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Machine shopping for a microscopy lab


Disclaimer: I believe that everyone who can hang a picture on the wall can work in a machine shop. However, if you are sloppy, forgetful, or messy, don't do it. Or at least read the manuals and learn safety instructions before you go.

If you are still reading this, you are not easily scared! Welcome to the world of DIY fun and creativity which a machine shop provides. Let's start with the most common myths.

Myth 1. Machine shop is for old-school dudes who like to fix their motorcycles - today one can buy online everything needed for science.
If you can buy everything - you follow mainstream, because your tools are old and popular enough that a company makes money making and selling them. If you hit an unbeaten path, or even make adjustments, you need to invent and make new tools. Of course, you can hire engineers - but research labs are rarely that rich.

Myth 2. Machine shop is a big and expensive enterprise, only big institutes can afford it. 
MS can be as big or small as you make it. I know an old Russian guy who was making custom-made cameras for wildlife photography using a lathe and a mill in his bedroom. If your budget and space are limited, you can fit a decent MS on one large table (more on this later).

Myth 3. One needs a lot of different machines.
One needs to understand which machines are most needed for his/her purposes. Usually this boils down to 2-3 machines used for 90% of the tasks.

Myth 4. Only trained machinists can operate the machines.
Operating basic machines is not more difficult than cooking. Like cooking, it be fulfilling your basic needs, or become a life-long obsession. A lot of machining can learned from youtube.

Now, enough with the myths. Which machines are most useful in a microscopy lab and why?
Most of the time your new gizmo falls into one of these categories:
  • Holders and mounts (for LED, lamp, lens, objective, projector, motor, etc)
  • Adapters (mating parts from different vendors, fitting imperial<->metric, adjusting height/offset from optical axis)
  • Cases, boxes and enclosures (lasers, electronic devices)
  • Heat sinks (lasers, LEDs)
  • Chambers.
Materials.
Most of the parts in microscopy lab can be made of plastic or aluminum. That is, if you need a quick test if something will work or not. If you shoot for part that are thermally and mechanically stable - you should go for steel.

Plastic is easy to cut and 3D print, but it has drawbacks:
Low dimensional and surface accuracy.
High coefficients of linear thermal expansion (6x of steel): parts made of it expand or contract more due to room temperature variations. This can be a problem in sensitive components like sample holders. Even temperature variation of 1 degree (a standard AC unit) can give a few micron drift, a big deal if you do microscopy.
Plastic dimensions are unstable - they can change over time as plastic absorbs moisture, or undergoes slow polymerization (some 3D printed resins).

Many plastics are poor choices for machining, because they easily melt and stick to the tool.
However, some plastics are machinable due to their good resistance to high temperatures, for example polycarbonate (aka lexan) and delrin (aka acetal). Check if the plastic has desired properties before machining from it.

Aluminum and brass are easiest metals for machining, and have moderate thermal expansion coeffients (2x of steel). They are go-to materials for R&D quick prototyping. Aluminum is more common these days, probably because it is much cheaper than brass, and can be black-oxidized, thus preventing stray light reflections off the optical components.

Steel (mild) is more difficult to machine, but it has lowest thermal expansion coefficient and it's much harder than aluminum and brass, so parts made of steel are very stable.

Tolerances. Typical machining tolerance can be from 50 micron (rough) down to 1 micron (ultra-precision), depending on machine, tools, and skill. However, to achieve and maintain precision is costly. Thankfully, tolerances in DIY microscope parts can often be quite permissive (~100 micron) which allows simple folks like us make stuff without special training. Often, we just need a quick mount or jig to test an idea. If it works, we can then ask professional machine shop to make it properly.
Also, even with crude machining, positional fine-tuning to 10-micron precision can be done by using micrometer screws or sometimes shims.

Must-have
 3D printer. The cheapest, fastest and most versatile way of making custom things. 3D print your part if you can - it's a big saver of time and money.
Downsides: low accuracy, rough surface finish, plastics used in consumer-grade printers (ABS and PLA) easily deform, cannot be threaded or machined, have high thermal expansion.


 Milling machine (mill): drills holes, mills surfaces, and cuts slots/grooves.
Typical use in microscopy lab: drilling holes for custom threads in metal parts; cutting off unneeded parts, drilling holes for cable routing.
One can also buy a drill press to make holes. However, a mill can do holes and additionally cuts in XYZ directions, so it is a better investment.
 Bandsaw: cuts sheets of plastic or metal, including aluminum breaboards,  pipes, rods and Alu-extrusions.
Indispensable tool for customizing breadboards and making laser enclosures.



Nice-to-have
Sander machine: used for finishing the cut surfaces, making them flatter and closer to the desired dimensions. Very useful and quite cheap machine (typically < $100). If you don't have it, you will spend more time filing your parts by hand.
Lathe: makes cylindrical objects, spheres, cones, threads, and precisely cut edges of pipes and rods. Typically used less frequently than mill, but if needed, becomes indispensable. Can be used for milling as well! More tricky to operate than a milling machine, but provides almost infinite opportunities if used properly.


Laser cutter: computer-controlled cutting of plastic sheets with high accuracy. Great tool for making custom boxes, holders, enclosures from acrylic plastic. Can also engrave your name and logo!
Caution: plastic emits toxic fumes when laser-cut, so a good air ventilation (or hood) required.


 CNC Mill: essentially a milling machine with full computer control over XYZ motion. You can make a CAD model, upload it to the CNC computer and (ideally) the machine will do the rest. Get one if your budget allows it.



Budget and considerations
Prices are approximate

3D printers.

Extrusion printers are budget-friendly, materials are relatively cheap and can be purchased from many suppliers. Prices fell rapidly in the last few years - now starting from around €200. Higher-end printer is preferred is you want to spend more time on science and less on printer debugging.
Example: Ultimaker 2+, €1900

Stereolithography printers use UV-curable resin and give higher precision than extrusion printers (50 um thick layer). Come at a higher cost and relatively expensive resin. The upside - it gives better quality of surface and small details (like holes and overhangs) than extrusion printers.
Example: Formlabs Form 2, €4100

There are a lot of reviews and resources about 3D printers: check 11 things to consider to start with.

Mills.
My favorite. Table-top mills can be very affordable, starting from less than €1000. But don't go too cheap - there are several catches:
  • Heavy is better, so cast iron base is good. If the mill is light-weight, it is more flimsy and prone to vibrations, which reduce accuracy.
  • Cheap mills have looser tolerances, large backlash and, again, vibrations.
  • The more power, the better. Good table-top mills start from about 1 hp (750W) power.
  • If possible, get a machine with digital axis position readouts (DROs) - they simplify precise positioning a lot, this will save you time.
I currently use Holzmann BF16V because it is cheap (€700), compact, and does its job for a buck. However, large backlash and wobbling of the XY table preclude doing any accurate milling. Still, it does 80% of what I want it to do. Looking back, I would rather spend 3-4K for a more reputable bench-top milling machine, with DROs and a good-quality XY table.

If you want accurate milling, invest in a more expensive machine, it will pay off. Expect spending at least $2000 on it. The more, the better - there is no free lunch. After some research, I found some options listed below. Your best bet depends on your jobs, budget, room space, etc. Make sure you buy one that accepts standard 230V AC power, rather than 400V three-phase, unless you have that in your wall, too.

Disclaimer: the list is a result of my own web search, and far from being complete. Neither it is endorsement of any machines listed.

USA
JET JMD-18, $2300
Shop Fox, $2200

Germany
Paulimot machines, starting at €1200 and up.
Optimum Maschinen, €1000 and up.
Wabeco, €3000 and up
Proxxon, €2000
Frada Shop.

Austria
Bernardo

Note that mills are typically sold bare and require a few extra things: sturdy table, machinist wise, end mills, and center finder. But these things are relatively inexpensive.

Good reviews about purchasing a mill.
Shopping Guide for Best Milling Machines
Tips for buying your first milling machine


Happy machining!

Comments

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