CNC Masters Baron accessories for PCB

[hbs1hbs2]

We have a CNC Masters Baron in our lab. I want to use it to make PCB.

Please tell me what accessories we should by to make pcb.

I only know that the line gap is 0.1mm or 0.004 inch.


Also pleae tell me how calibrate Z access to make pcb I think it is to hard with hand?

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[CitizenOfDreams]

The main challenge with PCB milling is the variation in Z height (due to machine misalignment, uneven stock thickness and warpage). There are two basic approaches to this, each one has its own advantages and disadvantages.

The first approach is to use a pressure foot attachment that rides on top of the circuit board and ensures constant milling depth.



The second approach is to probe the PCB and correct the uneven Z height with a software program such as AutoLeveller.

No matter which method you choose, you will need appropriate cutters for trace isolation, copper removal and board routing. Think & Tinker has a good selection of those: www.precisebits.com.

[A_Camera]

The main challenge with PCB milling is the variation in Z height (due to machine misalignment, uneven stock thickness and warpage). There are two basic approaches to this, each one has its own advantages and disadvantages.

The first approach is to use a pressure foot attachment that rides on top of the circuit board and ensures constant milling depth.



The second approach is to probe the PCB and correct the uneven Z height with a software program such as AutoLeveller.

No matter which method you choose, you will need appropriate cutters for trace isolation, copper removal and board routing. Think & Tinker has a good selection of those: www.precisebits.com.

You forgot to mention the third alternative, that is to use a very rigid CNC with leveled table and aligned/squared axes. That's the key of good results and it is really worth the effort. I also think that the warped PCBs are manufacturing defects due to very low quality. Most of the time I am using 30 degree V-bits, 22,000rpm and pretty low feed rate, 450mm/min first pass and 650mm/min second pass and mill at 0.04mm first pass and 0.07mm depth second pass. This results in track separation of 0.237mm which is very good for most cases. For SMD 10 degree 0.1mm tip at same depth gives 0.112mm, which is also very good, but the tip is easily broken... Never the less, no auto leveling software is used, which saves a lot of time.

Another thing is the fixture. I think that is more important than the pressure foot you show here. I would spend money on a vacuum table before spending money on that pressure foot. I think that pressure foot is more useful for vinyl cutting or engraving text in thin large sheets of soft material than PC making. It also prevents the use of dust shoe, which in my opinion is important, especially for a larger job.

[A_Camera]

[QUOTE=hbs1hbs2;1962124]We have a CNC Masters Baron in our lab. I want to use it to make PCB.

Please tell me what accessories we should by to make pcb.

I only know that the line gap is 0.1mm or 0.004 inch.

Also pleae tell me how calibrate Z access to make pcb I think it is to hard with hand?

What do you mean by that? Z = 0 it the top of the copper clad. How you set that up depends on the CNC and the software you are using. I don't know that "CNC Masters Baron" I have no idea if that is the machine or the software name.

The PCB I am using is FR4 and it has a copper layer of 35 micro meter, so in theory milling down to Z-0.035 should be enough. I am using V bits, found them the best alternatives. Spindle speed is 22,000rpm, feed rate is low, normally 450mm to cut through the copper and I run a second pass in the same track a little deeper. First pass is at 0.04mm second at 0.07mm. For SMD use 10 degree 0.1mm tip but reduce the feed rate dramatically, to about 200mm/min. Milling at 0.07mm depth you will get 0.112mm isolation, which is good enough even for SMD with 0.5mm pitch. BUT... it is a PITA so avoid if you can. Also, use only high quality boards to avoid warping and layer separation.

A very rigid, well aligned CNC with leveled table is necessary if you intend to get good results, so spend time on the machine before starting to make PCBs. Also keep the surfaces clean. Remember that 0.035mm is very thin, so a tiny bit of dirt in between the PCB and the CNC table may result in bad quality. Also, if you have vibrations in your machine... you can forget about the target isolation you have and should be happy if you can make PCBs for chips with 0.1" (2.54 mm) pitch pin separation. I have seem many naive people mistakenly believing that because PCBs are made of fibre glass with a thin copper layer, they are easy to make and any cheap, simple CNC can be used. Well, reality is different. If you want good quality PCBs you need a good quality, rigid and well made CNC also.

[CitizenOfDreams]

It certainly makes it easy if you have a perfectly aligned machine and perfectly mounted perfectly flat stock. But let's be realistic here, it is not always an option. Even "real" PCB milling machines like LPKF do not count on the stock being flat and use a pressure foot.

[A_Camera]

It certainly makes it easy if you have a perfectly aligned machine and perfectly mounted perfectly flat stock. But let's be realistic here, it is not always an option. Even "real" PCB milling machines like LPKF do not count on the stock being flat and use a pressure foot.

What's the definition of "real" PCB milling machines? I mean, really, they are no different than any other commercially made machines. They are high precision, super expensive mills with very high speed spindles, up to 100k rpm. The only other thing is that they are encapsulated for environment protection, otherwise just as any other machines. You are also mistakenly use the word "perfect". Well aligned and leveled table is not that hard to make, just use an MDF and level it with the mill on the original mill table. Really, leveling is no big deal at all, but must be repeated now and then. Aligning the axes is also no big deal, but it takes time and demands some patience. Never the less, it is worth the effort, even if it takes a few hours for each axis in the worst case, depending on the "perfection level" you apply. Also, of course, if you make large PCBs it is a good investment, but like I said a good vacuum table in my opinion is of better use for PCBs of more realistic sizes, like 100x160mm and for those, you don't really have any use for a pressure foot, since most of the time part of that pressure foot will be outside the PCB anyway.

Also... I think that the pressure foot the LPKF machines possibly are using are NOT the same as the one you are showing the picture of. The one in the picture seems to be a simple eBay or DIY version. I tried to find information about the pressure foot they are using, but failed. Anyway, it is quite different if you aim at doing what those machines are capable of doing...