from simple bolts and nuts to more complex arrangements). The motor shaft shown in black goes into one end of a Lovejoy (jaw) coupling, shown in orange. Although not shown, this coupling is three pieces. One end clamps on the motor shaft with a set screw; there is an elastomeric "spider" in the middle; and the far end clamps onto the feed screw with a setscrew. On the other side of the coupling is a clamp collar (light blue) followed by a washer (violet) that is smaller in diameter than the outer race inside diameter of the support bearing. Then we have the bearing (dark purple) enclosed in the side of the machine (dark blue) or in a bearing block (I think that's the way JGRO does it).

At the other end you have the bearing, followed by the same size washer, followed by two acme nuts (aqua). The first acme nut is used to take up any play in the feed screw, and the second nut locks the first nut in place.

This arrangement allows the motor to be misaligned from the feed screw by a couple of degrees, with the elastomeric spider taking up that misalignment. Also, no thrust is transmitted to the motor, because the clamp collar/washer/acme nut arrangement transmits the thrust to the side of the machine (dark blue) through the bearing.

I found that the best set collars are the clamp kind - they clamp without a setscrew damaging the feed screw threads. I had bought the other kind, and slightly damaged the threads on the feed screw before I discovered it. Fortunately the were the perfect diameter to use as the "washer" beside the bearing - so I took out the set screw and just used them as a washer. I bought my good clamp collars from ENCO at http://www.use-enco.com/CGI/INSRHM.

Some people feel there is a need for an actual thrust bearing in addition to the radial ball bearings, and that is certainly the most conservative approach. However, unless you are building a monster machine, you can depend on the traditional radial ball bearing's ability to take quite a bit of thrust.

Almost forgot - the bearings shown are 1/2 inch bore by 1-1/8 inch o.d. by 5/16 inch length that I bought from VXB bearings via Ebay (or VXB.com) I used a 1-1/8 Forstner bit and drilled a bearing pocket that was about 1/4 inch deep. The bearings fit those holes with just a slight push to go in.

[FandZ]

I would recommend you try the free version of cambam over Lazy cam. I've found it to be easier and more capable than the free version of Lazy cam.

http://www.cambam.co.uk/download/previous.html
And here are some tutorials for it.
http://www.cambam.co.uk/docs/tutorials.html
The tutorials are not for the free version but it'll give you more than enough information to use cambam effectively.

[FandZ]

You'll get several versions of answers to this question - here is mine. And just a warning - my machine is still in process.

I used 2 of these on each of my axis. http://www.thebigbearingstore.com/se...Bearing/Detail

Kind of wished I would have went with these as it would have been easier to implement http://www.thebigbearingstore.com/se...-Flange/Detail

Zeeway, I want to make sure I'm following what you are saying. The setup you have in your picture is, Stepper> lovejoy>acme rod> lock coller>washer>bearing>bearing>washer>acme bolt>acmebolt?

Now in your picture it looks like your lovejoy coupler is butted against the lock coller, Is that the case? When I upgrade to a faster acme rod, I plan on makeing my own bearing blocks so I may go this route to save space.

Also, there is one thing I'm not understanding. What keeps the acme screw dead center in the bearing. I have some 1/2 inner diameter bearings and 1/2 10 acme screw, it's a tight fit but there still is just a tiny bit of room between the inner bearing and the acme screw.

[zeeway]

Zeeway, I want to make sure I'm following what you are saying. The setup you have in your picture is, Stepper> lovejoy>acme rod> lock coller>washer>bearing>bearing>washer>acme bolt>acmebolt?

Now in your picture it looks like your lovejoy coupler is butted against the lock coller, Is that the case? When I upgrade to a faster acme rod, I plan on makeing my own bearing blocks so I may go this route to save space.

Also, there is one thing I'm not understanding. What keeps the acme screw dead center in the bearing. I have some 1/2 inner diameter bearings and 1/2 10 acme screw, it's a tight fit but there still is just a tiny bit of room between the inner bearing and the acme screw.

Hi FandZ

At the motor end, one hub of the Lovejoy coupling does clamp on the acme rod, and yes the clamp collar is butted up against that coupling hub. It was tempting to eliminate that clamp collar since the Lovejoy hub also clamps on the feed screw. But I thought the clamp collar would actually do a better job of securing the acme rod from moving in an axial direction.

The 1/2 inch diameter acme rod fits the bore of the half inch bearings with a close slip fit. I don't know what the clearance is - with my digital vernier caliper they both measure .500, so I am guessing it is a thousandth or less. I don't know how you can get around that clearance unless you machine and grind a precision concentric bearing journal on the acme rod, and go for a light press fit on a smaller bore bearing...which sounds like overkill to me. I would guess the whip of the feed screw and the natural give of the Delrin feed nuts cause more radial movement than the bearing to acme rod clearance...but I could be wrong (wouldn't be the first time).

[T_Brown]

Thank you for the diagram and explanation. In an attempt to avoid the expense of the 1/2" ID bearings, i want to try and use skate bearings and grind/file the acme rod down as Gerry showed. In that case i would do everything the same as you described, except i would be using ~5/16" hardware correct?
I think that i am going to have a coworker cut most of my parts out on his CNC. It looks like the original JGRO design doesnt have pockets for the bearings, i should be able to just enlarge the appropriate holes for the bearings and that should be good right? Sorry if these are very noob questions, i am just trying to wrap my head around everything so that my parts are cut out properly the first since i have no experience seeing a DIY CNC first hand. thanks again!