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Tinkerer
29-09-2014, 01:17 PM
G'day Everyone!

My name is Richard and I live in Melbourne Australia. I have very much enjoyed reading the various threads on building DIY machines and probably like many on this forum have found and very much enjoyed the learning curve in getting to understand the issues and parameters in building a CNC machine. Unlike many on this site, I have limited experience in building machines, but I am quite a handy person and accustomed to getting my hands dirty on DIY projects. I am waiting for delivery of my TIG / Stick Welder, so my practical learning curve will start with improving my welding skills. Meanwhile I've been on a steep learning curve getting familiar with Rhino as a CAD drawing package (also to be used in designing Kinetic Artwork).

I have created this thread hoping that those more experienced will be able to guide me on my build. So here goes....

1. My Machine Parameters

I plan to build a CNC Router, with the flexibility to use it for Plasma or Laser cutting of steel. It is intended to be a general purpose machine with a high degree of accuracy (if I'm going to the trouble of building something bespoke, then it may as well be accurate).

The main material I will be cutting is timber (plywood up to 25mm thick) and some aluminium (aluminum) to create Kinetic Artwork (wall art etc).

It will initially be a three axis machine, but I intend to build in capability to expand to a 4th axis to turn table legs, carving etc. If I honest with myself, I suggest that the challenge (and resultant satisfaction and no doubt accompanying frustration) of the build outweigh practical applications.

The general parameters of the machine are:

1.1 Working Area

X Axis - 1.5m
Y Axis - 1.25m
Z Axis - capable of 220mm travel, but anticipated generally working to 154mm
4th Axis Capability - Removable working platform to accommodate greater Z depth of 350mm (total) for an additional axis

As the machine will be residing in my garage, I need to make is as compact as possible (car parking will likely be a casualty!).

1.2 Router /Laser/ Plasma Capability

I intend to install a 2.2kW water cooled router as the main cutter.

I have designed a holding water tank and support to be able to cut steel. I understand that compromises are made to do this, however as it is as general purpose machine, speed etc. are very much a secondary consideration. I'm not sure where my Kinetic artwork will take me, so flexibility needs to be built in.

1.3 Frame / materials

I intend to build the majority of the frame from 89 mm SHS, 3.5mm thick.

The Gantry will be manufactured from Steel RHS (150 x 200 mm) reinforced with 10mm Steel plate to sit on the carriages for the X Axis.

I attach a spreadsheet showing the calculated weights expected to be carried by the X, Y & Z axis, which:

X = 112kg
Y = 27kg
Z = 19kg

For obvious reasons I wish to ensure that the removable Steel/MDF platform is robust to ensure accuracy. I have read threads where some members suggest simply building a removable MDF platform to vary the Z depth. Given the depth of the Z axis and flexibility to do some Plasma/ laser cutting, I have swayed away from this, but equally, I am conscious of the additional Steel / weight / work my design requires. Thoughts on alternative variable Z axis designs welcome! My requirement is to ensure accuracy prevails (no movement).

1.4 Motors/Drive

Having read in detail a number of threads relating to similar designs, I have landed on a design which utilises:

Ballscrews - still to calculate / determine whether I need 20mm diameter or can get away with 16mm when considering lengths of:

Y Axis - 1,694mm
Z Axis - 1,762mm

Z Axis Actuator - I will probably look to purchase one for the Z axis, believing that something 2nd hand may be more accurate than anything I will build.

Guides - Looking at LM guides for greater accuracy from the likes of THK or suitable alternatives.

1.5 Drive Mechanism

All Axis (perhaps with exception of Z Axis depending on Actuator used) to be powered by belt drives to reduce vibration and provide flexibility in changing gearing ratios if need be. Initially, I intend gearing to be a 1:1 ratio, but final calculations may dispel this notion.

I intend utilising stepper motors for their greater torque range, and wish to explore the use of an encoder function to provide a closed loop system reducing errors if steps are somehow missed.

Based on earlier research, I expect that I will be utilising something like NEMA 23 motors with outputs around 3 to 4 kN (424 to 566 oz/in) outputs.

I have purposefully held off on this hoping for some feedback on my draft design of the frame (gantry) suggestions on shaft diameters, etc., before calculating final requirements.

I am not sure what cutting speeds I should design to (and hence input for motor requirements). Speed is not essential as I will not be into major production runs, but neither do I wish to watch a job completed at a snails pace. Any input on appropriate / realistic tool speeds for cutting MDF (25mm) or aluminium (aluminum plate say typically 20mm) which I should aim would be much appreciated.

Plasma or laser speeds could presumably be much faster??, but router work should drive the design.


2. Drawings and Spreadsheet

For reference I attach various views and closeups of my draft drawings and spreadsheet showing materials and weights.

I am not totally sure how some components for drives/ LM / ballscrew Nut anchors should be attached, apart from the general understanding that everything needs to be adjustable to tweak tolerances (I/m sure my soon new found welding skills will challenge the need for this!). Thoughts / photos on how items should be bolted together or how I should alter my design to provide for this would greatly assist.

3. Your input

I now lay myself prostrate, seeking input from members who have the skills and experience in building such machines on matters raised or any other items which my design raises.

Please note that I have a thick Aussie hide and welcome your constructive feedback! My first objective is to order steel to build the frame, but also understand that I should have ordered and received guides, shafts etc, before starting cutting to ensure concept and practical application marry up!

Regards



Richard


PS The site wont let me upload images. Will post once sorted.

EddyCurrent
29-09-2014, 11:24 PM
Sounds like you've done a good research job, I think 20mm ball screws may be in order and if you use good digital drivers for the stepper motors then speed should be achievable.
There's not much to say until the pictures are up.

Tinkerer
30-09-2014, 02:17 AM
Thanks Eddy. I have very much enjoyed reading and learning from your contributions to this site. For some reason I cannot load dwg files, so have reverted to pdf format. Attached are images and Excel spreadsheet of materials:


http://www.mycncuk.com/attachment.php?attachmentid=13495&stc=1&thumb=1 http://www.mycncuk.com/attachment.php?attachmentid=13493&stc=1&thumb=1 http://www.mycncuk.com/attachment.php?attachmentid=13494&stc=1&thumb=1 http://www.mycncuk.com/attachment.php?attachmentid=13496&stc=1&thumb=1 http://www.mycncuk.com/attachment.php?attachmentid=13497&stc=1&thumb=1


13492

I look forward to your and other's feedback.

Tinkerer
30-09-2014, 03:01 AM
Some additional views with shelf removed and with shelf/Plasma tank:

http://www.mycncuk.com/attachment.php?attachmentid=13498&stc=1&thumb=1 http://www.mycncuk.com/attachment.php?attachmentid=13499&stc=1&thumb=1

AndyGuid
30-09-2014, 06:39 AM
G'Day Richard,
Looks to me like you've done a cracking job researching, planning, and drawing your ideas!
I reckon this forum's experts are the best in giving advice for DIY-CNC so welcome aboard.
Cheers, Andy
PS. Whereabouts-ish are you in this urban spread called Melbourne? I'm down Berwick way.

Tinkerer
30-09-2014, 09:31 AM
I have been asked to upload JPEG files. Here they are (slightly different perspectives but from same drawing). If someone can advise what the preferred file format for graphic uploads is, then I will stick with that going forward.

http://www.mycncuk.com/attachment.php?attachmentid=13501&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13502&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13503&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13504&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13505&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13506&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13507&stc=1

irving2008
30-09-2014, 10:25 AM
Jpg or gif or png all work and display in the web page. Pdf is good for downloadable documents but doesn't display in the page.

Boyan Silyavski
30-09-2014, 09:01 PM
Hi,

IMO you should reconsider some main points:

1. Z axis travel, bed depth ,4rth axis, gantry

-Z 200mm is ok and going more will lead to another problems, which would need reinforcement, that would l lead to more weight and that to servo motors.
I am doing a similar build so 200mm is ok for all, even for plasma, as i intend to do also.

-that singular gantry beam contradicts with the 200mm Z travel. 2 beams, say 100x100x4mm welded together will be better. Vibration wise.

-that removable bed you have drawn is mistake. Either make it proper removable bed like some designs here make it, not with angles but bolted directly side of the beams, or calculate the correct bed depth for 200mm axis and make it fixed. For a fixed bed, depending on design you need more or less 300mm from gantry beam when all mounted.

-4rth axis is no problem with say 300mm deep bed/from gantry beam/. The most ridgid 4rth axis worth for that type of machine, could be made from mini lathe, as i intend to, and it enters in 300mm bed from gantry, or you could make the axis inside the bed if you intend to spin things bigger than 300mm OD


2. Z
you should concentrate on the Z, draw it strong in all directions and all will start from there. Rails on the moving plate, and so on. Then the gantry, then the gantry sides...

3. Now that you have all this clear, you should decide how to move it. If you decide on servos, go back and make it as much strong as its reasonable.

4. Check if in real life the ball screw on the long axis will allow to be mounted like this. Will it pass once all welded.

5. As far as i read 4 inch deep plasma water bed is ok, so that will be removable, no need to be bolted onto anything.


Once you have it clear which way you would go, especially the motors, everything will speed up.

TonyD
01-10-2014, 12:15 AM
One consideration I fell fowl of was that I was also constrained on space, so as I order plywood for a project now I need it cut at supply. If I were doing it again and could have made the space I'd have gone for a design that could take a standard 8x4 sheet of wood straight from supply.

Tinkerer
01-10-2014, 09:15 AM
Hi Tony, thanks for the feedback. I have grappled with the same issue, but I believe I can source plywood at the smaller lengths here (or get the saw out!). Even if this were not possible, the space availability is an issue, so I will err on the small side for now...perhaps for the next build!

Tinkerer
01-10-2014, 12:00 PM
Silyavsksi,

Thanks for your feedback. I've learnt much from your posts (don't know how you keep up with them!). I'll attempt to address each of your points in the order you have raised them.


1. Z axis travel, bed depth ,4th axis, gantry

-Z 200mm is ok and going more will lead to another problems, which would need reinforcement, that would l lead to more weight and that to servo motors.
I am doing a similar build so 200mm is ok for all, even for plasma, as i intend to do also.



The Z travel I have is 220mm, which is a standard length by THK Actuators, so presume you are saying this okay. The THK actuators at this length are very accurate, so I need to concentrate on the gantry to ensure it is robust enough/will not flex. I'm not sure what it will cost me, but I still feel it will be more accurate than what I will construct, with less effort!


-that singular gantry beam contradicts with the 200mm Z travel. 2 beams, say 100x100x4mm welded together will be better. Vibration wise.


http://www.mycncuk.com/attachment.php?attachmentid=13511&stc=1
I wander if this is over engineering it? My gantry (pictured above) is RHS 250 (height) x 150mm (wide) x 5mm (thick), reinforced partially by two welded 10mm steel plates over carriages for X axis. I have utilised RouterCNC's extremely useful stiffness calculator posted, and using my dimensions and cutting aluminum, came up with deflection of Z = 6.3um and Z - 1.6um, which I find more than acceptable. Using the new Stand-alone Z axis calculator, at the extreme Z Axis extension of 220mm (which I would only use for wood turns), I get a deflection of 4.185um. Unless I am using this tool incorrectly, I would think this accuracy is more than enough for most builds?

Perhaps there is good reason to make it more robust. You mention vibration. Is this a similar consideration to deflection, or something else that needs to be factored?

I've attached the spreadsheet below.


-that removable bed you have drawn is mistake. Either make it proper removable bed like some designs here make it, not with angles but bolted directly side of the beams, or calculate the correct bed depth for 200mm axis and make it fixed. For a fixed bed, depending on design you need more or less 300mm from gantry beam when all mounted.

Thanks. I inserted brackets for greater accuracy so that the removable bed could physically sit on something solid (I am concerned that side bolts will have play and the removable bed would shift considerably when removed and then re-attached (without resting on something solid (i.e. bracket) - bolts move)). I could also bolt the removable shelf to the main frame for greater sturdiness. If there are sturdier and easier designs can you point me in the right direction?

The fixed bed is already there for the maximum Z axis / 4th axis (approx 373mm distance from tool).


-4rth axis is no problem with say 300mm deep bed/from gantry beam/. The most rigid 4rth axis worth for that type of machine, could be made from mini lathe, as i intend to, and it enters in 300mm bed from gantry, or you could make the axis inside the bed if you intend to spin things bigger than 300mm OD

Thanks. I think we have similar designs in mind, but I do need to give more thought on what the 4th axis will be (phase 2 of the build which needs more thought now!). I've discovered your dialogue on your most recent build which I'm absorbing!

Again, many thanks for your interest and input!:adoration:

EddyCurrent
01-10-2014, 06:03 PM
Nice drawings.
I can't compete with silyavski on the frame design but I did notice the spindle is cantilevered well out, have a look at this diagram where it shows the spindle should ideally be inside the footprint of the bearings at each end of the gantry. http://www.cncroutersource.com/do-it-yourself-CNC-router.html

Tinkerer
01-10-2014, 11:55 PM
Thanks Eddy. I thought my design was too simple. Now I know why! Thanks for the link. It was extremely helpful in explaining COG and design considerations. Conceptually, I will look to draw the shape of a RHS section at right angles to my gantry to move COG back towards Y axis rails.

I've noticed that a number of designs have placed Y axis screw on top of gantry (my design has it on side of gantry between rails). Placing it on top would help marginally with moving COG back. Is there an inherent preference for placing screw on top? Is my design inferior or not practical?

Boyan Silyavski
02-10-2014, 01:20 AM
The Z travel I have is 220mm, which is a standard length by THK Actuators, so presume you are saying this okay. The THK actuators at this length are very accurate, so I need to concentrate on the gantry to ensure it is robust enough/will not flex. I'm not sure what it will cost me, but I still feel it will be more accurate than what I will construct, with less effort!


Its very difficult to find the correct sized actuator for that job. I have been that way. And actually constructing it yourself you will reap all the benefits over ready actuator. You will waste more time and money searching for it. And most of the commercial designs have the rails mounted on the fixed plate, the fixed plate is too thing, all weights too much, travel is too short, the ball screw is not the correct pitch and so on. I spend months looking for a correct one. from the THK ones only the biggest ones are good.




I wander if this is over engineering it? My gantry (pictured above) is RHS 250 (height) x 150mm (wide) x 5mm (thick), reinforced partially by two welded 10mm steel plates over carriages for X axis. I have utilised RouterCNC's extremely useful stiffness calculator posted, and using my dimensions and cutting aluminum, came up with deflection of Z = 6.3um and Z - 1.6um, which I find more than acceptable. Using the new Stand-alone Z axis calculator, at the extreme Z Axis extension of 220mm (which I would only use for wood turns), I get a deflection of 4.185um. Unless I am using this tool incorrectly, I would think this accuracy is more than enough for most builds?

Perhaps there is good reason to make it more robust. You mention vibration. Is this a similar consideration to deflection, or something else that needs to be factored?

I've attached the spreadsheet below.


Yeah but you have 250mm side that can vibrate and i suggest you 100mm side that can vibrate. Which drum will make louder sound 100mm one or 250mm one? Think of it like aditional internal bracing.
Also i like working with one and only profile. And buy by the 6m. So as i see it i would do a machine from 80x80x3 to 100x100x4 and construct all i need from these ones. As they also cut perfectly with small saws at home.


Nice drawings.
I can't compete with silyavski on the frame design ...

Thanks Eddy but if you remember we all came together with that design on my build, i just calculated it the cheapest and lightest possible for acceptable rigidity for ali jobs. Its very funny though, instead of making steel instruments sound, i started to learn how to make steel structures not make sound. Its no much different than Romans did it- Divide and Conquer

EddyCurrent
02-10-2014, 09:33 AM
I've noticed that a number of designs have placed Y axis screw on top of gantry (my design has it on side of gantry between rails). Placing it on top would help marginally with moving COG back. Is there an inherent preference for placing screw on top? Is my design inferior or not practical?

It makes sense to have the screw central to avoid twisting forces, for example mine is central but it's on the back. Sometimes people make a gap between two gantry beams and mount the screw in there.
You have the rails mounted on your gantry front face, moving these to top and bottom would also move the COG back. Things look great on a drawing but when it comes to building it you have to consider how to align everything so it's accurate accros the whole working area. If you go through that setting up stage in your mind, such as how to get the two rails on your gantry ligned up in all planes, then that might help steer the design.

Tinkerer
09-10-2014, 03:53 PM
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.

http://www.mycncuk.com/attachment.php?attachmentid=13554&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13556&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13560&stc=1
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).
http://www.mycncuk.com/attachment.php?attachmentid=13557&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13558&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13559&stc=1


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.

http://www.mycncuk.com/attachment.php?attachmentid=13566&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13562&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13563&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13564&stc=1


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

Tinkerer
09-10-2014, 04:05 PM
Pictures of phase I, steel workbench and welder - it looks too clean to use. Will be having a play with welder this weekend.
http://www.mycncuk.com/attachment.php?attachmentid=13570&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=13571&stc=1

EddyCurrent
09-10-2014, 07:41 PM
Just going out now but will reply better later, however for the wheels design have a look at this video, at about 4:20 min. into the video it shows how to move it, I have one of those machines and the idea works great. It's two fixed wheels at the back and adjustable height feet at all other points.
http://www.youtube.com/watch?v=J2ry1DxNFA0

irving2008
10-10-2014, 07:13 AM
re bolting stuff. Generally bolt dia less 1 to 2 x pitch. So for M8x1mm pitch thread, 6 - 7mm is typical, though for light loads 4 - 5mm might be adequate. A simple rule is to look at the thickness of the standard nut : a useful resource is www.roymech.co.UK and specifically for this issue: http://www.roymech.co.uk/Useful_Tables/Screws/Hex_Screws.htm

Blackrat
10-10-2014, 08:48 AM
To maximise the strength of the bolt in steel you need to go in 1 1/2 times the diameter , m8 = 12mm. The bolt will snap before the thread pulls out
In ally it's 2x the diameter

But on a rail your forces are more on the shear , so going in the diameter of the bolt would be ideal

Tinkerer
12-10-2014, 12:20 AM
Just going out now but will reply better later, however for the wheels design have a look at this video, at about 4:20 min. into the video it shows how to move it, I have one of those machines and the idea works great. It's two fixed wheels at the back and adjustable height feet at all other points.
http://www.youtube.com/watch?v=J2ry1DxNFA0

Thanks Eddy. It looks like a simple solution, but I would not want the machine sitting in wheels all the time for rigidity. I need a simple mechanism to raise and lower the legs or remove them. How do you remove the two rear wheels?

EddyCurrent
13-10-2014, 04:03 PM
Thanks Eddy. It looks like a simple solution, but I would not want the machine sitting in wheels all the time for rigidity. I need a simple mechanism to raise and lower the legs or remove them. How do you remove the two rear wheels?

The wheels are solid nylon, they sit on a solid shaft across the back of the machine, there is no movement of any kind when it's sitting down. There are several feet at the front and side and the wheels are positioned such that the machine is level when it is sitting down on the feet, in this position the solid wheels also act as feet because they do not swivel or move sideways, it's rock solid.

13599 13600 13601

Boyan Silyavski
14-10-2014, 07:13 AM
Hi,
I see that you gave a lot of thought on the design. Where are the pictures from post #16, i dont see them?


-3mm is ok for threading, of course the thicker the better :-) , but rails can be bolted on 3mm profile.

-i see some I beams on your last table picture, under the top. I beam is way weaker than square or rectangular profile, though looking at it seems stronger. I don't see where and how in a CNC structure we can benefit from using I beam. It twists like crazy, its relatively heavy for what it offers and so on... I would revise that part. use the calculator and see for your self.

Tinkerer
14-10-2014, 07:29 AM
Thanks Eddy for going to the trouble to take photos. Now makes sense. I have already got some steel castor wheels (won't burn with plasma). Will look at Felder? design and also exploring a less complicated solution (than my original) I found on another welding forum where castor wheels were simply slightly raised above ground and then lowered via adjusting the legs, albeit this approach may be more tedious to get it mobile. Will dwell on both solutions!

Tinkerer
14-10-2014, 09:12 AM
Hi Silyavski. Pictures on #16 appear on my computer but not my iPad. I wander if size limitations causing a problem. Have attempted to post again in different formats. I wold really appreciate input from you/others on these designs before I commit to anything.


-i see some I beams on your last table picture, under the top. I beam is way weaker than square or rectangular profile, though looking at it seems stronger. I don't see where and how in a CNC structure we can benefit from using I beam. It twists like crazy, its relatively heavy for what it offers and so on... I would revise that part. use the calculator and see for your self.

I agree with your comments and was also surprised by the superiority of RHS. The workbench does not have to take any twisting or other loads and all I simply want is a strong base which can take significant vertical weight, hammering, etc. Its not a CNC design, just a workbench. I also like the idea of being able to clamp along the side (under the benchtop, facilitated by the I beam shape). Besides I've bught the steel, so will run with this. I agree not suitable for CNC compared to square beams.

Here is another attempt at the pictures. In uploading these, I advise that I have undertaken considerable re-design of a few items (after many days thought) and looking up physical sizes of required components. A summary of changes is given.

1. Gantry

I now have two designs:

A. A design similar to yours (Silyavski) which utilises welded RHS and SHS (per pictures previously posted but not seen),


http://www.mycncuk.com/attachment.php?attachmentid=13603&stc=1


this utlises 125 x 100 x 4mm RHS (top and bottom) and SHS 100 x 4mm (8mm at ends where I intended to bolt bearing supports but now moving towards bolting supports to Red Plates).

Note Y Axis will now be moved to back of Gantry (see below).

and

B. A single bespoke RHS shape, made out of 5mm plate (using 8mm for sides) which utilises key slots and tabs (some refer to this as 'toy slots' resembling construction of early steel toys. Beam is reinforced by two internal welded plates in the structure.

This later design appeals to me as the components fit together for greater accuracy and welds are more focussed. A draftsman friend of mine told me about the significant inaccuracies (twists, etc) inherent in extruded beams (apparently manufacture starts from a round shape which is then forced into a rectangular or square shape?). He works for a large American firm and they apparently fabricate most heavy industrial components (for heavy waste removal trucks etc) out of plate using this method.

I would have to get components for this design laser cut (he says this is relatively inexpensive - he works for a corporate who pays the bills - will see whats this means to a private budget!). Meanwhile I perfected my technique of drawing Toy Slots.

About to investigate the cost, but waiting feedback from my friend and others before doing so.

http://www.mycncuk.com/attachment.php?attachmentid=13604&stc=1

1.1 Gantry Drive (Y Axis)

Well the added weight has forced me to consider NEMA 34 motors. After looking at the increased footprint, I decided that I should mount the motor on the back of the Gantry like some other designs. This would marginally improve COG as well, but not a big issue.

2. X Axis

Larger motors and a more careful look caused me to make some minor modifications to brackets. Silyavski, I compared what you built on your first build, and I have headed towards a similar design.

I also moved the motors to the back of the machine, away from the operator and closer to the control box.
http://www.mycncuk.com/attachment.php?attachmentid=13605&stc=1

3. Z Axis

More or less the same, but I have also included 'toy slots' to facilitate easier fabrication/more accurate assembly.

http://www.mycncuk.com/attachment.php?attachmentid=13606&stc=1

This design is all steel and requires laser cutting/ machining. The front plate carrying the Rails has 2 of 20mm x 20mm support beams to provide rigidity with the balance of the face plate 10mm. The side plates are constructed of 20mm plate. All 'Toy slotted' and welded. Top plate 10mm thick.

Using the Siffness calculator I believe this will give me a reasonable stiff structure with deflection below 20um in various directions cutting aluminum. I think! It certainly has added to the weight of a purchased actuator which is now a scrapped notion due to their weak structures.

Happy to listen to any views how to do this differently.

Perspective View of Machine

http://www.mycncuk.com/attachment.php?attachmentid=13607&stc=1

Hopefully these pics are now viewable (I know I got close to the limit last time I posted them and perhaps why they did not appear?). Please let me know if problem persists!

If anyone can consider these with questions posed in my post of #16, I would be very grateful.

One additional question is to do with attachment of support bearings. As mentioned above, I am leaning towards bolting the supports to the plates at the end of the shafts, rather than to the side of the frame/gantry. My rationale is I can control spacing easier (or perhaps not), and that plates offer a flatter, 8mm surface to bolt to. What is the preference/others' experience?

Pictures look good I'm told. Proof of competency will be the building of it! :acne:

Richard

EddyCurrent
14-10-2014, 07:13 PM
I don't know what you have planned for limit switches and home switches but you might want to think about them now in case you want to incorporate them into your brackets etc. There's also the strikers for the switches and means of fine adjustment.