JGRO in Cinci - 1st time build

[andeew]

After several months of procrastinating I decided to go ahead and build my 1st CNC machine (I already realize this is not going to be the last!). I started to build a few days ago and am really enjoying the process so far - my wife is complaining about how much time I spend in the garage in the evenings though.
I decided to start with Jgro's plans as they seem to be very straightforwards for a 1st machine.

After 3 evening I have completed the 2 torsion boxes, the end plates and am partway through the gantry.

I haven't seen anything pertaining to how best to secure the torsion boxes to the end frames - I am not sure whether I should go ahead and use glue and nails of if the ability to remove the boxes would be useful down the road.... any advice on that would be appreciated.

[andeew]

So in the absence of any feedback I went ahead and dowel pinned and then screwed the end plates on the base torsion box. I spent a good deal of time making sure the base was squared up to the end plates and that the pipes we parallel to the torsion box in z direction. I haven't figured out the best way to check for square and parallelism in the x and y - does anyone have any advice on how to do this?

[louieatienza]

So in the absence of any feedback I went ahead and dowel pinned and then screwed the end plates on the base torsion box. I spent a good deal of time making sure the base was squared up to the end plates and that the pipes we parallel to the torsion box in z direction. I haven't figured out the best way to check for square and parallelism in the x and y - does anyone have any advice on how to do this?

Once your bearing trucks for your gantry are done, you can use the gantry itself to get the x rails parallel. A good square can help you with the y in relation to the x. It's probably easier to do the squaring and adjusting once everything's built.

[DeadTom]

Looks good, I modified the base on my JGRO build. Mine is 6+ years old and still going strong, I have had to upgrade/make new some parts but for the most part it has been a great machine. Especially if you consider the plans are free and have been proven to work by many people across the globe.
Good luck with your build,
Tom

[jckstrthmghty]

Wish I saw this thread sooner.

I used lags bolts to secure the base and support ends. I your idea of dowel pins.

I'd leave the adjusting till the end but before the leadscrews. Thier position is critical to the position of the rails.

[andeew]

aaaaagh!


I just got the gantry rails assembled and it looks like I got the measurements out by 1/16" on the width, the gantry doesn't seem to run true on the rails (I haven't taken the rails back off to check they aren't warped but rotating them doesn't seem to help which leads me to suspect the frame or the bearing blocks are totally square.

Unfortunately my over confidence led me to believe I would do everything right first time so I glued up the dowels that hold the gantry together so it will be very hard to separate them to correct whichever piece I didn't cut correctly. I suspect it will be easier and faster to remake the gantry again......

FYI I also found that the confirmat type screws seem to do a much better job of supplying clamping pressure to the mounting holes in mdf. I realize that I don't have the same capability for using a lock nut to set the position but the holding power seems so much better that I may stick with them until I can machine myself some inserted delrin blocks for the mk II table that alread looks inevitable...

[jckstrthmghty]

You didn't use cross dowels?

1/16" should be recoverable but mdf is cheap enough you can rebuild most part at little cost.

I'm pretty sure you'll come to the same conclusion I have. The reason you build the JGRO style is cause you don't have a cnc to build parts for a supported rail design like Joes2006 or lionclaws. Even then maybe it would've been worth giving it a try but the jgro is a good learning platform and it will cut mdf parts well if you wish to upgrade. I think the tslot builds are the way to go for the hobbyist but cost is a factor.

[louieatienza]

aaaaagh!


I just got the gantry rails assembled and it looks like I got the measurements out by 1/16" on the width, the gantry doesn't seem to run true on the rails (I haven't taken the rails back off to check they aren't warped but rotating them doesn't seem to help which leads me to suspect the frame or the bearing blocks are totally square.

Unfortunately my over confidence led me to believe I would do everything right first time so I glued up the dowels that hold the gantry together so it will be very hard to separate them to correct whichever piece I didn't cut correctly. I suspect it will be easier and faster to remake the gantry again......

FYI I also found that the confirmat type screws seem to do a much better job of supplying clamping pressure to the mounting holes in mdf. I realize that I don't have the same capability for using a lock nut to set the position but the holding power seems so much better that I may stick with them until I can machine myself some inserted delrin blocks for the mk II table that alread looks inevitable...

You should be able to asjust the rails for the gantry, right? I remember looking at the JGRO plans when I first started, there's got to be at least 1/16" of adjustment in the rail holders?

[louieatienza]

Looking at your pics, you should be able to adjust out one rail; if not, you can ream the holes to give you more adjustability.

I think the Solsylva design is a bit easier to build, and since it employs supported rails, a lot more robust...

[andeew]

You didn't use cross dowels?

1/16" should be recoverable but mdf is cheap enough you can rebuild most part at little cost.

I'm pretty sure you'll come to the same conclusion I have. The reason you build the JGRO style is cause you don't have a cnc to build parts for a supported rail design like Joes2006 or lionclaws. Even then maybe it would've been worth giving it a try but the jgro is a good learning platform and it will cut mdf parts well if you wish to upgrade. I think the tslot builds are the way to go for the hobbyist but cost is a factor.

Cross dowels would probably have been a good choice - but no I didn't. I think that when I remake the gantry I will probably do that.

I do like the low cost of mdf for exactly this reason but the stock JGRO is a little flawed due to it's reliance on tapping holes in the end 'grain' of mdf.

[andeew]

Looking at your pics, you should be able to adjust out one rail; if not, you can ream the holes to give you more adjustability.

I think the Solsylva design is a bit easier to build, and since it employs supported rails, a lot more robust...

Unfortunately I think it's the gantry that is off-square which I can't correct with adjusting the rails. When I remake the parts I will be very careful to dry fit everything 1st.....

[Ohioflyer]

Welcome to the wonderful world of building by hand. I believe dry fitting everything is a must, no matter how confident you are in how well you've made a particular part. You'll also find that no matter how well your parts fit together dry they just never go together that well when they (and you) are covered in glue. I'm convinced that there is a particularly malicious breed of shop gnome that is responsible for this phenomenon.

I was originally planning on building a JGRO, but the tapping of the MDF really bothered me as well. I would recommend getting some HDPE and making your rail blocks out of that. Another option I thought of, but one that will get pricey is to use threaded inserts to hold your adjustment bolts. with the MDF you'll have a problem with splitting, one of the ways I deal with the splity/flakey nature of mdf is to saturate a high stress area with super glue, it really helps to strengthen it in that regard.

Anyhow good luck with your build, I look foreward to watching it progress, post lots of pictures. Remember, a part is not correct until its been "prototyped" at least twice.