Although it’s fun to always be doing new things, sometimes it’s a plus to be able to reuse work that you’ve done in the past. It not only saves you time, but also gets you looking at old designs with new eyes. Here are two examples that I’ve worked on recently.
Puzzles:
5 or 6 years ago I was talking to my wife who works with a Pre-Kindergarten class about ways to make learning to spell a little more fun for young kids. I had been playing around with designing puzzle pieces to cut on my PRT benchtop and decided to try designing some pieces that would lock together in any order, with a single letter on each one. Eventually called “letter linkers”, these first pieces worked so well and were such fun for the kids that I ended up making sets with numbers and letters (using a chart showing the frequency of letter in the game “Scrabble” to determine the number to cut of each letter) for each pre-k, kindergarten, and 1st grade class in the school.
I forgot about them for a while until a friend, an avid (maybe rabid is closer to the truth) Virginia Tech football fan, asked about a present for his grandchild. I was trying to come up with something new and clever when I thought of the old Letter Linker files, and decided to cut a set in the Va Tech colors of maroon and orange. Everyone loved them!
That was 3 or 4 years ago and I hadn’t done much with puzzles since, until my friend Robert Bridges was renovating a building in town for a Pediatric Physical Therapy clinic. The original Letter Linkers only had puzzle connections on 2 sides, but I had wanted to do some that could connect on all 4 sides so that someone could create crossword puzzles or play Scrabble. As we were hashing over ideas for a floor that would be neat for kids and not too expensive to do, the idea of a puzzle floor out of plywood seemed a natural. A quick rotation of the “puzzly” parts of the original design created connections on 4 sides, and Robert scaled the parts to fit a dxf floor layout and cut them out. He even engraved the clinic’s name, “Little Hands, Little Feet” in the floor at the entrance, and made a sign for the entrance using the same shape.
We sent some images to Angus Hines of Hines Design Labs, who immediately replied that he was looking for an interesting floor for a hallway in his house and thought a floor like this would be just the thing. Here’s Angus’ floor, cut from Oak ply.
Next Robert got a job remodeling a home, and the owners wanted a map of the Eastern Shore of Virginia engraved into the entranceway floor. The same puzzle file worked for this application too, with some scaling and layout editing to split the map into puzzle-shaped pieces.
The most recent use of this puzzle design was to cut puzzle letters on the new ShopBot Desktop during the New York Maker Faire last month. These puzzle pieces were smaller than the original Letter Linkers and had connections on all 4 sides, so that words could be made in any direction. We had a pile of them on the table for kids to play with, and even made a set that spelled “Inventor” for the Autodesk booth next door.
Cutting crabs:
Roger, the owner of one of our favorite seafood restaurants the Machipongo Clam Shack, asked us one day about doing some crab cutouts to attach to their billboards. They had a sketch that the owner’s artist sister had done that was really nice…a very pretty crab!…that only required some digital tracing and editing to create a file that was toolpath-able.
We ended up cutting a dozen or so out of 1/2″ plywood for their billboards.
The customer liked them so much that a couple of months later they got us to cut some more for decorations for their restaurant that local artists could paint….
…and even one out of 1/4″ masonite to use a stencil for their parking lot.
We made a little bit of money on these (and ate a bunch of free crabcakes!), but since we figured that we would never have a need to cut out crabs again we forgot all about the files until Roger called a couple of years later and asked about making some double doors to separate the kitchen from the front counter. Those same crab files came in handy once again…scaled down… as both decorations and peepholes to keep the waiters and waitresses from crashing into each other.
Now the point of this posting was not to show off some of our projects, but to get you thinking of your cutting and design files, not as one-time uses but as something you want to save for possible future use. I freely admit to not doing a great job of backing up my files…this is more “Do as I say” rather than “Do as I do”…but here are some techniques and methods that have worked for me:
- Come up with a sensible naming and storage system for your work files. I tend to use version numbers in the name as I work on a project, but sometimes using the date works better. And be descriptive…don’t just name it “back v2.sbp” or you’ll never figure out what it is if you find it outside it’s folder.
- Along with selecting filenames that are easy to remember, keep all the files for a project in a folder with a name that will make sense years from now. You’ll probably forget what “Smiths chair” looked like, but won’t have a problem with “Clam shaped chair with dreadlocks” or something like that. And don’t skimp on the folders. It’s a lot easier to find a specific chair file if it’s in a folder named “Chairs” inside a folder named “Furniture”, than it is if it’s jumbled up in a gigantic folder named “Files” or “Projects”
- Do regular backups! Your computer probably already has a program to do backups…both Windows and Mac do…but there are lots of aftermarket ones as well. None of them will do you any good if you don’t set them up correctly and use them, so do your homework!
- Search is your friend! If you did a good job of naming your files, the search built into Windows or Mac will find them.
- A little hardware can be a big help. USB thumb drives and external harddrives are cheap and quick to use for backing up and can be stored for quite a while. Almost every computer has a writable CD or DVD drive these days, but be aware that those cd’s have a limited life so don’t count on them as your only option
- Some of the dedicated backup “appliances” like Windows Home Server can make backing up and restoring painless…that’s what we use.
- If your customer paid for the design work, think about giving them a copy of the files as an additional backup. They have a vested interest in taking care of them if they think they’ll have to pay you to create them again.
Your files are assets that might come in handy sometime in the future, so pick an archiving method that works for you and stick with it.
By Camp ShopBot, October 24th, 2010
We visited John Haggerty’s shop in Souderton, PA again, and got to see a number of new projects he, and Bob Dodd have been experimenting with over the last year. The majority of “Campers”at this one were new to the machine, or had never seen one before, and they got a very well rounded ‘tour”of the machine, and it’s capabilities.
Bob Dodd brought in some of his latest projects which ranged from bending fluorescent plastics, to cutting small ( 1/32″bit) components for doll houses ( see above) . Bob also has been testing a variety of exterior coatings for foam, and he brought in some samples of styrofoam coated with a product called “Styrospray 1000″. Bob also explained some of his techniques for doing rotary work on a number of shop built indexers he has created over the years.
Our host John has a shop full of “eclectic” projects ranging anywhere from a rack of noses he sells to people who need a place to stash their eyeglasses, to some serious mold making jobs that ranged from small statues to a cannon from the 1700′s…!
Much of John’s work this past year has been concentrated on the concept of making a variety of molds to increase his production capabilities, and he showed us some of his ‘poured corbels’ as well as some other pieces that involved using his machine to generate large numbers of pieces for other companies. He had just finished up a large “run” of egg and dart molding strips built out of HDU before we began the Camp.
John is also dabbling into the kind of jobs that others would turn down because of the complexity of creating specific shapes. He even “invented” a roller system which allowed him to turn a crank, and “bend” strips of zinc into an customer specified molding shape to use as an edge accent on a custom bar installation. And John’s Shopbot ( a 2002 PRT) is anything but “stock” as he has embellished it over the years with a variety of clamping, and indexing features , which gives him the ability to do repeatable shapes in volume.
All of the above helped to answer some of the questions our other Campers had about ways to incorporate the machine into some ideas they were considering as business opportunities, so we also got into a discussion about “what do you do after you get an idea in your mind for a product?”.
For some more info on these projects please look at the pix on the Camp Flickr page- http://www.flickr.com/photos/campshopbot/sets/72157625231286710/with/5111186448/
Here’s another, somewhat more complicated solid wood machining project I completed a while back. In order to get a nice kitchen cabinet job for a contractor I had worked with before, I had to match some curved mullions for several glass panel doors which the client had fallen in love with from a competitor’s catalog. I planned to order all the doors and drawer fronts for this set of kitchen cabinets from one of my regular suppliers, and they were only too happy to give me a price on the design that my clients had chosen – $350 per door. For a set of four doors that would be $1,400 above the cost of the door frames and glass. I figured I could do it myself and save some serious money.
 Two of the completed doors. I had to start with some basic decisions about how to make the curved strips and how to handle the joinery where the mullions overlap. I decided that bent laminations would be stronger and easier to machine cleanly than milling the curves out of solid stock. But the joinery almost had me stumped. I happened to be looking through a router bit catalog and noticed a router bit set for making the exact same joint with straight stock. That set would not work with my curved workpieces, but it enlightened me to the concept of using a fancy half-lap joint to get the pieces to mate cleanly, with the profiles matching up in all corners of the completed joint. I drew the overlapping shapes in my CAD program and zoomed in on the area in question to try to visualize what exactly had to be machined. It took a while, but I finally figured out that by bisecting the joint vertically and horizontally, I could rout out the top-right and bottom-left quadrants of one piece, and the opposite corners of the other piece. In fact, by holding one piece upside down during machining, the two halves could be machined exactly the same way, and when the upside down piece was flipped right-side up, the parts would mate. I had my plan.
 Using CAD to figure out what had to be machined. I saved all the narrow scraps of maple that were generated from the rest of the job, and ripped them into strips about 1/16″ thick. After measuring the door frames, I drew the shapes of the forms that would be needed for the glue-ups, and nested several sets of forms onto a piece of leftover 3/4″ plywood. The glued strips were clamped into the forms and left for a day or two, then wrapped with stretch-wrap to maintain their shape until all the glue-ups were completed.
 Cutting the forms out of 3/4 inch plywood  Each curved strip is glued up of 6 laminations  The glued up assemblies were kept in shape with stretch wrap until machining day. Once the curved shapes were ready for machining, I loaded a scrap piece of melamine on the table and routed out the area where the workpiece would sit. This allowed me to precisely place one of the male forms on the table and use the female form with some cam clamps to firmly hold the workpiece in the correct position. The routed area also created a flat reference surface for the workpiece to rest on, allowing me to start by surfacing the tops and bottoms of each strip to create clean surfaces and a uniform thickness. I then used a profile bit to shape the shoulders of each mullion. It didn’t matter that the bit also cut away part of the form.
 Some leftover melamine becomes the table fixture.  A workpiece ready for the first surfacing.  After the top face is cleaned up, the piece is turned over and surfaced to final thickness.  The same setup holds the pieces while a profile bit follows the curve. I machined the half-laps with a 1/16″ diameter straight bit. I had to order a “long” 1/16″ bit (with a 1/2″ cutting length), and I was sure worried about it breaking when I saw it. But with such small areas to be machined I was able to use small step-downs, slow feed speeds and ramp settings as gentle as I could get them, and managed to complete all the cuts without breaking any bits.
 One half of a half-lap joint. I thought I’d have to do some hand chiseling in the corners, but to my surprise the overlapping pieces fit together almost perfectly. They practically snapped into place.
 The completed half-laps. One of the biggest challenges was machining the ends of the mullions to fit the inside profile of the frame. I drew the profile and used multiple copies of the shape of the router bit to approximate the shape that the ends of the mullions would need. Then I used the offset and depth of each copy of the router bit shape to create a pass on the router. It was a little tedious but it worked. The parts fit together and into the frames so well they hardly needed glue.
 Calculating the end cuts using CAD  The ends had to be machined to fit the inside profile of the frame.  Big sigh of relief when the pieces fit perfectly the first time. Bottom line: this was a successful project. I started early one morning with the glued-up parts and a vague idea of how to proceed, and ended the day with four custom doors ready for finishing. Using only scraps, I was able to replicate what my supplier would have charged a high price for, and the customer was thrilled with the result. Adding up the time spent ripping and gluing, planning, cutting and fitting though, and I came to a realization: maybe $1,400 wasn’t such a high price after all.
By Camp ShopBot, October 17th, 2010
The picture above is a very good summary of our host’s philosophy about running a business. Glen Kadelbach, owner of Innovative Foam, ( as well as a number of other affiliated businesses) believes that sometimes you HAVE to act on instincts, and hunches, and then take a chance by trying to make these ideas into something tangible.
This was our second Camp at Glen’s shop, and he again showed us some of the ways he has incorporated this concept into building a successful business ( or two, or three…). Glen’s work is almost exclusively in foam, LARGE foam pieces. And he has found ways to make his work SO interesting that he consistently gets great projects to work on. Last year he was showing us some of his techniques for building large pieces, and then coating them for exterior applications. Some of you may have seen Glen’s work on the Shopbot web page, including pieces for the Department of defense, Macy’s, etc. This year he showed how a business can be built by developing a reputation as being “the guy who CAN get the job done, regardless of size…”.
When we walked into his shop he was starting to put the final touches on a “forest of foam” which will be part of a large ( NYC) Christmas display. The fact that Glen is in Central Minnesota, and getting this kind of work further points out the reputation, and success he has been developing. In addition to the “forest” there were various, huge projects all over the shop including a foam bridge, white board writing pads, and very large sets of numbers for other shops to work with. He even had to move a couple of 250 pound blocks of foam out of the shop so we would have room to place our chairs etc., inside.
Glen works with a Shopbot ( that has a very deep Z axis) and a CNC hot wire foam cutting machine, and there probably isn’t a shape he can’t generate in one way or the other between his arsenal of tools, and his ingenuity. In addition to his booming businesses, including one which exclusively builds props for photographers, he also finds the time to run an 80 acre organic farm as well, so he has some equipment around the shop which is waaaay beyond the scope of the average ‘Botter.
So we were able to use some of these ideas in our sessions during the Camp. We got into the ideas of how to develop some products, and then get them out into the public arena. Everyone attending shared some of their own business experience, and we had a pretty good interchange of ideas.
Eric Erickson didn’t have a Shopbot at last year’s Camp, but he bought one right after attending the Camp, and he brought along a few signs he has started to market from his new shop in Wisconsin.
Miles Thormodson, and his son Stephen brought along some wood pieces they have designed, including a clever wooden arrowhead . And Stephen, who is a high school student explained HIS “business plan”of developing a marble game he hopes to cut out on their machine.
Dan, and Bridget Nelson drove down from Wisconsin and explained how they are trying to develop their own business , so they were great catalysts for the discussions by asking a bunch of “how do you”type questions.
Stephan Voelkel spoke about his plans to build a plasma machine to go along with his Shopbot for doing larger sign work. And he brought along a friend who was interested in using CNC to build boats of different styles. So we covered a pretty wide range of topics in a short amount of time.
On top of all of this good information we hit what will probably be the last great weather in the area for awhile so we were able to do a quick “tour”of Glen’s facilities to see everything from his barn(s) which are currently housing 500 tons of hay, his diabolical looking arsenal of farming tools,to his now ( in)famous project from last year, the Shopbot built chicken plucking machine. Thanks again to Glen, and his family for having us around for the weekend !
In this series of articles, I am heading in a little different direction than previous ones. In the past, I have written how I use the ShopBot to cut parts, hold them in place, and little extra gadgets, tricks, and accessories that can be added to the ShopBot. This series will give you ‘food for thought’, and will give you insights from both myself and Scott, my son, who has been working with me each day since last November. Together we will put our knowledge and experiences together in a form that we hope will help you along the way while, as an industry, we evolve and change to meet the demands of the current economic state.
With the current economic situation people are turning to smaller business structure where they produce their own line of specialized products. We recognize that there are lots of questions involved with starting a business like this, and it can be quite overwhelming to suddenly be handling your own research/development, manufacturing, marketing, and shipping. That is why we have decided to publish a series of articles helping you with the various processes leading up to a successful small business based on a product line of your choice. Picking these products seems to be an area where most individuals fail. There is nothing hard about this step, and for some reason business owners make this a major obstacle.
The First step in picking your new product should be making a list of your current interests. Then, review this list with an eye towards, ‘what can I produce to further other’s enjoyment in this field’. You will find, that making a product that you have no interest or experience in will be much more difficult to be enthusiastic and knowledgeable about, thus making it more difficult to sell. For example: we live in a rural setting where there are many farms that raise horses. The extent of our knowledge with horses is limited to: they have 4 legs, hay goes in one end and fertilizer comes out the other! With that degree of knowledge, we would surely fail in trying to produce horse related items. However, take camping, or outdoor cooking as an example, and we would be more qualified to produce a camp gadget or some other item of interest to outdoor enthusiasts. If you will take a day or two to carefully make your list and then comb through it and find an area that most excites you, you have set the stage for picking your first product. From here, you will want to put every idea that comes to mind for products down on paper, save it, and come back to it a few hours or even days later.
When it comes time to pick your product, give thought to how wide of an appeal this product has. For example: If you come up with a perfect product that matches your interests, but would only have appeal to folks in your neighborhood, you more than likely will not be able to turn this product into a profitable business. However, if your product has national or even worldwide appeal your chances for success increase exponentially. You must also consider the method of delivery to your customer. We have found that smaller more easily shipped items are much easier for me to get into our customer’s hands than large more bulky freight items that require trucks instead of UPS or USPS for delivery. Also think about the time it takes to produce each product, remembering the more complex it is, the more expensive the product will be and thus, the smaller the audience you will have to promote your product to. Think about utilizing the scraps generated in your shop or other shops close by. If you can find a use for the material previously considered trash, this will allow you to keep the cost of your product down, and also keep the price point low. Another benefit will be keeping this material out of the landfill! Taking care of the environment is a project that we all should share, and with the prices of material rising as they are, every little bit helps. Try to utilize your CNC Router or other automated tools for production, any time you can decrease the amount of human labor, the less costly the product will be overall. And finally, be mindful of the quantity of product that you can produce, keep quality on the top of the list, and don’t sacrifice quality for quantity. You may find that you have to invest in additional equipment, or even expand your facility to meet the demand for your product down the line. Don’t be lured into over-extending yourself financially by what may seem to be attractive terms or lease agreements. Build your business on a solid cash base foundation, and you will not only sleep better at night, but you will be much more “recession proof” than the business next door that has monthly payments that exceed monthly income during slow periods. Don’t be discouraged if your first months are slow, you still need to set yourself up for large scale production. If you can’t get the product to your customer, you will find you don’t have repeat or consistent sales. Just because you aren’t moving 1,000 units this month, doesn’t mean 3 months from now you won’t be over your head swamped!
We have found that items priced under $50 each, no matter what they are, have a much broader appeal than items priced above that mark. In today’s economic times people are tightening their budget when it comes to nonessential or frivolous items. If your product is non essential, you must be sure that it has a “wow factor”. We define the “wow factor” as simply the expression you see on a person’s face or their exclamation when they first see your product. If you can find a way to partner this “wow factor” with the needs of their children or pets, you have now created a more appealing product. Remember to view your selling price not only from a business standpoint (you’ve got to make a profit after all!) But also view this price from your customer’s perceived value of the product. Some business owners will argue it is better to make one item and profit $10, than it is to make ten items and profit $1 each. While it is true that time is money, in the long run, we would rather have ten happy customers who are willing to buy from us again, than to have one happy customer who may buy from us again. Keep in mind that people talk. The word will get out to your customer’s friends and family if you produce a quality product that they find useful. Thinking these situations through will put you ahead of the game when it comes to that difficult question of “what do I charge for this?”
In future installments in this series of articles, we will cover the actual manufacturing of this product we have chosen, as well as promotion and expansion of your product line. We will also explore how to “think CNC” when it comes to production, as well as setting up your shop for successful large scale manufacturing.
By Tom Odoyo, October 12th, 2010
With my great interest in renewable energy I have been working on wind powered generator which is efficient and cost effective and so that’s how the Shopbot came in handy to help me produce the aerofoil design of the blades.
I used a combination of positive and negative molds for the blades. Below is the positive mold of the blade curved out of ShopBot.
One thing I did like about the Cnc milling is that it produces the exact design to the last detail and so I was able to design and cut my wind rotor blades successfully.
This are the blades after wrapping them with fiberglass.
One of the finished blades
These are negative molds milled out of the ShopBot.
And the following is a finished wind turbine Showcased at Maker Faire Africa 2010! Click the image to see a short clip of Tom at Maker Faire Africa, 2010
By Camp ShopBot, October 11th, 2010
After a hiatus of about five years we returned to the Pacific Northwest, at Mike Miller’s shop in Vancouver, WA. Mike’s business is based on building components for the marine industry, with everything from custom rod holders, to anchors, and anchoring bow rollers (see some of his inventory of parts above…). Mike explained how he has integrated his Shopbot into a business he has been running “part time”, and he pointed out many of the advantages of building his own parts “in house” when possible. Given the fact that his location is very near the Columbia River, it’s the perfect “testing ground” for many of the products he is now producing.
Mike works primarily with what I would call “industrial plastics”; UHMW ( ultra high molecular weight) and HDPE (high density poly ethelene) , and these products are not very “forgiving” when cut. That is, there is NO sanding these dense plastics after they come off the machine so you HAVE to get them right, the first time. Just to get into Mike’s shop you have to walk past his “testing vessel” which is a very heavy duty aluminum fishing boat which Mike uses to chase down large sturgeon, and salmon.
We has a good sized group ( over 40 “Campers” attended) , and there were some interesting talks and samples on hand.
Russ Wood described how he has let his retirement “hobby” ( building “buildings” for one of the largest scale railroads in the world) morph into a profitable sideline. His pictures showed how he incorporates his software ( Aspire) into the planning, and scaling of many realistic structures which from a distance could easily be mistaken for “real” buildings.
Ron Moorehead showed off a beautiful gift box for holding a bottle of wine which he built using spalted wood.
Dennis Rech showed a video of a VERY clever adaptation he has made to his Buddy machine; what I would called a “cable drive tredle lathe/indexer”.( We’ve asked him to post the video on his web page, and then let us know it’s location on the Shopbot Forum via a link).
Donn Busby brought in some carvings, and lithophanes he’s been creating, and he explained his technique for cutting lithophanes.
Mike McCarthy brought along three of his family, and his daughter Christy explained how she designed, cut, and painted a sign she had on hand.
Steve Knight explained some of his “learning curve” in figuring out ways to cut exotic woods into “mirrored halves” for assembling custom hand planes out of Purple heart, etc.
As a group we covered many of the “universal topics” which everyone deals with including, sign making,hold down systems, software options, and local sources for specific materials.
I had some samples of Russ Todd’s ((www.widgetworksunlimited.com) latest “after market” Shopbot device which were cut using his new, soon to be announced, “pressure foot” which allows people to cut very small parts without having to use “tabs/bridges”, and there was a LOT of interest in how well the tool seems to work.
Even though most “Campers” traveled from considerable distances there was plenty of interest in doing this type of meeting again, and more than once every five years, so a “Pacific Northwest user group” has been started, and they are now waiting for some input from the members before they plan their first event.I have no doubt that there will be more events in the area, soon…
By Camp ShopBot, October 11th, 2010
By Gary Campbell, October 4th, 2010
As we use our CNC’s we learn that we can assign virtually any position to any axis at most any time. We usually have a reason to do this, like a special purpose jig, or room for clamps for relocating the X & Y axis, but we routinely reassign the position of the Z for most every file we cut. Notice that I said, reassign the position of the Z axis rather than rezero the Z axis. I say this because in the complete range of Z axis travel, there are a finite number of zero locations.
Simply said, your zero location should normally be between the table and its upper limit of travel. If you have 6 inches of travel, then you cannot zero higher than 6 inches or below the bed. There are of course, other factors, but for normal cutting, these are the upper and lower limits.
Now for the relativity. Unless you have the world’s best eyeball, you can’t actually zero to the bed or an object, you zero to the Z zero plate. The control software has been told the thickness of this plate and it sets the position that it electronically senses (the top of the plate) as that thickness. The actual zero position is set relative to the top of the plate, by its thickness, to be the bottom of the plate. The same logic applies to fixed zero blocks. Its position, relative to the table surface, is adjusted for in the software during the zeroing routine.
Contrary to popular belief, zeroing a bit to any plate or block is very seldom exact. Due to electronic timing, the downward motion does not always stop at the exact same spot every time. Some bits dig into the plate. The plate can bend or have a low conductive spot on it. The bit can be coated. Individual control boards can react to the input signal with minute variations. All of these items can result in a few thousandths variation of position. Even more if one or more of them add together instead of canceling each other out. In most conditions, you can expect 10 thousandths either side of zero as the norm, 5 if you do some tweaking of your zero file and procedures.
These minute variations rarely affect our cutting until we wish to do a pocketing operation with multiple bits. Although irritating, it is common to see a second bit cut at a different depth. As users we need to develop methods to check for inaccuracy prior to cutting.
These electronic variations are nothing compared the variations in most processed materials, especially sheetgoods. It is not uncommon to see 30 to 40 thousandths thickness difference in a single sheet, even more across multiple sheets. More yet in inexpensive imported products. Our problem as operators is to find the actual or average sheet thickness from edge measurements. I usually take multiple measurements and average them to get my design thickness. In many cases, I have had to readjust the sheet thickness after cutting to reflect the actual material thickness in the interior of the sheet where my parts are cut.
Most sheetgoods cutters zero to the bed because we seldom know the real thickness of the material in the selected zeroing location. There are also variations with hold down due to material porousity. Prefinished and melamine are sealed, allow more vacuum to develop and therefore, suck down tighter than unfinished veneer plywood. Once a sheet is on the bed, should any problem, like position loss or broken bit occur, it is virtually impossible to rezero to the Spoilboard without removing the sheet. This is why most cabinet cutters use a fixed zero block, usually off the one end or side and below the surface of the Spoilboard so that it does not interfere with table surfacing.
The points that apply to the majority of users are this: Unless your material has been surfaced by the CNC you cannot assume that it is flat. Nor can you know the actual thickness at the zero location. These two facts added to the above electronic variations are the reasons for most of the depth inaccuracies facing small CNC users. There are also a number of variables associated with spoilboads, but we can save those for a later day.
As likely as a sheet cutter is to zero to his Spoilboard, most other users are not. There just seems to be something “off” with the way that most CAM packages treat zero to bottom of material. My experience is that it is harder to learn and more prone to error. Maybe it is just that we are programmed to think from the top down into the material. Even though I tested a number of files, my results were less than satisfactory and I followed the masses and prefer to design from the top.
I wanted the extra accuracy that zero to the bed gave me, but I also wanted the ease of use that I was accustomed to with zero and design to the top of material. There is a third way that allows both. Allows me to zero to my Spoilboard and then check the bit height against the Spoilboard in multiple locations prior to cutting. It also allows me to design my cutting files from the top of the material. It allows me to cut different thickness materials without a rezero of the bit. This method ensures that my actual bit zero is at the design thickness of the material. It does not eliminate errors cause by variations in that material, but will keep all other variables to the bare minimum.
I learned about this while beta testing for the ShopBot Link from the Thermwood programmers. Their files are all zero to bed, design and cut from the top. With their help I was able to understand the principle and implement it into my own Vectric post processors.
Here’s how it works:
The Vectric Software outputs the design thickness of the material to the post processor. The PostP, using some of the new features of the SB3 software applies a temporary offset called the “ZSHIFT” to the Z axis for the duration of the cutting file. When the file is complete the offset is removed. For the duration of that file, the Z zero is actually at the top of the material. If your next file uses the same bit, but a different material thickness, no rezero of the Z axis is required. The only time a rezero would be required is when a bit is changed.
So…. My theory is that the Z Zero should be automatically relative to the material thickness. Here is a screenshot of the Vectric material setup dialog showing that zero to top is selected. The red lines show the offset that the ZSHIFT applies.
This feature works with both MTC and ATC files, but may not be in the mainstream files distributed with the SB3 software. As such, it is most likely not supported by ShopBot. This means that you either need to be or know someone that can modify your post processor. Or, you can borrow a copy from someone that is using it. Although very seamless when installed, there is a certain amount of expertise required to modify the post and implement the changes. And did I mention no tech support? Enjoy!
By Camp ShopBot, September 12th, 2010
 Angus Hines has had a pretty busy year. He’s been doing the rounds of all the Maker Faires, as well as working on a bunch of Shopbot cut projects, and earlier in the year he held a User group for owners in his area.
After everyone attending was suitably screened, and sniffed, by Fabulous Frank, (the 165 pound Pyrenees who seems to hold some sort of management position in Angus’s shop) we started off the day with some catching up of the latest goings on down in Durham, etc. Unlike most Camps this one had a sort of “rolling attendance”as a number of people drove in from some distance so we finished the day with twice as many people as we started. 7 people showed up after 3PM… So a lot of the day was spent going over some machine info, with a bunch of one on one sessions all over the place.
We got into a great discussion about how to cut plastics, during which Howard Everton shared a lot of his expertise about cutting a variety of polycarbonates, PVC’s, etc. Then Ted drove in with one of the latest prototypes of the new Desktop tool and everyone wanted to play….. He got it out of his van, set it up, and then he went over some of it’s features for all of us. This version had a small ( .8 horsepower) spindle, but a small router will also be offered as an option in the final version. The entire unit can be plugged right into a 20 amp, 110 volt circuit. The VFD is small enough to ride on the gantry while the tool is in use ! Obviously this was a lot of fun for all of us…
Fred Fitzsimmons from Centurion Tools showed us some of his latest router bits; a 1/8″ball nosed version for 3D carving, and we chucked one into the Desktop unit and carved a file out of cherry, and maple with it. Nice bit. Then during the day Bill Young, and Angus showed off a few projects they have been working on. Bill brought in a kid’s “bank” made using another, new joint he invented. This time he created multi faceted joints ( see above…) that form a VERY tight final piece. Yet you CAN take it apart, once you know how….
And Angus and Bill worked on a set of “oak plywood puzzle tiles”in which they used a puzzle type of interlocking joint to tie together a “field”of tiles that Angus installed in a hallway of his home. It’s sort of a “puzzle parquet” project, and the concept should give a few people some ideas…Angus served one of his “local food” lunches, and bar b q, ham, muffins, etc. were enjoyed by all…
Much of the afternoon was spent going over some of the new technologies being created in the CNC, desktop printing, and robotic industries with a group of local guys ranging from ex Langley/NASA engineers, to hackers who have an active group/shop in the area, and are familiar with Angus and his work. They came by to hear about the Shopbot, and then before long everyone was trading ideas, tricks, ( and eating bar b q) etc. In fact the Camp seems to have generated a “field trip”next month with a bunch of the guys coming up to the Maker Faire in New York City…!
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