JGRO Cutting Area

[kmacht]

I have tried searching but haven't found anything diffinative. What is the usable cutting area on a stock design JGRO? Based on dimensions it looks around 17x33 to me. Is that right? Also, is there a reason it was designed with a distance between the two gantry rails of 23"? It would seem that 24 or 25" would have been a better design so that you could put a 2' stock piece of MDF on the machine without having to cut it down.

Keith

[dustin1706]

With limit switches installed, I get a total usable table of 17 x 30. I'm not sure why the table was sized as it is.

If you are going to build one, I would highly recommend a redesign for the rails. Reinforce the rails, or use double rails or use Angle Iron with V bearings. Besides that it is really easy to build with just a table saw and seems to work alright.

[kmacht]

Thanks for the reply. 17x30 should probably work for now. My plan is to build the JGRO first and then use it to build a bigger machine like the Joe 2006. I ultimatly want something I can just place a 2x4 sheet of mdf or hardwood in and cut away. I don't need the full 2x4 area to cut but I also don't want to have to rip down a piece of wood every time I want to use the machine. I have read about the X axis rails bending under load. I plan on building supports for them once the machine is up and running. I want this first machine to be a pretty fast build so i am trying to stick to the plans as closely as possible. The only change I plan on making is to use screws and glue instead of bolts and tapped MDF to assemble the machine. I will also probably change out the rail adjustment blocks to nylon if I can find a cutting board thick enough locally.

Keith

[dustin1706]

Yeah, I used screws and glue as well. Going with Plastic adjustment blocks is a good idea. My MDF ones have not held up very well. O am basically just using mine to build the carriages fora joes 4x4, and it seems capable of doing that. I also used 1/2" acme rod and anti-backlash nuts from dumpster CNC.

[kmacht]

What did you end up using for stepper motors and drivers? I was looking at hobbycnc.com. I was thinking of buying their driver board for $80 and three 200 oz/in motors for $44 each. For a power supply I was thinking of using two ATX computer supplies wired together. I have a bunch of old computer cases I can salvage for free. Any thoughts or suggestions?

Keith

[dustin1706]

The hobbycnc kit and a few PSUs would definitely save some cash.

Since I know I would be building a bigger machine later with the JGRO, I went with overkill electronics so that I could just re use them on a bigger machine.

I went with the cncrouterparts 3 axis kit CNCRouterParts

The kit makes things pretty easy since the motors are prewired and it comes with DB5 cables. The G540 is a very popular driver/BOB combo and thus there is tons of support from Gecko and on the forums here.

Either way you go, just be sure that you will have enough power for your next machine unless you want to rebuy all the electronics.

[kmacht]

I plan to go bigger in the future but when i do I will probably sell off the JGRO as a whole working unit. I can use that money to buy larger steppers and a better controller. After looking at the plans I decided to make the JGRO a little bigger to begin with. I am going to add 7 inches to the width so I get a full 24" of cutting area. I am not going to change the length because of the design of the single pipe construction. The wider area will let me put a 2x4 sheet of MDF in the machine without having to rip it down on the table saw.

I started making parts last night. I got the 4 large pipe adjustors and 6 of the 8 small pipe adjustors done. I couldn't find any cutting boards thick enough so I made them out of oak. I had some 1x3 oak laying around and did some tests with it. The oak seemed to have better holding strength of the adjustment screws after it was tapped. We will have to see how it holds up after using the machine for a while. I may buy some plastic online to make replacement blocks with. Right now I am trying to make the machine out of all locally sourced parts. Next up are the angle iron carriages. The plans call for aluminum but I went with steel since it is half the price and I have a metal bandsaw to cut it and a mill to drill to drill and shape it.

Keith

[dustin1706]

Right on. I did mine with screws and glue, and used steel angle also.

The one really nice thing about the JGRO, is that it can be build with just a tablesaw, drill and measuring tape/square.

The gantry rounded corners look nice, but there is really no reason not to leave them square. My gantry has square corners and no window. Another thing... The gantry sides have an extra hole for some reason. No point drilling that one either that I know of.

[u77171]

Make the window in the gantry, it gives you access to maintain, adjust, and oil the x axis screw and nut. It also makes the gantry a little lighter too.

The "extra" holes in the gantry are for the bolts on the z axis adjustment blocks. It gives you a little extra on the width.
Good luck with the build!

[kmacht]

Since you used 1/2-10 acme rod, how did you attach it to the stepper motor and what did you use for bearings on either end? A friend has some 1/2-10 acme rod I can use and also has access to a home made acme tap so i am leaning towards going this route. I have a lathe that I can use to turn the ends of the acme rod down but am not sure about turning it down such a long piece for the X (y?) axis. How did you end up doing yours?

Keith

[dustin1706]

U77171.. Thanks for clearing up the "Mystery Holes" for me LOL. I have limit switches installed, so I never go over that far anyway.

Kmacht, I used couplers and anti-backlash nuts from dumpsterCNC - anti-backlash solutions for home and industrial linear motion. Just click on acme componants and choose the 1/2-10 catagory.

I too was considering machining down the ends of my rod, but since I only have a 7x12 lathe, that is pretty difficult. I then tried using regular "skate" bearings glued to the rod, but I didn't really like them either. Eventually I got some flanged bearings. These work as a support bearing and a thrust bearing at the same time. The 1/2" rod fits nicely inside then there is 2 set screws you tighten down to clamp it to the acme(for the thrust part of it). If you buy these bearings, you do need to take the inner part out and clean up the flange and grease it well. These are the same ones used on the joes 4x4 hybrid design. you could use two per axis, but really one per axis and then a regular bearing on the other end of the rod would be fine.

You can find them on sale at vxb from time to time, and sometimes you can find them a lot cheaper on eBay. after searching around for a bit I think I ended up paying about $10 per.

FYH Bearings UCF201-8 1/2" Square Flanged Mounted Bearing:Ball Bearings

EDIT: here they are listed on ebay for $10 http://cgi.ebay.ca/1-2-Mounted-Beari...item22f9cfcbb1

[kmacht]

Great. Thanks for the links. I have known those types of bearings as pillow blocks but didn't think to use them for mounting the threaded rod. If turning the shaft down doesn't work I will definatly have to purchase some. For others that are looking, they can be bought brand new from Mcmastercarr.

McMaster-Carr

Part Number 5913K71.


Keith