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Discussion Starter · #1 ·
Hello,

I have a lot of problems with a CNC 3018 Prover from SainSmart.
I notice that the aluminum tray does not have a correct flatness.

In addition, this same tray is deformed.
I am very disappointed by the manufacturing quality and lack of precision of this CNC.

I acquired this CNC to get quality PCBs and the results are very poor. Runway losses. Offset original position. This shifts the holes. I have to reposition the machine to zero point before making the holes.
What do you advise me to improve this CNC?
Have you encountered the same problems as me?
Thanks for your help.

Sincerely.
 

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Official Greeter
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Welcome to the forum.

Are you a professional user?

Maybe you should direct you question to the manufacturer?

Someone may be along who may be able to assist...
 

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Discussion Starter · #3 ·
Hello,

I am not a professional user,
it is a CNC for making single and double-sided PCBs.
All my tracks are erased according to the position of my PCB on the board.

I contacted the manufacturer. I’m waiting for their answers.

I’m not going to be able to straighten the tray that’s deformed, it’s impossible to do manually
I think we need to change it and adjust the flatness with wedges under the tray.

Not easy to do, because I have 0.592 mm of gap on the left rear relative to the right rear.
I have 0.470 mm of gap on the left front relative to the right front.
Big trouble to adjust all that.
Thank you for your advice.

Sincerely.
 

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David - Machinist in wood
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Welcome to the forum! Add your first name to your profile to clear the N/a in the side panel and so we'll know what to call you. Add your location to your profile, as well.

We do like photos so show us your shop, tools, projects, etc. whenever you're ready.

That's a fairly low-end CNC and may well be within manufacturers tolerances, sad to say. That's probably not what you want to hear but if/when the manufacturer gets back with you I would ask what their standards are for flatness. As for repeatability and hitting the same hole twice in the same spot, again, it's a fairly low-end CNC so even the repeatability may be within manufacturer tolerances.

David
 

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Mike
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Welcome to the Router Forums N/a.

As David points out that is a low-end CNC machine so the specifications might be within the manufacturing tolerances if they even have any. Quality control for these low-end machines is also nonexistent, it is actually cheaper for them to accept a few returned machines than to pay someone to look for flaws in the product.

There is one solution to give you a flat a work surface, that even the more expensive machines use. Add a sacrificial spoil board or strips to the bed and trim that surface flat and perpendicular to the spindle. If you add strips then you can still use the T-trac clamps to hold your workpiece. If you use a solid one-piece spoil board then you need to decide what work holding technique you want to use. The big problem here is the limited Z-axis height of these small machines. Since you are using it for PCB cutting it will not be as much of a problem. You can use double-sided tape, or what people refer to as the "blue Painter's tape/super glue" method for work holding but these have been known to fail if you don't make sure the tape is down good or the surfaces are not clean, so make sure you prep the surfaces and that the tape and glue are used correctly.

Whichever method you chose to use, strips or solid spoil board, make sure it is mounted well then use a pocket toolpath to trim the worksurface flat using an endmill. This being a small CNC it is probably limited to 1/8" shank bits so it will take a while to trim the spoil board. Once it is trimmed you should have a flat surface to work with.

Just remember the results of using one of these low-end CNC machines might not be perfect but if you do some testing with the different bits you will be using you can find the limits of your machine. If you stay within those limits then you should be able to do some acceptable work cutting the PCB projects.
 

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no doubt that a table from the factory is not flat, don't think they are even expected. an additional table is needed - one that can be machined flat, rechecked and remachined again, many times. like mdf.

or a plate like Dan suggested which could be shimmed level and attached to your existing table. possibly, some of the threaded holes could be used in the "attachment and shimming" process. like if one corner is low turn a bolt to raise it kind of set up.

hopefully this machine can hold the tolerances and repeatability needed for your project. please keep us updated. hmmm, i think i have a stack of double sided pcb blanks laying around somewhere.....
 

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Ah, Yes, the infamous 3018 Chinese "engraver". There are many things about this design that are truly mediocre. Foremost among them is vendor support.

There are thing you can do to get it working better. I would go through and tighten everything you can (though don't over tighten). Then install a sacrificial spoil board that Mike mentioned above and skim flatten it with the router so your bed is basically flat with respect to the X and Y axes. It sounds like you will probably need to shave off about a half mm at the high spots.

Personally, I would toss the electronics and use real drivers and a low cost Grbl controller but you can probably make what you have work.

You mentioned milling PCBs. This needs a very flat bed but that's not enough as it is hard to mount FR4 PCB material exactly flat. I used double sided tape on the whole piece and they still have irregularities. In general, you are removing 14/10000 of an inch of copper and typically cutting about 4 mils deep so you need to dial your machine and process in pretty well. What I do is height map the mounted PCB and then transform the GCode to follow the height map. I use this GCode Sender on grblHAL and a 3D probe to create the height map and transform the GCode. 3D probes aren't cheap but you can do it by hand with a cheap contact probe or even a home made one. The Sender has manual support for height mapping. See the attached image - height map shown is a portion of my spoil board after skimming. The different between high and low is only .1 mm. I will get easily 2 or 3 times that with a mounted PCB blank. Don't forget to use high quality, sharp bits - those 10 for $15 ebay specials are a joke.

FWIW, I only mill PCBs for quick little tests when I don't want to wait for the fab. They come out OK but there really is no substitute for a real PCB with solder mask and silkscreened legends.
 

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