CNC Shark Forum

rungemach wrote:Hello 4d ...
I’ll be interested to see what you come up with, there is always more than one way to do just about anything. It would be great if an easy elegant solution like Bob’s fourth axis appears.. I say, go for it..

Thanks, rungemach. I'm a natural born tinkerer so am looking forward to my adventure. I was never bothered by the Shark's flaws untils I started making tiny parts for 1/5th scale furniture models. I've had my Shark for a couple of years now and worn out one Colt, and today took a close look at why there was so much error in X and Y dimensions, Found the flange nut on the X axis worn so much there was nearly a 1/16" of play in it. Makes me wonder if there are any threads left inside it as the screw is acme 3/8"-12 tpi or something close. Sent an email to NWA support for replacements for all the flange nuts. Found a (expensive) source for them online in case they don't/won't send me them.

As I ponder supporting the X direction travel it occurs to me that I may induce more forward rack than the router alone does by holding the back edge up. I may tilt the caster and it's track 45 degrees inward to counteract both sag and forward lean.

I'm more interested in fixing the Y-axis sag though as with the weight of the entire gantry + router it sags more that direction than my X-axis does.

Here are a couple of pictures of an upgrade that I recently finished.

It started with an extended table pro plus and ended up as you see it now. It is all aluminum or steel with the exception of the 3 original extended table base plastic pieces. There are fully supported adjustable bearings on all axes (including the Z). The aluminum parts were made on my modified shark pro.

So if you have an older pro or pro plus that you want to be a bit stronger, it can be done. I suggest doing the x axis first in plastic or aluminum, that gives the biggest improvement for the cost. Dxf files available if anyone wants them. Just send me a PM.

Bob

That thing just looks mean! Well done!

-Eric

Pretty awesome Bob. Thanks for posting and offering the how to's.

For any replacement parts look at our online store.
If what you need is not there then call our support number.

Thanks
Tim

"Oh yeah" Made my pro plus Z and X stronger.Thanks to Wireboot and a big thanks to Bob for the info and feedback on the finer points of the rebuild.Added the 1/2x2 alu and a new rail system with 4 linner bearings that are adjustable.Put in a 1/2 roton lead screw with a new nut.cutout all the parts for the carriage from Bobs dxf files.There is no flex in my system.This thing is rock sloid.You can see in the cut.I will upgrade y after i clear my work load.I too was one thet bought the pro plus and a few weeks later the HD comes out.Iam gonna make a new backing blate and some brackets to hold a larger router.Why sell the pro plus when ya can up grade. basecircle

I've just completed my X axis upgrade. Many thanks to winreboot for the files. Definitely less deflection now.
Some remarks:
1. I found the best price including shipping for the 1/2" HDPE at Graingers (USA).
2. You may need an angle grinder to shorten the shafts, since they are case hardened. Hacksaw or saber saw blades with tungsten carbide particles may also work. Or grind through the case hardening all the way around and then use a hacksaw. Be sure the new shafts are cut to the same length (or slightly shorter) as the original shafts.
3 The shaft supports and the 1/2 x 2" aluminum bar need to be at least 1/2" shorter than the shafts on both ends.
4. The shaft supports and the 1/2" aluminum bar position the shaft farther from the gantry cross plate than the original position. I cut .074" thick HDPE shims that went between the gantry cross plate and the gantry end plates to move the gantry cross plate away from its original position.
5. I built a jig to properly locate the bolt holes that you will have to drill into the edges of the new plates.
6. The counterbores in the new bearing plate are not large enough to accommodate a wrench for hex head bolts for the bearing blocks. Use M6 x 16 socket head capscrews (with washers) so you can use an Allen wrench.
7. Look inside the linear bearings and you will see that on one side the balls are closer to the edge of the opening. I oriented the bearings so the closer row of balls was above the upper shaft and below the lower shaft to get the most rigid arrangement. Be sure to adjust the bearing blocks so they just slide smoothly on the shaft (although they will not move as smoothly as the original bearings on their shafts) before you fasten the new bearing plate to them..
8. Last, but not least, I ground down the sides of a 7/16" end wrench to fit into the nut slots. It took time, but it was well worth it.

The new bearing plate needs to be notched two places at the top to clear the Z axis stepping motor mounting nuts.

Hi Mike

Glad you completed an HD mod for yourX axis. Winreboot has the original version 1 files and I am up to revision 4 now, which adds notches for the z motor nuts, has larger diameter recesses for hex nuts for the bearings, etc. In the machines I have worked on, the back gantry plate came up just about flush, so I'm not sure why yours is different.

You are correct about cutting the bearing bars, and an abrasive wheel is the easiest way to do that.

When you are ready to do your y axis, give me a PM and I can get the latest versions of that mod to you. That is actually an easier mod to do than the X was, and you can add length if you want to get a new lead screw and split your bottom base plate.

Bob

I did some quick calculations. Adding the shaft support extrusion and the 1/2" x 2" aluminum bar makes an assembly that is 20 times as stiff as the original 20mm shaft. The calculation took into account that aluminum is only 1/3 as stiff as steel. The increase is with respect to a force applied to the X axis shafts in the Y direction.

Based on this, I would suggest that bolting to the existing plastic structure doesn't add any significant additional shaft stiffness. It does of course add stiffness to the plate. Anyone making modifications may want to take this into consideration to reduce the amount of work required.