Automated 3D printed collet storage using Fusion 360 parameters

How sad is this ?

I recently bought an Imperial set of ER25 collets to compliment my metric versions. I also have a set of metric ER20 and ER11. They have all been delivered in little yellow boxes which is good from a shipping point of view but a faff when needing to use them. In the past I have made storage blocks using odd pieces of wood with tapered holes cut using a cone cut drill bit. The cone cut has a 6 degree taper and ER collets all have 8 degrees so it sort of works but not quite ideal for my perfectionist mind.

As ever, the 3D printer sits in the corner begging to be used and Fusion 360 challenges me to do something a bit more professional. The scene is set for an overengineered collet storage tray.

Now I could just model and print something to hold the twelve new Imperial size delivery but what if I add to them at a later date? What if I decide to get some ER20 Imperial versions also ? ……….. Could I create a Fusion based automated model that will cope with any sized matrix of holes and any size of collet?

The first exploratory step was to create an Excel spreadsheet (another of my fascinations) as a means of identifying the steps that might be involved in automating the design and to tabulate the different parameters of the various ER series collets. Here is a screen shot.

A little bit more detail will be needed for you to understand what this all means.

The top table just details the published specification dimensions of the ER range of collets. I needed the height of the tapered section and this is calculated. Note that not all collets have the parallel section at the top of the taper. If you extrapolate the taper it then coincides with the dimension D1 and this is one I have used in the calculations.

Each collet holder hole in the block will be an 8 degree tapered hole that the collet sits in such that it does not sit all the way through the block (I opted for a 1mm bottom gap) and such that a percentage of its height protrudes from the top of the hole (I opted for 30%). The middle right hand sketch shows the various parameters and the red outline represents the collet.

The lower table shows the set up for the model parameters with spacing and borders defined. This section allows entry of the all important ‘how many holes do I want’ and the aspect ratio of the matrix. The final two red lines shows how big the resulting storage block will be.

All with it so far ? This is so embarrassingly sad … should I even be thinking of posting it…

These various parameters are now mirrored and entered in Fusion 360’s Fx parameter set up. I have tried to be logical in the naming convention and the blue stars indicate a function that is defined and entered by the user and will also appear in parallel in the Fx Favourites listing. This allows a focussed entry of just the variable parameters without all the other background calculation clutter.

I wanted to round the resulting block size to a nearest whole number. My preferred function in Excel is “mRound” where you can define the rounding to an increment value. There is no such equivalent in Fusion. In the end I used the “Ceil” in Fusion and “Ceiling” in Excel but Excel’s “Ceiling” requires a ’rounding to value’ hence the entry line (R) in the Excel listing which is set to ‘1’ to make it match the Fusion calculations.

By setting the length and width hole count to ‘1’ a single holder can be printed and checked to dimension before doing a full matrix as needed. I found that on my first single hole print the collet sat slightly higher in the hole than designed but this was traced to a print artefact on the taper wall. This was was easily rubbed down. On similar tack, I have allowed a fudge factor for print shrinkage should this be needed. Any errors in this respect will cause the collet to sit higher on the block. This will be most apparent as the collet size reduces. The value entered (say 0.1mm) adds a linear amount to the top and bottom hole sizes and therefore the taper.

Once you are happy with the single hole print you can define the number and aspect ratio of how you want the holes to be printed on the finished block. A 6 x 2 print will match the normal 12 piece ER25 collet set. On the Qidi ifast printer this took around 4 hours at 0.25mm layer height. Note that I used the ‘Shell’ command on the block lower surface of the print to reduce material use. This means you need to place on the printer bed ‘bottom side up’.

Well I did say this was going to be a sad nerdy post but as ever I learned a bit more about Fusion, Excel, refreshed my school geometry and made the workshop even more tidy and organised. What’s not to like ? …..

While this is an almost facetious waste of time and effort, the principles used in the Fx programming has many other applications.

The planning spreadsheet has been added to my spreadsheet compendium which along with the Fusion file (for ER25) is attached on the following ZIP file link.

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Fusion 360 Keyboard Shortcuts

Fusion 360 Shortcuts Lookup table and keyboard overlay

In an idle moment I have updated my collection of spreadsheets to include the Fusion 360 shortcuts listing. The workbook tab also includes an edited version of the Fusion keyboard overlay.

You can download this and other eclectic tabs as part of my Engineering Spreadsheets workbook.

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Fusion 360 Parameter Lookup Sheet

A handy reference for Fusion 360 parameter functions

Fusion 360 has an incredibly useful facility whereby you can make a model dimensions fully flexible through not entering fixed dimensions but instead make them a calculation. The calculation will be dependent on other attributes of the model in conjunction with mathematical functions.

Clough42 quite often uses this facility in his designs and there are some good tutorials in the Autodesk resources.

I had two problems in a recent model. The first one was where I had a dimension that I wanted to convert into a plain value rather than being associated with mm. This would allow it to be used in an equation. The second problem was needing to round a calculation result down to the nearest whole number.

The answer to the first problem was simple and obvious – divide the value in units by one unit. So something 200mm long becomes just plain old 200 when divided by 1mm. I was a bit red faced on that one.

On the second problem I searched everywhere in the Autodesk forums and found people mentioning ‘floor’ ‘ceil’ and ’round’ but it took a lot of searching to find a tabulated reference for the workings of the Parameter functions.

Having found the lookup details on the Autodesk site I have transcribed this into Woody speak which you can download as a pdf below and I have also added it to my Workshop Spreadsheet and there is a link to the latest version also below.

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Spreadsheet Compendium by Popular Request

I have had a few requests for a compendium of all my spreadsheets created over the months and years.   This will be a work in progress as new sheets are created and then added.   Here are the current contents.   

A collection of my popular spreadsheets

Click on the link below to download the ZIP file.

Spreadsheets Compendium Jan 2022

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Spreadsheet for setting a lathe compound slide angle

Oh No …… Not Another Spreadsheet …..

In the course of making miniature taper reamers to bore injector cones I initially struggled to set the compound slide angle sufficiently accurately.  DAG Brown’s book details using geometry to set the angle and once I grasped this concept things improved.  This is shown below and uses the Sine Rule.

The application method involves using a dial gauge set to zero when touched off on the workpiece. The cross slide readout is also zeroed at this position (this can be on a DRO if fitted or the Vernier scale). The compound is then moved a known distance along the workpiece before measuring the displacement needed on the cross slide to bring the dial gauge back to zero.   Here is a picture.  This is not rocket science and has been detailed on many other sources.

setting the compound angle using Sine Law
Graphical view of the setting technique.

By making the Y distance as large as possible, the resolution of the angular setting will be improved.   The distance for Y is best chosen to sit symmetrically either side of the ‘closed’ position of the compound. By standardising on a fixed Y distance the process can be made more repeatable for day to day use.  Angles can be committed to a lookup table and hence my idea to create a spreadsheet as detailed below.

On my Myford Super 7 I decided that a distance of 50mm for Y gave me a reasonable travel distance (+/- 25mm on the closed position).   This could be accurately measured using the compound Vernier scale dial (my Myford is a metric version).   

To speed up the measurement process I scribed a 50mm spaced start and finish mark together with a datum mark on the side of the compound.   The datum mark is on the protractor ring. These ‘scratchings’ are shown below.  (The extra cap head screw and pin are the Geo Thomas ‘Red Book’ compound lock mods).

These markings remove the need to tediously count revolutions of the Vernier scale when making an angular measurement.   I simply set the Vernier ring to zero at one mark and then keep winding the compound until the second mark is reached.  I then check once again on the Vernier ring scale. The movement distance is then finely adjusted to zero by referencing to the Vernier ring scale zero.  If you have a DRO on the compound this process becomes more flexible.

To mount the dial gauge I used my 3D printed gauge holder in the tool post.

With all the setup tasks decided, the spreadsheet was created.  I chose to have 0.5 degree steps through to 69.5 degrees (it could be extended beyond this).  I also added two standalone look up  calculations. One to allow a single angle to be spontaneously calculated and one to back check a measured X distance to find its associated resulting angle.  The latter would allow set up errors to be quantified to allow a knowledgeable ‘tap’ of the compound in the right direction.

The spreadsheet can use any units for Y as the table will automatically reflect this change.  Here is a screenshot of the table based on my chosen value for Y of 50mm.

The spreadsheet .XLSX file can be downloaded from this link.

Accurately setting the compound slide angle

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