PDA

View Full Version : BUILD LOG: Game on!



Voicecoil
20-02-2019, 09:52 PM
After some lurking, quite a few questions, a lot of sums and some FEA I've just started building my first machine. It's not as big as I really need (I want to cut out large loudspeaker cabinets amongst other things), but I'm having a lot more difficulty finding larger premises than I thought I would. So having kind of got the bug and wanting to get on and do something I thought I'd make a small (but capable) one anyway, the experience will do me good, it will be useful for machining up metal parts and a lot of it will be transferable to the big machine design when I get the space.
Sorry I've not shared any of the initial drawings, but I don't really do 3D CAD and without being able to turn layers on and off and have the thing in your head, the 2D drawings are a bit of a nightmare to interpret. The design ethos is:
1) To try to keep all individual deflections of the gantry extrusion/side beams/bed to less than 1um for a 50N cutting force - this has been determined by calculation (thanks @routercnc for the spreadsheet) + FEA
2) Minimise twisting moments by keeping all assemblies as compact as possible - no massive spindle overhang please!
3) Keep the number of bolted joints to a minimum.
4) Try to get a good price performance compromise
It's being made out of aluminium extrusions/plate simply because I'm able to machine that better and more accurately - and you can anodise it to a nice finish :congratulatory:

Not having any CNC machining capability until it's made, I'm having to "bootstrap" the process, apart from one or two pieces that I need to get laser cut, it will all be done using the trusty Elektra Beckum chop saw, a drill press (Axminster ED16B2) and my little lathe. First job was to fettle up the saw and make a decent clamp for it:
25467
With a new blade fitted and a few minutes true-ing it up it goes through 15mm plate like a knife through butter. Squareness is about 0.25mm across a 125mm cut, and with a wee drop of WD40 to help the cutting, the cut ends are smooth as a b******s bottom.
First parts to make were the carriage plates for the Y axis (please note I denote X & Y from the point of view looking down at the front of the machine i.e. the X-Axis runs L to R along the gantry):
here's marking them out using the trusty optical centre punch:
25468

Voicecoil
27-02-2019, 08:48 PM
I've found time to do a bit more on this in the last few days, firstly got the gantry extrusion fully end drilled and tapped..... it just fitted under the pillar drill with 15mm to spare :tears_of_joy:
25480
talking of tapping I soon realised that there were going to be A LOT of holes to tap and if I wanted to save a lot of time (and avoid w*****s cramp!) machine tapping was the way to go. Tapping machines looked a tad expensive for the moment, thought about changing the motor of the pillar drill to give a quick reverse function, but some bits were on a couple of weeks lead time.... then I tried one of the Europa tool interrupted-thread spiral point taps:
25481
These seem to require a lot less tapping force than anything I've tried before and seemed hence offer up the option of tapping with a cordless drill (which convieniently has a torque limter to stop breaking taps, and a reverse to extract them). In order to keep things straight I added a circular level to the back of an old drill, using the pillar drill and a length of tool steel rod to get it properly level whilst the glue dried.
25482
With this and a known flat surface I seem to be able to tap holes pretty straight and all for the outlay of a 1.80 level off the Bay of fleas; and you can do it in large pieces that wouldn't fit under a normal pillar drill.

AndyUK
07-03-2019, 02:05 PM
In order to keep things straight I added a circular level to the back of an old drill

Nice bit of customisation! I've taken to using a guide for my taps to pass through; find a block of something (wood, aluminium) that is about as thick as your tap is long, minus 1cm and the length of the square drive section. Using the pillar drill, put a guide hole through the block - diameter to be as close fitting as to your tap as possible. Now you can place this block up against the surface you're going to tap, passing the tap through for the first bit of the hole - hey presto, nice and straight tapping every time.

Voicecoil
08-04-2019, 09:58 PM
I've got most of the pieces machined up now and waiting for the dozy anodisers to do their stuff on some of the beams - whilst it's obviously a home built machine I wanted it too look vaguely OK and I don't really have the space for some 3ft long anodising batths at the mo. Today I finished off making the spindle clamp, I'd cut the outside profile and done the holes a few weeks back, but I've been waiting for a friend to have some free time so I could use his mighty steam-powered lathe to bore the hole. Here it is after putting a 30mm drill through to start things off: And yes, that's a 300mm chuck and it's a heavy lump!
25634
Then it was something like 3 hours gentle boring out, with a few minor hiccups and several Km of swarf - here's the end result:
25635
The internal finish wasn't quite as good as I'd hoped as he had a rather limited range of boring bars and with 80mm of tool sticking out from the toolpost there was a certain amount of resonance going on; never mind, no-one will ever see it, and as long as it grips the spindle I'll be happy.
The reason for making the spindle clamp was initially because I couldn't easily source an 85mm part OTS, then it kind of led to some lateral thinking about how to implement the Z axis with good strength and minimum width - all will be revealed soon when I start putting it together :encouragement:

Voicecoil
20-04-2019, 02:45 PM
I've been cracking on with stuff the last few days, here's a pic of some of the parts:
25691
From LHS clockwise we have Z axis slide with clamp sitting on top of the bed cross beams, front bed end plates, Z axis top plate, gantry end plates and the Z axis back plate. Just hit a bit of a snag though - the big bit of plate for the top of the bed has been cut well off square by the folk at Smiths - thus even with the 2mm tolerance oversize by the time it's trued up it will be 2mm short causing a few major headaches - I will be bending their ears on Tuesday :mad:

Voicecoil
28-04-2019, 08:50 PM
Marking out the bed plate:

25731

I need a bigger surface plate!!!

AndyGuid
29-04-2019, 03:02 AM
Marking out the bed plate:

25731

I need a bigger surface plate!!!

As a pen-pusher, I'm guessing that your method is a very accurate way of manually Marking Out Using a Surface Plate and Height Gauge ?

Voicecoil
29-04-2019, 08:59 AM
Yes, I bought the height gauge and optical centre punch for this project and I've been suprised at how accurately you can do things - I reckon on smaller pieces the max error isn't much more than +/- 0.1mm and maybe twice that on longer bits: quite a novelty not to have to file out holes to get things to line up! Mind you, when you think about it people were making accurate stuff 60 to 70 years ago before CNC was even thought of, so it had to be possible.

Voicecoil
01-05-2019, 07:33 PM
Yesterday and today I've been assembling the various parts of the bed/Y-axis to check fit before doing a bit of anodising.
25739
25740
25741
25742
All went reasonably well apart from a couple of screw heads (that need to be moved) fouling stepper motor bodies and a small CAD error on the carriage side plates that I'd transferred really precisely into metal - time to get the file out! :disillusionment:

mekanik
01-05-2019, 08:31 PM
Looking Good:thumsup::thumsup:

Voicecoil
04-05-2019, 10:37 PM
Having found it very difficult (or very expensive) to get anything done on a reasonable timescale by the local anodisers, in desperation I thought I'd have a go myself. 50 worth of chems and some plant troughs later I managed to get the gantry box done this evening, took a bit of fiddling with the process but not too shabby in the end.
25748

Gav74
05-05-2019, 01:56 PM
looking good

Voicecoil
09-05-2019, 05:33 PM
With all the beams now anodised I thought it was time to indulge in a bit of damping, as handling the box sections in particular showed that they were ringing a lot at mid-audio frequencies (which match up nicely with the stimulation given by typical spindle speed/cutter flutes). I thought I'd try my old fave Tecsound, but wasn't overly confident of it working as I've never used it on anything thicker than 2mm thick metal sheet before, and the box sections I've used for the side beams and gantry are 7 & 10mm thick wall. However in reality it seems to work pretty well, hanging an untreated section up on a piece of wire and giving a gentle tap with a hammer gives something not unlike a tubular bell, whereas a damped section is just a bit of a thunk. Here's some sound files from the tapping to illustrate the difference
25765
25766
Looking at the decay time in an audio editor, the damping has been increased by something like 6X - a useful improvement I think - now to do some of the other parts!

Voicecoil
31-05-2019, 07:25 PM
Thought I'd better check fit on the Z-axis before assembling the gantry as the X carriage is integral to it: all fitted suprisingly well once I'd clocked that the Z slide extrusion was supplied under-width and was causing the assembly to sieze at the end of travel
25817
25818

Voicecoil
05-06-2019, 09:58 PM
So, the last few days I've found time to build up the chassis/Y axis. Getting the side rail assemblies properly aligned was a bit of a faff, but it's done now!!
25830
25831
25832

Lee Roberts
10-06-2019, 08:56 PM
Looking good, nice to see something diff to the norm :thumsup:

Voicecoil
12-06-2019, 08:45 PM
Looking good, nice to see something diff to the norm :thumsup:

Cheers Lee - I thought it was worth going back to basic principles and trying a few slightly different approaches to see if was possible to make an aluminium machine that was a bit more rigid than normal. I've learned a lot as I've gone along and come up with some improved ideas which will be incorporated into this build once I've got it cutting metal and can make more accurate and complicated parts - those ideas will also go into the big machine which is the long term goal.

kingcreaky
13-06-2019, 07:48 AM
as lee says its great to see new methods. thanks for posting, keep it coming,

routercnc
17-06-2019, 07:14 PM
Somehow I managed to miss this thread and have just caught up. Great work Voicecoil and I heartily approve of the twin Z ballscrews. Glad the stiffness spreadsheet is still helping people out.
Let the over build commence - great machine !

Voicecoil
30-06-2019, 10:42 AM
Somehow I managed to miss this thread and have just caught up. Great work Voicecoil and I heartily approve of the twin Z ballscrews. Glad the stiffness spreadsheet is still helping people out.
Let the over build commence - great machine !
The twin ballscrew thing kind of evolved, it came from trying to minimise twisting moments on the gantry - I'll be finding out in about a month's time how well it works I guess! Meanwhile lots of wiring and screwing together to be done :-)

Voicecoil
17-08-2019, 06:49 PM
Had to take a break from this for a few weeks due to the pressures of (paying) work, but now I'm back with a vengeance and looking to get it finished ASAP. First I've installed the steppers and wiring into the base:
26239
then it was time to start putting the gantry together:
26240
here's getting the rails levelled:
26241
Just realised I need to get the oiling sorted before I go any further, so there's been some frantic buying of bits on the bay of fleas this afternoon: more pics coming it a few days when they land!

Voicecoil
02-09-2019, 12:35 AM
So I've mostly gone with an idea Lee suggested, using 4mm pneumatic connectors/tube to supply lubrication to inaccessible parts:
26376
26377
On the HGH15's I couldn't find any suitable adaptors so had to turn up some barbed brass push on thingies:
26378
26379
Tried the same on the long axis, but then realised they would foul the ballscrew covers:
26380
Tried spinning the ballnuts through 180 degrees but then found everything was seizing up - turned out the ballnuts weren't concentric on the screws - thanks Fred :sour: - so those are going to have to be a manual lube.
On the subject of lubrication, does anyone know where I can buy a sensible quantity of synthetic semi-fluid grease please? Looks like to be the DB's for this sort of setup.
Z-axis ont' gantry:
26381
So onto the wiring... Found that the closed-loop steppers have the connectors on the encoder cables of such a length that they would sit in EXACTLY the wrong place - half way down the drag chain :mad:
26382
....so had to do some inline splicing......
26383
and to finish off added a touch off probe socket into the base :congratulatory:
26384
So onto the wiring

Wal
02-09-2019, 03:33 PM
>On the subject of lubrication, does anyone know where I can buy a sensible quantity of synthetic semi-fluid grease please?

My mini-mill has no practical way to get oil to the ball-nuts or the bearings riding on the supported rails, instead I lift the rubber skirts every once in a while and squirt a load of a TF2 Teflon oil onto the shiny bits:

https://www.google.com/search?q=tf2+oil&safe=strict&client=firefox-b-d&tbm=shop&source=lnms&sa=X&ved=0ahUKEwjA3f2VrLLkAhVl5OAKHdX9DVkQ_AUIDigC&biw=2560&bih=1286&dpr=1#spd=17336399006240699812

No doubt this isn't the done thing, but having done it for five or so years, I'll probably keep doing it. There's logic for ya.

Nice build BTW.

Wal.