1st Build, Second machine

Okay folks,

Starting the design and materials work on a new CNC Mill. Reasons are the current kit that I use does not have a long enough table, or Z travel, and a few other issues. So instead of trying to improve on what I have (though I will be doing that as well in the process); looking at building from base.

Size looking at is an X between 750mm to 1.5m, an Y of 500mm, Z of 150 - 175mm and adding an A with the ability to handle between 100 - 125mm dia. max.

Currently looking to go with profile rails for the guides. drive will be by either ballscrews or trapezoid screws (down to cost and how tight I can get tolerances for the work I am doing).

Looking at move over to a control spindle from the Kress I use on the current set up.

Structure is an area that I am still looking at as extruded has good points as does box frame. Also doing design work and as things move will be posting the designs up and then as things move into real pieces will be adding those as well.

On the router currently in use will be raising the Z and converting to anti backlash nuts on all three axi' which means a rebuild of the Y and Z. The X axis will just need a mounting bracket milled and taped for it to be converted.

I will be asking questions along the way as while I have learned alot there is always more to learn.

Michael

And Life marches in....

While working on the design for the new machine, I am having to improve the current machine do to production requirements. Sooooooo......... I have a couple of questions. The machine I am working on improving on is a Marchant Dice A3 Trapezoidal screw driven model. I am working on improving the rigidity and milling speed. I am looking at a dumpsterCNC anti-backlash nut for the 12mm X axis and would like folks opinions on that idea. Drawing up a mounting bracket in ViaCAD v8 and wondering if 6mm (or 1/4") thick alli' will be thick enough to transfer the force down to the cross brace. Main reason for going this route is that while business is picking up I really need to be a bit tight on the expenses side of things (which is why upgrading this unit has become first priority instead of second).

I will post a jpeg of the drawing in a bit and could use any input you folks want to give.

Thanks ahead of time and hope to pay it back or forward sometime soon.

Michael

Any chance of that drawing?

And did you mean to say X-axis for the 6mm plate, as in the process of trying to figure out where the plate is going, I found your old thread where you say the X-axis is a 16mm screw...

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Originally Posted by m_c

Any chance of that drawing?

And did you mean to say X-axis for the 6mm plate, as in the process of trying to figure out where the plate is going, I found your old thread where you say the X-axis is a 16mm screw...

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m_c,

Still working on the drawing (need to get product work done so drawing is going to be a bit). What I am looking at is using the 12mm Trapezoid screw that is on the mill and fitting on of DumpsterCNC's anti-Backlash nuts on it. Using a piece of angle Alli' that is approx' 6mm thick and taping the holes on the flange to 5mm (they come at 4.39mm) and then adding a lock washer and nut on backside of that. bolting it to the cross member that moves the X axis via four bolts clamped into the rails of the alli' extrusion. This should give enough strength to hold it in place and still stay inside the 40mm of space I have to work with.

I am working with ViaCAD v8 and new to it. So some of it is taking a bit to learn as I am drawing it. Good part is being able to put in threading on the holes and build the spring for the anti-backlash nut.

Well hope that explains things a bit better.

Side note switched the steppers to parallel from series as getting the new 3A boards from Roy at DIYCNC. I am suprised at the speed increase even at 2.5A (max the current driver boards can put out). Looking forward to the 3A boards and the enclosure kit for my BOB. Which will help in dust control and tidy things up a bit.

Michael

Given the cutting forces involved, I'd say the angle should be sufficient. Even if it does flex, I'd suspect any flex would be less than backlash in the existing nut.
However, if flex does become a problem, provided there is enough room, you could add a couple triangular pieces to brace the angle, using countersunk screws on the underside it can still be bolted onto the cross brace.

Other option would be to get a mount machined from a bit solid bar.
I'd offer to help with any machining, but I'm of on a fortnights holiday in 10days, and already have a queue of jobs I'm needing to do before I go!

m_c,

Thanks for the offer and I might take you up on it after you get back from the holidays. As right now swamped in getting product done and designing 4 new combs for chromatic harmonicas (different makes and reed count) cover sets plus variation for 6 different chromatic models, plus I have have clients work in bound that I need to have everything ready for and then add building concertinas to ship to folks as demo's and to see response in sales. Let's just say the days are busy and long (but I like them that way or I get bored and depressed, better to have things to do).

Folks,

Would 12mm thick alli' with precession rails (Hiwin type) 15-20mm be strong enough for a Y axis of 410mm (current machine) 600mm (project machine). Looking at bolting it to the uprights for the gantry as don't have access to welding equipment and from what I can figure 3-4 bolts per side should be strong enough (spaced to spread the load) looking at having having 100mm between centres on the rails with a 12mm Trapezoid or 10mm ballscrew (depending on what I can afford at the time) driving the Z body on it. Z would have 150mm travel and looks to be 15mm precession rails with a ballscrew. The Z would be 150mm wide to help decrease some of the torque forces, even though that will decrease my available travel in Y (the trade off is worth it to me). Any and all opinions would be welcomed even.

Michael.

12mm alli is pretty substantial, and I'd hazard a guess it would be fine, but I'm sure others will have a better idea than me!

Regarding the rails, I was actually reading about them the other day (can't remember if it was on HSM, CNCZone, or the Mach Forum!), and the general consensus is most hobby builds are majorly over engineered, as there was some big commercial machine running 15mm rails for the long axis. The only reason I was reading about them, is I've got plans for a new machine bubbling away in my mind, and linear rails are featuring.

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Originally Posted by m_c

Regarding the rails, I was actually reading about them the other day (can't remember if it was on HSM, CNCZone, or the Mach Forum!), and the general consensus is most hobby builds are majorly over engineered, as there was some big commercial machine running 15mm rails for the long axis. The only reason I was reading about them, is I've got plans for a new machine bubbling away in my mind, and linear rails are featuring.

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Looks like we've been reading the same things. I agree that if you calculate based on the load ratings they seem plenty strong enough...I'm going to use them on my machine unless some >15mm turn up cheap on eBay. I think that's the reason most people use bigger, because it's what was available at the time on eBay.
You may need to watch out for the moment ratings, though for the size of your machine it should be fine, just space the rails out on each axis as far as you can.

(That's a bit vague I know, I can give some numbers/examples if required)

Jonathan are talking to m_c or me on the rail spacing issue? Also you what would you charge to mill the bracket we are talking about for me? Well back to working on the drawing and setting things up as need be.

Michael

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Originally Posted by m.marino

Jonathan are talking to m_c or me on the rail spacing issue?

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I was talking in general really. On the axis the Z-axis is attached to in particular (Y in your case), the further apart the bearings are the lower the force on each when cutting and (to a lesser extent) accelerating. If you take moments in the X-Z plane then it's pretty obvious why...

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Originally Posted by m.marino

Also you what would you charge to mill the bracket we are talking about for me? Well back to working on the drawing

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I'm not so sure what's required. I can let you know when you've done the drawing...

If I've worked it out right, all that's needed is a bit angle, with four holes on one side for bolting to the cross brace, then on the other side a big hole (21.5mm) for the anti-backlash nut to pass through, with another two holes for bolting the nut on via the flange (having looked at the dumpsterCNC site, I'm guessing you're for the 25mm cut-down flange option?).
Something suitable could be made with a pillar drill, a couple drill bits, and a hole saw.

Regarding mounting the nut, I'd use a couple nyloc nuts with plain washers to spread the load. I'd also put the bolts through from the alloy side, tighten them into the flange, then use the nylocs to make sure the bolts can't move.

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Originally Posted by m_c

Something suitable could be made with a pillar drill, a couple drill bits, and a hole saw.

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Yes, I was thinking that so thought there must be more to it.

Okay,

Let's see if I can get these files up properly.



Attachment 4375Attachment 4374

Sorry that they are jpeg's as it would not let me load the .dwg or .iges file format. That is the bracket I designed to go with a dumpsterCNC anti backlash nut for a 12mm trapezoid leadscrew. Clearance is only 40mm in height. Any opinions???

Also Checking on available box Aluminium in the area but is looking like I have a really good source of off cuts (some over 2 metres) of 12mm Aluminium plate. Any and all views would be greatly appreciated.

Michael

How are you joining the two pieces together? That joint needs to be strong so that an axial force on the screw does not bend the bracket. I'd be inclined to either make it out of one piece, or use something thicker for the vertical part.

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Originally Posted by m.marino

Also Checking on available box Aluminium in the area but is looking like I have a really good source of off cuts (some over 2 metres) of 12mm Aluminium plate. Any and all views would be greatly appreciated.

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Excellent, can I have some :wink:?

Looks fine. If you can't find a bit suitable angle, it could be roughed from a bit solid alu with minimal effort.

Or if you could survive with steel, I might even have a bit suitable angle lying around (I think I came across some 2 or 3" angle during a search for something else the other week!).

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Originally Posted by Jonathan

Excellent, can I have some :wink:?

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I'm nearer and can collect :naughty:

The idea was for it to be of a single piece of either angle or mill from block. That should insure the rigidity of the piece. As far as the Aluminium is concerned drop me a line folks and will try to arrange something. I need to be going down there any how to see if they have any square tube stock that could be drilled and bolt together for the new frame.

Looking through old threads hear for sources of materials and looking like I just might be able to get both up and running (which would be great as I have work to keep two to three mills going for the next month and a half at least).

Still building and still kicking.

Michael

What took so long and what is taking time. Is a drawing I am working on to improve my skill working with the new program. I really like ViaCAD 2D/3Dv8 for CAD work over the program I was using. To give you an idea of what I was doing here is a Jpeg of the Nut.Attachment 4382

So that is one of the projects I am working on. Also designing replacement combs for Bends Chromatic harmonicas (48's,56's,64's)as the business closed their doors down in Brazil (but have not sold off their stock so who knows). Hohner Meisterclasse acrylic comb and once the new mill is built acrylic mouth pieces for the Hohner and Suzuki Bass harmonicas. As well as slowly plugging along at reverse engineering the Hohner harmonetta (which I am now considered and OEM parts provider for that instrument by Hohner). That and other odd bits and pieces. Then milling them. Oh, yeah and jigs to make for more accurate set up.

Michael

Okay,

Ordering the 2 - 12m anti backlash nuts from Dumpster. One for the 12mm on X axis and one for the Y axis. Looking at getting a piece of 12 Aluminium to go across the gantry to add a bit of ridgeness and boring out the section of Z axis that rides on Y so that it will accept 16x20x30 mm Oilite bushings to it and most likely do the same to the bushings on the Z itself to get less flex and better wear as the current bushings are looking to need replacing and with less then 300 hours cutting time on the machine, I think upgrading if possible would be the wise way to go. Only need to drill out the 30x120 extrusion to accept the new bushings.

Also putting in new Bearings on the end and switching to stainless steel with rubber seals and see how that goes. Still working on the new machine and have bought the Z ball screw from Gary at Zap and just need to earn the rest of the money to buy the parts (also need to draw up my ideas and let you folks have a field day with them).

Anyway take care folks and have a great day. More information as it happens.

Michael

Okay on a space and accuracy level, are using Oilite type bushings worth doing over linear bearings? This is doing improvement and part rebuild of a Marchant Dice MDL-TR-2 gantry router. I am building a new Z for it so that I can mount the A axis I have for it on board and starts being able to cut both sides of an item and let the machine do the flip. Going to linear bearings takes about 30mm of travel out of Y due to the required widening of the Z body to allow for the bearing blocks. On the other hand it will increase smooth play of travel.

So, any and all input as I am really up in arms on it and it is bottle necking this point in the design structure.

Thanks for all the input you have given.

Michael

It will be far easier to get linear bearings accurate.
Oilite bushes would have to be sized (either via boring, or reaming) after being installed to ensure accuracy, as oilite bushes are pretty soft things and will deform during installation, unless you use an accurately sized mandrel to press them in (even then chances are they'll deform slightly)

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Originally Posted by m.marino

Okay on a space and accuracy level, are using Oilite type bushings worth doing over linear bearings?

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Hi Micheal,

Dont do it.!. . They dont even compare in the slightest. Even with the best alignment and boring, reaming etc they still dont hold candle to linear bearings and will wear far quicker, far too much hassle IMO.

If you do go with linear rail drop me a PM before you buy I probably can help.?

Okay with the advice given and working in ViaCAD to get things set up would like folks opinion of the following set up for a Y Z axis set up.
Attachment 4390

The dimension marks are left over from getting the height right from the table surface and still having space for the 4th axis.

So please folks opinions. This is not complete. The Y is a little to long (was learning how to download files from Hiwin, great set up they have) and the screws on the Z and the Y are yet set in, nor is the anti back lash nut for Y (it will be between the two rails).

There are 4 carriages holding the Z axis to the Y even though you only see 2.

opinions please.

Michael

Put the rails on the front plate and the bearings on the back plate. This way the rails help stiffen the front plate.
The carriages then go low on the backplate and it makes for a very stiff z axis with max support where it's needed.! close as possible to the cutting end.!

Edit: Also if you pocket the bearings into the back plate slightly you regain some of the lost stand off from gantry. Also you can use one of the pocket edges as a datum ref point for alignment of the bearings. If you also do the same with the rails into the rear of the front plate, (but not quit as deep) this as the same affect and also another datum ref edge.
The net affect of both brings the stand off from the Y axis down slightly and also creates accurate ref edges to work from which are essential for setting up profiled linear rails correctly.

Hope this makes sense.! If not just ask and i'll try to explain better.

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Originally Posted by JAZZCNC

Put the rails on the front plate and the bearings on the back plate. This way the rails help stiffen the front plate.
The carriages then go low on the backplate and it makes for a very stiff z axis with max support where it's needed.! close as possible to the cutting end.!

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If the rails are contributing significantly to the stiffness of the material you are using for the Z-axis then that material should be made thicker/stronger. Still definitely put the rails on the front plate, but primarily for the second reason - the supporting carriages are closer to the bed.

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Originally Posted by Jonathan

If the rails are contributing significantly to the stiffness of the material you are using for the Z-axis then that material should be made thicker/stronger. Still definitely put the rails on the front plate, but primarily for the second reason - the supporting carriages are closer to the bed.

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Not sure why you felt the need to post that.? . . . My point was the rails on front plate is much stronger way and no where did I suggest useing it prop up a flimsy front plate.!! . . . Thou if we are splitting hairs then a correct design should factor in all materials plate rails etc to give optimum strength without over engineering which wastes money and effiecency.

Bottom line rails on front is stronger.!!

Okay will do rework with those ideas in place and try to add the rest of the pieces in place as well so that it makes sense. I have to say that i really like working with ViaCAD 2D/3Dv8 (yes I am an unpaid broken record but it is soooo easy to get things right where you want them and surfacing is extremely easy. Will make the changes and see what other gems and insight you will be willing to teach me.

Michael

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Originally Posted by JAZZCNC

no where did I suggest useing it prop up a flimsy front plate.!!

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This, in my opinion, suggests that:

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Originally Posted by JAZZCNC

Put the rails on the front plate and the bearings on the back plate. This way the rails help stiffen the front plate.

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Either way obviously I agree that rails on the 'front' is strongest. It's one of a number of things virtually everyone does wrong to start with, myself included. It also reduces the length of material required for the Z-axis. The only disadvantage I can think of is that you're also having to move the stepper motor and screw against gravity ... but that's almost certainly negligible.

Ideally you should also machine a slot in the plate for the rails so that one of them can be clamped in place. The same is true for the bearing blocks. If the machine crashes it helps stop them move out of alignment. I don't know if you have a milling machine though?

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Originally Posted by JAZZCNC

Not sure why you felt the need to post that.?

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Perhaps there wasn't much point. I thought I was reinforcing/clarifying it.

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Originally Posted by Jonathan

This, in my opinion, suggests that:

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Ok obviously miss understanding but either way flimsy or strong it's fact the rails would help support.!

First let me say dont be fooled by the lack of post's, I've been building diy cnc machines both for my self and others for meny years so I know very well all the newbie mistakes and pitfalls I just havent posted on here.

Regards the down side and your thinking you have to move the steppers with the front plate. It makes no differnce rails on rear or front both you can still have the motor static with the right design. Your right thou the difference is negliable.
I have 2 machines a large and small the large machine use's the moving screw,stepper arrangement with nema34 stepper and the smaller machine use's the static stepper,screw with nema23 stepper both work equally well. The only difference or advantage to the moving stepper arrangment is that it use's slightly less material because you dont need the high backplate but again the saving is negliable.

Eh eh now here's my chance to point out or clarify something you said.!!! . . . When using Profiled linear rails it's important you have a datum referance edge but not for helping stopping them move when crashed, the main importantance is for the alignment when installing. The point being that you fasten one rail tightly up against the referance edge using the correct edge of the bearing or rail depending in which orientation you have them ( they do have a right and wrong way).
Then you tighten the opposing or what I call floating rail or bearing losely then slowly move the gantry or table along the rail nipping the bearing or rail as you go along feeling for any tight spots and losening adjusting the floating rail or bearing to eliminate tight spots. . . . Simplezzs.!

Why do my posts keep getting sent to the moderator for approval.???? . . . There's nothing wrong in any of them. . . Arghh My pet hate is sensorship.!

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Originally Posted by JAZZCNC

Why do my posts keep getting sent to the moderator for approval.???? . . . There's nothing wrong in any of them. . . Arghh My pet hate is sensorship.!

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This censorship is applied to all new users now by the moderators. Most likely to reduce people signing up purely for advertising or that sort of thing. Must be annoying, unfortunately I can't help.

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Originally Posted by JAZZCNC

Ok obviously miss understanding but either way flimsy or strong it's fact the rails would help support.!

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Of course, but if it's helping significantly you're probably doing something wrong.

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Originally Posted by JAZZCNC

First let me say dont be fooled by the lack of post's, I've been building diy cnc machines both for my self and others for meny years so I know very well all the newbie mistakes and pitfalls I just havent posted on here.

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I've read plenty of your posts on CNCzone. Well, I'm pretty sure it's you. It is obvious from the few posts that you have made here that you know what you're talking about! I have not posted on CNCzone since 5 years ago as I figured I would never have time to do any machining if I did it too much.

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Originally Posted by JAZZCNC

Regards the down side and your thinking you have to move the steppers with the front plate. It makes no differnce rails on rear or front both you can still have the motor static with the right design. Your right thou the difference is negliable.

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Fair enough, me not thinking...

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Originally Posted by JAZZCNC

When using Profiled linear rails it's important you have a datum referance edge but not for helping stopping them move when crashed, the main importantance is for the alignment when installing.

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Agreed, the more important factor is to attain good alignment of the rails. It also explains why the sides of the bearing blocks are ground. The reason I said about stopping movement after a collision is that I remembered reading it here, page 13 where it mentions that 'it is possible that the rails and the blocks will be displaced when the machine is subjected to vibrations and impacts':

http://www.hiwin.nl/DownloadCenter/f...9TE14-1006.pdf

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Originally Posted by JAZZCNC

Then you tighten the opposing or what I call floating rail or bearing losely then slowly move the gantry or table along the rail nipping the bearing or rail as you go along feeling for any tight spots and losening adjusting the floating rail or bearing to eliminate tight spots

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That's what I did and subsequently checked it with a dial indicator.

I won't pretend to be any sort of expert on profile rails - I've only just researched them and bought mine. I still may get some for my X-axis (2000mm rails). I gather you know of a good source?

Jonathan and CNCJAZZ,

Thanks you have given me a huge amount of insight into improvements for the gantry section on the rebuild and also on the new build (once the funds are in for that). I am having to replace the end bearings on the one I have and am looking at either getting replacements for now (to have the mill running and to get work done) or get the bearings that I am looking at getting for the rebuild. Think will go with a getting what will let me produce product and then buy the others as I build. Need to be able to make money to build better (more precise) machine.

Michael.

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Originally Posted by Jonathan

Agreed, the more important factor is to attain good alignment of the rails. It also explains why the sides of the bearing blocks are ground.

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Also Jonathan If you look carefully the rails are ground or have ref edge not just the blocks. . . Very easy to miss.!

Here ya go Lads. . . I knew I had some pics of a Z axis I'd made (really should take more pics of stuff made!!) that used linear rails on front plate with stationery motor, Also with pockets for bearings to give datum ref and slightly recovers some lost stick-off.!

It also inverts the stepper and drops it down the backside out the way connecting to screw with belts and pulleys. The number 1 looking bit in the pics is for a drop down bracket that attach's to the y axis screw.

Also a pic showing the Yaxis stepper again inverted in on it's self, reason being this machine was designed for small spaces or sheds so wanted to minimise foot print and eliminate any sticking out bits, The X axis does the same with everything under the bed out the way. . . Nothing protudes past the frame foot print.



In the pic showing rails n bearings they are just lent against the backplate for the pic, the bearings actually go to the bottom of the back plate. They also need cutting to length. . . . . ( Jonathan those are 20mm SBC bearings n rail.)

Okay,

Now you really got me thinking of ways to not only improve what I have but make the new one even better. Also with the two carriage stacked like that on the Z I would assume that you need to increase the length of plate to allow the travel I want to attain. Which might not be a problem. Though would only one set of carriages on each side for the current rebuild be enough with only 150 -175mm of travel.

Hope to get some drawings done tonight and trying to figure out a space issue with the required space for the Z leadscrew and backlash nut/mounting bracket versus the height that the rails and carriage require to function. Looks like I will be needing to mill some stock down with not only datum slots but also with channel to allow space for the screw. I have access to 12mm Alli' for sure and might have access to thicker. Having said that would milling the 12mm down to a 6mm channel in the centre reduce strength below the desired levels? I am still learning metal and it tolerances and what it can and can not do. Which is different then what i do with metal for making reeds in many fashions as there you want the metal to bend.

Michael

Hi Micheal,

First depends what you intend to do with the machine regards the plate thickness. I've made various differant Z axis but only one that was made with thin plate. This had a long 220mm travel and was mainly intended to cut soft materials like foam,plastics etc. It was made with with cast off's and scrounged parts that the owner and me between us gatherd (Hence thin plate was used).
It's not ideal for cutting hard materials but the guy does cut every thing from foam to Ali with it. . . It's a belt driven machine as well, very quick and accurate.!! . . I love this little machine "The Cavemill" was so much fun to make and resonably cheap being made mainly from scrounged bits. Attached a few pics of the Z axis and some stuff it's cut.

I love making "Junk yard dog's" I'm just finishing off another I'll post a pic of.

Personaly I dont like to use anything below 19mm for a Z axis that is intended to cut hardwoods or Ali. If your using profiled rail and intend to cut datum points and slots for screw etc then you really do need the 19mm else your weakening the structure. Again depends on intended use but for hardwoods and Ali using Profiled rail then 19mm is minimum IMO.
Also I wouldn't recommend using 1 carraige per side no matter what thickness material, it's false economy because it will flex badly and you'll end up making it over again.! . . Esp at the travels your wanting.
Imo the Z axis is one if not "THE" most important parts on the machine, remember doesn't matter how strong you build the rest of the machine if the Z aixs flexs you'll have BAD results.!! . . . It's also one area everybody new under estimates.

Regards travel most of my Z axis tend to be between 120-150mm the one in the previous pics had 150mm if I remember correctly.??

Attached a few pics of Zaxis made all ways. All built depending on machine and material requirements. Hope these will help you design something to full fill your needs.

Cheers.

PS: The upstands on the junkyard pics are temps just for affect to give idea too intended owner and have since been made lot shorter.

Edit: Added Cavemill pics of stuff cut.

Folks been buried in work.

Still chugging along but clients come first. Really need to get the rebuild on the first machine done though and if possible the second built as already have product that will need the length in it and have clients that want to buy. Why, oh, why do i get myself into these positions. Wish me luck and have the new drawings and hopefully more useful information up soon . Also mc_cnc I will try to drop you a line to see how to catch up with you.

have a good night folks need sleep.

Michael

I know all about those positions, but right now the brain is shutting down!
All I know is I woke up at 7am on saturday on the west coast of Canada, and I'm now sat at home having had about 2 hours sleep on the plane.

Okay,

Here is tha much promised and hard to get around to drawing of v2. You will notice that it is not complete. I am still working away at it but would like some input. Will let you know any other problems might be having in the near future. Due to problems (flex of Y axis and Z axis dropping up to 1.5mm from a set position) this rebuild has to be done like yesterday and been working on it the last three days non-stop. This is what has made far enough to be label a version and put before you folks for opinion and evaluation.Attachment 4546

Any and all opinions would be greatly appreciated as will be burningthe candle in to the long hours. Need this done to get product back up to stocking levels for a convention at the end of October. Yes thing s do go wrong at just the wrong time. Yes I know I need to increase the rail for Z to get 150mm.

Anyone wanting a DWG, STP, IGES file of this or the completed gantry router let me know.

Michael

id think about putting both Y axis rails top and bottom or you are going to lose valuable space...

the way you have them now will have your spindle over hanging further than it needs to buy quite a long way

try to keep your spindle as far back as possible... every little bit will help, it may not alter the flex by much but im pretty sure that each little fraction of stiffness you save will reduce sympathetic resonance or vibration by a sh*t load

good luck:smile: