Thoughts on Stiffening mod

I love to hear that. When you start out cobbling together a machine out of MDF, you learn a thing or two about the potential impact of rigidity mods. When I ordered the X-Carve, I was so excited because it wasn’t MDF! Then, I was really disappointed because my MDF machine was WAY more capable and sound. So, these are the first two things I did… and the third was ditch the spindle. Still, these mods are no biggie - quick and as you noticed, have an amazing impact.

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Full disclosure:
I just did a test on 3/4" oak cutting a wedge for a kicktail on a skateboard going back and forth across the grain.
I had to slow it down to 100ipm and .060 cut.

It throws such large chips now I may have to modify my dust collection rig to get all the big chips out of the deep corners. (or buy another shop vac :smile: )

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Go ahead and get a real dust collector. It makes an amazing difference over a shop vac.

So… I did the steel bar mod. And dewalt upgrade. Dear lord made it awesome. But when I do a cut in plywood. And it is cutting against grain I get chatter. No matter the speed of spindle or feeds. Etc. so far. Did research and found the part of the mod I missed was the L brackets for the x axis. Testes the flex without them and wow. No wonder I am getting chatter. Will be fixing that in the morning.

If you want to stiffen the Y-axes and still be able to remove the wasteboard, you may want to consider something like what I’m going to do instead of using L-brackets. You’ll have to cut plates out of 1/8" material, but you’ll be able to support it a lot more firmly. I was going to use makerslide end plates, but Inventables doesn’t have any to spare so I’m going to make a custom version out of aluminum. I was thinking about adding 3 plates on each end, maybe 3.5" wide.

Y Axis Mod.pdf (185.9 KB)

A similar idea to yours @RobertA_Rieke .
If the spoil board is cut as shown, it should still be removable without removing the extra y-axis plates.

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As far as removing the spoil board, I am not sure that is a big deal for the immediate future. At least for me. But I don’t do much, if any through cutting so…

On my machine, the outside of the bottom rail is about 1/8" in from the inside of the top rail, no notches necessary. Is that a custom oversized wasteboard?

Beyond that, it looks like we had the same idea. I just decided to take it a step farther and use the screws attaching the plates to the top rail to also hold a large shield, which I’m making out of mirrored acrylic.

I based my design on measurements from the X-Carve cad files, or so I thought. I did assume that the width of the spoil board was the width of the X-Carve, in my case 1000mm. I’ll go and check that again as I intend to cut the spoil board tomorrow.
The shield is a good idea, perhaps once I have a functioning X-Carve to make them.

Geoff

The waste board is only 940mm wide, 998mm tall. That should leave some room for plates without modification to the waste board.

Thanks for pointing this out.
If I measure between the inside faces of the Y axis rails, I get 945mm. I think I had the x and y measurements swapped.
Not having to mess about with the spoil board means all I need to make is a few plates out of 3mm aluminium.
After I make the X-Carve bench… after I finish making the X-Carve …

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I’m tempted to just buy some extra end plates and screw them directly to the rails. They already have the proper mounting holes and are the right color. It may be an easy (and inexpensive) bolt-on mod for stiffening the Y axis.

@ChrisSlaten, I was going to do that but they don’t have any to spare. All they have are going into filling orders.

Updated y-axis mod. Much easier this way :slight_smile:

Originally mentioned by @AngusMcleod

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Nice design.

They don’t have any waste boards to sell separately either. I don’t think they were expecting the number of orders they are getting for the X-Carve. They just can’t keep up.

If the y-axis is going to flex, it’s going to flex mostly in the x-direction. If you add plates like in your mod, it’s not going to do much to prevent that motion, because the lower extrusion will twist quite a bit.

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I mentioned this in another thread, but I was thinking of getting some 20x80 extrusion and drilling holes in the face to allow for bolting to slot nuts in the Y axis maker slide. This should add a lot of stiffness both for drop as well as torque. If there’s clearance you could bolt it so the 20x80 extrusion extends above the level of the maker slide to help block dust and chips from getting in the track. I was also thinking if done right it could allow for butting extra maker slides up to extend the Y axis beyond the 1800mm currently available. It might take quite a bit of work to get the joint of the maker slides aligned to prevent impact to the quality of the work, but it seems like it might work.

You can solve this with Lab Metal to seal and sand the gap. The stuff is amazing and brushes on like paint, just make sure to get the solvent along with it for cleanup, thinning and to put on top for storage.

http://www.amazon.com/Alvin-Durable-Economical-Patching-Compound/dp/B003GV46MI/ref=sr_1_1?ie=UTF8&qid=1442592555&sr=8-1&keywords=lab+metal

One thing to remember is to get you rail as close to straight as possible. This is not as easy as it sounds. There are no good reference points that you can verify as straight. One way that takes some time and engineering is to use tight wires.
With the belts off and the top holes in the Y end plates clear get some .010" music wire. Mcmaster-Carr sells it.
You stretch a wire from one plate to the next and make it harp string tight. This wire is now for our needs straight. There are engineering references that will give you the amount of sag due to gravity but it is so small we do not need to worry about it.

Now you have a known reference. using good measuring equipment you can check the distance from the wire to the rail at both end and make sure they are the same. then you can start measuring along the wire to the rail and adjust your mid span supports to get the rails just as straight to your reference wire as you can.
Do this for both sides.
You can also use this to make sure you don’t have any bow in the rails that they are the same distance apart on both ends and in the middle.

If you really want to get serious about this you isolate the wires from the frame so you can use an ohm meter and a micrometer adjusted device that sits on the rail and as you raise a finger on it with the mic when it touches the wire and completes a circuit you see a reading on you ohm meter. Check the reading on the mic and move to the next test point. Repeat, is the reading on the mic the same or different. Is it high or low. Adjust as needed and retest.

This could give you a rail that is straight to a couple of thou.

The big thing here is if you want your machine as accurate as possible you have to have good reference points.

Hope this helps

Dave

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A good quality 4 foot construction level is a pretty good reference. The edges are ground, so they should be flat and accurate to a few thousands, if not better.

Careful using it as a level though. A good quality level is only accurate to around 0.0005" per inch at best. That’s about 0.024" of 4 feet. Good enough for construction, but not a CNC machine.