DIY Build of Aluminium CNC Wood Router without Workshop & Tools

Know I'm probably whacko even thinking of doing this in this way, and my Scot's blood rankles against using hard earned dosh that is rapidly dwindling in the absence of any foreseeable income, but....

I have read enough around this recently to already feel somewhat overwhelmed, so that's a challenge to be won!

I don't currently have access to anything like a proper workspace, as I'm currently living in my touring caravan (long story that I'm not going to explain here).

One corner-ish (1300 x 900) of the caravan will be allocated as workspace to get everything assembled and (ostensibly) working, and I obviously need to invest in a few more tools, and build a small wooden bench thingy.

I don't intend creating any sawdust in the caravan for obvious reasons, but reckon wee amounts of nice clean aluminium swarf can be reasonably contained and won't do too much harm.

This machine will probably only be used in real anger after I hopefully get to emigrate downunder to join my kids in Oz in a couple of years.

So far I have only done tutorial-1 on Sketchup so please excuse lack of plans or level of plan detail initially.

My hope is that the build will help me retain what is left of my sanity, but am also a tad worried that it may actually have the opposite effect, as it's already got my staying awake until morning birdsong!


Requirements:

1. To be used primarily as a hobby machine, but the way worldwide income prospects are looking in my field (IT-technical-mainframe-software-old-fart) who knows, this machine may even help provide some income in future.

2. Mainly to be used for routing/drilling wood, but poly-plastics and smallish pieces of aluminium for making woodworking jig-thingies is bound to follow although less frequently than wood.

3. Needs to allow for machining the top faces of pieces of wood up to around 100mm thick, as might be used for making workbench legs.

4. Tool cutting area, measured tool centre to centre, needs to be 600mm wide but the length is less important... maximum 900mm would be nice... but I still have to define this within my limited workspace, considering rigidity and the cost of available rails and drivescrews, etc..

5. Needs to be able to machine the top edge of boards that are clamped upright at the end of the X-Axis to allow for cutting of matching (M&T / finger / dovetail) joints.

6. Fixed-Bed and Moving-Gantry machine with 3 Axes initially and speed is not that important for the initial build, though it would obviously be a nice to have.


Thanks to the advice already received on this forum I feel my understanding has already advanced in leaps and bounds from where I was 4 days ago thinking of doing a build in MDF with unsupported rails and M8 drivescrews.

Very recent additions to my vocabulary (not to suggesting my understanding is correct) include Profile-Linear-Rails, Supported-Linear-Rails, Ball-Screws, Trapezoidal-Screws, Acme-Screws, Backlash, Whipping, Resonance, Chattering, Breakout-Boards, Stepper-Drivers, Stepper-Motors, Mach3, G-Code, and others.

My next post will hopefully have defined the hardware and components to be used, only after I've spoken to a helpful gent near Wakefield to help guide me in the right direction.

Cheers,
Andy

I'm finding far too many variables floating around in my grey-matter, causing me to go off at tangents researching multiple different options of anything and everything, so am taking some decisions to lessen the load on my limited mental capacity.

Have decided on the adjustable bed type design similar to Iwant1's, but will do the initial build on a flat aluminium frame in the caravan, and only weld up the steel frame when I eventually get it into a workshop before using it in anger.

As I don't have machining facilities in said caravan, have bought a set of pre-machined ballscrews from linearmotionbearings2008 for about £330+duty:

- 4pcs anti backlash ballscrews
- RM1605-300/850/1150/1150mm-C7 (4 screws+4 balnuts+4endmachinings)
- 4 sets BK/BF12 with locknut and circlip
- 4pcs of 6.35mm*10mm flexible couplings

Have also roughly decided on using the following, but will only buy these later:

- SBR20 supported rails and SBR20UU blocks for all three Axes
- PM752 drivers x 4
- 3Nm NEMA23 steppers x 4 (SY60STH88-3008B ?)
- Mach3
- Ethernet SmoothStepper

Meantime, I will work on the rough design in SketchUp, thanks to the help from the forum, and only determine exact dimensions when the ballscrews arrive.

Btw, many thanks to JAZZCNC for giving me plenty of time and great info!

Surprised you have ordered 1605 do you need higher resolution than 1610 provides.?

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Originally Posted by JAZZCNC

Surprised you have ordered 1605 do you need higher resolution than 1610 provides.?

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Damn... That's a perfect example of how too many variables have been fogging my mind.

You are spot on Jazz... Thanks...

On the positive side my use of "have bought" was temporary poetic licence and I was subsequently distracted and haven't placed the order yet, so will change it to 1610.

I'm busy with my design and have a query that references aspects of some incomplete bits within the circle in the attached pic.

The back part of the Y-beam and the top part of the X-carriage is going to be formed out of 152x51x9.5mm aluminium angle, which is coloured yellow.

I had decided to put the ballscrew-nut housing midway between the X-bearings as depicted by the grey block, but am now wondering whether it might not be better to maybe beef up the end of the Y-beam, attaching it securely to the vertical angle on the X-carriage, and simply make that into a ballscrew-nut housing, which would result in more "direct" drive to the Y-beam? The fact that this is towards the end of the X-carriage may not be ideal, but would it be acceptable or likely to cause problems?

Cheers,

EDIT: Have now cancelled that idea and am going back to Keeping it Simple!

Does anyone perhaps have a legible dimension data sheet for Chai's 1610 ballscrews?

I have a copy off eBay but these old eyes canna read the dimensions even after sharpening and increasing the image size.

Particularly interested in the BK12 and BF12 bits.

Thanks,

Here's the end-machining drawing I got from Chai a couple of years ago:

Attachment 6490

Which dimensions do you need from the rest?

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Originally Posted by Jonathan

Here's the end-machining drawing I got from Chai a couple of years ago

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Thanks Jonathan. I had already saved those up off a previous post of yours I think.

Quote:

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Originally Posted by Jonathan

Which dimensions do you need from the rest?

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I'm after the size of the BK and BF support blocks, and particularly the dimensions from the centre of bearing to each of the edges. My current design looks like too tight a fit for these blocks, so would like to know what I need to cater for.

How do you guys normally accurately align the bearings and ballnut?

I'm guessing I need to allow some leeway in order to be able to adjust during setup.... Is this normally done at the ballnut or at one of the bearings and if so which bearing?

Found the dimensions I needed for the BK12 and BF12 mounting blocks.... they are 60x43 and the bearing centre is 32.5 from the base. So just the one remaining query:

How do you guys normally accurately align the bearings and ballnut?

I'm guessing I need to allow some leeway in order to be able to adjust during setup.... Is this normally done at the ballnut or at one of the bearings and if so which bearing?

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Originally Posted by WandrinAndy

How do you guys normally accurately align the bearings and ballnut?

I'm guessing I need to allow some leeway in order to be able to adjust during setup.... Is this normally done at the ballnut or at one of the bearings and if so which bearing?

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Yes some leeway is exactly what you need. Ideally you have 'leeway' in the plane perpendicular to the axis of the ballscrew, not just in one direction. So to answer your question, a bit of both. If you mount the bearings in slotted holes then that gets adjustment in one axis, to get adjustment in perpendicular direction you should be able to use the small amount of clearance in the ballnut mount to adjust the ballnut centre height, but clearly it depends on the mount.

If one bearing is fixed, then spin the ballscrew so the ballnut is at that end, move it back and fourth a little to make sure it centers then tighten up the 6 ballnut bolts. Spin ballscrew so ballnut is at other end, now tighten that bearing mount so it aligns to the ballnut and the other bearing mount by default. If the ballscrew gets noticably more difficult to turn (by hand) towards either end then there is an problem with alignment, so loosen the nut/bearing depending and try again. A tiny amount of misalignment will impose a high radial force on the ballnut which well cause excessive wear since they're not designed to tolerate radial forces.

In my journey so far, you lot... you know who you are... have already warped my thinking to such an extent... thank Thor... that for now I intend using the following components/concepts:

- 20mm supported-rail on X
- 20mm profile-rail on Y,Z
- RM1610 ballscrews on X,Y,Z
- Gear+Belt drive on X and Y, and suppose this may well be used on Z as well... in for a penny.... but this aspect probably worries me more than anything else!

I am now feeling very comfortable with SKP/SketchUp, and how I wish I had used such a tool when designing the odd thing in the past!

I'm starting to make good progress with the design... I think... so have included two SKP pics of my design so far for feedback.

The structure is mostly to be formed out of 6"x2"x3/8" aluminium angle which the Aluminium Warehouse website converts to 152.4x50.8x9.53 mm but let's call it 152x51x9.5 which is what I used in SKP. There are two other materials used so far:

- Blue = 100x50x5 rectangular tube
- Yellow = 45x45 extrusion from KJN

More research is needed before I complete the drive for the X and Y, and do the Y-carriage and the entire Z axis.

Am trying to do the build with standard components, but already need a ballscrew-mounting for Y to be machined and think more will come out of the design of the Y-carriage and Z.

The ballscrew lengths... between bearing blocks... are about 1060 on X and 707 on Y.

When I move on from the touring caravan in the future, this machine will be mounted on a rigid frame with an adjustable bed, so the obviously limited depth below the cutting point is temporary to allow me to get to grips with getting the thing working. Bracing the base of the frame... particularly behind the cutting point is still to be included in my SKP pics.

Please "holler" about the problems... I'm that thickskinned that I cannot recall ever having taken offence at anything!

Thanks,

PS. Is 5mm aluminium sufficiently thick to make a M6/M8 tapped thread reasonably strong?

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Originally Posted by WandrinAndy

Please "holler" about the problems... I'm that thickskinned that I cannot recall ever having taken offence at anything!

Thanks,

PS. Is 5mm aluminium sufficiently thick to make a M6/M8 tapped thread reasonably strong?

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Ok I'll holler first but not too much. . Lol

45x45 extrusion is pretty weak so I would consider going larger.!

5mm in aluminium is NOT enough. M6 = 1mm pitch so only 4 full threads M8= 1.25mm pitch so 3 full threads no where near enough and it will strip.!!

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Originally Posted by JAZZCNC

Ok I'll holler first but not too much. . Lol

45x45 extrusion is pretty weak so I would consider going larger.!

5mm in aluminium is NOT enough. M6 = 1mm pitch so only 4 full threads M8= 1.25mm pitch so 3 full threads no where near enough and it will strip.!!

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Thanks Jazz.

I had thought that the heavy version of the 45x45 would be strong enough as it is bolted along the back of it's whole length to 9.5 plate. I will look at replacing the top section with 45x90 then. Do you think this will be enough?

I'm hoping that tapping into 9.5mm plate... 90% more threads.... is just ok then?

Quote:

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Originally Posted by WandrinAndy

I had thought that the heavy version of the 45x45 would be strong enough as it is bolted along the back of it's whole length to 9.5 plate. I will look at replacing the top section with 45x90 then. Do you think this will be enough?

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Nah even the heavy version isn't has strong as you think.!! The 45x90 will be better but I'd put it top & bottom and have the wide bit flat.
This way it ties into the sides better and gives more resistance to bending in lateral cutting directions.! It doesn't Add much to the vertical up & down strength plunging will inflict but the 10mm plate will help here and plunging should be avoided if at all possible anyway.! Most of the time the machines cutting and the forces are lateral.!!

10mm is just about ok for threading in Alu.

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Originally Posted by JAZZCNC

The 45x90 will be better but I'd put it top & bottom and have the wide bit flat.
This way it ties into the sides better and gives more resistance to bending in lateral cutting directions.! It doesn't Add much to the vertical up & down strength plunging will inflict but the 10mm plate will help here and plunging should be avoided if at all possible anyway.! Most of the time the machines cutting and the forces are lateral.!!

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I would have thought that my design as pictured already provides lateral resistance roughly equivalent to what you're suggesting, as a cross-section of the bottom of the gantry consists of 45x45 bolted close to the backwards pointing 51mm leg of the 9.5 angle? And the 9.5 angle extrusion is bolted to both the base and the uprights of the X-carriage hopefully creating a very rigid joint?

Quote:

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Originally Posted by WandrinAndy

I would have thought that my design as pictured already provides lateral resistance roughly equivalent to what you're suggesting, as a cross-section of the bottom of the gantry consists of 45x45 bolted close to the backwards pointing 51mm leg of the 9.5 angle? And the 9.5 angle extrusion is bolted to both the base and the uprights of the X-carriage hopefully creating a very rigid joint?

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OK then go for it.!

9.5mm is definitely fine for M6 since none of the forces on this small machine will get anywhere near the rating of an M6 bolt. I'd advise using threadlock to make sure any bolts don't vibrate loose.

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Originally Posted by WandrinAndy

- RM1610 ballscrews on X,Y,Z

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Good choice for X and Y but there's no need to use 10mm pitch on the Z-axis. Keep the resolution by using RM1605 on Z.

Thanks for the feedback guys.

Last query on the limits of thread in 5mm thick aluminium... When attaching the supported round rails on top of the beam on the X-axis is it then necessary and best to run a length of thicker flat bar through the box section to take the bolts?

I've decided to go with Jazz's GREEN design for the Y-beam..... It's a great KISS solution... can't for the life of me recall why I dropped the idea in the first place! Have attached updated pics.

Although my gantry end plates are only made from 9.5mm angle-section.... it helps makes the design compact and build easier what with my current limitations... I'm hoping that with the end plates and gantry being relatively squat, this will be rigid enough. Or should I include some bracing to the angle?

Quote:

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Originally Posted by WandrinAndy

Last query on the limits of thread in 5mm thick aluminium... When attaching the supported round rails on top of the beam on the X-axis is it then necessary and best to run a length of thicker flat bar through the box section to take the bolts?

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To be sure then Personally yes I would.! . .BUT. . If you use M5 bolts then with smaller pitch and keeping the centres closer together with the higher quantity of bolts you could get away with it.?
I've done this with steel 4mm box section and it's worked ok.! . . It's just with softer Ali @ 5mm could be marginal.?

At the worst you can just add the thicker bar through at a later date if it doesn't feel right or causes problems.?

The Angle gantry sides should be ok because of the squat nature and the fact it's driven from both sides.! The thing to watch out for is that the Angle both internal and external are close to 90deg.? The round rail bearings will handle some discrepancy but you don't want too much.!! . . . Bracing will help absorb any resonance and can only help.

I've noticed from the pics you have 2 plates on the bearings and cutaways in the gantry sides for what looks like access to the bearing bolts.?
If you use 2 plates then you don't need access to the bearing bolts and can bolt the top plate direct to the bearing plate so no need for access slots. The beauty and point of 2 plates means it makes gantry squaring easier without having to worry about bearing bolt access.

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Originally Posted by JAZZCNC

I've noticed from the pics you have 2 plates on the bearings and cutaways in the gantry sides for what looks like access to the bearing bolts.?
If you use 2 plates then you don't need access to the bearing bolts and can bolt the top plate direct to the bearing plate so no need for access slots. The beauty and point of 2 plates means it makes gantry squaring easier without having to worry about bearing bolt access.

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Splendid... I wasn't looking forward to "hacking" out those cutaways, but thought I had read somewhere that one should allow access to the bearing bolts... and now know that's to allow for gantry squaring.

It will be so much easier doing it the way you suggest. I had already included four bolts (M8?) holding the plate and angle together, so will maybe tweak these to be a tad closer to the bearings and add two in the middle for good measure and just drill holes in the angle to accomodate the bearing bolt heads.

I guarantee that an M5 or M6 hole will not strip in 5mm of aluminium for the loads that are imposed upon it on your gantry.
When calculating the length of thread engagement required the standard method is to calculate the required thread for it to require a higher force to strip the thread than for the bolt to snap when placed under tension.

For M5 the calculation (reference here) results in minimum 4.0mm engagement and 5.0mm engagement for M6. However this assumes the thread is steel, so you have to compensate by multiplying by the ratio of the material's tensile strength. This clearly results in slightly greater values.
This is still not a problem since the force on each bolt is small in your application, particularly if there are a lot of them. You are not going to get anywhere near the force required to snap a bolt. The concern is more ensuring they do not work loose, so I would thread-lock them to be safe. Since you are using SBR rails I reccomend thread-locking the bolts that fix the rail to the aluminium mount since they can also work loose.

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Originally Posted by Jonathan

I guarantee that an M5 or M6 hole will not strip in 5mm of aluminium for the loads that are imposed upon it on your gantry.

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Argh but I bet you won't guarantee he won't strip one while tightening and that's the danger with so few threads.!! . . . . Carefully does it.!!!

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Originally Posted by JAZZCNC

Argh but I bet you won't guarantee he won't strip one while tightening and that's the danger with so few threads.!! . . . . Carefully does it.!!!

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How did you know that Jazz? I have been known to strip thread in thick steel on more than the odd occasion. lol

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Originally Posted by JAZZCNC

Argh but I bet you won't guarantee he won't strip one while tightening and that's the danger with so few threads.!! . . . . Carefully does it.!!!

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Yeah if we're taking this seriously then use a torque wrench, but I prefer to calibrate my hand and shout 'click' :barbershop_quartet_

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Originally Posted by Jonathan

Yeah if we're taking this seriously then use a torque wrench, but I prefer to calibrate my hand and shout 'click' :barbershop_quartet_

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Yeh I,ve always said bet you have a good wrist action. .:whistle:

Following the change in gantry design it made sense to rationalise some material used, as the minimum profile length from Aluminium Warehouse seems to be 2500.

Have also tweaked and simplified my overall design... and am sure there is still more tweaking to come... Gawd I can go off on a tangent and over-complicate things unnecessarily!

Have corrected the collision-ing at the extremities of the X-axis travel in the virtual world... Can now easily slide the gantry along it's entire length of travel within SketchUp with a few mm to spare!

From pics I've seen I'm guessing that the drive shaft of the Nema23 motor is too short to accommodate a pulley if the motor is mounted with the shaft going through 10mm plate... Please shout if this isn't the case... So still have to design a mount to solve this.

I think that so far virtually everything is within my limited capabilities and my limited workshop/tools facilities, particularly if I can get Aluminium Warehouse to cut the aluminium profile to the required lengths. The one exception is that I am looking at ballscrew housing mounts (purple) on the X-axis that also serve to brace the gantry-end angle profile.

Have just started on the Y and Z carriages... Will probably use Zapp's Hiwin HGR20R profile-rails (800mm and 400mm) and HGH20CAZA medium-preload four-row bearing blocks. Pretty sure it will require machining to keep
the Z-Axis really close to the Y-Axis, so when I get there I'm hoping that someone on the forum offers machining as a service and would have the time to build these for me?

Drive shaft length of a Nema23 is 20mm of the main face, 19mm off the reference lip and you need a 38.1mm hole to accomodate the reference lip on the face of the motor (or bigger if you are not using the reference). So if your pulley is <38mm dia and <10mm wide you can fit the pulley before mounting the motor. Otherwise you'll have to recess the motor by milling a 56mm wide recess, 5mm deep, in the 10mm plate... or find another way

Apologies for chopping and changing like the weather... In mitigation I have never built anything out of alu, so reckon it's best to get the design correct-ish up front in the virtual world. My fault is being far too hasty in posting newer versions!

I have further rationalised the frame material used... Have got my head around bolting plates at 90deg so am rid of the unequal angle profiles. Main materials are now KJN 45x90 alu-extrusion and Cut-To-Order alu-plate from Aluminium Warehouse. And the frame is now far easier for me to build and assemble.

Have also decided to go with profile-rail on the X-axis... Am more than a tad worried about the rising costs, but suppose in for a penny... and if a job's worth doing...

Although some relatively minor tweaking will be needed once I get into the Y and Z carriages, I am finally well pleased with the frame and won't bore you with any more iterations of it.

Quick question... my supports for the BK and BF blocks... made from 20mm plate... do these look strong enough... particularly the BF side that is not braced?

I'd replicate the bracing in reverse as per the near end, it'll look better too, not sure thats rigid enough and thinner pieces can resonate unexpectedly.

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Originally Posted by irving2008

I'd replicate the bracing in reverse as per the near end, it'll look better too, not sure thats rigid enough and thinner pieces can resonate unexpectedly.

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Thanks Irving... I've changed it and you're right.... the spinoff is it looks far better too.

The BF side bearing is only there to stop the screw whipping which does not require particularly great rigidity in the mount. This bearing should only be subject to radial forces, so as long as the mount is strong enough in the Y-Z plane it will be fine. I would make it a bit stronger than you have currently drawn, but wouldn't go so far as replicating the other end mount exactly - you can save a bit of material.

If you're buying the Hiwin rails new then there's no need to get 20mm for this size machine - 15mm is perfectly good for the vast majority of CNC routers. This could help with making the Z-axis more compact. If however you find the rails cheap on eBay then by all means use the larger sizes. You shouldn't have much difficulty finding a good deal there at least for the shorter rails.

As irving's said, recessing the motor mounts is an easy strong way to get round the short shaft problem, here's a few examples:

Attachment 6602Attachment 6603Attachment 6604

Quote:

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Originally Posted by Jonathan

If you're buying the Hiwin rails new then there's no need to get 20mm for this size machine - 15mm is perfectly good for the vast majority of CNC routers. This could help with making the Z-axis more compact.

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Thanks Jonathan... Pics really help visualise things... Looks to me like those mounts are milled down to about 3mm? Have you noticed you're missing a bolt in pic-1... or is that one an optional extra... Lol

I've drawn my pics with 20mm rails because I had already created them as components under Sketchup, but am seeing more and more comments stating that 15mm is plenty good and that would save some dosh, and might bring Z 2mm nearer to Y.

But, I am a wee bit worried about aligning 15mm rails on this particular profile as the slot itself is 10mm wide and then there is a wee surface rebate on each side of the slot, that looks to be about 1mm, which makes a total gap of 12mm resulting in the rail only being supported by 1.5mm on each side! So am thinking that 20mm would better... supported by 4mm on each side?

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Originally Posted by WandrinAndy

Looks to me like those mounts are milled down to about 3mm? Have you noticed you're missing a bolt in pic-1... or is that one an optional extra... Lol

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Yes something like that... you don't need much thickness if there's plenty of material around the motor mount surface to stop it bending. I missed two screws in that picture as it was just a test fit.

Quote:

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Originally Posted by WandrinAndy

I've drawn my pics with 20mm rails because I had already created them as components under Sketchup, but am seeing more and more comments stating that 15mm is plenty good and that would save some dosh, and might bring Z 2mm nearer to Y.

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The drawings are available from the Hiwin website by the way...
You can also get Z closer to Y by milling pockets in the Z-plates for the rails and blocks. That's required anyway if the plate isn't nice and flat...

Quote:

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Originally Posted by WandrinAndy

But, I am a wee bit worried about aligning 15mm rails on this particular profile as the slot itself is 10mm wide and then there is a wee surface rebate on each side of the slot, that looks to be about 1mm, which makes a total gap of 12mm resulting in the rail only being supported by 1.5mm on each side! So am thinking that 20mm would better... supported by 4mm on each side?

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Ahh didn't notice that. With either size rail I would prefer to see them mounted on a strip of aluminium and have that bolted to the aluminium extrusion to spread the load. Hiwin 20mm linear guides are 36mm tall and the 15mm variety are 24mm tall, so if you mount the 15mm rails on a 12mm thick strip the rest of the drawing stays the same. In addition this maintains a good spacing between the 4 blocks which is necessary for good rigidity.

Quote:

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Originally Posted by Jonathan

With either size rail I would prefer to see them mounted on a strip of aluminium and have that bolted to the aluminium extrusion to spread the load. Hiwin 20mm linear guides are 36mm tall and the 15mm variety are 24mm tall, so if you mount the 15mm rails on a 12mm thick strip the rest of the drawing stays the same. In addition this maintains a good spacing between the 4 blocks which is necessary for good rigidity.

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The Hiwin pdf I downloaded from Zapp about a week ago gives the height from bottom of rail to top of block as: HGH20CA = 30 and HGH15CA as 28, so much of a muchness. Are you figures for a different model or have I cocked up?

Yep, I will also need some milling done in the Z/Y plates.

Quote:

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Originally Posted by WandrinAndy

The Hiwin pdf I downloaded from Zapp about a week ago gives the height from bottom of rail to top of block as: HGH20CA = 30 and HGH15CA as 28, so much of a muchness. Are you figures for a different model or have I cocked up?

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Edit, sorry I accidently looked at the dimensions for HGL and completely misread the table. You are correct.
Page 6.

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Originally Posted by Jonathan

Edit, sorry I accidently looked at the dimensions for HGL and completely misread the table. You are correct.
Page 6.

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Ok, that looks like the same doc but I'm taking the specs from page 6 for Model Series HGH (Square type) which is what Zapp is advertising on their website currently, whereas your page 5 is for model series HGL (Square type3) whatever type3 means... Maybe low "profile"... Why oh why can't things be simple...

Quote:

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Originally Posted by WandrinAndy

Ok, that looks like the same doc but I'm taking the specs from page 6 for Model Series HGH (Square type) which is what Zapp is advertising on their website currently, whereas your page 5 is for model series HGL (Square type3) whatever type3 means... Maybe low "profile"... Why oh why can't things be simple...

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It is simple - if you get 15mm HGH from Zapp it's 28mm. If you get 20mm HGH it's 30mm.
Sorry for causing the confusion...

No probsh... My confusion was caused by me not realising the blocks come in that many different models.

Two quick questions please.... I'm considering again how prone the ballscrews and profile-rails are to contamination from chips etc. particularly on the X-Axis.

I'm guessing it might be prudent to get the optional bearing-block scrapers fitted to protect the seals on the X-axis, but that the other axes are far enough removed from the cutting point to not be too much of a worry?

Let's say I am machining small alu parts... would this be best done at the BF end for better accessibility and to reduce contamination, or best at the BK end that is closer to the motor?

Thanks,
Andy

As I've never made much of any mechanical rotating thingies before, the whole aspect of Timing Belts and Pulleys was a worry. But now that I've absorbed the relevant postings on the forum... particularly thanks to Jazz's pics... it seems quite simple.

I am again thinking of using RM1605 ballscrews for maximum possible resolution and torque and then gearing 2:1 to achieve "longer pitch" and speed. I understand this will increase load on, and reduce life of, certain components... but it somehow still gels better in my grey matter than doing it the other way around. Please persuade me if the other way is really the far better balanced solution... afraid I can't quite get my mind around that... yet?

On the X-axis will use 5mm pitch 15mm wide HTD Timing Belts and HTD5M-15 Timing Pulleys - 16T [o.d=28mm] and 32T [o.d=54mm] from http://www.beltingonline.com/5mm-htd-timing-belts-4575.

On the X-axis the Ballscrew pulleys will be 16T and Stepper pulleys swappable between 16T and 32T as a start :

- Stepper pulley bores modified to be 8mm and with 1 off M4 grubscrew hole
- Ballscrew pulley bores modified to be 10mm and with 1 off M4 grubscrew hole

Each idler will be made of two bearings 8mm i.d x 28mm o.d x 9mm wide from http://stores.ebay.co.uk/xtremesportandleisure-uk-online?_trksid=p4340.l2563 sandwiched between large washers serving as guides on each end.

Two quick questions please -

- Apart from asking Chai to machine F increased to say 30mm for coupling, does Chai grind the small flat on the shaft for the grub screw to grip and stop the pulley spinning or is that something I would have to do?
- Are M4 grubscrews about the right size for 8-10mm diameter shafts?

The costs are mounting... but after my massive shock at the cost of profile-rails and bearing-blocks, these components seem comparatively cheap!

Thanks,
Andy

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Originally Posted by WandrinAndy

I am again thinking of using RM1605 ballscrews for maximum possible resolution and torque and then gearing 2:1 to achieve "longer pitch" and speed. I understand this will increase load on, and reduce life of, certain components... but it somehow still gels better in my grey matter than doing it the other way around. Please persuade me if the other way is really the far better balanced solution... afraid I can't quite get my mind around that... yet?

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No no no wouldn't recommend that route.? Yes I know my machine use this setup but that was purely because 1610 or 1605 where not available from Chai and at that time ballscrews from anywhere else were very expensive and out my reach. Even 2nd hand they were more than Chai wanted for new ones. Thankfully things are very different now days.!

It's always better to obtain the required speed from the using correct pitch screw so 1610 is far better option if you need the speed. Plus you'll have more torque from the motors has they won't be spinning has fast and in a much better area of the torque range while cutting which is where it matters most.
If you need resolution then you can always gear down, yes you'll lose speed but the torque will double. Still use belt drive even if your running 1:1 because of the fringe benefits of resonance dampening and flexibility to gear if required.

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Originally Posted by WandrinAndy

Two quick questions please -

- Apart from asking Chai to machine F increased to say 30mm for coupling, does Chai grind the small flat on the shaft for the grub screw to grip and stop the pulley spinning or is that something I would have to do?

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No it's DIY but turned portion is soft so a decent file and it's done in 2mins

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Originally Posted by WandrinAndy

- Are M4 grubscrews about the right size for 8-10mm diameter shafts?

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Use the largest you can fit in the boss of the pulley.! If going between teeth on pulley then just make sure you sink deep enough doesn't foul belt and no sharp edges.
I mainly use M5 and M6 some times M4. Bigger the better because the larger allen key means you can get good purchase for tightening plus more surface area on shaft flat.

If you end up using 1610 1:1 then I'd use 20T pulleys has it's a nice radius and the belts aren't quite so prone to cracking from the tight radius smaller pulleys give.