Getting Metal Parts Laser- or Waterjet Cut: a Beginner's Guide

Sure, there are many maker-friendly sites that will lasercut or 3D-print your designs in plastic or wood, but what if you want to make something in steel, aluminum, or brass? What if you don't have access to lots of metalworking machinery? You can make amazing things out of metal with very few tools by designing parts and having them cut out of sheet or plate at a waterjet or lasercutting shop. There are thousands of shops around the country cutting out pieces for industry and fabrication, and although they may not seem as inviting to newcomers as web-savvy "DIY" shops, they can help your metal dreams come true.

Cutting shops have been slow to adapt to the web-based world, many don't even have websites, and the people can often seem gruff. As a newcomer, this might be daunting. That's why it's important to know as much as you can before you contact shops, and that you take some time to find a shop that communicates well and is open to working on small projects.

Lasercut vs. Waterjet

For a basic overvew of the two processes, see http://en.wikipedia.org/wiki/Laser_cutting and http://en.wikipedia.org/wiki/Water_jet_cutter

Lasercutting is faster, and therefore generally cheaper, than waterjet. The laser kerf (the width of the cut) is very small at about 0.007" (the thickness of two sheets of paper), which means you can have very tight corners and small piercings. However, the laser produces a huge amount of heat, which means pieces can warp or even melt if there are too many small cuts. Although technically possible, you will not find a shop that will lasercut brass. The laser also leaves slag on the cut edge which will need to be cleaned off. Most shops will tumble/deburr your lasercut parts for you unless you ask them not to.

The waterjet kerf is about 0.040", so the smallest piercing you can expect is larger than 1/16". The waterjet produces no heat, and the cut edge is raw metal, very crisp (as opposed to the burned lasercut edge). The raw metal edge will take patina better than the lasercut edge, but will also need some deburring or filing to soften the sharp corners.

Opinions abound about which method is "more accurate." In the end, this depends on the quality of the individual machine and the skill of the operator.

Design Considerations:

• Many shops will be reluctant to cut any openings, with laser or waterjet, that are smaller than the width of the material. Not that it can't be done, but you might have to look around for a bit.
• You can draw your part in any software that can export to a DXF or DWG file. I have never encountered a shop that accepted SVG files, but that doesn't mean there are none. Your drawing should be made up of lines, not fill or text.
• Generally speaking, don't worry about drawing in rounded corners to compensate for the kerf of the cutter. The software the shops use to turn your drawing into a tool-path will handle that (see close-up tool path picture above)
• The exception to the above is when you have very tiny piercings. The same close-up picture above shows the tool path as the machine operator might see it. The red area is where the tool will actually cut, and the purple line is the drawn line. You can see where the software doesn't know how to handle the tiny openings. The more you can avoid that, the less time the shop is going to spend messing with your file, which means the less they will charge you to cut it.

Cost Considerations:

• There is a certain amount of time a shop will spend setting up your project whether it is one part or 200. They've got to deal with the files, communicate with you, get the material on and off the table, etc. Some shops have an up-front 'Setup Fee' of $60 or so, others just add it to their quote. Keep in mind when designing that the smaller your order, the larger that setup cost is going to look in relation.
• You can always let a shop know that your project is a prototype, and that you plan to order much more if it works out. They might offset some of the setup cost onto future orders. Do not do this unless you really plan on making more parts in the future.

Make it easy for them

• Include a dimension on your drawing that the shop can use to verify that they've imported your drawing correctly
• Alternately, you can add a drawing of a 1 inch square (see picture). If your software doesn't have a dimension function, just tell them you added a one inch square for verification, not for cutting.
• Export to DXF or DWG (or both, you never know if one will import better than the other on their end)
• Also export to PDF, so they have an easy reference of what your part looks like to you. Sometimes their software will change things around, or someone needs to look at your part who doesn't have a DXF viewer. A PDF is a handy reference.

Know what you want

Material

• The most common aluminum sheet/plate is 6061
• The most common brass sheet/plate is C260
• The most common steel sheet (up to 10ga. 0.1345") is hot-rolled A1011
• The most common steel plate (3/16" and up) is hot-rolled A36
• The most common stainless steel sheet/plate is T304 with mill finish

There are tons of different alloys available, as well as surfaces such as hot-rolled or cold-rolled. Big Blue Saw has an excellent list of commonly available alloys and thicknesses here. I would do as much research as possible before ordering a less-common alloy.

Thickness

Thickness is almost always specified in thousanths of an inch. Sheet steel is commonly available in gauges up to about 10ga (0.1345"), thicker than that it is usually fractional (3/16", 1/4", etc.). Gauge measurements for Brass, Aluminum, and Stainless are all different, so most shops just use decimal measurements for everything, as it avoids confusion. You can always put something like '0.188" or similar' on you quote request, in case the shop doesn't have that thickness but has something close.

Let them know

Put a note in your email (and on the DXF if you can) with the following information:

• A project name for reference.
• "Please quote lasercutting" or "... waterjet"
• Material and thickness
  • Redundancy is fine. Ex.: " 3/16" (0.188") A36 Mild Steel"
  • Specify finish if applicable. Most materials only come in "mill finish" (i.e.: how it looks right out of the mill). Some materials, like stainless, offer surface finishes for an added cost. Don't get into this unless you really need to. Just know that if they ask, you probably want "mill finish".

• Quantity. If you want several copies of all parts, put it here. If you have several parts and you want different quantities for each (i.e.: 5 copies of A, 3 copies of B, etc.), put the individual quantities next to the parts, and put the total part count here.

• Your name and contact info. Sometimes the person reviewing your DXF doesn't have your email. Make sure they can contact you with questions.

Here is an example for the piece shown in this tutorial:

Byzantine Buckle

Please quote waterjet

Material: 3/16" (0.188") T304 Stainless Steel mill finish

Quantity: 10pcs

Benjamin... ben@...com

Staying Local

Chances are there is a waterjet or laser shop within 10 miles of your home. They don't advertise much, because most of their business comes from word of mouth and established contracts. You can ask around at metal fabrication shops, or just do a search for "waterjet" or "lasercut metal" and see what pops up. Many shops don't even have websites, but that's no reason to write them off. As long as you can find an email address, you can get a quote.

Working with a local shop can be great because you can pick up your parts in person, meet the shop people, and develop a relationship.

Broadening the Search

• You can get an instant online quote from Big Blue Saw. This can be valuable even just as a reference point.
• You can create a free account with MFG.com, upload your project, and get quotes from all over the country or the world. This site is definitely geared toward larger scale projects, but it is very useful, and not limited to metal cutting at all.

Get A Few Quotes

It is a good idea to get quotes from a few shops, especially at first. You are not just checking the cost of your project. You are also trying to find a shop that communicates well and is open to working on small projects with creative individuals. Some shop people can seem a bit gruff, and part of that is that they actually make very little money on small projects. The easier you can make it for them, by preparing your files well and knowing what material you want etc., the more interested they will be in working with you.

Make sure to put "Request for Quote" or "RFQ" in the subject of your email.

Award your project

Some shops will want a purchase order authorizing the project (you can find Google Doc templates here), but either way it is important to make it clear that you are authorizing the project. I usually reply to the quote with something like, "Please proceed with cutting."

Some shops will ask for payment up front for a first order, although this is not common for established customers.

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