Do I need to use a jig?

What is a the purpose of a jig and should I have one with my new Snapmaker machine. I intend to look briefly at what a jig does and then illustrate this short article with one that I made earlier and then discuss it in the light of the newly modified jig that I made.

A jig is a device for ensuring the precision of a piece of work where one operation has to be repeated many times. This improves the accuracy of production numbers as they roll off the production line and a jig is usually removable and can be exchanged for other jigs which support different manufacturing operations. The advent of CNC (computer numerical controlled) machines has largely made jigs obsolete.

However, when you are working on a job at home (that has to be repeated many times with a reasonable degree of accuracy) and you do not have access to machines costing 100s of thousands of pounds/dollars/yen, then a jig still has a place in small scale manufacturing/making.

In terms of the Snapmaker (model SM1) that I use, I would suggest that a jig is not especially useful for 3D printing and probably it is of limited use in CNC machining. Where I have found a jig invaluable is when laser etching pieces of wood. The initial requirement I had was to etch a character centrally on the face of a wooden cube of a known size. The character had to be central on the face and the face edges had to be oriented correctly so that the character did not appear to be falling along one edge of the wooden block.

Enter the jig: It needed a CNC hole cutout which I had originally made 1mm deep. The cubes were 40mm deep and my thought process was that I would find it easier to locate the cubes in a shallow guide if there was not too much depth to the guiding cut out. The jig worked and allowed me to produce my first set of 20 blocks. Once the origin had been set, each wooden cube was etched from the same 0,0 point so that all of the characters were centrally placed on the block.

When refining my work technique, I decided to update the jig and to refine it as well. I made the CNC tool cut to a depth of 10mm. The rounded corners of the endmill left me with a fair amount of cleaning up of the hole. I need to have square edges and I used a very sharp chisel to cut right-angled corners into the rounded corners. This jig (number two in the series) worked well and I refined it further by roughly cutting it to the table size of the machine (130mm square) and then drilling holes at 5mm in from each corner of the jig.

This was another one of my new worker mistakes because my jig base was not sized exactly to the dimensions of the CNC table. The drill I had chosen was 4mm in diameter. The drill press kept the drill perpendicular to the workpiece. The screws were a very tight fit in the wooden jig and the ease of use left a lot to be desired.

There was insufficient material at the edges of the pine wooden base, despite it being 20mm in thickness. As the holes which I had drilled had broken down with time and use, it became harder to locate the jig onto the CNC table after doing some different operations to other workpieces. This made the use of the jig pointless because it was not quite able to place the workpieces with any precision.

In the final analysis, I wanted to continue to engrave wooden blocks using the laser cutting module of Snapmaker so I decided to make a more permanent jig. The material I chose was a white Maple wood which was 40mm in thickness and which, to my mind, is so much nicer to machine than pine. The reason being that Maple wood is far more tightly structured and much harder than pine. Maple wood also takes a great finish and it is easy to work on with machinery or by hand.

I used the CNC cutter to cut my 40 x 40 x 10mm square hole. I did not use a chisel to make the round corners into right angled corners. Instead I took advantage of Maple’s strength for machining and drilled small holes at each corner of the 40mm hole. I did this without any runout from the drill bit (which is a problem often) as it was cutting just ⅔ of a hole. This removed enough material from the corners to provide the much needed easing which would permit my 40mm cubes to fit, even if they were slightly oversized. Furthermore there was no need for me to use a chisel.

I used a rule and marking gauge to find the centre of the drill holes at the corner of the CNC table. I transferred the reading to my Maple wood base which had followed the size of the CNC table precisely and I drilled holes that were precisely 5mm from the edges of the newly made wooden base.

I drilled the holes with a 5mm drill so that the 3mm M4 cap head screws would have an element of adjustment laterally in each of the holes (about 1mm). I bought some 45mm M4 cap headed screws with a low cap head (so 2,5mm hex socket rather than the more widely available 3mm hex socket on standard cap heads) and some 50mm M4 cap headed screws in case 45mm was too short.

It turned out that there was enough length in the 45mm screw for the thread to secure my base and the threaded section just filled the threaded holes in the CNC table. I wanted to add washers to the cap heads so that they would not pull through the holes. This meant that the 50mm length screw was a better choice.

This jig is most useful in letting me put a brand new cube into it and knowing that it will be in the correct position for engraving. I know that the cube edges are parallel with the CNC table sides and I know that each block will be correctly etched once the origin has been set for the first cube after the centring gauge has been used. This gauge is a cube that has had a tightly focussed laser beam aim at the physical centre of the block. When the line is a as fine as possible, then the beam is sent to its origin and any item can be etched onto a block.

The following image is demonstrating how the base sits on top of the CNC table for Snapmaker 1.

The next image shows how I used a drill bit to ease the corners of the jig space that would be receiving the block faces to etch.

Another image shows how I used a gauge to locate the origin on the workpiece.

The final image shows how the block sat in the jig for etching. Only a little tiny space existed between the block and the jig. This was to ensure the reapeatability and accuracy was acceptably close.

Overall… with 1200 blocks to etch, The jig simplifies the task and makes it possible. Jigs of this type ensure a high degree of accuracy within accepted tolerances for wood machining. I highly recommend a jig, if you are trying to do a lot of work with the laser cutter. Of necessity, they are almost always produced by the machine operator.

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@jepho

You are a true artisan. Thank you for your contributions.

Keep having fun

Doug
@hyeii

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Thanks for your kind words Doug. If these small contributions are able to shine a light in some odd corner, for other new members, I will be content.

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I am unsure if the SM1 works the same way as the SM2 for setting the work origin but when I laser etch coasters I too need to etch them centrally.

For myself, I have found the easiest way to do this is to affix the coasters to the laser grid with double sided tape and then using a paper template of the same shape/size as the coaster with the centre marked, I align the work origin.

Would this not be simpler that needing to create/affix a jig each time? Do you think there are any specific benefits to using a jig over the method I described above?

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Thanks for the response Christian. I don’t think I have a laser grid because all that was in the package on delivery was the CNC table (130mm square) with 12 drilled and tapped M4 holes arranged from the corners inwards, starting at 5mm in.

The double sided tape would possibly work for face number 1 of the six on each cube. Removing the sticky tape and repositioning it for faces 2 ~ 6 would be doable if very fiddly for one cube… possibly. I have 1,200 cubes to etch which adds up to 7,200 faces. At say… 5 minutes per face that is 3,000 hours of working time for the machine. That equates to 125 days of working 24 hours per day.

I think I would be adding an unnecessary time burden to this work if I had to stick and unstick each cube face. Accuracy would also suffer a bit after a few cubes. Using the jig I have made has reduced my input to flipping the cube face and pressing the file button to select the relevant file on the handset. I guess industrial machines could program such an operation but this domestic level machine cannot.

I only need to affix the jig to the CNC table once per session. After using my gauge to centre the origin of the laser beam, I have no more involvement with that side of things for the duration of that particular work session. I only need to select the file on the handset and press start, after flipping the cube over to present a blank face to the laser beam.

For me, the benefit to using a jig for any repeating operation is that I only need to do the set up work once. My cube etching jig can be removed and replaced by undoing or doing up 4 x M4 cap head screws. The work involved in making the jig is easily repaid by the ease of use when trying to repeat an operation with a fair degree of accuracy many times. Wood does not really permit the precision which one would get working with metal so making a jig makes sense to me.

I can get my results to be acceptably accurate (within say… .5mm) without having to stick and unstick tape. Trying to tape a 40mm cube to the CNC table would probably be quite a difficult act and it is inevitable that the operator would want to provide some sort of mechanical guide to assist with a process that has to be completed many times.

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Ah I see, yes in your particular use case I can see how a jig would definitely speed up the operation! I was unaware you were engraving multiple faces on those blocks. I agree that if you are processing units in the hundreds let alone the thousands that a jig is suitable.

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I thought you might agree. :grin:

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The snapmaker does seem uniquely capable for making and using jigs. Affix a block of wood, then use the CNC attachment to carve out the shape of your work piece. Then use the laser to etch them.

I would also consider designing and printing something, using my snapmaker bed cover as a starting point. Although a block of wood will hold up better over time. And it should be faster to CNC carve the wood than print a jig.

Thanks for sharing your ideas!

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Thanks for your comments Craig. I would like to propose the idea of having a basic universal jig. I guess the elements of it would depend on the CNC table. Possibly they could be provided as extras with M4 tapped hole numbers and spacings different for different work.

I would possibly get a table with holes drilled every 10 mm. It would make for a more versatile approach to clamping. As for clamping the workpiece… there appears to be far too much of an encroachment into the workpiece space for CNC work and I would look for another solution to clamping the workpiece. I wondered if something could be attached to the ‘Y’ axis rail itself that could then be extended around the bed.

Today I printed a test print on a 200mm long workpiece. It needed some thought about how to split the Luban output .nc files but it was possible. I placed the workpiece aligned with the ‘Y’ axis rail and was able to laser etch my workpiece in two halves. more anon.

I found your Snapmaker bed cover an interesting piece of work. Your very full and complete descriptions made the issues clear. I would like to try to copy that piece but I have no experience with filament printing as yet.

I would also want to modify your cover. My feeling is that a Carbon enhanced filament would be a great modification and then I think it should be possible to put rails that would take ‘T’ shaped fittings along the underside or possibly mould them into the edge of the cover so that the clamps did not have to impinge on the workspace. This would then help with clamping options (says the person with nil experience of 3D printing) and could add some functionality to the CNC bed of Snapmaker.

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@jepho, modify away. That’s what the Creative Commons license is for. :slight_smile:

There is a small amount of slop in the X and Y axis. I wanted it to be easy to remove, so I made the opening 130mm square instead of 128mm with rounded corners. I’m still a beginning modeler, so this is already the most complicated thing I’ve modeled.

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@clewis I get the reason for building in some slop to permit removal. I think the possible solution to that problem is to accurately machine ‘X’ & ‘Y’ axes on one edge only. The two dimensions with slop inherent would still permit easy removal and the cover would have to be applied (and held) by pushing say… backwards and left. This would mean the two exact sized faces would need to be front and right edges.

I think (speaking in general terms) that the notion of deliberately sizing a spatial aspect of something larger than is needed so that it fits loosely is not a great engineering principle but you are limited to a great extent by the materials in use. The conditions of use also dictate how easily a part can be manufactured. The user should also consider whatever compromises would be necessary and choose between making the object with the easiest and the most useful set of values.

I suspect that it is not any fault with the machining of the part. I would probably start my search for an improved solution in the ingenious manner in which you got the parts to fit together. That method does not permit much in the way of adjustment either looser or tighter. It can be very hard to visualise how a product will work until we see it made real.

The only form of adjustment of parts that does not call for metalworking skills and springs, that I can think of right now, is the use of cams to close and lock pieces into place. This type of arrangement would probably allow for fitting a series of pieces together and tightening them in situ. Regardless, the cover you have made is very impressive in its concept.

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You could create a wasteboard for your snapmaker with thread inlays like the wasteboard of snapmaker 2.0
You can create it manually or even let your snapmaker create it.

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Thanks Stefan. I could look at doing that but I have no idea how to place and hold threaded inserts into MDF or wood. Possibly the threaded insert would fit into a counterbored hole and may need some sort of glue or key to hold it in a set orientation. I could see if I can obtain some parts and then examine methods of fixation and creating the right size and type of wasteboard.

I also noted the clamp design in Snapmaker 2 images. It is an improvement on the Snapmaker 1 supplied clamps. I have managed to damage mine with only mild to moderate clamping forces. The attached image shows the very clearly bent clamps which occurred with just moderate tightening. The cap headed screws and washers bite into the metal and that too can be seen in the image which I have attached.

I think that I would much prefer a clamping system that locked via an adjustable cam rather than using a wingnut as is portrayed in the online images of Snapmaker 2 that I have seen. I would have thought that the main advantage is that a cam may be set to apply the same pressure on every application. It is tough to do that with a wingnut that is being tightened and loosened many times during a project. Marking a wooden project is also inevitable unless a wide clamping area and packing is used.

The mark one clamps impinged far too much on the available working area, in my opinion. they also marked my workpieces if I was not too careful about the force being applied through the clamp. I often used additional packing under them but the mark 1 clamp system becomes very unwieldy when the clamp has to be tightened using two independently adjusted screws.

I understand that the working area is defined by where the ‘X’ and ‘Y’ axis rails are but my latest test gave me some indication of where the limitations of movement sit. I could possibly extend the available work area using that data. I had tested a 200 x 40mm workpiece on the ‘Y’ axis yesterday and I applied the laser cutter in two separate file segments. I am happy to say that it worked well and the segments that were etched were joined at the predicted points, without the workpiece crashing into anything despite the fact I am using my Snapmaker in an enclosure.

edit: to show 200 x 40mm workpiece and to comment on how tightly focussed the laser beam appears in this shot. :thinking: Pure serendipity. :crazy_face:

a second edit to show an enlarged image of the laser beam… the photo was taken on a phone.

I believe on the 2.0 they use something like this:

https://www.amazon.de/dp/B07MQFGTJ7/ref=cm_sw_r_cp_apa_i_Rzm4EbCAJS5ZP

I would recommend putting them in from the bottom.

I also hope to use a clamping set as seen in the following drawing when my snapmaker will arrive

https://a360.co/2YixMEQ

Hopefully I will be able to clamp all different sizes of workpieces with these

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Excellent response Stefan! :+1: That helps me to understand what may be required. Looks to be cheap too. :smile:

Loved the design of the clamp… makes a lot of sense to me.

I might upload my design at thingiverse when I get a little bit of time at my computer.

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That would be great. Interestingly enough, a search of several different locations did not reveal any of the fasteners to which you linked. I need to look a little harder, otherwise purchasing from Amazon in Germany should be a simple process. Thank you for that information.

Hello again stefan; I was able to buy the fasteners from Amazon in Germany. Thank you for your help.

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I just uploaded my lever set to my wasteboard project as step file

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Nice project Stefan: Thanks for uploading the details. I will look to make a similar wasteboard for my SM1 once the fasteners have arrived. I have to consider the size because I want to try to utilise the maximum module movement without shifting the table and then add the movements in each direction. My intuition is that I can skirt some of the dimensional limitations with smart Luban use. I was able to address 200mm in the ‘Y’ rail when i was etching my book mark.