fusion 360 – Page 10 – Woody's Workshop

July 29, 2018July 30, 2018

Rosebud Grate CAM and manufacture on Tormach PCNC440

While doing the drawings for the Rosebud grate on Fusion 360 I cheated slightly. From my measurements, I made a best estimate sketch of the needed grate size to fit the firebox floor and having drawn this up, I did a 3D print of an equivalent size thin piece of PLA. Having trial fitted this printed plate I did some trimming on the Fusion drawing ready to create the CAM.

I had bought in some 150mm square black mild steel plate and cut it roughly to width but left the length at 150mm this being longer than needed. This allowed me to clamp the ends of the stock to my tooling plate on a piece of MDF. I had one clean cut edge on the cut stock to use as a reference. When mounted I checked this with the Haimer to make sure it was running parallel in the X plane. Note I cut the MDF to roughly the same size as the plate so as not to interfere with the clamping.

I did a PathPilot width and length measure using the Haimer and found the centre of the plate and set this as G54. My Fusion drawing and CAM were referenced to centre. I was now ready to go.

First operation was to spot the matrix of holes and the second op was to drill them out to 4.1mm. Third op was to countersink the holes to 3mm depth. This was a bit interactive. I just worked on one hole only to start with and did repeated cuts using a BS3 countersink until the depth was correct. I then did a ‘chose similar size’ selection in Fusion CAM and then ran the full op.

This now left machining of the profile of the plate to the size of the fire box floor dimensions as per the CAM and my dummy PLA plate.

rosebud grate first operations — First Ops on the Grate, spot drilling and then hole drilling. Note the clamps on the outside of the plate area.

Clearly the clamps were now a problem as the end areas were excess material on the length. To get round this I removed the drilled plate from the MDF (the MDF had already started to degrade and swell with the cutting fluid) and mounted a new piece of MDF on the tooling plate with M8 fixings. As you will see below I went a bit OTT with these …. there is even a hidden countersink one under the plate to stop the MDF bowing upwards …

I remounted the grate on the new MDF with a single woodscrew in one of the grate holes and checked and adjusted the angle of the plate so the good edge was running true in X as before. I then added a ‘sprinkling’ of more wood screws so the plate was firmly in position and running true. I then re-referenced G54 to the centre of the grate as before.

Plate remounted on a new MDF backing plate and held in place with randomly placed wood screws using the grate hole matrix.

Now I hate making swarf (chips) of material if it is not necessary … so having got the plate securely in place on the MDF I then took it off again and cut off the excess material on each end of the length. Sad really but you never know when you might need a couple of small pieces of steel …

The grate could now be mounted back on the MDF with the plethora of screws positioning it back as before. I did re-check with the Haimer and also rechecked the Z height once again.

The CAM adaptive profiling was with an 8mm cutter. Obviously I was cutting air at each end of the grate where the stock was now missing but not a problem.

Profiling almost complete. The MDF is starting to degrade and swell.

I could have used a super glue and masking tape holding method but the black mild steel does not have a smooth surface like BMS and I was doubtful how well it would hold. With hindsight the method I adopted did give me some flexibility in the process method.

The final process on the Myford Super 7 was to make four posts to sit the grate at the correct height spacing above the ash pan to match the old bar grate position. These posts were fixed onto the grate by sacrificing four of the holes. This of course reduces the hole count and therefore the hole area percentage occupancy from 15.17% to 14.62% – but not worth worrying about.

Finished grate standing in the ash pan and also the 3D printed test shape

So now I have to prove that all this effort was worthwhile and the grate will make a difference to the Polly V steaming. More to follow on this in due course. We have had some rain over the past couple of days so the Club track will no doubt be open for steaming in the near future.

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July 26, 2018December 1, 2021

Rosebud Grates for Live Steam Locomotives

The Rosebud Phenomenon

I recently had a discussion with a fellow model club member about fitting a Rosebud grate to a Polly V locomotive. There is quite a lot of discussion on various forums of this style of grate so I won’t repeat what has already appeared in the likes of Model Engineer. The gist of the design is to replace conventional live steam bar type grates with a plate having a matrix of holes with back countersinks such as to occupy around 15% of the grate area. The effect of this change is to get better combustion of the fuel and better efficiency. Most users report only a fine powder residue after steaming and have observed that the fire appears to ‘float’ on the plate surface. The back side countersinks appear to create a sort of Venturi effect to boost the draught to the fire.

How to Calculate the 15% matrix

So all this got me thinking. This would be an easy job to run on the Tormach and all I needed was the design entering on Fusion 360. Which brought me round to the calculation of the 15% surface area for the holes on the new rosebud plate. Those who know me will bear witness to my weakness for doing spreadsheets and this little problem suggested a spreadsheet was needed.

Below is a simple sketch of a rosebud fire grate with dimensional attributes. In the calculation I have allowed for a border around the holes in case there are any no-go areas for the hole matrix. I have now updated the spreadsheet to allow holes to be ignored such as where used for mounting pillars. I also give the XY coordinate of the corner holes relative to material centre to help the machining layout.

Below is a screen shot of the resulting rosebud grate spreadsheet and you can download it as a ZIP file via the following link – rosebud_grate_calculator 2

Here is the finished Fusion 360 drawing ready to run on the Tormach. This shows the bottom surface with the 4mm through holes having been half depth countersunk. Clearly four of these holes will need to be sacrificed for mounting legs onto the locomotive ash pan and these are removed from the above calculation.

So all is in place ready to cut metal and I will keep you posted on the progress and steaming results in due course. (There is a slight problem at the moment in that we have a steaming ban in place because of all the dry vegetation at the club track).

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March 31, 2018May 31, 2018

Tormach Post Processor G53 Edits for Tool Change

The Tormach PCNC440 is a lovely machine and is more than big enough for my present needs. The one problem I had encountered was when coming to a tool change on a CNC job sometimes there was not enough Z height to get the TTS collet out of the spindle. This was particularly difficult when using larger diameter drill bits in a chuck style holder.

Once in program there did not seem to be any option to break the run and do a G30 or similar. What I really needed was a move of the spindle upwards and outwards to get it clear of the job and allow TTS access.

Reading up in Peter Smid’s excellent CNC Programming Handbook I could see that care was going to be needed to ensure that any movement was first of all a Z action and then X and Y to avoid the danger of crashing the tool into the job or its fixtures.

I had some discussion with John Saunders at NYC CNC and John was working on a video around this subject. He helped enormously.

The end result is to use G53 machine coordinates to first do a Z and then and X and Y to move the tool up and to the side for tool change access.

This involves edits to the post processor in three places. The first two edits (Lines 44 and 66) are there to give an option for this movement in the drop down selection box. (The line 24 edit is an earlier modification to allow Mill Turning – see separate post).

tormach, post processor, G53 — Line 24, 44, 66 edits

g53 tool change edit to post processor — Change that appears in the Property selection box where the Custom Tool Change option now appears

The third edit gives the instructions for this as a G53 Z move than a X and Y move (Lines 543-538). Note that I later found that I had to add a G54 after the G53 movements as some CAM actions did not include a G54 as part of a tool change.

custom tool change edit — Line 534 to 538 edits

I later on decided it would be nice to include this G53 movement at program end so this is a fourth edit (Lines 1404 – 1405) and not forgetting the change for Mill Turning edit (Line 25) there are five changes in total.

cnc g53 tool change edit — Line 1404 to 1405 edits

That concludes the changes. I recommend that you spend time watching John’s videos on Post Processor edits on NYC CNC.

If you can’t read the edits then drop me an email and I can send you a full listing.

Note that these are changes to the Tormach standard post processor code and if you are tempted to do this you should do a ‘Save As’ on the original code and only edit the newly created and saved file so you have a fall back position. Likewise I accept no responsibility in documenting this and putting you up to potential mischief messing with your machine and causing damage.

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March 29, 2018March 30, 2018

You say Vise and I say Vice but we agree that Clamps are Clamps

When I put together the package of items that I would be ordering with the Tormach PCNC440 I probably made a mistake. I wanted a machine vice (vise if you over the Atlantic) and the recommended size for the 440 was a 4″. However a jaw set was not available with this size the same as it was with the 5″. After checking with Tormach I ordered the 5″ in the belief that it would be usable.

The 5″ is serious lump of metal and really only fits on the 440 table long ways on. The jaw set is really nice however. Sad to say that none of it has been used so far and if I am honest it is unlikely to be used. A large and heavy white elephant sits in the corner of the workshop. It is going to cost more to freight it back to swap out than is economic. Offers gratefully received !

What to do ? Looking around I found that Arc Eurotrade offer a range of machine vices. In particular I liked the look of the SG Iron Milling Vices as they have flexible jaw positions and had a ‘pull down’ action of the jaws on closing. They do not offer soft jaws but at a pinch these could be made as and when needed. I ordered a 100mm (4″) version and it is a nice piece of kit, seems solid, but not as heavy as the 5″ Tormach.

The vice did not come with any useful fixing clamps so what to do ? I had already made a tooling plate for the 440 table that has M8 holes on a 25mm matrix. The plate also has additional 4mm tooling pin holes within the XY limits of the spindle movement. The vice sits nicely between the M8 mounting holes and just needed some simple ‘L’ clamps to hold it down.

Designing and making the Clamps

I designed something suitable on Fusion and did a 3D print of a prototype on the Sindoh 3DWOX to do a trial fit. This seemed to work fine so production of four metal ones was now needed.

Fusion 360 drawing of the clamping block

A debate now ensued. Options at this point were : –

Use the Fusion model to CNC/CAM repeat produce four individual clamps which would need three set ups to face and cut.

Use Fusion to extend the model to have four clamps in one piece of stock to be cut to length as needed but machined using a full CNC program of all four on one piece of stock. Each clamp would still need facing after cutting

Use the single clamp already drawn in Fusion and use WCS increments to hop along the stock and create four separate clamps for cutting off as needed. Still would need facing after cutting.

Finally given their simplicity there was the option to run them on the Myford manual mill ….

Outcome

Well my hand goes up to say I funked it and made all four on the manual mill. I cut four pieces of stock (24mm x 19mm) to 40mm on the Kennedy hacksaw and faced the ends to length on the Myford mill. I jigged the Y position while sitting on parallels in the machine vice before cutting the clamping step on each. Next came an 8mm hole central in the slot before mill extending it out 2mm either side. Job done.

Would it have been faster on CNC ? I don’t really know. If I had drawn the ‘four in one bar’ version I think it would as there would have been only one setup apart from the facing off. If I had done the WCS based version of a single clamp then four set ups would have been needed, one for each WCS plus the facing. Either way both of CNC options would have increased my knowledge on CNC and I could have chalked another ‘result’ on the 440 fuselage mission tally board.

No excuses I know, but there is just something about manual milling and the intimacy of being in touch with the metal ……

The finished clamping blocks were made to suffer heat and then an oil dunking to blacken them off to make them look almost professional.

Tooling Clamp for milling table — Vise Tooling Clamp

Vise in place showing clamps and tooling pins

vice, vise, tormach pcnc440 — Wide view of vise in place on 440 table. Note the NYC CNC training course handle finding a home.

So all of that was a bit of a ramble but you get the gist – CNC or manual.

Placement Tooling Pins

In closing the last thing I made was a couple of top hat tooling pins that sit in the tooling plate and align the vice position. This ensures the vice clamps can sit symmetrically either side of the vice. It makes for a quick set up if the vice has been off table. Note in the picture below the small piece of shim to get the alignment correct. (Lazy man syndrome creeping in again).

So the shop is now ready and better prepared to cut metal. Note also the NYC CNC training course produced vice handle being pressed into service on the new vice. Thanks to Kevin & John for that – was it nearly a year ago ???

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March 28, 2018

A Parallels Rack in Fusion and Sindoh with free Spagetti

Some time ago I made a rough and ready wall mounting rack for my parallels so they would sit to hand adjacent to the Myford manual milling machine. I used double sided printed circuit board for the construction and while not elegant it worked OK …. until after I had finished it when I found two of the set lurking in a box with a half finished job. I had not allowed for them in the construction and being OCD me, it annoyed me to have two lose ones that did not fit in the grand order of things.

An idle half day lead to a Fusion design to replace the tired old PCB disaster. This lead to some thinking on how to design it. I wanted a rack that sat on the tooling board with the parallels stacked on it with a slight upward angle to keep them in place. I chose therefore to draw it slightly strangely with the ‘back’ at an angle and extruded it accordingly. See below.

All well and good you might say. Less messing with angles etc.

I squirted the job into the Sindoh 3D driver software and then tried to be clever and print it with the backside down on the printer bed …. or at least what I thought was the backside down. You will no doubt spot that that this is not a simple rotation of 90 degrees but I didn’t.

The printer began producing spaghetti that was not bonding to the printer bed. After three re-tries I took a closer look at my design and realised that the only part of the job that was in contact with the bed was the leading edge (red arrow below). The rest was airborne at an angle all due to the way I had chosen to draw the object and rotate it.

Reset brain and reset printing so it would be now vertical. All was good and my nice new rack sits on the tooling board.

A little bit more brain engagement next time perhaps ?

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