JGRO Revisions?

[Wolfspaw]

Now that so many people have built the JGRO Router, what is the one thing that you would do differently if you had the chance to build it again?

Wolfspaw

[phillby]

There is a discepancy between the parts list and the parts diagram round the router carriage supports. The clearance is to small to clear the pipe adjusting bolts. If the detail drawing is used all is ok.

When drilling and tapping into the edge of MDF support the outsides with clamps to stop the fibres separating. Make sure all threaded holes are coated with superglue left for a day and re-tapped. This helps prevent thread stripping. Repairs can be made by coating the thread with 5 min epoxy and redrilling and tapping. Tapping can be done very carefully with a slow speed battery drill.

The main modification I am going to do is

Replace and extend the bottom torsion box skin out to the edge line of the whole router footprint. Use 3/4" instead of !/2" MDF (the bottom bolt heads on the carriage may have to be recessed to give suffient clearance). I will then use 3/4" MDF to put some sides on the unit that will be supported by bolts into the edge of the extension. This should provide a stable platform to provide some additional support to the Long Pipe rails. The support can be packing or bolts and lock nuts.

Others have lamented on the size of the X bearing pipes also. It may be worth considering using the larger size pipe on this axis. This would mean the larger adjustment blocks are needed with a corresponding change to the hole sizes in the carriage sides.

I have only cut one Item 3days ago just as a test. I still have items to complete on the unit so am being good and resisting further temptation. So these modifications are really only solutions to comments on the forums. I however have noticed the flexing while adjusting the linear rails (pipes) into position.

These modifications IMHO although very minor in nature would make this excellent machine even better.

[Jason Marsha]

First let me state that these are excellent plans (Ten cheers to JGRO ) and my modifications were only made because knowing myself I would want to stretch the machine to its absolute limits. That being said thse are the changes I made during assembly and some slightly after.

1: I added sides to the machine from 3/4 plywood.

2: Screwed a cut down 2x6 to the inside of the new sides to help support my Y-axis
(long axis). The sides also helped me to control the outward push of the Y-axis as
the gantry moved closer to the middle of the Y-axis.

3: I did not build the base or the torsion box bed support (Lazy), instead
screwing a cut down sheet of exterior plywood to the complete base of the
machine, encompassing the sides as well. The bed support uses .75" square steel
running the length of the MDF table surface.

4: I used lots of threaded inserts, especially in the adjustment blocks.

5: The X-axis pipes may need to be solid drill rod (or stronger) of equal or very slightly
greater diameter (to avoid changing bearing runner dimensions). I am using black
pipe on this Axis for now but I have it so tight on the x-axis runners It may soon
explode (lol).

6: The Y-axis pipes are seamless shafting rod (hollow in the middle, but not like normal
pipe). Drill rod of equal diameter may be used here or black pipe. It will need the
support I described or similar.

7: Since I did not build the base of the machine, I had room underneath to add 3 ,
5/8" threaded rods running from one side to the next. These allow me to pull the
sides together thereby stopping all outward movement.They cannot be too tight or
they will distort the sides of the machine. A straight edge should touch the whole
side of the machine after turning the nuts on the threaded rod. ( pics in JGRO
PICS FINALLY thread)

8: I have not done this yet but you may want to consider using at least 5/16 - 18
threaded rod, instead of the 1/4 -20. the reason for this is that "skate bearings", or
the 608 series are readily available and the 5/16 rod fits right into the hole with
almost no play. If you wanted you could you could use ACME rod 1/2 -10, it seems
to be pretty popular here in the zone or even ballscrews if you get a great deal on them. Some may not to waste ballscrews on this machine but after all of the
enjoyment and pride this machine has given me, why not.

9: Do not use Galvanised pipe for this project, trust me it is not true enough at the
very least use black pipe or drill rod.

10: Use a drill press for all holes.

After saying all that sometimes its just better to get something done and then after you understand make the changes. Too much planning will kill this project as well as too little. A little something I learned from a veteran of hobby cnc, Build the machine first and deal with electronics after. A little everyday and you will finish

Good Luck

Jason

[Lionclaw]

Originally Posted by Jason Marsha A little everyday and you will finish

No! :-p You have to work on it 20/7 until it's done. You can use the extra 4 hours for sleep and food.

I got so excited after downloading the plans I spent 3 days straight working in the garage to get it done. I'd be out in the garage until 8 or 9 in the morning and go to sleep when the sun started to shine through the windows. It wasn't very safe though. I got tired and ended up catching a finger in the drill press.

But yeah, like Jason said, the leadscrews need to be beefed up. I used 5/16-18 and they still whip. They might be better if I used skate bearings at each end and put them under tension. With 200oz motors, I can rapid around 70ipm before the whip gets too bad. The 18tpi is a problem though. I'm going to use 1/2-10 acme on my next machine.

Also, the jgro style AB nuts didn't really work out for me. They had too much friction. Take a look at Joe2000chevy's build log. He came up with a good method of using captured nuts. I'm just going to opt for Dumpster's nuts on my next machine though.

I would also recommend painting the machine ASAP. I think I can see a bit of sag in my machine's table after almost a year.

Lastly, don't rely on the stock sizes listed in the plans. Some of them are wrong. Double check before you cut your materials.

[mrbaseball]

Do you guys have any photos?? It would be nice to see along with the comments as sometimes it tough to conceptualise what your speaking of

[jcoats]

I know this is a silly question, but what does JGRO stand for anyway?

[sdantonio]

His first hame is John, I remember that from his home page.

Thats part of the JGRO.

He has built a generation II machine (generation I got flooded to death) with some really good modifications (see my post to starting from subzero for a few of them). He also has pictures

Steven

[ger21]

JGRO is his username here.

[sdantonio]

Here we go, the JGRO home page (It's in his contact info with the router plans). He is a bussy man, please respect that, and post you questions here instead of bothering him at home as he requests in his contact info.

http://www.nconnect.net/~jgro/

[carlnpa]

MDF or ply for JGRO router?
Replace the x axis rail with something that won't deflect.
See my post #23 in the thread. That 8020 rail is fully supported.

[Wolfspaw]

Carlnpa:

Are you happy with the performance of your machine using the UHMW bearings that you made? I have seen a lot of posts trashing the 8020 bearings.

Wolfspaw

[carlnpa]

I have seen the posts trashing the 8020 bearings also. The UHMW bearings I made are very different from the 8020 manufactured ones. The 8020 system uses removable inserts. The mount I made has the insert profile milled to mate precisely with the rail and the JGRO gantry (or any other gantry). I am cutting plastic parts for an OEM manufacturer with my K2 machine. The UHMW material was on hand so I made these to try to correct the problems I had with the roller bearings on my JGRO. This bearing is much longer than the 8020 bearings I have seen (8.75" easily made longer or shorter).
The UHMW bearing on the JGRO machine is a major improvement, there is far less gantry flex, the rail provides a known reference point of alignment, the UHMW on the rail is very low friction and slides freely. The rail is fully supported so the 1020 rail profile is adequate unlike the pipe that does deflect. The machine has not been reassembled yet, but will be within a few days. I don't expect any operational issues.