Another first build

[chrisb691]

Hi All.

I've been lurking for a long time, and been fascinated by what you guys are doing. I've always thougt I'd love to build a CNC
router, but considered it beyond me. However, I stumbled across buildyourncnc.com, and having watched the guy build one in his bedroom, and use the bath tub as a router table, I decided I must be able to build my own.

I looked at various plans on the internet, and decided to buy a set from buildyourcnc.com. I figured an mdf machine was a good starting point, and this particular machine looked as if would be buildable for me.

10 days later. the plans, plus a dvd, arrived. These comprised of 17 A3 drawings, and 73 mpeg files on the dvd. A quick review of the plans suggested that they were good quality. and a look at a couple of the mpeg files, indicated that they would be extremely helpfull in the construction, even though they were obviously very amateur.

Unfortunately. I got sick, and they sat here for over three months whilst I was unable to work in the shed. Last weekend I made a start, and got some more time in this weekend. It's going to be buildable, but some parts are going to be made more than once as I nut out some problems.

What problems can there be, I hear you say. Well where do I start. First up, the drawings aren't as good as I thought. There are 'hanging' dimensions. ie. they go from a specific point, and end up in the
middle of no-where. I can only assume that they are the result of design changes, where old dimensions haven't been cleaned up. Then there are dimensions that would be easy if your were using a cnc, but are downright awkward doing them manually. For instance, I find drilling holes at 6 25/32" centres to be problematic to say the least. The workaround, is to drill a
little oversize, to try and compensate for inacuracy.

A fairly significant issue, is building an imperial design in a metric country. I have opted to cut to imperial measurements, and not try to convert to metric. But figuring out the compensation needed, can be a challenge, hence the need to remake parts as I proceed along. For instance, the plans are based around 3/4" mdf, and I am using 16mm. He's using 3/4"
aluminium angle, and I've got 20mm. It's not insurmountable, but there certainly is a bit of "oh crap" going on. Then there are the silly errors, like using the wrong side of the ruler and marking off 5/10 ths, instead of 5/8 ths.

Overall, the plans detail the mdf parts, and nothing else. Without having seen one of these before, some things are only becoming obvious as I get sub-assembles done. But mdf is pretty cheap, and there is no value associated with my time. So I intend to continue to build, and to replace parts as it becomes neccesary. Eventually, I'll end up with the best machine that I can currently build, and will learn a lot along the way. I will then use this one, to build the next one.............crap! I'm already
addicted.

I'm not concerning myself with the electronics yet, and will leave these until last. I'm doing a fair bit of research, and starting to get an understanding. But I will be asking a lot of questions further down the track....... before I do any ordering.

The pic shows the z axis, plus part of the Y axis assembly. I will be using all-thread on this machine, and still have to decide what to use for nuts.

[snowyskiesau]

As my first machine is going to be based on the earlier design from buildyourcnc.com,
I'll be watching your thread with interest.
While I have purchased some ballscrews, my first attempt will be with allthread. I have a couple of 1M lengths of 12mm allthread so this will set the size of the build.

[crocky]

Hi Chris,

Seems like a good place to start, the outside bbq is making a good place to take your photo's too

There are heaps of us here so you should have no trouble with your questions.

[Ch4iS]

18 mill would be closer to 3/4" as its 19.01mm

Looking good so far.


I did read over his site when looking to build a cnc machine and he makes it seem so simple when he does it.

I opted to wing it and I have a thread here also


I remember reading someone using Nylon as a nut, I bought some when my local bearing mob was flogging off the offcuts, seems like it would do if you had the proper thread for the threaded rods. But Delrin I think its called is spose to be the bees knees, never seen nor used the stuff.

[chrisb691]

18 mill would be closer to 3/4" as its 19.01mm

Looking good so far.


I did read over his site when looking to build a cnc machine and he makes it seem so simple when he does it.

I opted to wing it and I have a thread here also


I remember reading someone using Nylon as a nut, I bought some when my local bearing mob was flogging off the offcuts, seems like it would do if you had the proper thread for the threaded rods. But Delrin I think its called is spose to be the bees knees, never seen nor used the stuff.

Hi blue^ray,

I agree 18mm is closer, but 16mm was a lot easier to get (ie Bunnings). It's going to need making adjustments, no matter what size is used if it isn't 3/4".

Delrin is a brand-name for an engineering plastic called Polyacetal....more commonly known as just acetal. It's readily available, and easily machinable.

I've got some 50mm acetal rod, and am considering a 2 part spring loaded nut as an anti-backlash mechanism. I suspect it should work okay.

[Ch4iS]

Hi blue^ray,

I agree 18mm is closer, but 16mm was a lot easier to get (ie Bunnings). It's going to need making adjustments, no matter what size is used if it isn't 3/4".

Delrin is a brand-name for an engineering plastic called Polyacetal....more commonly known as just acetal. It's readily available, and easily machinable.

I've got some 50mm acetal rod, and am considering a 2 part spring loaded nut as an anti-backlash mechanism. I suspect it should work okay.

lol you know more than me :P

18mm is the largest they stock at my local.


Would love to see how that anti-backlash mechanism works out

Is the Delrin/acetel expencive?

[chrisb691]

lol you know more than me :P

18mm is the largest they stock at my local.


Would love to see how that anti-backlash mechanism works out

Is the Delrin/acetel expencive?

40mm dia acetal rod X 500mm long at $28+ from this guy. Just search his store for 'acetal'.

EDIT: He's also listing under 'Delrin'.

[snowyskiesau]

40mm dia acetal rod X 500mm long at $28+ from this guy. Just search his store for 'acetal'.

EDIT: He's also listing under 'Delrin'.

I can highly recommend offcuts_galore (George). I've bought bits of black delrin for only a few dollars. I've also bought lots of aluminium plate and round bits from him.

[seafurymike]

Good start there Chris,

Have you worked out how your going to drive it?

/M

[chrisb691]

Good start there Chris,

Have you worked out how your going to drive it?

/M

It's a bit premature yet, as I haven't discussed options with anyone yet. I'm leaning towards a xylotex 3 axis kit, with 269oz steppers. I would think a breakout board as well. However, I will listen very hard to any advice offered.

This one will be running 1/2" allthread (maybe with dampeners).

[chrisb691]

2nd axis starting to look okay. However, the whole imperial to metric issue, is a mega PITA.

[chrisb691]

Just realised that I didn't attcah the picture to my last post, so here it is in pic1.

Got the table constructed this weekend so fairly happy with myself, which is more than can be said of SWMBO. Table size is 900 x 450.

I've decided to go with 1/2" allthread on X & Y, and 3/8" on Z. If anyone can see a problem with this, please yell out.

[snowyskiesau]

And I thought my poor Triton Mk III was a bit beaten up!

Looking good so far.

[chrisb691]

And I thought my poor Triton Mk III was a bit beaten up!

Looking good so far.

The MK3 had it's 27th birthday last March.

[chrisb691]

Had a quick play on the lathe, and mocked up an anti backlash nut. It's made of acetal, and is in 2 parts with a spring between. The part on the right is the actual nut, and then the other one is screwed up until you get a bit of spring resistance. The nut and bolt is to stop the rear part unscrewing, and I need to come up with a better solution to this.

Even with a fair bit of spring pressure dialed in, it still turns very freely on the allthread. Seems like a good possibilty, if I take a bit more care with it.

The pics not the best, but the camera had real problems trying to focus with the black acetal.