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deannos
03-01-2012, 01:45 PM
If i wanted a cnc with a cutting area of 4' x2' what length rails and ball screws would i require for all axis. I like the look of the low gantry designs, i.e Jonathan's etc. I have decided to go with a frame made from steel box section. But that is as far as my knowledge goes. So plenty of help required and desired:smile:

JAZZCNC
03-01-2012, 04:25 PM
Hi Dean, What your asking is very hard to answer accurately without knowing the design and will change with different design.!
That said I'm soon going to be building for someone a steel framed machine with very nearly the same dimensions.! . . . .So to give you an idea i've just quickly changed the Cad model to give the length you want, width was the same or slightly more anyway.

With a design like the one in the pics below the X axis screw would be Approx 1400mm and the Y axis 825mm. The rail lengths would be approx 1475 and 850mm.
The model is just at a very rough concept stage so nothing is aligned or setup and things like gantry sides will change shape, position etc with more work on the frame and more trimmings will be added like covers for screws and igus chain etc but it should give you an idea of how it would look.

Every thing is 1/1 scale so motors, spindle etc are all correct and all materials can be got or cut from products that are available of the shelf, IE gantry sides (as can most of the gantry and Z axis) be got out of 200x20mm plate from Aluminium warehouse, 80x40x3mm Box section from local steel merchant etc. The adjustable bed is steel frame with KJN's 90x45 profile but could easily be replaced with MDF to save money.

Hope this helps and just ask if you want to know anything.

deannos
03-01-2012, 04:50 PM
Thanks for that Jazz, that design is what i was thinking of. The Aluminium warehouse is also 1/2 hours drive away. How would i work out the cut lengths for the steel etc

feel stupid now, the lengths would be the same as the rails

JAZZCNC
03-01-2012, 06:00 PM
Some good advice is get a decent cad program and start designing the machine before you start cutting anything.!
It really does help with checking fit etc and finding dimensions etc.
The time invested designing will be repayed as the build progress's because It helps keep the build on track and has time goes by having an accurate reference to look back upon really does pay back. . . . It's also a good motivator because you can visually see what your going to have at the end.:dance: (Amazing how several days or weeks of grinding,drilling etc can De-motivate.:thumbdown:)
Not only will it save you time but it will save you money because you'll not waste material making parts that don't fit or work how you thought they would.
You can also work out accurately easily if several compnents can be got from a single length or stock or if you'll need an extra length.! . . . . Nothing worse than buying Stock you don't require when your on a budget.!!. . Equallly nothing worse than running short by 3mm because you "thought" it would fit.!! . . .If you use the suck it and see method Sod's law nearly always bites you when you don't need it.!!

deannos
10-01-2012, 02:51 PM
Am i right in thinking that 300mm rails and 300mm screw would be ok for the z

Jonathan
10-01-2012, 03:25 PM
Am i right in thinking that 300mm rails and 300mm screw would be ok for the z

Draw it and you'll find out.

It depends what travel you require, but it's probably fine. Ballscrew isn't necessarily the same lengths as the rails.

deannos
10-01-2012, 03:32 PM
Draw it and you'll find out.

Fair enough, what is best to use, i.e free etc

apart from pen and paper

m.marino
10-01-2012, 03:51 PM
Not free but a very good CAD program for the money is ViaCAD 2D/3D V8 as it not only let's you design it but you can then extract 2D drawings from the model. I used it on my model and it really helped make designing and the build much much easier. Also I knew what materials where needed. Still ended up with a few tweaks here and there but that is better then major OS moment. Good luck.

Michael

Jonathan
10-01-2012, 03:53 PM
Lots of people use google sketchup.

JAZZCNC
10-01-2012, 08:04 PM
Fair enough, what is best to use, i.e free etc

apart from pen and paper

Pen & paper is just as good if thats all you have, you don't need to be Norman Foster just have the abilty to draw lines and arc's to scale. Also think you'll actually find if you don't have any experience with Cad then it will probably be quicker.!! . . . . Thou you are going to have to learn Cad at some point because without it a CNC machine is pritty useless.:rofl:

If you draw it 1:1 scale then you can use the drawings as templates for cutting and drilling.

Can't stress how much easier it makes things having a good drawing, it doesn't need to be drawn to the very last detail but with key parts like Z axis then it really does help. . . . If you have plenty of money and can afford the "Cut it & see" route then go for it, other wise get drawing to save money.

Ask if your not sure and need guideance but nobodys going to say you need exactly this length rail or this length screw because unless your copying there design exactly then really it's not possible.!

At the very least you will have to give some idea of your want's and needs. IE Desired cutting area, Z travel, rail type, screw type etc.

I'm more than willing to help you come to the final design for a machine, even help with cutting parts etc and I'm sure there will be others like Jonathan willing to make usefull helpfull suggestions but ultimately it's down to you and you that needs come too and understand the final design and components needed because your building it.! . . . . Nobodys likely going to do it ALL for you fully without plenty of beer tokens changing hands. (Unless your have 5'8" blonde nympo sister that likes fat bald yorkshire puddings.?? . . .In that case I'll be down shortly with the machine. .:rofl:)

Get drawing then asking and don't buy or cut a thing untill your sure.!!

jcb121
10-01-2012, 08:16 PM
Sketchup is in my eyes, the best program ever for designing. have you considered what parts you are going to use? Supported rail from Linearmotionbearings2008 etc?

MikeyC38
17-01-2012, 03:07 PM
Hi Deano.
I thorughly agree with JazzCNC and Jonathan about drawing out your design with a CAD package. You can see this from my thread here http://www.mycncuk.com/forums/showthread.php/4031-Design-Help-Pt2-Required-for-CNC-design-Build/page4 and it allowed me to get good advice from the guys here on the forum who have learnt the hard way! A picture tells a thousand words!! A 300 mm ballscrew does not have a thread length of 300mm - it is about 200 once you take into account the end machining to fit the bearings at either end. On my Y axis, this clearly showed up when I did the drawing. I use TurboCAD Platinum Pro 15 which I got from Paul Tracey http://paulthecad.co.uk/ at the Model Engineer exhibition some years ago for a fantastic price (very much less than retail!!). It does solid modelling which means when you draw the ballscrew, bearings etc, you can "assemble" them together just like real objects. Some of the stuff like the BF/BK bearing blocks, stepper motor couplings I got off the internet already drawn as 3d objects, so it was easy just to use them. Also as CAD is / will be part of my workflow to use the machine i.e. CAD draw object send to CAM software to produce toolpaths and tool selection then to CNC, then for me it is time well spent.

There is quite a step learning curve in using these programs (Google Sketchup is easier to get to grips with) so unless you are in a hurry, it makes you think through every stage. My mantra is "measure twice cut once" so doing the drawings etc will hopefully help me avoid some expensive mistakes.

All the best with you new project!

Mike

PS Also got my rails, ballscrews, bearings couplings from Chai at Linearmotionbearings2008 on ebay. Fantastic price and great service. Everything turned up within 10 days and was straight.

deannos
17-01-2012, 03:24 PM
Hi Mike,

I have been playing with sketchup and i can just about get a square on there at the moment. I'm in no real rush for a build as my work shop is basically out side. I'm thinking its best to start with the ballscrews and then design form those, i.e use the set lengths, or is that the wrong way

motoxy
17-01-2012, 04:12 PM
Hi Deannos
Sketchup is great. This link will take you to a thread on cnczone of a guy that started from scratch and learnt sketch up. Worth a read.
http://www.cnczone.com/forums/diy-cnc_router_table_machines/126312-guide_build_cnc_less_tools.html

For a true autocad clone then progecad smart (free) is very good indeed for cad design although only in 2d and rudimentary 3d. There is quite a learning curve for autocad but for simple work it is not to hard. This is the best clone I have seen for free.

Keep asking questions. I do and it is beginning to get me in the right direction. Stick with it here becauce these guys are the best.

Bruce

deannos
17-01-2012, 04:35 PM
Hi Deannos
Sketchup is great. This link will take you to a thread on cnczone of a guy that started from scratch and learnt sketch up. Worth a read.
http://www.cnczone.com/forums/diy-cnc_router_table_machines/126312-guide_build_cnc_less_tools.html

For a true autocad clone then progecad smart (free) is very good indeed for cad design although only in 2d and rudimentary 3d. There is quite a learning curve for autocad but for simple work it is not to hard. This is the best clone I have seen for free.

Keep asking questions. I do and it is beginning to get me in the right direction. Stick with it here becauce these guys are the best.

Bruce

Hi Bruce,

I was reading that very thread only this morning, a very good build considering it was built in his bedroom. I have just found some tutorials on sketchup, and it doesn't look to hard.:tongue:

I managed to do the chair as they show it, so getting there.

Dean

motoxy
17-01-2012, 05:07 PM
Thats fine, you will need a chair to sit and build your cnc.

If you are stuck and cannot find how to do anything on sketch up then just ask.
Sometimes its good to turn of perspective (in the camera menu) and then use the standard view and you will see it like a cad drawing.

On my last post redesign 5-1 is in non perspective.

bruce

MikeyC38
18-01-2012, 03:06 PM
Hi Mike,

I have been playing with sketchup and i can just about get a square on there at the moment. I'm in no real rush for a build as my work shop is basically out side. I'm thinking its best to start with the ballscrews and then design form those, i.e use the set lengths, or is that the wrong way

Hi deano
This is what I ended up doing, as buying the ballscrews, ball nuts, bearings and couplings from Chai's standard offerings seemed the cheapest way. I had a rough idea of the cut area I wanted - had to cut guitar bodies and guitar necks which are approx 575 - 660mm long and then estimate how much is lost from the X and Yaxis due to the gantry.

The guys on this forum were great in advising on suppliers they had used with success and on material sizes. On my x axis (longest) they are 20mm dia supported round rail and 16mm dia rails on the other axes.

BTW I've started playing with Sketchup and found a great set of tutorials here http://sketchupforwoodworkers.com/

Regards
Mike

deannos
18-01-2012, 04:47 PM
Hi Mike,

I have been following a set of tutorials and seem to be getting the hang of it. Started on the Y gantry and now have the basic shape etc. But I'm wondering if there are minimum dimensions that should be adhered to. The width of the " z plate" and the Y gantry for example.

Dean

JAZZCNC
18-01-2012, 06:34 PM
Hi Mike,
But I'm wondering if there are minimum dimensions that should be adhered to. The width of the " z plate" and the Y gantry for example.

Dean

Dean regards dimensions Gantry width, Y Axis etc then you want to get the dimensions of the actual bearings your going to use, these will dictate the minium width.
Also if you are planning on using ballscrews the chances are you will use BK/BF bearing blocks to mount the screws, these along with rail/bearing width will dictate the Z axis minimum width.
If you look around on the net there will be 3D models of BK/BF Blocks, linear rail/bearings etc these make it easier and save some work.
Try to model it close to spec of parts to be used as possible, this becomes more important in areas where it gets tight like the Z axis. It's very easy to think it will fit then find out it doesn't by a few mm's.!!!

deannos
19-01-2012, 01:31 AM
Well i have been searching for over an hour and all i can find are models for the BK/BF bearings. Could you give me a clue where to look please:redface:

jcb121
19-01-2012, 01:39 AM
search 'rm2005 cnc'

deannos
19-01-2012, 01:46 AM
Excellent, thank you.

I looked through the warehouse earlier and didn't find a thing.

JAZZCNC
19-01-2012, 07:31 PM
You'll find most things at Trace parts. http://www.traceparts.com/

motoxy
19-01-2012, 11:03 PM
search 'rm2005 cnc'

I had a quick check and it is there. Did you leave in the quotation marks? Remove these and you should find it

Bruce

MikeyC38
20-01-2012, 04:33 PM
Hi Dean

Sorry - I just saw your post. The advice Jazzcnc is given you is right. I had the parts to hand when doing by drawing so I could measure them and draw them reasonably accurately. I've put up a drawing of the latest Z axis design. Unfortunately I don't know what files the free version of SketchUp can import - the dwg and dxf exports from TurboCad 15 Platinum Pro are ok-ish. Surprisingly, the STEP format (Industry standard 3D format) is spot on and I can exchange drawings / objects with my cousin who uses CATIA at work!

deannos
20-01-2012, 05:38 PM
Thanks for all the info guys, i think i have enough to get on with the designing.

luke11cnc
21-01-2012, 02:23 PM
hello

Draftsight is a free cad program I started of with this and moved on to vetric punch and I must say it was the best 100.00 I've spent on software

James