John, you posted the same time as me. I wasn't aware that 0.004" was called 4 mils.....I would have said 4 thou. ??

1 mil = .001 inches or 1 thou. See here. I'm no machinist, so I just used the term as something I'm familiar with.

I'm also aware that a "extra fine" PCB trace width is one or two mils. So I was letting Anil know that the achievement of 4 mils using a CNC router was rather remarkable.

Hmm, I did not think about the flex in bit, I reran the file again (in slow motion :)) and noticed that all but 3 tracks on top left are milled clockwise !! But don't think its the cause in my case.

Sorry I forgot to mention that I used 30 deg V bit and closely zooming in the picture found that the depth is increasing from left to right, causing the isolation widening and track shrinking. (try zooming the pic to see what i mean)

(It must be level of the table or PCB that is fixed with double tape, even may be the level of my rails that's causing depth variation).

John, tested the continuity and the PCBs are very much usable :)

Thank you John,
This measurement stuff is confusing in PCBs even more as the track and components are usually measured in mils (fraction of inch) and thickness of copper on PCB in microns (fraction of mm) :)

what ipm did you get this done pal

Thanks John, I hadn't taken notice of "mils" before.

Anil, my first thought on the varying widths was V-cutter depth, but I read your post twice: "this pcb is milled using 0.2mm bit" Well, I had to believe you had a very thin flexible bit! :)

Very slow Irfan :)

Feed rate was 20 ipm but it was scaring to see the rapid moves in between with small bit.

I zoomed the picture. I can't see the depth of the groves. But your explanation of the problem cause makes a lot of sense.

Keep us posted. This is a very interesting development.

Correct Gerald, I too gone back and read it again, the smallest I have till now is 0.6mm used for rubout sometime. :) (to mill away the excess copper between track)

Anil,

for me this looks like an interference pattern like a moiré pattern, I have seen this a lot when I was working in the pre-press industry. This happens when the required design doesn't match your machines capabilities in such a way that sometimes the machine decides to add a extra step, or removes an extra step.

You can test this by creating a pattern of lines witj increasing distance.

So make a line of 4 mill thick and 10mm length (sorry I don't think in mils anymore... metric rules) spacing 2 mil apart and stack 20 orso on top of each other.
Then next to that use teh same 4 mil line, 10mm wide but with 3 mil spacing.
Then next to that use the same lines, but with 4 mil spacing. If you print this a pattern should appear of thicker and thinner lines and even if you stick enough on top you can even see a wave ....

Was I clear?

I think this is the problem....

Ries

Right, That was one of my thoughts and as I pulled up the freq/step calculator, can see that my full step resolution is .094mm, very near to the resolution (0.1mm) we are working.

Though the micro-step resolution is 10 times more, still there will be rounding off errors. And I think even if there was no rounding off error, the micro-step position is not held up as accurately as fill step position.

I have this nagging belief that the micro-step position is not held at all, but the smart people tell me that it is. If I am really bored one day, I could test it.

No more boring small PCBs this time :)

This is one of the two-parts divider ...
Attachment 8384

This is how I plan to use it, the upper part is yet to be done..
Attachment 8385

Measure 2.5' x 5' approx, used 3mm end mill cutting 2mm per pass at 80ipm. Total four passes in 8mm thick mdf and total time to cut about 3 hours.

please do a duco finish on that one - also probably enforce it with sheet of cast acrylic on bothside or on one side and yes email me the file :)

Talking of cast acrylic, how about casting acrylic (various colours) into the cutouts?

Nic job Anil!

I like I like well done

Thanks Gerald for the cutout idea, wish I had that earlier :(
I did not keep the original vectors and just have the outlines now. I think the cutouts won't fit exactly if I work reverse from outlines now.

Something to remember in future, to keep copies of file from each step as you design.

Hi
mil might come from french( millième ) thousand ,we say the same like 4 mill but :)with the french accent. Nice divider acrylic would be great !

Anil, I am thinking of pouring a liquid into the openings. Something like this: http://www.creative-resins.co.uk/lamresin.htm

Very nice divider, how long did you cut on this one. CV or exact stop?

Must get my MM running.... must get my MM running... must get my MM running...

Nice song Ken :)

Yes thats a possibility, need to find out the availability and price.

Claus, total a little less than 3 hours with CV on.

Other part of the divider done, need some finishing on other side.
Attachment 8395

Used (snapped) 4mm endmill, total time 4 hours.

good snapping :)

Anil,

Great work. Very impressive.:)

What's "snapping"? I'm sorry if I should already know this.

I was wondering if you are monitoring the temperature of the Drives and Motors. Since you have "Open", DIY built drives, their performance "under load" is of interest to some of us that are considering using them as well.

Last 2 jobs were about 2 and 4 hours respectively. I noted that the drives were getting hot (but nothing that can't hold finger over it).

The temperature was samilar for 2 hours or 4 hour job, so I think that's max it can go irrespective of the time after a initial period.

I mounted the fan blowing air over them and how they run cool :)

John, look at the text just below the pic. . . . I think snapped means "broke" :)

did you not choke to the dust of that mdf, i heard that ur machine is now locked forever in the room you built it in :D

I want to do something for dust but don't have space for anything more, at least for now I'll continue as it is with masks :(

I can remove a wall if I want it out :), I was advised to do a bolted design but as I said earlier I like welded stuff somehow.

You guessed it right Gerald , sorry John if that's not correct English :)

hey get the eureka forbes vacuum cleaner thats like 8k I think and get a 12 inch industrial exhaust fan - almonard brand is 2k

remove a wall- what do you have hinges on em :D

RGDS
Irfan

Nice work on the PCB Anil! A lot of guys that are doing pcb work seem to have jigs that they can surface right before they cut the pcb to make sure everything is flat as of that day. They also will raise up the work so that the Z has as little extension and less flex as possible.

Anil,
Excellent work.

I thought I was the only person that used the corridor as storage for my MDF and plywood sheets :D , it sends the others in the house crazy.

You may want to experiment with a slower speed like 40 inches/min but with a single 8mm plunge, that will reduce your cut times significantly and save your bits.
With a 2mm plunge you will cut one path four times and with MDF being very abrasive on tools it may lead to premature failure.

What brand bit are you using?
Is it a spiral upcut?

If possible post a closeup pic of your bit.

I have used Whiteside spiral upcut 3.175 mm and 6.35 mm diameter bits and they have worked well.

Jason

Anil - Claus,

I really like the dividers you guys are making.....very detailed design. What software did you use for the design work?

Heath, thanks for the tips. Anyhow I did the PCB job on MM because my other small machine is in not in functional state. I need to make some space for that and make it functional again to do pcbs )(thats was the reason it was made :))

Jason, I only had worked in metal before and I am just starting with wood/mdf stuff.
The bits I have are 4 flute carbide meant for metal work, I'll try if I can get (as you said) "spiral upcut" bits. Also will try your suggested strategy of low speed with more pluge next time :). Still learning..
Attachment 8430Attachment 8431

Wayne, I use Corel, that's the only one vector program I have a my work. In fact any vector program can be used, you just want node editing and weld/combine features.

Anil, those 4-flute metal cutting bits are not designed for drilling in the z-direction (the center of the bit has no cutting edges)

However, the 2-flute metal cutting bits can usually drill. And they have bigger space between the "blades" for clearing the sawdust out.

By far the most common cutter we use for MDF is the 2-flute solid carbide bit from the shop that sells to the metal cutters. ;)

4 flute cutter need to move faster or rotate slower so it dont end up rechopping chips into dust and creating heat and wear. Also a 1/4 inch step down only wear the first quarter inch of the cutter even going 2 '' down

Pardon my ignorant, what is the advantage of the wear pattern?

If you make two passes at a 1/4" deep....compared to one pass at 1/2" deep

The deep, low number of passes gives you double the bit life because you are only make half the number of passes. But the bit is worn for the last 1/2" inch.

1/4 inch dull and 1 3/4 sharp on 2 inch flute cutter

wow, good info here to learn from.

I'll probably get my spindle in few days and can then experiment with more plunge, right now my die grinder seems overworked with high plunge or high feed.