[Tweetihd]

Hi everybody. After several months of reading posts on this site, I've finally started building my JGRO. I'm probably about 50-60% of the way into the build, and have a few questions. I'd appreciate any advice.

Questions:

1. On the pages titled cnc_assy02, cnc_assy07 and cnc_assy09, there are close up views of the end of each lead screw. I see that there are nuts and lock washers placed there. What is the purpose of these? I would think that having a lock washer on there would cause the lead screw to tighten the nut (or loosen it) as it turned. I'm planning on using flanged bearings that have mounting holes in the flange, so if the purpose is to keep the bearing in place, do I need the lock washer and nut?

2. After much searching, I can't seem to find "gas pipe" in my area. I guess natural gas isn't very big here in SC. Lowe's has "water pipe", and I plan on going there in the next day or so with a caliper to see how close the ID and OD on them are to the plans. Has anybody used these, and if so, did you have to make minor adjustments to the dimensions of the bearing supports to accommodate them?

That’s it for right now. I’ll get some pictures in the next few days and get them posted. Thanks in advance for any advice.

-Rusty

[Albrow]

Gas pipe is thick-walled steel. Water pipe is thin-walled copper. You can't substitute one for the other.

Also, if you do the math behind the linear bearing design you'll see that they match the gas pipe diameter perfectly. A larger or smaller pipe could require a bearing redesign.


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[Tweetihd]

Albrow

Thanks for the reply. However, I did indeed go to Lowe's with my trusty digital calipers and did some measuring (side note: you should have seen the looks on the faces of some of the employees when I started doing this). The "water pipe" that I had looked at on their website is galvanized steel, not copper. I measured the inside and outside diameters of both the 1" and 1/2" pipe, and all measurements were within a few thousandths of an inch of those listed in the schematics. I'm linking the ones that I'm going to use below:

1/2" pipe
1" pipe

Those lengths are due to the oversize of my build, but there are plenty of lengths available through either their website or in the store.

Finally, I thought I had recognized your name from other threads that I'd browsed through, so I looked you up on this site. As soon as I saw the pictures of your Z Axis made from HDPE, I remembered. I'm wondering how that worked out for your build? I ask since as soon as I get mine up and running, one of the first things I'm going to do is use it to recut some of my parts, and had considered using some material other than MDF.

Cheers, and thanks for the info.

-Rusty

[Albrow]

Albrow

Thanks for the reply. However, I did indeed go to Lowe's with my trusty digital calipers and did some measuring (side note: you should have seen the looks on the faces of some of the employees when I started doing this). The "water pipe" that I had looked at on their website is galvanized steel, not copper. I measured the inside and outside diameters of both the 1" and 1/2" pipe, and all measurements were within a few thousandths of an inch of those listed in the schematics. I'm linking the ones that I'm going to use below:

1/2" pipe
1" pipe

Those lengths are due to the oversize of my build, but there are plenty of lengths available through either their website or in the store.

Finally, I thought I had recognized your name from other threads that I'd browsed through, so I looked you up on this site. As soon as I saw the pictures of your Z Axis made from HDPE, I remembered. I'm wondering how that worked out for your build? I ask since as soon as I get mine up and running, one of the first things I'm going to do is use it to recut some of my parts, and had considered using some material other than MDF.

Cheers, and thanks for the info.

-Rusty

Rusty,

I seem to remember someone saying that you should use the black pipe, not the galvanized. Maybe because the galvanized surface doesn't hold up to wear as well as the black pipe?

That must have been pretty funny with the calipers. I wonder what they made of it? Some of the guys at my local HD are actually pretty sharp and probably would have been curious enough to ask, but others would have been completely confused, I'm sure.

I'm still in my build, unfortunately. I've had so many delays and missed weekends along the way. Progress has been slower than I'd like. But after cutting the gantry parts out of MDF I do have some solid observations.

1. HDPE machining is much easier and cleaner than MDF. It produces big chips and corkscrews that are really easy to clean up. MDF produces dust that coats everything. You need a mask when machining it.

2. HDPE threading is better so far. If you have low quality MDF the core is very soft - so soft that the tap seems to wander a bit as you tap the hole. This can lead to some lousy threads. If you have better quality MDF the face and core seem to be harder and the threads come out a bit better.

I've tried the super glue trick on both types of MDF and my results have been mixed. The glue causes the MDF to swell slightly and the tap doesn't always engage the original threads well. That's why I purchased a bunch of cross dowels - I'm anticipating the MDF threads not being able to hold on and I don't want to glue and screw the whole thing together. I know that would be stronger but I do want to be able to replace individual parts if they fail.

3. HDPE thickness is perfect, but MDF was off by 1/32. I cut a dado using a 3/4 inch router bit and the HDPE fit it perfectly. There was no slop whatsoever. MDF was over sized. I had to take off an extra 1/32 to get the fit right.

4. It's relatively easy to split MDF from an edge hole. I haven't seen HDPE fail yet. The Z-Axis carriage is pretty well designed though (all dado connections and threaded holes) so I doubt there would be splitting, but I could see some stripped machine screw threads though.

Also, I've found that the MDF at Lowes seems to be of the harder variety than the stuff at Home Depot.

Hope this helps.

Where are you in your build?

[Tweetihd]

It’s funny that you mention the black pipe vs. the galvanized pipe. I’ve seen a few places mention exactly the opposite. I think it has something to do with the black paint (or whatever is used to coat the pipe) eventually wearing off and fouling the bearings. I’m going to research it more, as I haven’t bought the pipes yet. The black pipes are actually a bit less expensive than the galvanized ones, and I measured them too while I was at the store (they’re the exact same dimensions as the galvanized ones). Oh, and since I had a rare bit of foresight when I purchased my bearings, I got the kind that are sealed, thinking that a CNC kicks up a lot of dust and didn’t want that causing problems. So if that’s the only reason I can find that discourages the use of the black pipe, I should be fine if I end up using them instead of the galvanized ones.

I hear you about the delays. After six weeks of fast and furious progress, I’m at a complete standstill. Right now, I’m still at the point I was at this time last month. See below about the reasons for this, as well as how my build is going.

I know all about the MDF dust. I’ve done a few woodworking projects in the past where I used it, and after getting done was so covered in the stuff that you couldn’t even tell what shirt I was wearing. I almost always use a mask and eye protection when I’m working in my shop anyway, so having them on when I worked with the MDF wasn’t a problem… keeping my shop clean was.

About the threading… I had an idea that I’m going to try once I start buying parts again. I’m going to pick up some threaded inserts from McMaster (part number 92105A675). Basically, I’ll just make the holes for the ¼”-20 bolts slightly larger than the plans call for and then epoxy the inserts in place. I hope that this solves the problem with the MDF threads, and still allows me to disassemble and replace pieces as you mentioned. I’m glad you brought up the swelling from the glue; I’m not sure how much epoxy will make it swell, but it reminded me that when I thread them into the MDF cross grain, I should clamp the faces to help minimize this. I also plan on doing this with the machine screw holes as well.

To answer the build question, at the moment I have all of the MDF stuff cut out and mostly assembled. I still have the pipes, lead screws, Delrin and electronics left to buy, as well as purchasing the software (I’m using the trial versions right now to play around with them a bit) and various screws and other small pieces of hardware. I estimate that I have about $1,800.00 of stuff left to get for my build, but the majority of that is the Vectric V-Carve Pro ($600.00) and Gecko controller/motor kit ($520.00 from CNC Router Parts) which I plan on using. I actually tried to take some pictures of it the other day, only to find that my digital camera is on the fritz (the shutter won’t open when it’s turned on), so no pictures at the moment. I hope to rectify that in the near future.

I’m on hold due to my wife and I being in the process of starting up a woodworking, molding, and CNC business, of which my home built JRGO will be the CNC. Because of this, we’re waiting on the finances to come through so that we can get all the license stuff, buy the couple of machines we’ll need (one of which is a two-stage dust collector), and purchase the items needed to finish the CNC build. We hope for this to be around the end of this month, so if everything goes well I should be back to finishing it by the beginning of October. I really want to be up and running (or at least making adjustments and shimming) by the middle of October.

Finally, I originally planned on my JGRO being able to cut a 2’ x 4’ piece. I read somewhere on this site that a JGRO made exactly from the plans will have a cutting area of 16” x 33”, and so I added 8 inches to the width and 15 to the length. I’ve “dry assembled” what I have built so far, and my preliminary findings are that, even though a 2’ x 4’ piece will fit, the cutting area will be about one to one-and-a-half inches short in the width. This may be due to whomever posted that cutting area using a smaller diameter spindle (mine will be a Craftsman 3-1/2” diameter router). I’ll wait until I have it all put together to make adjustments on getting it exactly how I want it when I recut the pieces. I’m also going to have the cutting bed overhang the bearing support end by a few inches, thus allowing me to move the gantry all the way to the “stop” and still be able to cut.

-Rusty

[ger21]

The galvanized coating on the pipe will flake off. The best thing to do is probably buy black pipe and sand the black finish off. If you read through the Joe's 2006 threads, you'll see lots of examples of this, as well as jigs people have made to do it.

Epoxy won't cause the MDF to swell at all. The Super glue doesn't either, but it gives the appearance of swelling, by hardening all the loose fibers in the hole.
The only thing that will swell MDF is moisture (water), or substances with moisture in them, like wood glue.