People often ask me why the edges of their laser cuts are not square. The laser beam is being focused at an angle to a spot, so no cut can be perfectly square, but there are things that can make it worse. Note: All of the images are exaggerated to show the affects.
You first need to understand how the lens works. Laser cutters use a collimating lens. This means it takes parallel rays from the beam and focuses them to a single spot. For a couple of complicated physics reasons, it can never do this perfectly, but it should do it close enough not to be a factor in this discussion. Below is a picture of a collimating lens. A typical beam width is usually about 5mm-8mm and a typical lens is about 20mm-25mm wide.
You can see that the beam forms an hour glass shape. This can cause a little angle. With a 6mm wide lens and a 50mm focal length, this angle is typically 3-4 degrees.
To get the least affect on your part, you might want to center the focus in the middle of your material.
If you are getting a bigger angle than a few degrees, it is more likely because the beam is not in the center of the lens. The lens will still focus to that same point, but the hour glass is at quite an angle to your work piece.
This type of angle is offset in one direction, so you may see it more in certain directions of travel. If the beam is moving from right to left in the above image, you might not notice the problem at all.
Does a longer focal length help? It can, but due to the complicated physics issues I referred to earlier, a longer focal length creates a larger spot size, which reduces power density. See this calculator.
3D Systems recently acquired Geomagic. Several years ago they acquired Alibre. Alibre is a parametric CAD program. It appears that they are simply re-branding the existing version of Alibre as Geomagic, but will incorporate feature of the Geomagic product line over time. Here is the basic product line.
I have used Alibre and Cubify Invent and find them to be quite capable. Some day I may loose my easy check out access to Pro/Engineer and these products are on the radar as possible solutions. I found the even Cubify invent could do a few little tricks that are a pain in Pro/E.
In a couple weeks we are going to do a CNC V Carving night at Pumping Station One. We hope to fabricate a number of designs on the CNC router. This blog post will serve as a basic introduction to the concept and will help people get artwork ready.
What Can V Carving Do?
V Carving uses a V shaped bit to to “carve” a design into the material. Because the bit has a v shape, you can cut narrow shapes with the tip or wider shapes near the bottom.
You can even cut shapes wider than the widest part of the bit by doing multiple passes of the bit. The depth of the cut is proportional to width of the cut, so you need to make sure your material is thick enough. If you have very wide areas, you can set a depth limit and you can make that area have a flat bottom with a second flat bit.
Normally routers cannot cut square inside corners because you are cutting with a round bit. V Carving can get around this limitation because the bit can rise up into the corners until it gets to the zero radius tip.
Finishing Tricks
V Carvings can look great simply cut in the natural material, but they can really pop when you put a contrasting finish in the carved areas. This is a time consuming process and can be difficult to do well.
You can often shortcut this process by using masking materials. You start by applying a background finish to the work piece. This is then masked with tape or specialized masking material. The router then cuts through that as it is cutting the design. Now, only the cut area is exposed and you can simply spray paint the exposed area. If the design has multiple colors you can cut one color, paint, remask and repeat the process.
The files should in in DXf, DWG, AI, EPS or PDF format. Many programs like InkScape and CorelDRAW can output these formats. If you have hi resolution bitmap, some of these programs can convert to a vector format. Feel free to try that, but help with that will be beyond the scope of the session.
The quality of the masking material comes into play with very fine details. If your design will leave tiny isolated dots of masking, some materials may not stick well enough and break free during cutting. If that happens, you can manually touch up those areas later. I like to use Avery Paint Mask, but plain masking tape, adhesive shelving paper and materials for vinyl cutters also work.
What is good artwork to start with
Avoid very thin lines lines. The material needs to be needs to be perfectly flat and consistently thick for this.
Very large areas to cut will take a long time, so avoid them for this session.
Multiple colors. Multiple colors is OK, be each color needs to be separated from the other color so there is masked uncut area between them.
This logo would work. The red would be the base material and all other colors would be cut and colored.
This one would be very hard to do because of the adjacent colors.
How to bring the artwork to the session.
To save time, the artwork should be as ready to import as possible. Problem artworks will be pushed to the back of the queue and might not get cut.
The artwork needs to be in a digital, vector format. By digital I mean you can sent the file electronically. Vector files are created with actual geometry. Lines are lines and not a string of pixels. Scans and photographs are not usable. If you zoom in and the image gets pixelated, it is not ready to use. The shapes also need to be closed. If you have a square, for example, all the corners need to meet or the software cannot determine inside from outside. Tiny gaps can be closed in the CAM software, but if you can see them, close them.
Try not to be too complex or have large cut areas. These will take a long time and will limit how many people we can accommodate in one session. We can still create G-Code, but you many need to cut it at a later date.
If there is time I my cut small PS:One snowflakes for the people who did not bring any artwork.
Material
The idea material is a smooth, pre-finished piece of wood. It needs to be as least as deep as 1/2 the width of your widest feature if you are not planning a flat bottom. The material should be as flat and consistently thick as possible or the results can be distorted, because the depth of the cut is so critical. Avoid oily or wet finishes because the mask material may not stick well. Plywood does not look well and often interior layers have voids.
A Lazy Susan style filament spool system seemed like a natural addition to this printer. The problem was the filament had to go down the center. This was solved by a nylon bolt with a hole drilled through it. That bolts a flange bearing to the top. A disk to support the spool is glued onto that. It then uses a tube attached to a piece on the side to guide the filament from the edge to the bolt. It also has 2 extra keeper to prevent the filament from a full spool from falling off the edge.
Magnetically attached bed
When a part is firmly attached to the bed, I get a little nervous pulling hard on it when it is attached to the rods and carriages. The answer was to attach it with a few Neodynium disk magnets. I used (3) 3/8″ x 1/16″ thick diameter N52 magnets. The magnets on the end effector are in pockets with 0.75mm thick base. This means the magnets never actually contact each other. The bed has them in pockets too, but the pocket is only as deep as the magnet.
LED Lights
I added a ring of LEDs. These LED ring lights are sold for use on cars. I bought mine on Amazon.com.
RAMPS controllers don’t have a lot of options for high current I/O so I hooked this to the unused bed heater output. You can control I/O pins M42 Pn Snnn command where Pn is the output pin number and Snnn is the PWM level. The bed heater pin is 8 on RAMPS. The Marlin firmware protects you from messing with “sensitive” IO pins, so you need to remove HEATER_BED_PIN from SENSITIVE_PINS which is defined near the end of the pins.h file. For some reason “M42 P8 S255″ only flashes the LEDs briefly. All other values below 255 work. You can put M42 P8 S254 at the beginning of the G-Code of your parts or in a script of the host program.
My name is Greg and in this blog post I’d like to give you some tips on working with a laser machine. I own a Trotec Speedy 300 laser engraver/cutter. Most of the time I do my own designs, but from time to time I take a look at the Trotec website to find some samples and templates there. The samples are located here: http://www.troteclaser.com/en-us-us/laser-samples/Pages/Samples-Overview.aspx
Laser Engraving
My Speedy 300 laser machine is great for engraving all kinds of materials. I prefer working on wood and glass, because the precise engraving results you get are just awesome. Below you can find some of my work I did in the last few months.
I tried a lot of different wood types but I think alder wood is the best for laser engraving because it’s very dry. The dryer the wood, the better the engraving results. I do wood engraving mainly to make birthday presents or decorative items.
Glass engraving also offers many possibilities for picture engraving. You can engrave virtually anything on glass trophies, bottles or dring glasses. On their website Trotec mentions that you can engrave any design that can be printed. Just take care about the right contrast of the image you are using.
Laser Cutting
Laser cutting can be pretty useful if you want to make some nice invitation cards made out of paper or cardstock. The software that comes with the laser lets you use any graphic as a template for the cutting.
My favorite cutting applications are greeting cards, business cards and decorative items made from wood. The tricky part is to correctly set the laser parameters according to the material you are working with. I really recommend having enough material to test the parameters several times. At the beginning it might be a little difficult to find the correct settings and you have to test them a couple of times. As soon as you have got some experience with the laser settings it will be very easy to set the parameters right.
Here are some examples of what I cut with the laser:
If you have any questions regarding laser cutting or engraving feel free to contact me.
Greg
Editors Note: This is a guest post from Greg Weber. Greg lives in Detroit and is not affiliated with Trotec. He has has the Speedy 300 for about three years. The machine with a lot of accessories and exhaust system cost about $28,000.
The 3D Printer Experience is opening on Monday April 22 in Chicago. The store is design to introduce people to 3D printing. They have 20 printers in the store including an awesome looking EOS Formiga P100.
They are going to have 3D printing workshops, scan and print people and have some cool interactive apps to design your own things.
I know several of the people involved and I wish them the best of luck.
I love using these jumper wires for prototyping. They work great for breadboards and Arduino headers.
You can buy them all over the place including SparkFun. They are available male/male, male/female and female/female in various lengths.
Sometimes you need to hook up something that already has wires attached. I got these pins and single pin housings from Pololu the other day.
I really like them. The housing works for either male or female pins. You can either manually crimp the pins with a needle nose pliers or use a real crimper. The crimper works for both the male and female pins.
Here are the links to the parts. If you know of other sources, please add them in the comments.
Proper use of a crimper is a learned skill. You need to take the time to learn it. I lend out my crimpers all the time. Many people try to use their first attempt in project. The pin falls off or does not have a connection. They then give up and use pliers. The bottom line is there is no better way to put the pin on than a proper set of crimpers. This is how the professionals do it. It only takes a few attempts to get it right. Take the time.
One of the biggest mistakes newbies make is stripping too much insulation. It is usually just a tiny amount and only the length of the wire barrel portion. It is very important that the insulation barrel of the crimp grabs onto the insulation. That is the thing that really holds the pin from being pulled off.
I always buy my crimpers from eBay where they are usually about 25% of retail. Avoid generic or all purpose crimpers. Try to get the manufacturers brand.
The crimpers I used are Ampmodu Mod 90418-1. The can be found used on eBay for around $50. Pololu suggests you can use this general purpose crimper. I also have that crimper and it works better than anything you could do by hand, but is no where near as good as the real one. The 90418-1 has a little “gate” thing that fits between the part the crimps on the insulation vs the part that crimps on the wire. This allows it to crimp just right on each part and sets the depth of the inserted wire. It also has two different wire size ranges.You can see this gate in the picture as the shiny bit with the square cuts.
I was doing an “Intro to 3D printing” event at the Chicago HackerSpace, Pumping Station One. We were showing about 5 or 6 flavors of printers. Someone commented how complicated the delta printer looked. I tried to explain that they were actually simpler in my opinion. Rather than having 3 different designs for each axis, a delta uses three common linear actuators. The delta was a Rostock Max and it does look a little complicated. I decided to try to design the simplest delta I could.
I wanted to make it small to keep the cost down. Once I decided to make it small, I decided to make it really small. I used the Tantalus and Up Mini as the benchmark for small.
Try to use parts I had laying around. I only had about 3 days to before the first build day.
Try using the Spectra Filament instead of timing belts.
Clean look and simple wiring.
Limit fabrication to 3D printed parts, laser cut parts and simple tools.
Try to build it in 1 night at the weekly PS:One meetup and involve as many people as possible.
Somewhere early in the design I got the idea to invert the end effector. The bed would move and the extruder would be stationary. This vastly simplified the design and I could use an extruder I already had. If I limited it to PLA, the bed would not have to be heated and no wires would have to go to the end effector. With the extruder on top, all electronic items except limit switches could be placed on a single laser cut plate.
The design was bounced off Jeremy BP of tinyworkshop.org a few times in an email thread titled “Latest Crazy Idea”. This is the rendering of the design going into the build. There is a pop can rendered on top for size reference.
Meetup 1:
I sent a note to the CNC Build Club forum asking if a few people wanted to help with the build. About 10 people showed up. I spent all my time handing out jobs. Jeremy BP was the primary fabricator and ran the laser cutter and other shop tools. There were a lot of newbies there so many of the jobs like setting the current levels on the stepper drivers turned into mini classes. There was a little SNAFU with the laser origin which wrecked the middle round piece. PS:One had plenty of replacements, but no black, so the middle piece is a creamy white
Here is a part of the team, One is tapping extrusions, one is pressing inserts into brackets, one is assembling V wheels and Jeremy is setting up the laser job.
Everything was going well until it came time to assemble the Spectra filament driven linear actuators. It was sort of a puzzle to work with the tiny pieces. AVRC and I could not agree on the best way to do it. Finally we each grabbed one and did it successfully different ways. The actuators worked but it was clear the design was not robust and might wear quickly. At about midnight we had the basic thing assembled less the rods and end effector.
Meetup 2:
I had posted the progress on the Delta Robot 3D Printers forum and several good suggestions came through. The best was the suggestion to use off the shelf rods. At this rod size there were a few that would work right out of the box. These are Traxxas 5538 parts. They are actually a turn buckle so they can be finely adjusted. I ordered them from eBay and got them just in time. They were only about $3 per linkage.
We laser cut a template that was used to set the rods all exactly the same length.
The template holes have been added to the lower circle piece so an extra piece is not require in the future.
The Spectra drive systems was replaced with pulleys and 1/8″ wide MXL Belt. Jeremy laser cut some toothy clamps out of delrin.
Motor mounts for the NEMA 14 motors and 18 tooth pulleys. The mounts have a captive nut on one side that can be used to pull the motor up to tension the belts.
Here is the electronics plate. It gets pretty tight even with small motors.
Limit switches were wired with a common ground under the base and (4) wires were run up to the controller inside one of the edge t-slots.
We assembled the end effector but the rods touched parts of the carriage as the outside edges. This was limiting the range. We installed some spacers to fix the problem. We also configured the firmware. We called it a night early this time at about 10:00pm.
Meetup 3:
All that really needed to be done was to setup the limit switch actuators to level the bed and enter the Z height information into the firmware and Repetier Host.
The first test was a simple calibration cube and printed perfectly. The part stuck tight to the tape and was a little tricky to get off the bed.
Everyone kept saying the printer looked inverted so we tried flipping the printer upside down while it printed. It finished the print without any problems. You could see a little line in the layering where we flipped it but both sides of the line looked perfect.
OK, that’s a lie. This is a 3D printing themed longboard. The project started by wanting to do something artistic with the Open Source Hardware logo. I stumbled across the Prusa tattoo as I was researching the logo.
The tattoo is the OSHW logo with a simulated 3D printing hexagonal infill. The tattoo is fantastic looking, but I really did not want to just rip an existing design, even though I’ll bet it is open source.
I played with some ideas and thought it would look cool to make the lines look more like filament by giving them some height off the surface. I kicked around a lot of materials from paracord to thick wires, to actual 3mm filament. I finally decided to use rubber oring cord stock. It would be a low cost, practical material and also be durable with a nice feel under the feet. As I played with that, it hit me that I should switch concepts and make it look like the whole board was printed. The OSHW logo was a little complex to work in the new design, so I switched to the simpler reprap teardrop logo.
I start by loading some really ludicrously large values into Slic3r, like a 4mm nozzle diameter and giant work envelope. It actually did not mind and sliced the long board up like it was ready to print it. I snipped out one of the inner layers from the G-code and loaded it into a CAD program. I had to manually make a lot of changes for aesthetic and practical purposes. The oring was going to lay into a groove cut with a ball end mill. To look best, the number free ends needed to be reduced and I needed to add a reasonable bend radius to the corners. I really wanted to do a hex infill pattern, but there was just not enough space on the board to do a good job of it, especially around the logo. The logo was printed about 4mm thick in bright green ABS.
Here is the process I followed
Cut the blank on aa CNC router out of 18mm baltic birch
Pocketed holes for inserts for the truck mounting screws on the back (I did not want them to show on the top)
Rounded the edges with a 1/4″ radius bit on a manual router table.
Finished with several coats of water based semi gloss varnish.
Cut a pocket for the printed logo using a 1/8″ bit.
Cut the grooves for the oring with a 9/64 (0.141) ball end mill.
Glued in the oring using super glue. For some areas I pretreated the oring with accelerator.
Installed the oring.
What I learned
I normally use spare varnish for a job like this, but I had to do all the coating inside and had limited time. Oil based spare varnish cuts cleanly on the router. The water based stuff did not cut cleanly and needed about an hour of manual cleanup arfter.
I would get a needle tip for the glue. A tiny bead down the center of the groove would have been best.
This is the Delta ORD Bot. Just like the original ORD Bot, this was done in a crazy short design, fabrication build cycle to have something to bring to ORD Camp this year. The only way I could pull that off is through the people before me that have paved the way.
Help helpful advice from my forum friends on my buildlog as I went along.
This is purely a project for my own enjoyment and as another demo use of Makerslide. This was a clean sheet design. All of the pieces were custom designed and fabricated for this project. I really wanted a clean look to it, so I planned way ahead for all the wiring. I went back and forth a few times on whether to put the electronics on the top or bottom. I decided on the top top and am happy with the decision. It was really easy to work on with the top plate removed.
I started with three linear actuators made with MakerSlide. The motors are mounted on blocks with integral limit switches. The wiring is done inside the blocks and exit a hole that is hidden in the final installation.
The linkages use stock hobby ball ends from Dubro. The rods are carbon fiber tubing. They are adjustable, but they were assembled on a build fixture to insure they are all exactly the same length.
The linear actuators were mounted to a CNC routed piece of 18mm Baltic Birch. The four point mount made it easy to adjust the angle of them.
Electronics
The electronics (Except LCD) were all mounted to the middle plate. This is what I used.
Azteeg X3 (does everything I need and is the coolest looking controller)
12V 30A switching power supply from eBay
ViKi LCD and control panel.
Anywhere a cable or wire had to go from top to bottom, it went inside the MakeSlide. Any exposed wires like ones to the hot end or filament drive stepper were decoratively sheathed. The wiring on the plate was covered by a piece of black acrylic.
Base
The base is made out of 18mm Baltic Birch. The hot bed is a custom 1/4″ thick 6061 plate with power resistors. It takes about 8 minutes to reach 90C due to the mass of the aluminum. It also takes forever to cool down, so you need to be careful removing prints.
It will be replaced with a round PCB style bed when that is available. There are screw on rubber feet underneath set in from the edge to give it a floating look.
Extruder
To keep the weight of the end effector as light as possible I went with a custom designed Bowden style extruder.
Hot End – I used the heater block, nozzle, cartridge heater and tube for a QU-BD extruder. The parts were mounted to a CPU heatsink, which is cooled by a small 30mm fan. The cables were run to the top inside a mess wire cover. The high current heater circuit was run on super soft and wire strand count 16AWG test lead wire.
Drive End. I used the motor from a QU-BD extruder and an MK7 drive gear. It is connected to the system on a 4 pin microphone connector. The mate is mounted to one of the MakerSlides and has a hidden hole drilled to pass up the center channel.
Tube – The tubing is 1/4″ O.D. Teflon tubing. The fittings are super light, Delrin quick release fittings.
Spool Holder. I mounted the drive end on top of my existing filament cartridge. This was a quick and easy solution, but also provided a near perfect position, length and bend for the tubing leading between the drive and hot end.
Firmware
Firmware – I am running the development version of Repetier. I have also run the customized version of Marlin, but I found Repetier a little easier to work with.
I want to try a double drive end bowden. I will put a NEMA 14 at the nozzle and a NEMA 17 at the spool end. This might eliminate bowden issues while still keeping it light.
Lighting. I want to add something to light up the work area.
Release the source (soon)
I do not plan to sell and kits or parts. If you want to buy a Delta consider the Rostock Max or this Kickstarter Project.
