The blog of a newbie

[Quicker]

I see some posts about "where are the newbies?", etc, etc. I've been on the forum for a while, made a few posts, but I'm finally actually going now so I thought I'd start this "blog" or running journal. I should have started this about a year ago, but I'll do what I can to get caught up to current time.

First, if this is the wrong forum, please let me know and move it.

A little history on me. My online nickname just about everywhere is Quicker. I spend 90% of my online time at http://theprofilebrotherhood.com/forum where I am one of the site admins. When I'm not on that site I'm on RGroups or the Flying Giants. I own and run http://kalteisen.com where I design R/C airplanes...mainly 3D electric planes. I've had a number of airplanse produced as ARFs, but due to getting many designs stolen by Chinese factories I focus on kits now. Ever rising laser cutting fees prompted me to want to buy a laser cutter, but I quickly realized this was out of the ballpark so I decided on a cnc router to make my kits.

I tried building one from scratch, but I have kids and a life and the parts just sat in the garage. I did buy a controller and a bunch of steppers off ebay, but that controller turned out to be a piece of junk. Search here and you will find that thread. I finally settled on buying a built unit from a great guy called cardin1 on ebay. His name is Ricardo Mendonca and he has been great to work with.

OK, that out of the way the next post will start to get closer to current time in my saga.

Q

[Quicker]

My desire here is to cut parts for my kits, which are mostly balsa that is 1/4" thick or less. I have some 1/16th ply in them, but not much. After doing a lot of reading I settled in on a 1/16th tool in my Dremel. The table came with a RotoZip, but I am also very concerned about sound levels. I'm going to try a brushless airplane motor as a spindle at some point.

The table I bought came with a full copy of Mach3 and I'm using TurboCAD to draw the parts. When I first started playing with all of this I learned that Mach3 could import the DXF from TurboCAD and it would convert it to gcode and I was running simulations on my laptop. pretty cool. I also ran a program called CNCSimulator for almost a year playing around before I got my own CNC Router.

I was familiar with the process of drawing parts to be cut out because I have been sending my files out to a laser cutting service for nearly 3 years now. I figured this would be simple.

When I got the router Mach3 had evolved into a bit more complex application and it now used something called LazyCam to import the DXF files. This looked cool because it could set cutting speeds, offsets, etc, etc, but I was lost. I now knew the chain here was:
TurboCAD -> LazyCAM -> Mach3 -> finished parts
but LazyCAM seemed odd and it doesn't seem to always do what I want.

On the ProBro site I started chatting with a guy named jspencer who also had a CNC router and was messing around with cutting balsa. He is in the same position as I am with a bit more knowledge, so he's been lending a hand. He got me going with LazyCam and pointed out that most functions are tied to lead-ins. If I want to set an offset I have to turn on lead-ins. OK, so I turn on lead-ins. The only problem is they are all over the place. My files are pretty complex with lots and lots of parts on each sheet of wood.

I spent the last 2 weeks messing around with LazyCAM trying to get the offsets to work right, but it's VERY frustrating. Half the time the tool is cutting on the wrong side, not doing what it said it was going to do. jspencer confirms this on his router.

I tried just setting the lead-in length to 0, but it still puts little notches in the wood. I have attached a pic of the latest cuts. This just is not going to work. Also, I put cut-outs in the parts to hold them in the wood for shipping. I don't want the parts floating around. The kit builder just uses his knife to "pop" the parts out of the sheets. LazyCAM's toolpath is all over the place. WHAT A MESS!!!!!!! Maybe in the future LazyCAM will be OK, but this is one buggy pice of software right now. To be fair, I know it's early in the development cycle.

I remember way back in my early readings finding a program called ACE that would generate gcode from a DXF. It does not create offsets or cutting speed settings, but I thought I might be able to set those by hand later so I tried generating some gcode with it and comparing the toolpath with that from LazyCAM.

WOW!!!!! it was WAY more optimized and the code was 1/2 the size. LazyCAM's was over 800 lines and ACE's was only 400.

Look at the pics to see.

Q

[Quicker]

In the above post I attached a pic of some ribs I cut using code from LazyCAM. Not good.

I was very happy with the finish of the cuts, though. I'm using some cheap micro bits from Harbor Freight. You can get a set of about 15 or so for around $7-$9. They range from the thickness of a hair to just over .0625. They seem to be mix-n-match. Those ribs were cut with an .030 bit with my dremel at full speed and moving at 12 IPM. Not bad. The wood is 1/16th balsa so I tried stacking 2 sheets to cut 2 at a time. I had to drop the speed down to 9 IPM because I broke a bit, but it worked. That still figures out to be 18IPM since I'm cutting 2 sheets at a time.

The .030 bits do not like the 1/4" balsa though. I broke 3 bits even at 5 IPM, so I'll move back to 1/16th bits for that.

Q

[Quicker]

As I'm getting caught up here I noticed I forgot a few things that I learned. Mostly around offsets.

When I was first starting I was very confused about how I would know where 0 was on my table for X/Y and Z. I quickly figured out that at least for me, I manually jogged the table to the lower left and then touched the tool to the top of the material. I would then zero out the X/Y and Z axis in Mach3. In LazyCAM I would tell it to then go negative z down the thickness of the material for each cut. If I was cutting 1/4" wood than I would tell it to go down -.25. Zero was the top of the meterial.

As I am now switching over to ACE, I find that it treats the BOTTOM of the material as zero. OK, that's an easy switch. I will just jog over and bring the tool down to the bottom of the material on the side of the piece of wood and then zero the Z axis. I could also just do a global search and replace for the gcode that moves Z to 0 and replace it with -.25, or whatever I'm cutting. I think I'll just zero the table to the bottom of the sheet of wood. It's easier for now.

When trying to do offsets I 1st tried to do it my my CAD program thinking that I would then not have to mess with a CAM package to generate gcode with offsets, or mess with tools in Mach3, etc. Bad idea. I did get 1 of my airplanes totally setup with offsets in CAD, but it quickly hit me that I was locked into the tool diameter I chose and I decided it was too big. Now I had to go back and redraw all the offset lines. Even with TurboCAD's offset command it took me a week.

Note to self: This is stupid. Setup the tool table and use offsets in gcode.

I went into Mach3 and put my tools into the tool table. This is simple. Just give your tool a description and set the size. My first one was the .0625 bit I had, so it's tool #1. Cool, now I can make some gcode and select that tool. I saved my CAD file as a DXF, then used ACE to convert it to gcode. change the file extension from .txt to .tap.

Open the gcode in an editor. I use Crimson Editor, but any text editor will do. I added this as the 1st line to the gcode program.

M6 T1

That selects Tool #1, my .0625 tool. How did I learn that? I looked over the gcode that LazyCam had generated and it's not hard to figure out.

Offsets when I have more time to get caught up.

Q

[ger21]

ACE does not need to use the bottom of the material for Z=0. Are you entering the depth of cut as a negative number? Haven't looked at it in quite a while, but you enter negative numbers for the cutting depth.

As for offsets (cutter compensation), you'll need to add lead ins and lead outs and use G41 and G42 commands.

[Quicker]

I think my copy of ACE is old. I have no option for setting Z. I'm going to look and see if I should download a new version.

Q

[ger21]

You need to double click on something to get to the window to set the depth, but I don't remember what exactly. Layer perhaps?

[Quicker]

DOH!

Found it.......

Q

[Quicker]

By far the cleanest cut I've made were just made on a modified Dremel 2 flute down cut 1/8" diameter bit. Stock it's about 2" long and gravitates like crazy at my dremel's full RPM's so I cut it down to only a .25 cutting area and put it in at full speed on the Dremel. I was cutting at 20 IPM with NO hairs or fuzzies. The cleanest cuts I've made to date, except for the .030 bits in the thinner wood at 5-7 IPM. I think I could push that 1/8th bit to 30 or 40IPM just fine.

The downside is it's LOUD!!!!! My wife said she could hear it plain as day in the bedroom on the other side of the house. She can't hear the 1/16th and smaller bits. The flutes are huge on that 1/8th bit which I'm guessing is what makes it so loud. Totally not usable. It would make the neighbors upset.

I think my 1/16th bit would do the same quality if it was a down cut instead of an upcut. I was just watching it and you can watch the strands of balsa climb up the bit, then break off leaving hairs all over the place when cutting with the grain. When going cross grain the cuts are nice and clean.

I'm ordering a few different 1/16th bits, like a 2 flute down and a diamond pattern. I like the .030 and .040 bits I have from Harbor Freight, but they keep breaking off unless I keep the speed down under 7-8IPM. That's like watching paint dry. It would take over an hour to cut a Skeeter 30 which is my best seller. The .06 bits that came from Harbor Freight cut well at high speeds, but since they are an upcut I get really bad fiber strands all over the place.

Q

[Quicker]

Back on the subject of making gcode. I think jspencer's thoughts that LazyCam is best and designed for closed objects is correct. When I play around with my files and leave each part as a closed object it generates a nice clean toolpath and I can usually get the offsets to work right. Problem is that just won't work for me. I need to leave the parts in the sheets of wood.

On a positive note, I'm learning much more about the process by using ACE. For me it's much more intuitive since I'm a Unix admin and have a lot of programming experience in my day job.

Q

[Quicker]

So far the best compromise in speed, tool size and clean cut looks to be the .0625. I ordered in a bunch of diamond pattern .030-.0625 downcut bits. With my current .0625 upcuts I'm getting strands and hairs, but I can clean up the sheet very easily. The strands pull off and leave a very clean cut. It will work as a temporary solution until my downcut bits get here. The 1/8th bits are just too large, not to mention noisy. Even if it was quiet it's too large to cut out the notches for 1/16th wood spars notches and rib notches.

The guy at that company was very helpful and has many more diamond bits than what is listed on that page. He recommends coarse teeth over medium teeth for what I'm doing and also said downcut is the best. I ordered a few medium and a few coarse just to see what I really like better.

Here's a pic of the bones of a couple of my planes. These were laser cut, but you can see the type of work I'm doing. Everything is interlocking and the plane can mostly go together without glue.

Q

[Glidergider]

Hey Quicker,
This is a great thead. I'm a newbee and have learned a bunch about speeds, bits and software. Thanks,
Dave