Starting to design out my build, looking for critique

[AndyUK]

Normally I would now lay-out what was on my mind, when it comes to next steps, but I cannot come up with anything concerning the CAD model, it looks pretty much done to me. What I need to now look into, however, is the electronics side of things: Find out what I still need in terms of controllers, motors, Power delivery, etc. and get some rough pricing, as well as model it into the CAD as needed. Where would be a good way to start here? For the gantry and machine design there were some helpful collection threads on here, comparing different gantry designs, for example. Is there also something like this when it comes to the electronics?

Suggest you start here:

http://www.mycncuk.com/threads/1524-...otor-do-I-need

Once you're up to speed with the description, open the spreadsheet and customise to your needs (its setup for a smaller machine). Find reasonable values for your cutting forces and repeat for each axis in turn (increasing the moving weight as you go - ie. Z has a small moving load, Y has slightly more, X even more). I rebuilt the sheet from scratch to show all axis at once with individual inputs which helped.

Next is the leadscrew calcs - lookup typical efficiencies of the system you're using, and what each of the measurements mean. This will give you screw inertia and critical speeds. From your screw pitch, you then have your maximum permissible speed on that axis. Tailor the ballscrew configuration until you're happy with the maximum speed.

Now you have to decide what max cutting speeds and rapid speeds you want. I aimed for 5m/min rapids - some people here can get 7.5m/min. Cutting speed depends on the material (as does the cutting force).

Then you can start plugging motors into the spreadsheet. Find a few example motors online, look at their specs, and put them in the sheet taking best guesses where needed. Then play with your power supply settings, and the sheet will tell you if the motor is up to the job or not. This is how I came to the conclusion that NEMA23s on each axis were more than suitable for my application.

The motor drivers are then somewhat dictated by the current required, and the PSU is calculated by summing the maximum currents on all axes, then multiplying by a stepper usage factor (I think its 2/3rds? but you'll find this in the Power Supply threads). The voltage for the PSU is dictated by the inductance of your motors - the sheet will tell you an ideal voltage, and the drivers will have a maximum voltage - aim somewhere between those two allowing for variations in mains supplies.

Rest of the electronics are essentially personal preference. Many ways to skin a cat...

[Chrono]

I have been dabbling in the motor sheet, and found motors that would work, but i hit a couple road blocks...

The weirdest one was not finding german stores that sell steppers. I could only find one real store, that sells for okay prices, but even that one only sells to companies. The general electronics sites here, only sell steppers for horrendous prices, and only around about 10 different models max.

Another issue I was having with the sheet was the cutting forces and speeds. Is there a good summary of what to aim for, a collection thread of sorts? As it stands I am kind of lost here.

What that post also left open, is what the different types of support (like supported-supported) actually are. What would a ballscrew with its two bearing blocks count as? Supported-Supported?

On the upside, I could find motors that work for the X and Y axis (At the store that only sells to companies). This one in fact: Link. Using the weights I calculated, those motors would manage to get me 7.5m/s rapids as long as the axis is 1.5m long at max, as well as 2.5m/s cutting with 50N of force, a value that i chose at random judging from the values mentioned in the post.
I did not yet look at a NEMA 23 for the Z-Axis, because of the aforementioned problems I was having with the spreadsheet.

I also attached the spreadsheet with my values, as well as another spreadsheet I used to calc the masses, so that it becomes more transparent.

Another question concerns the other electronics. At this point i am wondering what I need in total. As far as I understood, the following is needed (mostly going off of Joe Harris' Build http://www.mycncuk.com/threads/4513-...0655#post90655):

• A PSU
• A Controller
• A driver per stepper
• A VFD
• A Water Pump
• A Spindle

Am I missing something here? Also, again, is there some kind of collection post of different options for this?


Now, for a bit of a curveball... The problem I am currently running into, is that I am not going to be at the company I am currently at for much longer. They do allow me to use their hardware, however, which would come in really handy, building the machine. I am wondering now, if it would be okay to start ordering parts and building the frame/gantry now, while I still have access to the tools and the mechanical engineers willing to help, in parallel to getting the electronics planned out, or would should i wait to be done with that?

I also want to take a quick second here, and really thank you for all the help you have been providing me. I don't think I could have been here without all of the assistance you provided. Thank you a lot!

[AndyUK]

Will reply with a more detailed look at your spreadsheets when I get time, but to quickly answer a couple of points:

The weirdest one was not finding german stores that sell steppers. I could only find one real store, that sells for okay prices, but even that one only sells to companies. The general electronics sites here, only sell steppers for horrendous prices, and only around about 10 different models max.

As you're in the EU, pretty much any EU store is an option. CNC4YOU.co.uk is where I got mine, Zapp Automation also seem pretty good.

What that post also left open, is what the different types of support (like supported-supported) actually are. What would a ballscrew with its two bearing blocks count as? Supported-Supported?

So here you may need to read up on ballscrews and their mountings. Free means no support (an end which is floating in mid air), Supported means on a bearing but with no axial constraint (like a BF mount), and Fixed means a bearing that can take axial force (like a BK mount). Typical configuration is Fixed-Supported, with a BK at the motor end and a BF at the other. You'll need to know this when ordering your screws, as they need to be machined appropriately.

Another question concerns the other electronics. At this point i am wondering what I need in total. As far as I understood, the following is needed (mostly going off of Joe Harris' Build http://www.mycncuk.com/threads/4513-...0655#post90655):

• A PSU
• A Controller
• A driver per stepper
• A VFD
• A Water Pump
• A Spindle

Am I missing something here? Also, again, is there some kind of collection post of different options for this?

Oh wow. Theres like a billion different options. Finding a path is tricky! Ultimately, you need some way to turn GCode into motion.

That often starts with a PC sending the Gcode to a parallel port - but PC's aren't great at realtime and they're not often made with parallel ports these days, so some kind of motion controller is often used to simulate a parallel port and deal with the realtime aspect. Recommend ethernet variety. Then you may or may not need a breakout board depending on which controller you use - a UC300eth for example just gives you five headers with lots of pins, its nicer to have a board like the UB1 attached to output all those pins nicely and deal with a few other things like relays.

Next, the controller sends off pulses to the drivers. Depends on the motors you choose, but the Leadshine AM882/EM806s are popular around here. Nice to have a decent current range and voltage range that are applicable to your motors, and missed step protection is nice. As you point out, one driver per stepper.

PSU to power the drivers. Calculate the right voltage and current, then size appropriately. Some folks like Joe build their own, its not too hard. Other PSUs will be needed for the sensors and auxiliary components, you'll have to draw up a diagram to figure out what you need. Typically a 24/12/5V, or maybe even multiples.

Spindles and VFDs often bought together from China. Recommend ER20 or ER25 for the larger tooling. Water cooled will be a lot quieter. Some even come with a pump - to be honest, it doesn't seem like the cooling requirements are massive, an aquarium pump will probably do.

Other electronics - Circuit Breakers, Contactors, Switches, Relays, loads of wire, Limit switches, Home switches, fans.... the list is endless. Don't forget software, and somewhere to keep all these expensive electronicals.

Now, for a bit of a curveball... The problem I am currently running into, is that I am not going to be at the company I am currently at for much longer. They do allow me to use their hardware, however, which would come in really handy, building the machine. I am wondering now, if it would be okay to start ordering parts and building the frame/gantry now, while I still have access to the tools and the mechanical engineers willing to help, in parallel to getting the electronics planned out, or would should i wait to be done with that?

Up to you. If that was my situation I'd probably be making a start while I've got the opportunity to utilise the expertise, but be prepared to backpedal slightly more than if you've got a plan sorted from the start.

[Chrono]

More progress, at least in the design department!

I did decide to design out the Z-axis a bit and plan on how to build it up, especially since one of my coworkers asked me the fateful question of: "Well it is technically possible to manufacture, but are you sure, that you can actually put it together like that, when it is in front of you?". With the earlier draft, I have no idea if that would be possible to actually assemble without a huge hassle, so I thought about it and came up with a better design, using screws and bent steel plates. The pink plate I will probably be changing out for a thicker aluminium one. Also something of note is that the bends and such are not accurate. I simply don't have enough time in Fusion's Sheet metal work-space, so I just went with the default settings for convenience's sake. After taking another look at your machine, since I was asking myself how to get more length out of the Z-Axis, I will probably also switch the rails to be on the sled and the bearing blocks to be on the gantry, like you did.



I also changed the size of the machine in my Fusion design to reflect my "updated" plans for size. This broke a couple things that I did not yet get around to fixing, like the floating plates and angles, as well as those two Z-Axis bearings floating in the middle of nowhere. The original size was guesstimated around 1m x 0.8m x 0.2m while I was still messing around with the base design. The "new" size I plan on having is: X: 2m, Y: 1m to 1.2m, Z: ~0.3m to a max of 0.5m. I am not quite sure about what a good measurement for the Z-Axis would be, so if there are any values that have generally found agreement in what not to exceed, let me hear it :D



For the linear motion setup, I am planning to use Chinese 1610 Ballscrews and HIWIN-style rails (note: not original HIWINs). The reason for that is that I started pricing out the build to where I now have a pretty "final" (well, as final as it can be at this stage) price for it, bar the uncertainty of import tax and the like. All in all this puts me at around a 3k € to maybe 3.5k € total, if taxes end up really high, and of course, planning in a cushion in case something goes wrong. The difference of the Chinese rails to the original ones is quite significant in that, however, with the bundle of ballscrews, ballnuts, BK and BF blocks, linear rails and slides, being 50% more expensive, when using original rails, with all other things being constant. But I still have to ask: Are those rails okay to get, or are there any known problems with them, accuracy-wise or otherwise?

I have also checked these lengths in the motor calc spreadsheet, and with the 2m axis, I would now be down to 5.2m/s rapids from 7.5m/s. Should I reduce this to get back up, or should I be keeping it? My reasoning for going as big as possible, is to get the "best value", so to speak. I don't want to be caught standing there with my pants down, when a project requires me to have big machine. Alternatively I could also go with 2010 ballscrews and up-size my stepper on the X? I might need to properly calculate the increase in price for that out.

Another thing that caught me off guard is just how much the motion controller, and especially that breakout board cost! 300€ for a control board and its breakout sound properly astronomical to me :D But alas, I also know not to skimp on the important bits.

With the leadshine drivers, and a spindle, that should nearly do it for electronics. Speaking of spindles, however, I was looking at this 2.2kW one. Is 2.2kW a good amount of power for my uses (wood, plastics, some aluminium, PCBs)? They also do carry a 3kW model.

Regarding Sensors, so far I have only been able to think of Endstops and homing switches. What else would I be needing? Another question that was on my mind, is why I need homing switches? Does the "home" need to be different from {0,0,0}, or am I missing something here?

You also mentioned software in your post. I know of Mach 3 and I also saw that they now make Mach 4. Are there any others out there, or are these ones the ones to get?


Now, on a completely new note: I have finally taken into account that I still need a table. I have chosen to keep this one on the back burner for a bit, until I got a preliminary pricing done for the machine itself, and I am now considering how to do this. Most machines I have seen so far, are using a steel table, that even reaches above towards the Y-Axis, where I have those big plates. Since I am using aluminium profiles already, I was thinking that I could just buy some more and make the table out of that. This would also allow me to slightly redesign my machine and allow for a similar design like yours, for example, with the raised sides. I am guessing that would be a huge plus in terms of rigidity, compared to my steel plates approach? I would, of course, loose some access and some space on the sides, accounting for the width of the extrusion, but with how wide the Y-Axis sled is, that should not be a problem in terms of actual cutting width loss, if executed correctly.

[Clive S]

I have also checked these lengths in the motor calc spreadsheet, and with the 2m axis, I would now be down to 5.2m/s rapids from 7.5m/s

You could also think of using rotating ball nuts 2Mtr is a long way with 16mm screws

[Chrono]

You could also think of using rotating ball nuts 2Mtr is a long way with 16mm screws

How would I mount the rotating nuts? I guess I would need the motors on the gantry then? Would that also mean that I would either need an elaborate timing belt setup spanning the gantry, or use two motors?

I can also just use 2010 or 2510 ballscrews and get a stronger motor for the X, which is something I am actively thinking about. According to the motor calc sheet, the Y and Z are perfectly fine as is, at 7.5m/s rapids, using 1610 ballscrews.


On another note: After thinking more about the changes I talked about and talking them, and other things, over with my colleagues, I am remaking the CAD file from scratch. While doing that I am also reworking everything to be 100% parametric, which is taking a while, but is paying off massively. Basically fixing mistakes made the first time around.

Current progress is the following: The table and X axis are done, except for the X axis ballscrews. The Gantry and Y axis are complete. What is yet missing, is everything concerning the Z-Axis, pending a complete revision, Motors and timing belts, and E-chains, that I want to account for. All in all, it is progressing nicely.

[Chrono]

Hey everyone! More progress on the redesign. I sat down and actually worked on it everyday this week, and got some real progress done, finally. I am much more satisfied with how that one turned out, compared to the old one. Here is a side-by-side:


It is probably obvious, but the old one to the left, the new one to the right. This will be the convention for pictures for the rest of the post as well. (On a side note: The blue extrusions are going to be changed from 45x90 ones to 45x45 ones, to save money. I just have not gotten around to fixing them in CAD, since they were pretty low on the list in terms of priority)
While being at it, I also changed a whole couple of things: Like the Z-Axis

New:

The Z-Axis got completely changed. Where it was a complex part before, it is now a rather simple bent sheet steel piece. The motor is now also affixed to the Z-Axis itself, and is moving with it. This is to keep the Gantry-side Y-Axis sled small. It also theoretically means, that I don't need to change anything but the Z-Plate, the rails and the Gantry sideplates to add more Z-space later on, if I ever decide on it. All in all, I like the design change of putting the bearing blocks on the Gantry sides, and the rails on the Z. Allows the parts to shrink a bit. That is one design change I picked up from AndyUK's build. The Ballscrew is also mounted on the moving Z-Axis, with the Ballnut being fixed on the Gantry Sled. One question that I still have, however, is how the cutting spindles actually get mounted to the Z-Axis. I understand that the spindle itself is mounted in the red aluminium ring, but how is that ring mounted? None of the pictures I could see in the offers showed any mounting holes. Are you meant to drill those yourself?

The Gantry itself got a revision as well!

New:

The obvious thing is probably the size and shape change. I went from an L-Assembly to a C-Assembly. This is so that I could move the rails up front, which should not only give me more rigidity overall, but also allowed the massive simplification in assembly for the Z-Axis and Y-Axis Sled. This is one change I really took a liking to.

Something that was not quite obvious from the last post, but was already in it, is that one of the side plates fixing the gantry beam to the X-Axis is much thinner than the other one, in this case the left one is thinner (3mm of steel) than the right one(10mm of steel). This is to give the machine a way to have a bit of play, should something not be fully aligned, and off by a tiny bit. Another measure to the same effect has been brought up by my colleagues multiple times now: To only put linear rails and bearing blocks on one side, and have the other only constrained against translation/force, not torque, and we finally came up with a workable example, I want to discuss here:



Let me explain. The plan would be to put the second linear rail on the lower extrusion on the right (looking from the front of the machine), and have both of them on the same side. Then, instead of a rail, have a supported smooth steel rod, and a cylindrical type round linear bearing on the left side, to replace the rail. That way, the linear bearing still constrains the movement on the translational axes and takes on the forces, but it would permit torque, which would fix the problem with it being statically overdefined. What do you guys think of that? None of the Logs and posts I have read here, so far, have reported any real problems with any of this, but one of my colleagues who has had contact with similarly built machines, with a different purpose (cannot exactly remember) is bringing it up as the thing they and their competitors did, to avoid problems in the same vein. And looking at the budget, one rail with linear bearings should not be the point that bankrupts me here :D

Another question I am having is regarding the long ballscrews on the X-Axis and the motor calc sheet. As discussed way earlier in this thread, I want to stay with a single stepper for the X axis, even though I have two ballscrews, linking them with timing belt. Now my question is, in the Calc sheet, don't I need to input a "times two" into the calc of the torque needed to spin the ballscrews, since the stepper needs to drive both of them at the same time? Since I want to go to 2010 or even 2510 ballscrews, that is one hefty variable to think about. From my initial messing around, I can either go less fast with a 2010 ballscrew (Around 6.3m/s rapids) with a weaker stepper, or find a much stronger one to drive the 2510 ballscrew at the full 7.5m/s rapids. Of course, cutting is another thing entirely, and I am still not quite sure what speeds to aim for here, but for reference, I have managed to get around 2.5m/s with 50N of cutting force, in my testing. Another way would be to stay with 1610 ballscrews and scale the X down from 2m to 1.7m, but that is something that I only want to be doing as a last ditch effort, so to speak.

And another on the ballscrews: Would I just mount normal timing belt pulleys to them, to connect them to the motors, or would I need special machining or parts here?



Regarding the Electronics: other than the Steppers, I have also been looking at all the other electronics. And I think I have it down to the following:

• X-Axis Stepper: Still looking
• Y-Axis Stepper: ST8918S4508-A
• Z-Axis Stepper: ST5909M2008-A
• Stepper Controllers: Either Leadshine AM882s or EM806s times three, after AndyUK's recommendation, still trying to figure out the exact differences there.
• Controllers: Either the UC400ETH or the Smoothstepper ESS, although I am still dabbling about the electronics section of the forum. I don't think that I will be getting breakout boards, since I can easily deal with electronics, and just soldering the proper cableing sound much more reasonable to be, instead of buying a 130 pound breakout
• The VFD will likely be a YL620-A packaged with a chinese 2.2kW watercooled spindle, alongside a water pump
• And finally: six microswitches for end stops. A thought here: would there be any profit had from using proximity switches?

Regarding the choice of controllers: I had a quick dabble with the Mark 4 demo, and as I understand, it is pretty much indifferent to the exact board I choose, and the board itself does also not really need to be wired up in any special way, since I set all the necessary port/pin assignments in Mach 4 itself (granted that I match input pin to input, output to output, etc.)?

When it comes to schematics: I just installed AutoCAD today to get something done, and thankfully I have got some people with a background in high-power electrical installations to help me with the cabinet and all the safety measures needed. After I have everything in there, I can think about all the PSUs needed.


All in all, I am really satisfied with the progress had in a week's time, and I am constantly working to finally get to the point where I am comfortable with the end result. If anyone spots anything that seems off with the revision, however, I would be very glad for any criticism on it. Ultimately, the more eyes and voices are involved, the less likely that mistakes fall through the cracks. And to that effect, here is the link to the web interface of Fusion, where you can take a look around the newest, up-to-date version of the 3D CAD Model yourself, and take a closer look.

On the note of getting a lot of feedback, however, I am noticing that other post here get a lot more traction, when it comes to user response. Don't get me wrong, I am by no means meaning do downplay the contributions made my AndyUK, CliveS and Washout(Who literally brought me here), you guys are the reason I have comes this far, and I cannot thank you guys enough , but at the same time, I am wondering if my post broke etiquette, or if I did something else, that made people not want to engage here? Because if that is the case, I would like to work on fixing that.

Anyways, I am already staying up way too late to finish up this post, so I am just gonna end it here and head to sleep.
Thanks,
Chrono