[Louis_Cannell]

Been busy of late and the conversion of the Seig X1LP super has been succesfull to date, now time to build something from scratch. Started badly as I couldn't resist a bargain and came across a couple of sets of Rails Bearings and screws at the right price Sub £300 delivered. So my starting point now is:
4@ SBR20-300mm Linear guide
4@ SBR20-600mm Linear guide
4@ SBR20-1000mm Linear guide
24@ SBR20UU Linear blocks
2@ SFU / RM 1605-350mm- C7 ballscrew with end machined
2@ SFU / RM 1605-650mm - C7 ballscrew with end machined
2 SFU / RM 1605-1050mm- C7 ballscrew
2@ with end machined
6@ BK12 support for ballscrew
6@ BF12 support for ballscrew
6@ Couplings
Major considerations, I have a workshop in a spare room in my first floor flat so everything gets carried up and down as required, and I try to limit noise to be considerate to neighbours. Been looking at Fusion 360 which I find simple and straightforward to use with the Seig conversion so knocked up a quick mock up of a machine to get some comments and advice sure there are lots of traps I have fallen in to pictures below .
My requirements call for a 700x400mm work area and max 100 mmZ axis. Not included in pictures are 2 SFU / RM 1605-1050mm- C7 ballscrews driving Y axis, either 1 or 2 SFU / RM 1605-650mm - C7 ballscrew driving X axis and single SFU / RM 1605-350mm- C7 ballscrew driving Z axis with a Chinese 2.2 water cooled and VFD. A lot of my strength I am relying on a solid base I intend to bolt whole thing solidly down onto a welded steel framed table with a solid cast iron top.


Material wise two bed sides are100x100x10mm T section which can be backed up by another 25-35mm plate without losing work area, X and Z main components 25mm and 30mm Ecocast, first draught so nothing much fixed apart from overall size, my idea is based on ease of build, welding in the flat is not an option, also all materials used in the design are available so no brainer to use them pricing them up would be close to £500 plus to obtain.

[Louis_Cannell]

Time to reflect and rethink design a bit of input from others so a few changes made.

Knocked up version 2 this is a draft few peices omitted till I collect stock material acquired today like side of gantry just turned original on side for now and nor bothered actually mating same to bearings more for concept than actual design, also brackets mounts for screws, motors etc missing. Hopefully overall design and more importantly rigidity improved pics below sides now 6x2x1/4" Aluminium Box, cross member on X axis now original 150x30mm Backed by 2@3x1x1/4 Angle faced to 75mm x 25.4 to fit.

[louieatienza]

Looks cool, though I think the dual gantry leadscrew is unnecessary. Even large industrial machines use a single screw.

[Louis_Cannell]

I was thinking that too just dropped in to see no dhance of twisiting on the X axis if built correctly, I brought both sets of screws and rails at the right price as I wanted two screws on Y axis don't like the idea of one down the middle, sure I will find homes for the spare screws and rails.

[Louis_Cannell]

First chance to do any work on build today half a day off so made a start, first job decide what to do about the steel and cast iron base I intended on using, top has been ground flat and its ready to go but Base weighs in above 3Cwt and Top just over 4Cwt all to be carried upstairs.

For time being I am going to put base into my lock up and try a different base to as all work in flat is likely to be lightweight, I will be selling my flat and buying a property with a workshop so the base will either be used then with this machine I originally designed for it or with version 2.0 which I have no doubt will be built.

So alternate base? As welding out of question in flat I have gone for simplicity, two sheets of 25mm MDF to make my base, bed laminated 75mm MDF whole base sealed glued and screwed, it's solid, time will tell if its solid enough, I cannot see any problems with type of work it will do whilst in the flat.

As base was drying I decided to drill and tap side rails which are 6"x4"x1/4" Ali box I used M6 with 30mm washers to attach rails to bed, M4 to mount external supporting ribs 300mm 38x38x6mm T section, M4 again to mount 20mm supported rails quite happy with the afternoons work, rails have a little adjustment available and I intend on locking them down with either loc-tite or epoxy when final adjustments made, currently as close as I can measure having just dropped them on and pinched up they are within 0.5mm over 1000mmm on the parallel.

Couple of pics below showing latest design and progress.

[Louis_Cannell]

Grabbed a couple of Hours this afternoon again and made a start on the X axis, by far biggest lump of aluminium thats been machined on the Seig since conversion, think I upset it when I put the fly cutter on to true and parallel top and bottom to accept rails, it started spitting needlles at me with a vengance!

635x150x30mm 5083 Plate backed by two lengths of 3x1X1/4" angle which was drilled and plate drilled and tapped for M4, top and bottom trued, paralleled, drilled and tapped M4 again to mount rails.

Stomache was thinking throat had been cut so stopped now to eat, just two ends of crossmember to machine true and parrallel and it is about ready for ends/gantry sides to be mounted, I am thinking pocket the gantry sides 1/16" to accept crossmenber for strength and ease of alignment doing so also positions them nicely to centre of Y axis bearings.

Spindle and VFD just arrived got a good deal on these £146 delivered and they look ok, now I'm cooking with gas.

Build is going OK a good start with 9 hours in its starting to take shape, if you sort of squint and look sideways that is, as my old dad always said "a blind man would be glad to see it"!

[Louis_Cannell]

Have a Y and now almost an X and I have a few spare hours over the weekend to come up with working drawing for Z and start machining. Impressed with Fusion360 so far simple to use and with a little tinker of the code before running mach3 the little seig conversion goes about its business with little complaining, nice to get some decent size lumps on it to cut eventually and make some decent chips.

Ended up pocketing 4mm each side to centre the gantry raiils onto Y axis bearings. the work area I will be able to use now confirmed as minimum 780x450x100mm

[Louis_Cannell]

Managed to get a couple of hours in over the weekend, and made some progress with Z axis, now have three smooth free moving axis and screws mounted for Y and Z still waiting on delivery of some parts so limited to working with parts already available. Time to start thinking about motor sizes required, being a novice I was surprised by the weight accumulation with the 20-30mm 5083 plate, rails, ballscrews etc used so need to work out totals and ensure adequate power from steppers drivers etc.,

[Louis_Cannell]

Progress being made not been able to keep up with posts as everything has been done in snatched moments as and when the free ones occured, all wired and connected ready for a test run tomorrow work permitting. Went with 5 axis BOB, 4 x DM542 4.2a drivers, 4 x 425oz Nema 23, 2.2kw HY VFD and Spindle, linkage I used 2:1 ratio from motors to 1605 ballscrews, power supply a pair of 36v 9.7amp units I had, option to swap in a pair of 48v 10.4amp will be available soon if it will be beneficial.

[fretman_2]

Wow...looking fantastic!

[Louis_Cannell]

Thanks pretty happy with it so far for a first attempt considering total cost less than a chinese 6040 or Ox etc and specification far better total cost around £1000.

[wizard]

Progress being made not been able to keep up with posts as everything has been done in snatched moments as and when the free ones occured,

You must work for a living too! This is how I approach even simple projects around the house.

all wired and connected ready for a test run tomorrow work permitting. Went with 5 axis BOB, 4 x DM542 4.2a drivers, 4 x 425oz Nema 23, 2.2kw HY VFD and Spindle, linkage I used 2:1 ratio from motors to 1605 ballscrews, power supply a pair of 36v 9.7amp units I had, option to swap in a pair of 48v 10.4amp will be available soon if it will be beneficial.

I must say it looks nice. A unique design is always refreshing.

[Louis_Cannell]

So much for a day off only ended up working till 9pm, had to plug it in a try it when I got back, spindle fine, Z axis fine, Y axis with A slaved no problem, X axis just a rumble and rock from motor, too tired to even think about it tonight can't be too serious it didn't go bang! The two working axis have proved already it has all the speed I will ever be able to use in the flat and then some if it lived in a shed the shed would have been rocking. Would have been nice to have it all work but 4 from 5 is better than a kick up the backside.

[Louis_Cannell]

Been thinking about my pulleys and how to secure them over breakfast, it may be obvious that I have little or no engineering experience so is this an acceptable way to lock pulleys securely.

My problem:
Each pulley is drilled and tapped and fitted with opposing 4mm grub screws, but motor and ballscrew shafts to which they are mounted are both round so not an ideal situation and I sure they would eventually move at some point.

My intended solution:
To drill into the pulley and shaft from the end effectively making a semi circular keyway into which I can insert a pin, I am thinking that 2-3mm drill giving 1-1.5mm semi circular key slot in both shaft and pulley would be enough to lock these connections and prevent slippage.

I know keyways tend to be slotted and have vertical sides, but as an amateur who did not consider the amounts of torque involved moving weight at speed
a) is my solution viable?
b) is 2mm or 3mm with a steel pin sufficient to do job?
c) is there a simpler way I haven't considered?

[jfong]

If any shaft doesn't already flats on them, I take a small grinder and make one. It doesn't need much, just a small flat area that the set screw can press against. Then locktite blue to prevent vibration from coming loose.

[wizard]

Been thinking about my pulleys and how to secure them over breakfast, it may be obvious that I have little or no engineering experience so is this an acceptable way to lock pulleys securely.

My problem:
Each pulley is drilled and tapped and fitted with opposing 4mm grub screws, but motor and ballscrew shafts to which they are mounted are both round so not an ideal situation and I sure they would eventually move at some point.

You are right that the pulleys will eventually move on the shaft without additional prep. It isn't even a question it will happen.

My intended solution:
To drill into the pulley and shaft from the end effectively making a semi circular keyway into which I can insert a pin, I am thinking that 2-3mm drill giving 1-1.5mm semi circular key slot in both shaft and pulley would be enough to lock these connections and prevent slippage.

I don't like the sounds of this though I never have seen it done that way. What I've seen done though that is similar, is to align the pulleys on the shaft, spot the shaft though the set screw hole and then remove the pulley and drill a slight divot into the shaft deep enough to sink a set screw into. This might require longer set screws. I'd only do this with one set screw.

A word about setting set screws. The tips of set screws are hardened to allow them to bit into and upset the shaft. If you just run them in till tight they might not get the bit you want. Instead torque the set screw down then back it off and reseat it twice. This has a tendency to embed the set screw in the shaft a bit better. You want to make sure that the set screw isn't free to Rock on the shaft as if it starts to do so it won't be long before the pulley is spinning on the shaft.

I know keyways tend to be slotted and have vertical sides, but as an amateur who did not consider the amounts of torque involved moving weight at speed
a) is my solution viable?

Probably not! I've never seen it done that way so I can say for sure but I can see that pin rocking back and forth under load. Once rocking starts you won't have long before significant problems show up. Beyond that you need to be careful about drilling holes in a shaft as the hole can impact strength. A small divot for a set screw would be better in my mind.

b) is 2mm or 3mm with a steel pin sufficient to do job?
c) is there a simpler way I haven't considered?

Yes a German milling machine! OK if you aren't familiar with European trade schooling a German milling machine is a file in the hands of a student. What you want to do is file a flat on the shaft for a set screw to bear against. This is simple and allows pulley adjustability. You don want a massive flat either, rather a flat just big enough for the nose of the set screw to press upon. In an ideal world you would have a flat for each set screw but getting the angles right manually fileing can be a challenge.

There are a number of other ways to address the pulley mounting problem some require more tooling or expensive pulleys. Just to highlight the additional approaches:

1. Cut a key way in the shaft and pulley. For the most part this requires equipment not in a home shop. You can however get pulleys and motors with pre cut key ways. In some cases shafting can be ordered with the key way already cut.

2. Various types of taper lock pulleys are available. Some of these are good enough to lock on a plain shaft with no key way nor flats. The problem is this adds considerable cost especially for the better grades of taper lock pulleys.

3. Buy a locking collar (collar at clamps to a shaft) designed to clamp on to the shaft in question then bolt a pulley to that collar using the shaft to keep the two aligned. This has actually worked better than I imagined it would on some equipment we purchased at work. Admittedly the collar was beefy for the shaft size. If you DIY a solution like this you will need tools to drill and tap with.

4. Some of the stuff we purchase from Japan apparently takes a belt and braces approach. Here they install press fit pulleys on the shaft, use set screws to lock to the shaft and then drill all the way through the pulley and shaft for a roll pin. Generally drilling though a shaft for a roll pin is a bad idea, especially on small shafts, however in this case the pin is put at the extreme end of the shaft. I have never seen one of these fail, loose position on the shaft or otherwise have issues. Trying to take the pulley off the shaft is another issue though. Further most pulleys sold are sized for a tight slip fit not a press fit.

5. One last idea, though not practical for a DIY build, is to lock the pulleys onto a tapered shaft sort of like a machine tool taper.

There are probably other approaches that I've missed but the simple solution for a DIY home build is to file flats for cheap pulleys. However there is one problem here, the hubs on some of the smaller aluminum pulleys leave a lot to be desired for thread engagement. So on a cheap pulley make sure the hub has enough material to properly support the set screws. There are two issues. One is to prevent stripping the threads and the other is to reduce the potential for the set screw to rock. Both problems are addressed in the same way, use a long set screw and make sure the hub is thick enough to support the set screw. In some cases you might have to drill through the pulley itself and tap, to get the screw support required. In other words prefer longer set screws over shorter.

One other thing when it comes to set screws holding pulleys in place. I often find that the diameter chosen for a set screw is a bit wanting. Sometimes I upsize the set screw by one diameter. This can have a big impact for set screws bearing on flats. Of course this will require drilling ant tapping. It also depends upon what the manufacture originally installed as a set screw size. And of course you can't do this if the hub can't support a bigger set screw. I'm not sure how manufactures come up with set screw sizing on pulleys but sometimes you have to think what the hell!

Finally torque the set screws down no matter what approach you take. It is better to use them once and throw them out after removing a pulley for maintenance. You can visually inspect the point on a set screw but set screws are really cheap these days. In a nut shell a set screw can't do its job unless it has bit into something.

[jfong]

Spot drill a divot for the set screw! Why didn't I think of that.

[Louis_Cannell]

As the ballscrew was much harder than the Steel pulley drilling would have wandered so I did grind a flat but deep enough to prevent any movement in either direction and replaced grubscrew for an A2 stainless which
I used loc-tite 470 to secure.

[DonKes]

Spot drill a divot for the set screw! Why didn't I think of that.

The only problem is if you have to adjust the position of the shaft.

Don

[jfong]

The only problem is if you have to adjust the position of the shaft.

Don

Yes that is true.