Wood clamping

I’ve been making a lot of wood parts lately. Here, I show the three main ways I use to clamp the wood.

Long stick on vise

This is easy.

Pros: Low setup time, great for series.

Cons: Final cut-off should be carefully planned.

Disposable wood support

This is my favorite. You¬† just glue a piece of “decently” squared wood to the base of your blank, and use it to clamp to the vise. After machining the top and the sides, you cut away the base block and machine the underneath.

Pros: “Indexable”: you can use a vise stop so you can put your part on exactly the same position several times. So, if you have a lot of parts, you can make a round, use one tool on every part, and do another round with another tool. Of course this only have sense if you don’t have an automatic toolchanger.

Cons: Setup time: you need to cut a piece of wood squared enough, and glue to your wood. Also, if you make “rounds”, re-clamping can time consuming and, depending on your setup, prone to positioning errors.

Base block and screws

Here you machine a piece of wood and use some screws from below to secure the part. The block itself should be bolted to the tooling plate (or held on the vise). If your part has some straight holes you can look for a wood screw that thread on that hole without damaging it. I use this method for a second step on some parts clamped on previous ways (you can see the remaining of the disposable block on the back of the picture). This is the method I’ve used on my last video.

Pros: You can get a very precise positioning with the proper setup (e.g. using index pins). You can also clamp several parts at time.

Cons: Making the base block can be time-consuming. Also, you need holes where you screw can attach to, or you would need to make some holes on your part if you don’t have enough or appropriate ones.

As a final note: wood is a nice stuff to work with, but you should be careful and plan ahead your cuts to avoid tear out.

Automatic

It’s been about a year since I move all my stuff to a new location. I’ve been doing, silently, a lot of things: machine tunning, fixtures, furnishing, prototype design, components procurement, coding, etc. And I’ve been working hard on my latest project in the past months (there will be another post about that).

I’m not good at social media; I’ve been publishing just some instagram pics from time to time last year. But it’s time to start to publish content again, and i3micro.org will change to automaticartisan.com from now.

So what we have here is the final step in making a PVC, 70 tooth HTD3M pulley. Grooves where made using the Sherline rotary table and a custom tool bit, in a the same way as on my old “making gears” post.

CNC Lathe making chips and choosing a video editor

I guess I should have chosen a curvy part instead of this boring one… maybe the next time.

Now some words about my search for a decent linux video editor. I did my previous video using OpenShot; It was a bit crashy and I really don’t like the way it handles titles. So after checking some reviews and doing some tests, I finally settle on Kdenlive, which is really nice.

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).

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.

Aluminum Sheet Cutting

My actual cutting parameters for aluminum sheet:

  • Material: 1100 aluminum (I’ve cut 1mm and 2.5mm sheets)
  • Feed: 600mm-min or 24IPM (I’ve used 800mm-min, but now I’m being conservative)
  • End-mill: 4-flute 1.5mm carbide. I’ve used 2-flute and 3-flute; the more flutes, the more quiet the cut.
  • DOC: 0.2mm
  • Spindle speed: max (2800 rpm)
  • Lubricant: some WD40
  • Finish pass required.

sheet_cutting-01sheet_cutting-02sheet_cutting-03

A lot of peoples says 1100 is a¬†nightmare to machine, but as always, you just need to know it. I settle in these parameters by a test-error process, but I don’t now if these are the optimal ones. I just know these values work for me. And of course these small carbide end-mill would enjoy more rpm.

For 5052 I’ve used the same parameters, but you need to lower the feed a bit; a friend broke some end-mills at 800mm-min because of my speed thirst (nevertheless that was fun).

One last thing… the part in the photos is 2.5mm thick, so it was strong enough to withstand all the cutting with just a few screws. If that were a 1mm sheet more screws would be required.

The Perfect Paper

I’ve been building a leadscrew cover for the Sherline’s I’m going to sell. I think this is a must on any cnc machine.

I like the classical accordion-like cover, originally designed by ixen-cnc.com. So far, the main obstacle has been to find an appropriate paper. But I guess here is: Fabriano Tiziano Paper. This is a acid-free, 40% cotton, 160 gsm drawing paper. Very high quality and strong paper.

sherline-cover

Folding has a trick; you should use a ballpoint pen to trace each line, pushing hard (kind of emboss). Even if you do this, folding is difficult, though not impossible.

And the best thing… you have a lot of color options!. I like the black-red combination.