Diary of a FoamCutter building a jgro router table

[tajord]

Lucky you, would you believe i ordered bearing since late November and have not gotten them as yet , i don't know, maybe got lost in postal, had to order a new set, usually take two to three weeks to get them, still waiting........

[mcyr]

Originally Posted by Glidergider Mike, I've always wondered how a CNC router would finish the bottom of a wing? See the attached picture. The top is no problem, there's no easy way to finish the bottom. What would you do? You can't turn a complex airfoil on Now if I were cutting a foil for a mold, then no problem, because you would cut a top, the cut a separate bottom. Dave

Dave,

Great question. I've only given it a little thought and all I can come up with is about the same as you suggest: Route the top and bottom separately with a lip around the edges. The lip could be used for alignment before gluing, then cut off??? I guess since the two would be mated together it might be a good time to put some spar material in. This might be good for DLG wings if it doesn't add too much weight. Do you think the material would become too thin routing this way that it wouldn't be feasible? Might be a particular problem with Drela et al foils.

Another option would be to use a 4-axis machine so that you route both sides (not a perfect solution either I realize). Biggest drawback of this is I haven't got a clue how you'd keep the piece stationary enough.

Mike

[HayTay]

GliderGider,

How did you make out with Sporqster's JGRO router plans modeled in CATIA format? Did they open OK for you?

[Glidergider]

Hi HayTay,
Yes, the Catia files opened perfectly. Full 3D solids with all the trimmings. Very nicely done. Thanks for the link. I had John Miller in my cube and we were zooming around looking at the details. Most of it we already knew, until we closed in on the back of the long axis bearing mount. It turns out that on the back side of that mount, there is a MDF block, which appears to be an adjustment feature or just a structural backup block. Its detail 21. Its also shown on assy07.

Can you shed some light on its purpose?

Thanks again for the link.
Dave

[HayTay]

Originally Posted by Glidergider ...until we closed in on the back of the long axis bearing mount. It turns out that on the back side of that mount, there is a MDF block, which appears to be an adjustment feature or just a structural backup block. Its detail 21. Its also shown on assy07. Can you shed some light on its purpose?

Are you sure you got the drawing number correct. According to my PDF plans CNC_dtl21 is a GANTRY - CORNER BLOCK. Are you talking about the ANTI - WHIP BLOCK SPACER (cnc_dtl24) and the corresponding ANTI - WHIP BLOCK (cnc_dtl23)? If you are, then the purpose is to help keep the long axis leadscrew (1/4"-20 x 43.50") from 'whipping' around like a jumprope while moving. This is apparent at higher feed rates (motor RPM) and the farther you get from the drive motor. The sound is horrible and results in reduced accuracy and repeatability. The A-W Block Spacer also seems to help stabilize the gantry a bit.

If you used 3/4" Delrin/HDPE for the ANTI - WHIP BLOCK (cnc_dtl23) you wouldn't need the A-W Block Spacer (cnc_dtl24). If you're converting to a larger ACME leadscrew the A-W Block is one of the parts that requires modification.

[Glidergider]

HayTay,
I was talking about the corner block that I saw in the fly thru. Still, thanks for the info about the AW block, thats good stuff.

It was the corner block that I'm wondering about. I'm wondering, is it for structure or adjustments or both?
Dave

[HayTay]

Originally Posted by Glidergider It was the corner block that I'm wondering about. I'm wondering, is it for structure or adjustments or both? Dave

The GANTRY - CORNER BLOCK (cnc_dtl21) is primarily for structural support. It's used to connect the GANTRY - BOTTOM (cnc_dtl18) to the GANTRY - LEFT SIDE (cnc_dtl16) and GANTRY - RIGHT SIDE (cnc_dtl17). It also helps to 'stiffen up' the area where the bearing slides mount so that they better withstand the racking motion of the gantry. There may be other reasons. I'll leave those to JGRO or a mechanical engineer to explain (please).

Most of the adjustments to the machine are made to the rails via the ADJUSTMENT BLOCKS - LARGE & SMALL (cnc_dtl07 & cnc_dtl13).

Any more progress, or are you currently in the 'hunting and gathering' phase?

[Glidergider]

Regarding my progress. Nothing this week because of various life activities. My Daughter had a High School Basketball game, I had a Sailplane Club meeting, then a Volleyball tournament last night, but tonight, I should be cutting timber.

[Glidergider]

What are your thoughts for servo sizes and Controller boards? Since I've been hanging around CNCzone, my opinions have changed. I was planning to get the HobbyCNC.com 200 in-oz combo, and but now I'm wondering if I really would benefit from something in the area of 450 in-oz.

[Glidergider]

Started assembling the skate bearings to the aluminum angles. Almost finished with the first skate. Notice I'm missing the counterbored peak. How am I going to do that with hand tools? Help me out please.

[edo]

I bought the HobbyCNC 200oz kit, primarily for cost, and I actually enjoyed putting the board together. The motors seem to have plenty of power and speed for my JGRO using 1/2" Acme lead screws.

For the aluminum angles, I marked the space to be cut on the angles with a Sharpie and took most of the material off with my bench grinder. The width of the cut isn't critical and the size of my grinding wheel was just about right. I finished it up the cut with a hand file to get it flat.
If you don't have a grinder, use a hacksaw and make multiple kerf cuts, then finish it up with a file. It's also easier to drill the holes after the flat is cut.

[Jason Marsha]

I filed them flat with only a file (.75" wide) in a few minutes.

Jason