Counterfeits

I know, I know, a Mitutoyo Micrometer and Caliper set for US $60, shipping included, can’t be true. Chinese tools aren’t so bad, but these Mitutoyo chinese counterfeits are a joke.IMG_3106IMG_3107IMG_3110The mic doesn’t even look like the real one, and the caliper is the typical chinese cheap caliper (well, a little bit better may be, but not a Mitutoyo). The mic is usable, but I think the caliper needs some tweaking to make it a worth tool. The seller, jingshengyang2088, has a 99% positive feedback. Lesson learned.

Power Supplies

Are you searching for a new, cheap power supply for your CNC project? Well, here you have two options for a 24V / 8A supply.

supply-comp_2I bought Sonyang for $35 just here. I don’t remember how much I paid for the MW one, but for sure it was in the same range. So here are the guts, Sonyang on top, MW below.

supply-comp_1

Some things to point out:

  • Yellow plastic cover on MW is not well designed: can’t be fully opened (I will just remove it).
  • Soldered fuse on MW, socket fuse on Sonyang.
  • Dual output 24V terminal on MW; triple on Sonyang.
  • Way better output rectifier heatsink on Sonyang.
  • Overall larger components on Sonyang.

Of course a visual inspection of the boards doesn’t tell the full history, but to me, there’s a obvious choice.

Update: Second power supply brand is “Meang Wel”, not “Mean Well” as I thought. Real Mean Well power supplies seems to be a lot better.

 

Nema23 mounts

I’ve got these motor mounts from rattmmotor88 ebay seller for just $15.67 each one, shipping and hex screws included. Shipping was really fast (fedex), just eight days (I use to wait 30 to 50 days for items from china).

IMG_2908

Packaging could be better; there are some scratches, but nothing you can’t fix with a file. Internal milling is great. External sanding finishing looks nice, but flatness is somewhat compromised; milling finishing for mounting surfaces would have been great. I don’t understand why they make motor recess 42mm diameter when it should be 38mm; anyway this is not a serious issue. Of course a critical parameter in these mounts is the space they add between motor and mount surface; 40mm in this case.

As this kind of mount allows a lot of play between leadscrew axis and motor axis, you should be careful every time you install X or Y motors, especially if you’ve got heavy motors and/or your couplings are “flexible type”.

CNC6040Z

Cheap chinese routers: will be worth? That’s the question (or was, for me). So here’s my new machine; well, just a frame. US $1040, shipping included. Here’s the link.

IMG_2862 IMG_2868 IMG_2872 IMG_2874 IMG_2875 IMG_2876 IMG_2877 IMG_2878 IMG_2879 IMG_2881 IMG_2882 IMG_2883 IMG_2887

I’d rather choose this machine instead the most popular chinese router (I have my reasons). You can search the complete machine by googling “CNC6040Z-D300 router”.

This was my first aliexpress experience. Seller was kindly, shipping really was fast, packaging could be better but was ok. No instructions, of course.

So here’s my first impression: solid parts, clean design, rough finishing. There are some  ugly faces on these parts, and sometimes it feels like you should really cross your fingers before attempting to assembly this thing. But of course, for this low price you CAN’T expect neat finishing, and most of this is just aesthetics, so it’s ok.

More info soon!

Things you don’t know you need

I’m quite tidy. But when I’m working, I should move from my chair to get any tool. So every tool I grasp ends on my table (because I’m too lazy to put it back), and after some days my work area turns into a mess, so later I should spend a lot of time putting everything in its place. But now I have this:

IMG_2787

This is a really cool tool organizer: compact, cute, wheeled. Having your tools at hand, fast and easily, makes a difference. I’m in no way associated with Keter, and for sure there’re another brands similar products, but this is a great product.

Learning the hard way

When I was a CNC girl, I thought things like “Once you make one, you can do thousands, easily!”, “Acetal is the perfect plastic for precision parts and cuts like butter!”. OMG I was so naive. Making these parts were really a pain in the ass. That’s why.

IMG_2782


IMG_2774

Acetal has internal stresses. This mean that if you remove a significant mass from a block of acetal, the final shape will warp a bit. I knew that. But what I didn’t know was that sometimes this natural “stress relief” can take hours. So one day I was turning a lot of these parts, everyone having a perfect bearing fit. But then, on the next day, the bearing fit was really tight; the parts have had shrank a little bit. May be acetal I got wasn’t annealed? Or may be I should anneal these parts? (yes, plastic annealing is a topic).

BTW, in this specific case, a bearing housing should, ideally, not divert more than 5-7um from the nominal size: 10um less and the bearing will not fit; 10um more and the bearing fit will be too loose.

Now the other issue: long aluminum crosslide = noticeable thermal expansion. So the table temperature will change after stepper warm-up. And, it will change again after some machined parts. From what I remember a machined radius can easily divert 0.03um because of thermal expansion. And rehomming after temperature changes can be a bit misleading.

The good thing is that, once you understand these issues, making something to avoid or reduce them is not too hard. The bad is that now I have a full bag of black plastic decoracion parts (not the ones in the pictures, of course).

i3lib – native gcode CAM subroutines

One of the things I’ve been working is a set of gcode subroutines meant to make easy to write gcode. Well, in the end you write very little gcode if you use it. Here are some examples:

gcode

So, for example, here the code for the hexagon pocket milling:

    #<s> = 30
    #<h> = [SQRT[3] * #<s>]
    o<i3_c_new_group> call [80] [0]
    o<i3_v_add_vertex> call [#<s> / 2] [0]
    o<i3_v_add_vertex> call [#<s>] [#<h> / 2]
    o<i3_v_add_vertex> call [#<s> / 2] [#<h>]
    o<i3_c_mirror> call [0] [1] [0] [1]
    o<i3_do_cut_mill_by_layer> call [19] [10] [0] [-1] [0] [0]

Most of hard work has been done, there’s some cleanup and documentation left. At some point I would like to release this code as open source. It makes really easy to create paths for simple parts (please note all the generated paths account for tool compensation, not G4X).

Boring stuff

Currently I’m doing some modifications to my Sherline lathes in order to add a cover, very similar to the one on my cnc mill. This will result in a really big changes in the lathe look. I don’t feel comfortable doing these brutal changes to these beautiful machines, but it’s something I need to do.

cncworkOf course there are always some things that go wrong. If I were a professional machinist working on big machines I will be dead for sure. So be careful when you start cutting on a corner using traditional milling (not climb milling; I’m not saying climb milling is more secure, btw).

cncerrorI’m doing a lot of work with my cnc mill. I’m working on and with a really useful set of gcode routines that I will like share at some point.

Finally, here’s one of the more simpler yet useful accessories you can make for your Sherline mill/lathe, the “no hammer” (not my idea of course).

nut-01 nut-02 nut-03 nut-04

Can’t believe didn’t did this before.