It has been a year, beyond the 525...

Okay I have a few updates in mind but I think I like doing this in sections.

First issue the legs. They are currently the weakest link.

Options, ideas?

1)Get rid of the locks, legs, and feet then just use a 4"x4"? Hard to level…
2)Use angled braces? Extra parts…
3)Make all 4 corners the z axis? Yikes…lots of hardware and electronics
4)Hard mount the corners,make the z axis the bed? harder to make a table, lots of carpentry involved.
5)Rework the current parts use two tubes side by side, make the lock and feet fit both? A little extra tubing.
6)Use the current setup and add allthread from the top through the table and bolt it all together? I see a lot of parts getting crushed this way.
7)New feet, the corners and locks seem solid to me, the feet seem to be the weak link? Easiest.
8) #7 plus a place top mount guy wire for the taller builds? Options are cool.

Or…

9)Leave them alone they only seem to be an issue with more than 4" of Z axis.

1)Get rid of the locks, legs, and feet then just use a 4″x4″? Hard to level…

Easy and effective solution. The leveling can be done relatively easily using shims or a few layers of paper. The only concern I have would be wood expansion/contraction overtime.

2)Use angled braces? Extra parts…

Better than nothing but it will be weak.

3)Make all 4 corners the z axis? Yikes…lots of hardware and electronics

Too complicated, and it will need 3 more motors. Leveling will be a nightmare and rigididy will vary depending of the height of the machine, so results won’t be constant.

4)Hard mount the corners,make the z axis the bed? harder to make a table, lots of carpentry involved.

In my opinion, the best solution, but it will not be for beginners and it will ruin the whole point of the MPCNC: being an entry level easy machine for people to experiment with.
But it could be another complementary version. Like beginner version, versus experts version.

5)Rework the current parts use two tubes side by side, make the lock and feet fit both? A little extra tubing.

Could be an easy solution and this should work better than the original, if I understand correclty what you are saying (putting two tubes at each corner, oriented at 45 degree, one inside the frame and one outside, right?). I don’t see any downside aside from extended printing time for all these corners and supports. Might do the trick. Could also add more tubes, 3 or even 4.

6)Use the current setup and add allthread from the top through the table and bolt it all together? I see a lot of parts getting crushed this way.

It will improve rigidity, but needs to be crazy tightened, which will be hard on the plastic parts, but they can be made pretty solid. Tightening will have an impact on leveling, so it will make things complicated: people will have in some cases to chose between a leveled machine and a rigid one.

7)New feet, the corners and locks seem solid to me, the feet seem to be the weak link? Easiest.

In my opinion, new feets will greatly solve the issue, but I can’t think of any feet design who can solely solve the problem, unless having massive feets that will take hours to print. Unless, as mentionned above, a feet design using sereval tubes. Could be two or cound even be 4.

  1. #7 plus a place top mount guy wire for the taller builds? Options are cool.

Didn’t understand this point.

In my opinion, if you wish to have maximal rigidity without making too many changes, the solution 5 is the best. It will not solve everything, but it will definitely be better.

An other solution would be to print the feet/tube/bottom corner support as a whole, single part. But it will take a long time to print.

I believe the best way to have something rigid is either the technique I used for my table, which has a lot of other advantages, like versatility but makes things very hard to square the first time, or, as someone else suggested a few days ago, to attach the structure to a wall, which is clearly the best thing to do but might not be practical for everyone.

As for other suggestions I have:
-add parts or spots to fit the endstops, especially on Z axis
-Add some cable management parts,
-consider a more rigid center carriage, maybe using two parralel tubes instead of just one per axis. I think this is not easy to do but it should be feasible.
-Same remark for the Z axis, it may be possible to use 3 or even 4 tubes intead of 2, by mirroring it. This could greatly increase it strenght, which could be useful for tall builds. Not sure this is a priority though.

Hope that helps!

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@Dui, ni shuo de dui.
Don’t want to add more crap to the Z. It will make it heavier, which will sag the X Y tubes.

@Ryan

I have an idea. Have to go to work though, will post later.

I’m not finished building mine, so take this with a grain of salt.

To me, the best plan would be to add bracing in the corners. Any time you have a 90 degree turn in a design, there’s the chance for racking. In the steel stand I just built for my reef tank, I added 45’s in every corner… probably overkill, but I’m supporting 2,000 lbs 3 feet off the ground.

In your design, this could be added either as a printed part, or some type of metal. It could even be as simple as using metal barstock and bolting it from the leg to the horizontal pipes.

The hard part is, you don’t want to do this in a way that sacrifices x-y travel of the gantry. Having to make the horizontal parts longer to accommodate more bracing would be a negative.

If the corners and locks are solid and it is just the feet, then maybe they just need a larger footprint. Maybe try to incorporate some type of metal L bracket into the feet design to help brace the xy load on the feet that causes them to flex.

2+5+7/8=7 7/8
Make new feet. But add a mounting hole. Small builds can leave it at that. Paranoid people can add a brace at a 45. Other people can attach another piece of conduit. Large builds can add a wire to the other corner.

One of the key design pieces is how you mount it perfectly square, especially if it will have the conduit continue through the table. I remember I printed the first 5mm of the feet to use as a guide to get the holes in the right place. It would be nice if there was something that would hang over the edge, and register to the corner, even if it’s just for drilling. Sort of like the jigs used to mount handles on cabinets in the right place.

I have considered using 3/4" threaded pipe flanges and 4" pipe nipples for the corners.
http://www.homedepot.com/p/VPC-3-4-in-Black-Malleable-Iron-FPT-Floor-Flange-16-521-604/205955667

Jim has my idea, except I’m thinking of using either large diameter threaded rod, or a long bolt with an adapter plate to do the fine adjustment for leveling.

How feasible would it be to replace the two tubes on the Z axis with four 8mm smooth rods and either linear bearings or brass and graphite bushings? Seems like that wouldn’t affect the weight much and would increase the rigidity. I don’t know if dust would then be more of an issue though.

I’ve replaced original legs with this design

I’m listening and thinking through all of these critically. There seems to be no issues at all at 4" and under, which is ideal and what was intended. But I ripped apart one of my machines to try a few of the ideas out.

I appreciate the help!

I think we’re overthinking it. I don’t have the parts to check, and I’m pretty sure I have the scale off on my example picture, but wouldn’t this work? Two pipe flanges, and a section of pipe. Use a pipe clamp(red line) through two of the top flange bolt holes. The bottom flange gets screwed to the table. The pipe is screwed in loose, so we can turn it like a turnbuckle, this will move the top flange up or down, depending on which way it needs to go. Once you have it where it needs to be, a dab of superglue, or even some silicone will fix it in place. Shouldn’t need to go crazy with the glue, it’s just to keep the pipe from turning from the vibration.

I love the CGI on that!

I had originally looked into those flanges but they are something like $8 each.

Were any of you around for my 2nd or 3rd version of the legs? They were printed and I had intended on making them parametric.

That’s a lot of plastic!

It’s hollow.

But still a lot of plastic.

@Barry: that is why I was asking for a double tube mod for each axis. It would greatly limit the flex and would allow people to put heavier stuff on the gantry. In my opinion this is the only “flaw” to an otherwise great design,
So my point is not to “add more crap” to the Z axis, it is to strenghten it to allow people to “add more crap” if they need to. Like a more powerful router motor, for instance.

@vicious1: those printed feets that you posted seems to be a good solution. What was the result of your tests?
The only issue I see on the pictures are:
-the little hole on the top is a bit small. The bigger bolt you can fit, the better.
-how do you attach it to the table? The way it is attached will be critical, it needs to be super strong.

You would get more more rigidity in a smaller area with a larger diameter tube instead of 2 tubes with much less hardware involved. The LowRider is supposed to fill the need for a larger machine gap instead of trying to maintain a 4th size machine. If I do a large diameter build I would have to know that size is available everywhere in the world, but then why not just the lowrider?

Do you really need more power? I can’t bog down my 660 even a little bit. I smashed it into some aluminum and damn near broke my MPCNC because the dewalt just kept chewing. The dewalt will easily rip apart the machine before it bogs.

Those legs were from 2 years ago, they worked great. The hole in the top matches the corner bottom same as the current part has, and some glue in the gap is still ideal there. The table screws were at a 45 degree angle you can see one of the holes in the pic.

Sort of off topic but I want a sanding bot… I hate sanding, after spending 12 years in auto body If there was a machine that could sand for me, I would build it.

Quick question, I have just seen another comment about “shapeoko being so much more rigid compared to the MPCNC, but that’s why it cost thousands” I have seen this so many times. Along with other comments from people that do not own one saying how weak it is by its looks alone.

I promise I won’t get mad at anyone or hold it against you but has anyone ever tried the two machines, are the other ones that much better? I honestly can not imagine if the had the same cutting volume there would be much rigidity difference. Aluminum is pretty flexible, the extrusion is not ultimately rigid. It was designed as a quick building platform like an erector set not as a rigid rail, not even getting into any other design aspects. Is it that people assume that it is super strong or is it actually more rigid? I have never been able to touch a shapeoko or xcarve, I have tried to wiggle a few others.

This machine does what I need it to, I can cut everything all the way up to aluminium. A steel cutting machine is not on the near horizon, so the only thing I can see to do is increase rigidity and speed without tripling the price. Hence the leg questions, but I am starting to feel like it would be better if I just put a suggested maximum z length instead and focus on the next improvement.