Hi everyone, I've been off the air, school holidays, etc. I have taken on board comments from Eddy and Silyavski and embarked on a substantial redesign after spending literally days going through numerous design iterations, stiffness calculations, etc. The resulting redesign now has the following inherent features:

1. Frame

Largely unaltered, however, removing cantilever from the Z Axis (thanks Eddy!) required Y axis lengthening one side and reducing on the other.

I have shown inserted bolts for the removable bed. I have used a combination of bolts as well as angle to attempt to remove and play movement when removing and re-installing it. I've review some other designs on the forum which appear to just use bolts to the side of the frame. I feel these designs would result in a significant shift in the bed from the original leveling. If I can avoid needing to re-level the bed, it would be a major advantage.


As regards the Frame, most material is SHS 89mm, 3.5mm thick. I have gone to 6mm thick on the top where I need to weld brackets for motors, bearings, bolt Rails on X Axis. Can anyone advise whether 6mm is thick enough to directly tap (thread) and bolt bearing supports and rails to it?

2. Gantry

I was initially wedded to the simplicity and robustness of my RHS Beam - 250 x 150mm. After comments from Silyavski, I recognised the weakness of the extensive cantilever in my design. After several designs (utilising welded steel plates in triangular shapes) to reinforce the Gantry (to remove cantilever), I then had a further look at the RHS beam I was using.

Although the beam was certainly robust enough, I grappled with the issue of the square face, necessitating me installing the ball screw shaft on the same front face (per my original design), thereby increasing the Z Axis overhang / cantilever by about 25mm. I then looked at placing the Y Axis screwball shaft on the top of the Gantry, thereby eradicating the increased Z Axis overhang. I had considered this in an earlier design, and for all purposes it is a better design (for Z axis), however placing the screwball behind the Y axis rails adds another leverage point, this time, on the Y Rails. I am sure this wold have been fine, but I knew that the ballscrew was better placed between and in line with the Y axis rails to avoid any leverage.

So, I came to the conclusion many here already know, and that is, my Y Axis Beam needed to be formed (welded) to provision for the Y screwball shaft behind / under the Y rails. Silyavski, I looked at your design and thought there was way too much welding in it (like you I am a relative novice!). I experimented with all manner of available steel materials and eventually came to a close solution to yours. That is, after eventually discounting the following designs largely because of their added weight, with flow on impacts on motors, etc:

Considered Gantry Designs (subsequently discounted)

a. RHS 200 x 150, with 2 RHS 65 x 35 welded to the face to lift Y Rails away from beam (preferred solution as less fiddly/welding/cutting but added another 15kg+)

b. Silyavski design - Two SHS 100 stacked high with smaller welded tube (75 SHS) to create the void for the Y axis. This would (and has) worked well for Silyavski, however I preferred utlising lighter material and therefore reinforced the X direction by utilising RHS (see final solution)

c. 2 x RHS 150 x 100 separated by SHS 75 along the whole length (less cutting/welding). Again too heavy with too much unnecessary continuous length.


My final solution - Utilising 2 x RHS 125 x 100 x 4mm, separated by 7 cut SHS 100 x 4mm (I have used 9mm for the end SHS separators to give more meat to tap into to bolt the Bearing Supports for screwball shaft).



So Silyavski, I looked at your design and thought I would be able to improve on it/ create less work for myself. Ultimately, I have no doubt gone through the same process as you, and although I have changed some of the materials, I ultimately came to the same conclusions as you and intend to build a similar design (just not as bomb proof as yours!). Where you have opted for SHS 100 10mm thick, I have gone for 4mm, but increasing thickness to 9mm where bolts are to be fastened. I have used some RHS 125 x 100 x 4mm to strengthen the beam in the X direction due to use of lighter thickness.

You have used 20mm and 12mm plate I think. I have opted for 10 and 8mm plate believing it to be more than adequate. I have checked most against the stiffness calculator and believe there will be relatively little movement below 10um in all cases whilst cutting aluminum.

Z Axis

I was looking for a simplistic solution, researched and found actuators which I could largely bolt onto plates, etc. There are a number of Actuators in the market from THK and others and I resolved that they would be able to manufacture a far more accurate product than I could. Feedback from Silyavski caused me to delve into designs a little more thoroughly and yes Silyavski, they are all quite flimsy, using thin walls and I believe would never have withstood cutting forces for a router.

I spent considerable time playing with the stiffness calculator mentioned in my first upload. To get reasonable accuracy with up to a 100 - 200mm Z axis travel, I have needed to utilise Steel plate with perpendicular reinforcing ranging between thicknesses of 10, 20 and 30mm. I got myself a little challenged with the material stiffness calculator, as its design is really for gantries, but I think I was able to interpret it to apply to the Z Axis.

So with my easy purchase solution ended in tatters (bug.er!), I embarked on more research to understand how Z axis work (I confess to initially glossing over what pieces were attached to each other - I thought I'd get to that once I purchased one!), looking at numerous designs and then designing my own.

So, you will all be somewhat relieved to know that I now fully understand what parts move ( are driven) and are to be fixed to create a working Z axis! That is unless anyone advises me that I have got it all wrong!

Here are views of my design. All steel construction. Yes, more welding and I think I will have to get at least one plate machined.




Okay, after many many hours of toil, I lay myself open to criticism/comments from everyone. As I have found out, there is no easy way getting into this build. For me it has all been a big, but enjoyable, learning curve, and all the shortcuts I had hoped to take are not available for good reason. So, in time I expect top be able to provide you all with a few laughs - welding has me a little anxious, as is putting together the electronics. All in the fun I suppose.

As always, I welcome any comments, but I will slash my wrist if I have overlooked something fundamental. This is a time consuming process which has taxed the brain and resulted in many hours of drawing and getting to understand Rhino software (which incidentally is great)!

I'm anxious to start actually building, but thankfully did not leap into things ordering material, as my design has evolved considerably, thanks to your input and my own quest to optimise use of materials and the accuracy of the machine.

I have made some progress:

1. Bought my Everlast Welder and purchased (rented) my first bottle of Argon and consumables.

2. Designed my steel workbench, which will be built first to get into a bit of welding practice and to assist in having a good surface to square things etc. I had in mid to utilise this to also act as a stand/ frame for my Router (to minimise workshop space), but eventually dispelled that notion when I realised my 'portable benchtop' router was a little heavier than expected!

On that note, if anyone has got a good design for attaching raising/lowering wheels so I can move both router and bench around, I would be most appreciative. I have designed wheels utilising an inner and outer SHS, with a bolt, Contemplated inserting springs which can carry the load when bolt released, with springs compressed (and wheels up) when bolts tightened? Not sure how practical it will be?


My learnings along the way

I thought I'd share my experience for any new builders as I enter my Build logs. To date:

1. There are no shortcuts. Be prepared to invest considerable time reading through this and other forums to get a good handle on many of the issues you will encouter/ must consider.

2. Investment in design is key. I have found a CAD program invaluable in testing my ideas, redesigning, redrawing. Doing simple things such as determining the size of the frame to accommodate designed working bed areas is so much easier when using a CAD package. To view the extents of my working axes, to date, I have simply copied and dragged critical drawn components off to the other extreme of the axis and see if it fits, or if I have overlooked a component, such as provision for limit switches, ballscrew nut hits bearing support, etc. This should be backed up by math, but CAD is an extremely useful tool. I am using Rhino and although a big earning curve (as any CAD program), it has been worth my investment /perseverance, particularly for future capability in kinetic design needs.

3. Where possible, incorporate manufacturers drawn CAD components into your CAD drawing. They are often readily available, they save work and the dimensions are there for incorporation into your design.

4. Don't order materials before your design is near complete. If I ordered materials before now, I would have incurred much cost and great waste. I am about to order steel, but still wait for the valued input of the forum members to see what may need to be tweaked.

5. Don't start cutting materials until you have many of the drive components to practically consider against your concept design. I have read on this and other forums how manufacturers' components vary from the written material. I am yet to fully research and order the drive components. Until this is done and I have the components, I know I will probably need to tweak final dimensions of the steel work.

6. Set realistic parameters (cutting area, accuracy, material to be cut, speed, max floor dimensions etc) regarding use of your machine as they will dictate components purchased and your ultimate design).

7. Useful Design Tools

Apart for a CAD package, essential to getting your design right, is an understanding of:

1. Motor torque requirements
2. Material (steel, aluminum) Stiffness Calculators
3. Material Optimisation software (freeware or trial software) - assists in optimising cuts for ordering materials (plate, RHS/SHS lengths etc. I started this process manually as then Googled to learn the best approach and found useful tools which save much time and effort
4. Spreadsheets (e.g. Excel) - I have found it invaluable to input all parts/materials and their weights to assist in calcuating mass (kgs) to determine motor torque requirements
5. Material weights - generally readily available form steel suppliers and manufacturers of other components
6. Cutting speeds - apart from mass, acceleration and inertia, motor torque also needs to take into account your designed cutting speed and whether under load (router) or little load (e.g. plasma). Having an understanding of the speeds generally recommended for cutting different materials will help in setting realistic parameters.

I will ultimately package these items together to create a useful toolkit for others, rather than as I and I am sure many others have done, stumble across threads where these tools are provided or are mentioned. It would be a good idea if this forum had a central repository for useful tools, which are then voted on by the members to gauge their effectiveness. If it already exists, then my apologies, but it is not easy to find?


Lastly, this forum is very useful, and individuals are very happy to lend a hand, but you need to do your homework first and read and search the threads.

Although a recent member, I have already saved myself from design errors through the simple guidance of individuals such as Silyavski and Eddy and tools provided by the likes RouterCNC. Thanks guys!

Assistance Please

If anyone can assist with the following then I would be most grateful:


1. Frame

Whether 6.0mm thick SHS is sufficient to directly tap (thread) and bolt rails and bearing supports to (no nuts).


2. Gantry

Comments on the design


3. Z Axis

Comments on the design

4. Transmission Components

I have read much but not enough about suitability of components. Current design parameters are:

Working Area
X - 1,500mm, Shaft circa 1,787mm
Y - 1,240mm, Shaft circa 1,662
Z - up to 200mm (generally 100mm working), Shaft circa 355mm

Weight carried by axis
X - 158 kg
Y - 53 kg
Z - 49 kg

Are these weights unusual for the size / type machine?

Questions
I still need to thoroughly research manufacturers' specifications (which can be rather daunting with options provided) regarding suitability, but I would appreciate learning from others regarding the suitability of the following:

A. Ballscrews (supports to be fixed both ends)

X & Y Axis - 20mm diam (sufficient for length?), Pitch 10mm
Z - 16mm diam, Pitch 10mm (motor calculator show little torque difference between 5 and 10mm Pitch)I will be using belts and pulleys, but anticipate a 1:1 ratio at this stage.B. Manufacturers / suppliers

a. Drive components - Members appear to have a preference for Hiwin. Is Hiwin as good as / cheaper than THK? Why the preference?

b. With so many variables - Bearings/Nuts, Machining ends, etc, can anyone provide me with what they used for a similar machine t mine. It may be a good starting point for me.

c. Motors

Weights have changed for the worse with the Z Axis re-design (in lieu of inadequate actuator) and now heavier Y axis. I have used the motor torque calculator which recommends (at a 3 times safety margin) the following motors:

Motor Type - considering Leadshine Steppers with encoder feedback.

X Axis - 2 x NEMA 34, 5.5Nm (they only have a 8Nm)

Y Axis - 1 x NEMA 34, 4Nm

Z Axis - 1 x NEMA 23, 3.0Nm

I have looked at cutting speeds, etc and as mentioned previously, speed is less of a consideration. I will be aiming for speeds in the order of 2,000 mm/min

Does this sound about right? The heavier weights have bumped the motor size up to NEMA 34 for X & Y axis, which if correct, means I have to relook at brackets etc for these axes (currently drawn fro NEMA 23).

Any alternative motor recommendations appreciated. I am considering encoder feedback (on steppers). Is this deemed very important, or an unnecessary expense if motors are sized appropriately?

Recommended suppliers

- Transmission
- Pulleys and belts
- Motors and electronics


5. Portability

Designs or solutions on wheels for moving workbench and router around. Will post bench drawing separately. At my 10 image limit.


Bye from Oz for now. I look forward to all/any feedback.

Regards



Richard