New Design/Build: CNC router (steel plate construction) + Raspberry Pi

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Originally Posted by mactec54

cmadki4

Now just bend the ribs down and make longer where needed, to run down through the center of the Linear Bearing mounts and you will have a good rigid side plates

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Smart. Like so?
Attachment 373844

I'm also thinking about the offset gantry support/upright plates and whether it needs to be offset at all (it runs out of linear guide before it runs out of table). Simplify it and then box in the plate? Just a thought...
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Not sure why I thought this was aluminum. I must be getting tired. Long day.

Even though, my previous comments still stand. It's still not a good design.

With steel, I'm guessing you may find it hard to find plate that is very flat to begin with. That may complicate things further.

Laser cut aluminum with ribs and epoxy granite filled, using rivits and glue or tapped and bolted holes to minimize distortion. That's where it's at. If you can't bring yourself to do that, a square steel tube is a better choice.

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Originally Posted by mactec54

My post # 8 already said the same as what you are trying to say, when a piece of bar is add in this way it is called a Rib, it would help if you understood the correct terminology, of fabrication, here is a little information on Ribs

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I know what gussets are. What he drew may be ribs and not actually what I suggested. I suggested gussets because that is what most guys at the zone seem to wind up using. Boxed elements were also suggested. My point was that a flat plate is structurally insufficient. Especially thin plate being used here. Since the whole design revolves around single laser cut plates, the next logical step for him in this design is flat bar support to back the side plates. That is what he has drawn.
That is probably sufficient for this design, however I would not build the current design. I would likely use boxed or plate weldments to build off of. Then of course, we are talking about a different design and another thread.
That is not to say this base design will not work or meet the OP's need. Just that this design could use some help.
Personally I would scratch the entire gantry now that I have seen its design.

cmadkik

You are making good progress, still with the support plates, make where the bend is into a radius, not a sharp corner, from 2" to 4" radius, the Ribs can also have a 45 degree cut on the ends, not to a point leave at least 3/8" flat

Next a look at the Beam for some change, the main base frame is fine the way it is, the base is a good example of how to construct a torsion box in steel

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Originally Posted by NIC 77

That's probably the worst advice I've seen on this forum. 5lbs is nothing. Aluminum Profile (I assume you mean T slot) is a better choice Than a 3/8" aluminum I beam with lightening holes.

Really, you've made this design and it cuts aluminum well? What a load of hogwash!

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He is using all steel, not aluminum

And you would know, have you even built a machine, or just dreaming about it

I have designed and built hundreds of machines, I have not only made similar designed machines, I test the machines, to see what they can do ( if the spindles are suitable ) my favorite is cutting 420 Stainless steel, I also make spindles, for cutting steel and aluminum Etc

This machine I built some years ago, was able to cut any kind of metal, and not like the chewed up cuts you see people trying to do here on the Zone, this was a 24" X 18" X 6" single Ballscrew, I build machines all the time so no what works and what does not, most who comment on Here have never built a serious machine

https://www.youtube.com/watch?v=iTBr_rJXZSw

cmadkik

I should of added a sketch of the Rib Design

Since you built a good solid torsion box base on this, you can do the same thing for the gantry sides and get by with 2 1/4" plates. For the bolting areas, use solid plate. Everywhere else just attach plate supports like the table. Straight flat bar members. No bends to contend with. Use epoxy and get by with only a few fasteners.
Consider the very same approach on the gantry beam.

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Originally Posted by LeeWay

Since you built a good solid torsion box base on this, you can do the same thing for the gantry sides and get by with 2 1/4" plates. For the bolting areas, use solid plate. Everywhere else just attach plate supports like the table. Straight flat bar members. No bends to contend with. Use epoxy and get by with only a few fasteners.
Consider the very same approach on the gantry beam.

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Use epoxy, why not throw in some duck tape as well;)

The whole design, would have to be changed to have any benefit of having the gantry sides turned into a box, or torsion box style, the weak link is where and how the linear Bearings mount, this determines the type and design of side plate supports

What he has is more than enough with the Ribs add, to do anything he was planning to do

Duct tape has it's uses. ;)
As does epoxy. A good use is to assist mechanical fasteners and reduce chances of member movement due to loose fasteners. Locktite (thread locker) helps too of course.
His design criteria so far has been laser cut plates bolted together. To get the most strength and rigidity out of that would be the goal I think. Torsion box approach will achieve that and still remain relatively lightweight and about the same footprint and work area.
Or leave it as designed.

First off i realize that this is a smallish machine which is a big factor in the discussion. I also understand that part of the goal here is to use materials that are on hand. That being said i really would try to avoid a welded up iBeam or an i beam of any sort for the gantry beam.

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Originally Posted by cmadki4

Here's a look at the gantry construction. In blue the 1/4" thick on top and bottom and 3/8" in the middle. Beam length is 811.35mm.
Attachment 373816Attachment 373818

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Id most certainly would reconsider the I beam in this design. The short span might help but the issue is torsional resistance. Since this is an uncommon design the only way to know for sure what your beam will do is to run calculations on the mechanical design. Or build and test it.

If you have the materials you could just as easily do a box beam. In either case though you would need to weld the beam up and then have to deal with the distortion. I would expect the distortion to be far worse than what you would get on the machines base likely requiring post welding heat treat and machining.

Frankly it would be far easier to simply buy a square beam and save existing materials for the rest of the machine.

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@wizard: Nice find. I kind of implemented some of the Tabandslot.com ideas, but could clearly do with some refinement. Watched a few of their videos. Their design/assembly methodology definitely inspires some confidence I can keep these pieces relatively flat/straight.

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Tab and Slots approach is very interesting to say the least. You would likely get good results for the base of the machine but im not getting good vibes about the approach for the gantry. It comes back to being able to resist torsion.

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And back to the gantry supports...?
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I keep fidgeting with a 3/8" thick scrap. I just can't imagine that much deflection while cutting wood or aluminum (6061 and 5053). But I'm more than happy to add rigidity if it doesn't make any major compromises elsewhere.

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As others have pointed out weight is generally a good thing as long as you don't go too far. Your gantry can easily weigh 200-300 pounds without significant problems moving it. This assuming low end "hobby" like controls. The weight of the base can be as heavy as you can handle. The heavier the better. If the base isn't heavy it will have a tendency walk all over as the gantry and y axis are slewed around.

One guy posted a video of a half finished machine with a light base on wheels running the gantry back and forth. It was a bit funny but certainly demonstrated for every action there is an equal and opposite reaction.

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The gantry supports don't necessarily need to be offset. They could be more rectangular. Then I could box them in.

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Generally built up boxed sections are easy and provide good results.

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This isn't a very big machine:
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Yep, i realize it is small but that doesn't dismiss the stiffness issues some of us have pointed out. For instance the gantry side plates others have focused on would be a problem no matter the size of the machine. Note too this isn't a huge problem by any means as you have plenty of suggestions that can address the issue.

You could do the side plates without ribs or box sections if you had thick enough plates. However 1/4" is a non starter in my mind and even 3/8" is too thin for comfort. This the need to supplement the plates in a way that increases stiffness.

By the way do you have access to machine shop equipment? I just see a need for a milling machine at some point in this build.

Wow, really nice looking workmanship in the photo and video. If you made that then you know how to build things very well. I'm not saying you're a good designer, but certainly, a great fabricator.

I'm guessing that is much thicker than 3/8" plate you have used for the gantry as it is bolted in from the top and bottom. Clearly the top and bottom plates the rails are mounted to are larger than 1/4".

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Originally Posted by mactec54

He is using all steel, not aluminum

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Yep, I was very tired last night when I look through this. I already mentioned this.

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Originally Posted by mactec54

And you would know, have you even built a machine, or just dreaming about it

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I have built a machine. It wasn't very good at cutting aluminum. I am correcting those issue on my current build. Also I have looked at many build logs and videos to see what actually works, and I have figured out the math on acceleration and torque including inertia looking at different gantry weights for different designs.

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Originally Posted by mactec54

I have designed and built hundreds of machines, I have not only made similar designed machines, I test the machines, to see what they can do ( if the spindles are suitable ) my favorite is cutting 420 Stainless steel, I also make spindles, for cutting steel and aluminum Etc

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Perfect. Show me a video of the similar machine you made cutting stainless, and I will be quiet.

Here's the thing. This is a typical rookie mistake. To design the table with a torsion box, then to have the gantry as an I beam with lightening holes cut out in it. 5lbs is nothing. He should be adding weight on. Alot more. It's a small machine with two motors driving the gantry. It's such a shame to see the potential of having laser cut parts being wasted on a design that could be so much better, and the OP has already said he wants to cut aluminum.

I stand by my statement that the advice you gave previously was the worst I've seen on the zone.

A laser cut steel gantry to make a machine to cut aluminum should be built like a torsion box, with internal ribs, ideally filled with epoxy granite, and the nice thing about using a laser is that you could have it all cut out nicely to hide the ballscrew inside the gantry. So much potential to make something awesome and high performing here, and IMO, you are leading the OP down the garden path so to speak.

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Originally Posted by NIC 77

Wow, really nice looking workmanship in the photo and video. If you made that then you know how to build things very well. I'm not saying you're a good designer, but certainly, a great fabricator.

I'm guessing that is much thicker than 3/8" plate you have used for the gantry as it is bolted in from the top and bottom. Clearly the top and bottom plates the rails are mounted to are larger than 1/4"

I have built a machine. It wasn't very good at cutting aluminum. I am correcting those issue on my current build. Also I have looked at many build logs and videos to see what actually works, and I have figured out the math on acceleration and torque including inertia looking at different gantry weights for different designs.

Perfect. Show me a video of the similar machine you made cutting stainless, and I will be quiet.

Here's the thing. This is a typical rookie mistake. To design the table with a torsion box, then to have the gantry as an I beam with lightening holes cut out in it. 5lbs is nothing. He should be adding weight on. Alot more. It's a small machine with two motors driving the gantry. It's such a shame to see the potential of having laser cut parts being wasted on a design that could be so much better, and the OP has already said he wants to cut aluminum.

I stand by my statement that the advice you gave previously was the worst I've seen on the zone.

A laser cut steel gantry to make a machine to cut aluminum should be built like a torsion box, with internal ribs, ideally filled with epoxy granite, and the nice thing about using a laser is that you could have it all cut out nicely to hide the ballscrew inside the gantry. So much potential to make something awesome and high performing here, and IMO, you are leading the OP down the garden path so to speak.

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You have absolutely no clue what you are talking about, keep doing the numbers, and looking at other builds that will get your machine built, you have to design it your self, you have not shown anything here on the zone except numbers, that most high school kids can do

Again a big rant with zero input, because you have nothing to give, this post here tells a different story, he is cutting aluminum, on a not such an ideal machine for aluminum cutting, ( Chinese built x6-2200L similar to the common 6040 ) and making a great job of it, this machine that he is using is a light weight, compared to what cmadkik has started to design here

http://www.cnczone.com/forums/diy-cn...752-cnc-8.html

I have not got to cmadkik machine Beam as yet, it does need some changes

UPDATE: I was able to acquire some 80/20 extruded aluminum. 15 series 3030S. So, I'm revising the design to be built around those extrusions. Work in progress, but don't know how much more I'll be posting.
Attachment 373890

Now that is a lot more common design. Far easier to build too. No where near as much machining to do. Think CNC kit.
The very first thing I would do on that one is to move the bed rails to the top of the profiles. Then you have both sides of the trucks bearings supporting the load. Then on top of the horozontal plate that the bearings mount to, you have an edge either inside or outside of the gantry risers to use gussets.

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Originally Posted by mactec54

You have absolutely no clue what you are talking about, keep doing the numbers, and looking at other builds that will get your machine built, you have to design it your self, you have not shown anything here on the zone except numbers, that most high school kids can do

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I haven't seen anyone else here on the zone do the math properly. You're right it's not hard, a high school kid who is good in math could do it. That's why I posted sample calculations and equation sources in several places to show people how to do it for themselves. Clearly this is something that you don't understand, or you would have realized that some extra weight and stiffness is a good thing.

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Originally Posted by mactec54

Again a big rant with zero input, because you have nothing to give, this post here tells a different story, he is cutting aluminum, on a not such an ideal machine for aluminum cutting, ( Chinese built x6-2200L similar to the common 6040 ) and making a great job of it, this machine that he is using is a light weight, compared to what cmadkik has started to design here

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Why are you bringing him into it? Is that a gantry mostly consisting of a 3/8 steel plate with most of it gone to save 5 lbs? Nope. Keep it relevant.

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Originally Posted by mactec54

I have not got to cmadkik machine Beam as yet, it does need some changes

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Oh, so NOW it needs some changes and you just haven't gotten to it yet. Whereas before it was......

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Originally Posted by mactec54

The way that he has this designed, is more than what is needed, having it as a solid plate would be just add more unnecessary weight with no purpose

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and

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Originally Posted by mactec54

Stick with what you have, 5 lbs. is a lot when you start moving it around, the design is more than what is needed to do the job, and much better than what most use, ( Aluminum Profile ) the webs are large enough, for support, and the top and bottom plates add the strength that is needed, I have made the same design in aluminum and it works very well

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IMO, you give bad advice, and then resort to personal attacks when someone calls you out on it, instead of actually considering what was said, and keeping the response relevant. There's too much arrogance there for me to deal with.

You could have just reconsidered your opinion, that would have been an easy out. All respect for you now....poof.....gone.

Oh, and the bit about adding stiffeners to the side plates, that I agree with.

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Originally Posted by cmadki4

UPDATE: I was able to acquire some 80/20 extruded aluminum. 15 series 3030S. So, I'm revising the design to be built around those extrusions. Work in progress, but don't know how much more I'll be posting.
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That's a way better idea.

Are you planning on running your ballscrew in between the extrusions?

As a suggestion, you could add an aluminum plate to the back and bolt it to the back sides of both T slot pieces. You could also add some internal aluminum ribs and fill the T slot with epoxy granite to dampen vibrations.

If you are going to run the ballscrew in front, you could alternatively put plates on front and back and ribs inside and fill all the voids with epoxy granite. I bet that would handle aluminum well.

I agree with adding gussets to the side plates. Big ones.

The last suggestion is to consider your ballscrew lead. This is a small machine, so 5mm might be fine. Also, it depends on the motors. A_Camera is running 5mm ballscrews on his build and they are plenty fast, but his motors are better than most at higher RPM's. Do you know what your goals are for top speed and acceleration on this?

If you find me a torque vs speed graph for the motors (at the voltage you plan on using) and let me know the lengths of the ballscrews, I can make you some graphs where you can see the effects that different gantry weights and ballscrew leads will have on your performance. Of course in practice, it may not match exactly, so you have to give yourself some wiggle room from the calculated, but you'll see for yourself the difference.

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Originally Posted by NIC 77

That's a way better idea..

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15 series 30/30 extrusions, are better than his steel frame design, what are you smoking

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Originally Posted by mactec54

15 series 30/30 extrusions, are better than his steel frame design, what are you smoking

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They're not better than a proper steel frame design, but relative to the first I beam design consisting of a 3/8 flat plate, heavily cut out, and two 1/4 inch plates on top and bottom, yes, it's a better idea. Those are 3" by 3" extrusions, yep, that's a better idea.

Also, he can bolt some plates on front and back and add some ribs and fill with epoxy granite, as I suggested, or make other changes that LeeWay suggested, or think of something on his own, etc.

Even better would be to use solid aluminum, perhaps 3" or 4" x 1" with 3/8" or 1/2" plates bolted on front and back and ribs in between and the voids filled with epoxy granite. That would be like a little aluminum torsion box and could be bolted together without welding. He could even incorporate the gantry risers into that design, similar to what linux_fan did. You could do something similar out of steel but it might be hard to maintain the same degree of flatness, and I don't know what access he has to machinery.

He could also use some square steel tube, and that would be better than the T slot on it's own. Of course, with each design change, his ability to build it with the tools he has and how much time and money he wants to spend should be considered and only the OP can answer that.

There are all kinds of things you can do, all kinds of design variations, what he has now isn't the best, but certainly better than what was by a long shot.

Perhaps you can reconsider and make some suggestions, I have no desire to spend any more time propagating the discord between us. The only thing I have a problem with is I beams with extensive cut outs and 1/4 inch plate on top and bottom.

And no, I don't smoke any illegal substances, or even recently legalized ones, although I may have a few beers tonite. :cheers:

Just did a FEA Analysis on just the 3/8 plate that cmadkik had in his first lot of photos, with some close dimensions to his, the plate by it's self is 19.8 times more than what is needed to cut aluminum the tested steel plate as in snip is 3/8 x 8 x 34 sitting of course in it correct orientation for testing, even with the cutouts, the aluminum extrusion buckled quite bad under the same loadings,

As I said in the first posting the gantry Beam was fine, it can have some refinements, mostly how the linear rails are mounted, and how it is all put together

I didn't really have a problem with the first beam design being sufficient to cut aluminum. My main issue was with fabricating that beam. It would take a lot of work machining, drilling and tapping the parts to assemble this beam. If it does warp when laser cut, then there really isn't much he can do to straighten it out during assembly of that beam. We all know that mounting profile rails directly to a warped beam is unwise. You could instead purchase an I beam or C channel. Bolt additional pads to mount the rails to and have them machined flat.
Don't get me wrong. It all can certainly be done as designed and it can be done well. It's just not a design that I would recommend given the difficulty of fabricating when off the shelf steel profiles could be used with as good or better results.

And as for aluminum extrusions being sufficient, they most certainly can be. They are also not nearly as challenging to fabricate a machine with.