[picbits]

Well I finally got my finger out and ordered some linear shaft and bearings from Marchant Dice (www.marchantdice.com).

They had some attractively priced shaft, supports and bearings on Ebay for £148.50+vat for a complete kit. Worked out at around £185 delivered.

Not cheap but its going to be a lot easier to use this than the original drawer slide design I originally planned on using.

Just for those who are wondering why I called it the S.H.I.G - well it stands for "see how it goes" machine . There is nothing written in stone on how this is going to be built and while its being built on a budget its not a very strict budget.

The shaft and bearings evenutally turned up at 5:45pm the next day after a lot of discussion with the couriers and a lot of excuses. It was all very well packed so top marks to Kevin at Marchant Dice for that.

While I was waiting for the shaft to turn up I fired up good old Corel Draw and had a hack at working out how I was going to stick it all together.

The main use for this machine will be to drill PCBs and to mill out plastic panels. I came up with the following specifications/requirements :

Drill/routing area : around 12 inches by 12 inches by 4 inches
Accuracy: better than drilling by eye with a Dremmel on a stand
Speed: not really bothered but would like to drill a 160mm x 100mm board in the time it takes me to solder one up to keep production going .......
Noise: who cares - I can turn the in-workshop hifi up to compensate
Drive system: allthread/stepper with the option to upgrade to Acme when I get bored of the allthread
Fixed gantry design
Bipolar motors (just to be awkward)

Cost today: £185
Cost so far: £185

[picbits]

Will try and get pictures up tomorrow but today sorted out my Z axis.

Took a bit of thought as to how to get it together - space is a bit tight so it was like a jigsaw puzzle. Got it together in the end though and it slides pretty freely - binds a bit at random places on the travel but the ball races I've got were fairly cheap so I'll blame it on them as it happens at random places and rarely in the same place twice. Will be good enough for what I want to do with it.

Managed to split a piece of 18mm MDF by not drilling a deep enough pilot hole on one side but its not a vital piece and its easy to replace.

Also laid out the Y Axis to give me a confidence boost - everything seems to fit as it should so tomorrow morning will be spent getting everything lined up and bolted down - might even manage to make it to the X axis if business is slow.

I had to quit at 2pm to get some orders ready and posted and do the school run so thats today over.

I did however manage to score a bargain - I'm getting 6 brand new 170 Oz/in stepper motors from Ebay for the grand sum of £6 ($12) a piece - at that price I thought I'd get 6 of them so I've got a few spares. Including postage that came to around £44 which isn't too bad If you do a search for Sonceboz on www.ebay.co.uk you will find the guy who's selling them I've also put him onto this forum as he has around a hundred of them left ........

I will be designing my own Bipolar stepper motor drivers from scratch - I've got a box of toroidal transformers which through a full wave bridge rectifier give me around 28 volts at 4 amps which should just about be enough if I use one per axis - the motors are rated at 2.4amps each phase.

The controller will be a PWM chopping type using an 18F1320 PIC microcontroller per axis. The design will be my own and I have in-house PCB facilities so building them isn't a problem. It will also be capable of Microstepping.

So today spending brings us up to :

Todays spend: £22 (for 3 motors)
Total spend so far: £207

[picbits]

Well today made some progress - taken a few pics and will host them tomorrow (I know I know - been rather a hectic day today).

First thing this morning my box of stepper motors turned up - nice looking beasties as well and should rip my machine apart quite nicely.

Finished off the Y axis and lined everything up. It runs a lot more smoothly than the Z axis but that only has a temporary plate on it at the moment so that could be causing it to be a bit stiff.

Built the base out of two sheets of MDF sandwiching some 60x18mm strips to give it some bulk.

Then progressed to the X Axis. This is a 350mm by 400mm table (18mm MDF) riding on 2 x 800mm rails and 4 linear 16mm bearings. I was going well and getting into a rhythm with the drilling and making lots of nice holes in the table to mount it onto the bearing housings.

A little too cocky though - always measure twice and drill 16 times I'd managed to get the bearing housings the wrong way round on my Corel so nothing lined up

Half an hour later I had new holes drilled and everything fitted like a glove apart from two holes which I was doing a Stevie Wonder impression when drilling - I'll elongate these by a couple of mm and they should fit fine.

Also had a 26mm forstner bit turn up so I'll be able to make my bearing blocks for mounting the screws onto

Only got 2 days left before I have to pack this project in for a week - the missus has booked a week off work, littleun is going to his Grandparents in Cornwall and I have a weeks worth of decorating to do

[picbits]

Ok - bit of a back to front one here but here are some pictures in chronological order :

Firstly - the bearings turn up from Marchant Dice - I couldn't resist laying them out on the table to get an idea of the footprint of the machine.

[picbits]

Now I've got an idea of the sizes of the blocks I can get down to my local budget machining shop (read local B&Q Diy store) where I spend most of the afternoon trying to track down Doug. Doug loves his machine and is pretty damn accurate. Unfortunately by the time I've found him (I swear he hides when he sees me coming into the store) its time to leave to pick up littleun from school. Fortunately I have produced a cut sheet with all the dimensions and layout of cuts and I leave it with Doug. An hour later I return to the store to find a trolley of my wood all nicely stacked and cut to size

[picbits]

Now time to get on with the fun part. I laid out the Z axis and it all seemed to fit give or take 1/2mm. I drilled the pilot holes and screwed it together with 4x40mm woodscrews. Unfortunately I didn't drill deep enough on one hole and split part of the MDF. I've since fixed that with a new piece. The blocks are secured by M5 x 20mm bolts and nyloc nuts.

[picbits]

I then used a piece of scrap MDF to make a temporary plate for aligning the shaft mounts - the theory was to fix one shaft as parallel to the frame as possible then slide the axis to its maximum extent each way and then fix down the other shaft. Seems to work ok.

[picbits]

......... and on to the Y Axis - this went very smoothly using the same kind of techniques for the Z Axis. As there was more room to move, this axis only took an hour or so to build and line up.

[picbits]

Now onto the base. This is made of 2 x 18mm sheets of MDF 400mm by 800mm with 60mm spacers screwed inbetween them. This went together suprisingly easily without too much fuss

[picbits]

Now on to mounting the rails for the X Axis. I decided to drill and tap the MDF for M5 screws and mount the blocks directly onto the base. I printed out the template for the holes to line up with the bearing blocks and carefully stuck it onto the MDF with masking tape. Then it was off to the pillar drill for some 10mm countersinking and 5mm holes.

[picbits]

First major disaster - I'd got the bearing block measurements the wrong way round (damn that copy and paste from the Y Axis) and had to redrill all the holes as nothing lined up

With everything lined up I drilled the 4mm holes as central to the shaft mounting block holes as I could by hand then tapped them with my £5 special tap and die set. I then dribbled some superglue (cynoacrilate) down the holes and used a bit of wire that was sitting on the workbench to work it into the holes. Unfortunately I managed to glue my fingers to the wire but hey ho. I also ran out of M5 bolts to had to rob a load from the Z and Y axis until I can get to Screwfix in the next town to replenish my stock.

[picbits]

Time to screw the side plates to the Y axis - no major disasters here and it all went together rather nicely.

[picbits]

A quick trip to McDonalds then Screwfix later I came home with the bits they missed off my order last time plus some M6 bolts for mounting the gantry to the base. I've used 4 x M6x60mm bolts either side with spring washers, washers and nyloc nuts. There was just enough room inside the base for me to get my hand and a small spanner in to screw it all up (pardon the pun). Seems to be reasonably rigid as it is but at some point I will reinforce the gantry with box steel or angle iron to make it even stiffer. Thats all for the build to date - I will be working on screw bearing mounts and the drive systems tomorrow.

[Kammo1]

Hey Picbits that is a great looking machine and a lovely quality build. I too am starting the addiction to build a CNC machine and where are you in the UK?? I am in Nottingham. Did you design this yourself or did you purchase any plans ?? Nice to see this build from start to finish. What spindle or router do you intend using ??

[picbits]

Hi Kammo1

I'm in Wellingborough, Northants.

I designed the machine from scratch (probably not a fantastic idea) but its something I've been wanting to do for a long time and I wanted everything to be my design (including the motor controls).

I will be using a Dremel for the router - I only need PCB cutting on it at the moment and the Dremel is nice and light.

[picbits]

Well got the X Axis table moving today - I used a length of stainless allthread and an M10 nut housed in some MDF held rigid by some polymorph. Lined everything up and it seems to be pretty freely moving on the screwthread.

Gave it a test with the electric drill and it moves as it should

Also picked up my motor couplings .............

Read that as some 1/4 inch bore fuel pipe and some jubilee clips. Fits snugly on the motor shaft but I need to machine down the 10mm allthread so I can get it over the end of the rod.

Thats it for the next week and a half - we've got a shedload of decorating to do and the missus has taken a week off to help me.

Will update with pics and stuff as soon as the build recommences

[picbits]

Ok - been a while since I've updated this thread - I had to have a week off for decorating and other things.

Next I made some bearing blocks to hold the 6000 type bearings I got off Ebay



Luckily enough they have an outer diameter of 26mm which is exactly the size of a kitchen hinge cutter

A little fettling with the Dremel and the bearings pushed in snugly.

[picbits]

Homemade nut housing - the first one is shown in the picture. I cut out a weird shape, packed it full of polymorph plastic and a nut and centered it with some 10mm rod before it all set.

The second and third ones I managed to do without packing them with polymorph - my Dremel routing skills must be getting better

[picbits]

Next for mounting the stepper motors.

I had some great plans for these but ended up using a couple of M10x100 bolts and botching it together to see how it held. It was suprisingly rigid so I've done both the X and Y axis in this method.

[picbits]

Now I got a bit bored of cutting up MDF and as the motors were now mounted I thought I'd have a bit of fun and try and get the motors moving the x and y axis before I did anything else.

I vaguely remembered purchasing around 200 x IRF540N Mosfets - after half an hour of digging around in boxes I found a couple of tubes of them.

Now these are great little Fets rated at 100v and 28A with built in blocking diodes. Only problem is you can only use them on the low side of a H Bridge for Bipolar motors. Did a bit of research and came up with some great chips from Intersil. I am using the ISL83202IPZ full bridge driver ICs to control the IRF540N mosfets. They have the advantage of turning off one set of fets with a delay before turning on the other pair to prevent and magic smoke from appearing.

My plan is to make a custom serial and parallel port based controller using Microchip PIC Microcontroller. Not sure if I'm going to go the microstepping route yet but I've made sure my Motor Power board is compatible with anything I'm going to be throwing at it in the future.

If you look closely at the picture you will see an ST L297 on the breadboard temporarily controlling the H bridge for test purposes. The current sensing resistors are a little underrated for these motors but I'll sort that out when I'm building the "proper" controller board





Now I know it works I can build up the other half of the bridge board and get the other axis moving

Thats all for the moment - its going to be a couple of weeks until the next update as I'll be working on the stepping controller board and the firmware for it.

Dom