Thread: Chris's First CNC Build

Hi Chris
It is the type of paint that causes this. It is normally slow drying enamel with accellerators to speed up the drying process. It makes the surface brittle and easy to chip.
By the way the contents might say 350g but a lot of that is thinners in the mix which is lost to evaporation when used.
I usually assemble the machine then strip it and then paint but there are usally a few nicks on re-assembly. Touch them up or just forget it and you won't notice after a while.

Originally Posted by rodm

Hi Chris
It is the type of paint that causes this. It is normally slow drying enamel with accellerators to speed up the drying process. It makes the surface brittle and easy to chip.
By the way the contents might say 350g but a lot of that is thinners in the mix which is lost to evaporation when used.
I usually assemble the machine then strip it and then paint but there are usally a few nicks on re-assembly. Touch them up or just forget it and you won't notice after a while.

Yea. I'll leave it for now and will reassemble what I can tommorow.

I have to get some alu bar for the top (1.6mm) otherwise it will ruin the paint job.

That machine is looking good. keep it up.

Originally Posted by twistedfuse

That machine is looking good. keep it up.

Just hoping everything is level, I can measure but I wont know till I start cutting.



On to the cable carrier. Just got some Alu channel from bunnings some time ago and this is what I came up with, I think I saw it ages ago for homemade carriers but cant remember where I saw it. Its just a bit of alu with a bolt, 2 washers and a nylock nut, im not sure how it will perform but it should be ok for the machine I am using it on.

I'll probbaly be going with the smaller version.

They look very good

Do a search on cnczone, there have been quite a few there.

A couple of current pics. I love seeing pictures so I hope everyone does also

some parts I made early in the build so they do not look pretty ie. belt guide for the big bearing

Hi Chris,
There is a lot of work in your machine - very neat workmanship.
Not long to go now.

Hmm, not sure if a problem or not but my gantry has a difference of ~0.5mm in height from one side to the other would it be a problem? (Start with a 1.05 gap and end with around 1.6mm gap I determined this by the sizes of alu I could fit under it)

There are a number of things it could be, but I can easily fix it by putting something under the aluminium slides for the X axis (I planned ahead but I was expecting more of a difference).

Now I cannot mount the Z axis till I get the height right otherwise it will be on a 2 degree angle or something like that if I fix it up later.

Too small to worry about?



Attached a image of the mount I made, after working with aluminium and steel I see how easy it is to work with wood again .

Hello Blueray


I might as well jump in first, I think the angle is " about ".05730 degrees, given that your Y axis looks to be about 500mm wide, or about 1mm in 1000mm, 8-)

What you can do is when you have finished the machine to get the bed " level " is to run your router along the bed from end to end and side to side,if you cut 1mm off, on one side it will be .5mm and will taper to 1mm on the other side, yours is a fairly common problem and is easily solved.

Your build looks good to BTW.

Ed

Hi Chris
I notice that you do not have diagonal bracing in your frame so just to make sure your base is solid stick a plate or bit of MDF under one leg and measure again. If you get a different reading then stop here. The base needs to be rock solid before you start to adjust your machine. A simple solution would be attach diagonals or to fill in the sides of your base frame to make it a cabinet.

Once you are sure the base is right then get yourself a dial gauge (less $20 on ebay) and attach it to Z axis and start measuring points on your table. At least each corner and in the centre of travel. This will give you a better picture of what is happening. Shim your axes or adjust through the bolt holes until you get it within 10 thou. Final adjstment can be done by shimming the table itself once you shake your machine down.

I am not a fan of planning the table surface as all you are doing is replicating the inaccuracies of the machine onto the table - eg a twist in the machine will produce a twist in the table. The other issue is you probably will not get to the edges of your table with a cutter so you end up with a ridge around your cutting envelope.

In an MDF machine becasue of their construction there is little option other than to plane the table surface. Your design IMHO can and should be made as accurate as possible. As Ed says if you are going to plane the table then do it in both directions otherwise you end up with little steps in the table top.

By the way I think you have done well to have a starting point of 0.5mm variation.

I am going to agree with Ed here.

Yes in the finished machine it is critical that the bed is true to the axis but there is many ways to get there.

If it is a simple matter to adjust the axis, then do that.

Most of us use a sacrificial sheet of MDF on the bed which gets cut up and replaced every now and then.

Simple matter to skim cut the bed to be true. That is what I do on my machine.

If the bed was going to be aluminium then a system like Rod uses comes into its own but MDF, just true it with the router.

Greg

WOOPS: Rod posted while I typed.

Chirs,
I should have had a looked at your photos before shooting my mouth off.
Your Y axis is welded and it does not look like you have any adjstment unless you do as you say and shim under the aluminum the bearing runs on - is that right??
A 0.5mm shim that long might be a problem.
As long as the variation is the same front and back on your machine (means no twisting) then go with shimming the table down that side.

No Greg I was posting again while you were posting.

OK, got a scrap piece of 1.05mm alu and 1.6mm alu, theres my .55mm difference.

I got it down to I would estimate .1mm MAX difference. I do not mind wrecking the top I had planned to get some 8mm MDF from bunnings its about $9 for a 2400x1200, should be able to get 2 tables out of each sheet, with a 16mm as the base

Mounted the Z axis.

Lowered the Z axis and the router will pass over the MDF with just slight scratches on one side, but i can easily move it, it is also on a slight angle as I could not get some aluminium from bunnings to fix that issue but I did use scrap before and it fixed it just fine so it had a 90 degree angle with the table.

BTW Rod just 12mm box for diagonal bracing? I have some left over from failed prototype. The Table was made up by a local steel mob as at the time I did not have a welder nor know how to weld. Being a small table I didnt think it would need bracing. If so where do I weld it? half way down the table? or where the other braces on the bottom are? Or by turning it into a cabinet do you mean cut a piece of MDF the correct size and force it in the bottom to force a rectangle?


My dad mentioned counter weights, has anyone ever used these, any ideas on what to use? dad said lead but duno where to get it unless I start melting pools of solder, or melt a bunch of sinkers. Im looking at atleast 2kg. Yes I know lead poisoning.

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