Author Topic: Replacement Knobs, Feet and Fittings for Test Equipment  (Read 6835 times)

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Offline TERRA Operative

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #50 on: March 14, 2019, 03:09:05 am »
You can fairly easily buy Flat Head Rivets in all sorts of lengths and diameters if you want to keep it more like the original. Try a Google search for "3mm flat head aluminium rivets" The 3x5mm collar and spring should be easy to sort out.

The few older Nixie Counters I have with those feet came with all attached  ;D But keep on with the design  :-+

Oh cool, I'll check those rivets out.

I have a few bits of gear that need these feet (There seems to be a test equipment foot fairy here in Japan that is stealing all the feet from the second hand equipment listed online....) and with how hard these seem to be to find online, I know I'll be printing a few for myself. :)
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Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #51 on: March 14, 2019, 03:14:15 am »

Understood and still reminding you the feet should provide full insulation so any metal fixings needs be recessed some.

Version one with the 6mm full length still allowed for 6mm recess and 12mm OD head. The hardware 6mm ugly below is 4mm x 12mm so it should be easy to get one for a long bolt option.Bumped the diameter of the recess to 12.5mm. 2mm clearance should be ok to 1000V+
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Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #52 on: March 14, 2019, 03:34:55 am »
Foot - Generic replacement for HP 5040-7829 cord wrap foot, fits HP174* CRO's.

40mm Long generic  foot as shown. Two STL's in the Zip a high strength 6mmx34mm depth and a drop in HP hardware replacement for 3.5x13.5mm screws on the scope. Also included is the Fusion 360 Cad file for others to play with.

Suggested 3D printer settings 6 top, bottom and side perimeters and 40% infill. Material choice minimum PETG or better Nylon if you can. 0.2mm Layers and support on the build plate only to keep the recessed hole looking nice.
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Offline bson

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #53 on: March 14, 2019, 04:27:53 am »
I printed the HP knob to check it out; this is how it works out for me.  I printed it with the top down to avoid filling it with supports.  This is with a 0.1 layer height, PLA with a 0.4mm nozzle.  I didn't spend any time cleaning it up, just pulled off the skirt and removed a few wisps.



It would work great as a knob, it's just the knurling looks a little haphazard and feels a bit rough.  Maybe replace it with a smooth recessed grip area (basically remove the ridges) and slip a rubber or plastic sleeve over it.  And, replace all knobs for uniformity.
 

Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #54 on: March 14, 2019, 04:37:24 am »
Did you look at the Gcode on your slicer before printing? Switching off the 'detect thin wall' sorted mine out a lot on the flutes and they came out much cleaner.

Printed the other way up with no supports the alignment slots work fine due to the curved tops and the just the top of the main chamber finishes up a little fury until it bridges properly. This could be fixed by adding a 450 chamfer to the roof but it will likely require a shorter shaft or stick out further from it.

For a more generic knob cutting back the flutes to 12-15 would sort a lot of issues but then it wouldn't be a HP clone.

Interesting to see other printers results  :-+
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Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #55 on: March 14, 2019, 06:05:53 am »

Understood and still reminding you the feet should provide full insulation so any metal fixings needs be recessed some.

BTW, we might be best for someone that has a HP1740 to chime in with the correct length for the feet.

So my design guess was WRONG it seems the real deal only had a lip on the outside ;) From here http://hpmemoryproject.org/an/pdf/sf_1700.pdf

Let me know if you want the design shortened to the 1 3/8" and I will tweak it, what isn't shown is if it is measured from the case or rear fascia so 40mm is safe. I think for strength keeping the more blocky 3D printed  version is sensible pending anyone having better images or one to measure from?

« Last Edit: March 14, 2019, 06:07:51 am by beanflying »
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Online tautech

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #56 on: March 14, 2019, 10:29:11 am »

Understood and still reminding you the feet should provide full insulation so any metal fixings needs be recessed some.

BTW, we might be best for someone that has a HP1740 to chime in with the correct length for the feet.

So my design guess was WRONG it seems the real deal only had a lip on the outside ;) From here http://hpmemoryproject.org/an/pdf/sf_1700.pdf

Let me know if you want the design shortened to the 1 3/8" and I will tweak it, what isn't shown is if it is measured from the case or rear fascia so 40mm is safe. I think for strength keeping the more blocky 3D printed  version is sensible pending anyone having better images or one to measure from?
:clap:
Good find and checked the 1 3/8" (~35 mm) which seems perfect with ~4 mm clearance from the CRT cover to ground.(excluding any fascia height measurement)
IMO ~35 mm is the height we want to work with in this metric day and age.  :-+
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Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #57 on: March 14, 2019, 10:38:14 am »
Looking at the bad photo I am actually wondering if they were made from the same soft plastic on the 5300's I made new feet for rather than a rubber. What was left of mine basically crumbled into pieces and the rear shot of Daves looks like that same sort of issue?

Edit Adding the 35mm Foot here due to the 1Mb file size limit   |O I will add it to the link index on the front page and leave both available.

Modded Fusion file and both STL'in the Zip for 6mm Long Screw and the Genuine HP screw options.
« Last Edit: March 14, 2019, 11:06:54 am by beanflying »
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #58 on: March 14, 2019, 10:52:33 am »
Looking at the bad photo I am actually wondering if they were made from the same soft plastic on the 5300's I made new feet for rather than a rubber. What was left of mine basically crumbled into pieces and the rear shot of Daves looks like that same sort of issue?
My memory thinks hard rubber but they may have been some soft crumbly plastic IDK.
Sorry I don't have a sample to do some chemical or heat tests on.  :(

Use your bestest judgement.  ;)
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Offline kirill_ka

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #59 on: March 14, 2019, 11:19:02 am »
Some time ago I made a power/input switch button cap for HP3478A. You may like to add it. There are STL and OpenSCAD models in there.
https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1255227/#msg1255227

Edit: can't fix the url to make it clickable
« Last Edit: March 14, 2019, 02:55:50 pm by kirill_ka »
 
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #60 on: March 14, 2019, 11:43:36 am »
Odd.. found a file for a Wavepro/wavemaster bezel some time ago but the page is gone. I still have the files if anyone wants them but I guess there's a reason why it was redrawn so I'd rather not upload the files here...

Those who ever serviced one of those know why you'd want a replacement bezel   :-DD I actually considered having one 3D printed and perhaps order a small batch injection molded if the file was OK. If there's ever enough interest for that I may still attempt it...
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Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #61 on: March 14, 2019, 12:07:56 pm »
Some time ago I made a power/input switch button cap for HP3478A. You may like to add it. There are STL and OpenSCAD models in there.
https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1255227/#msg1255227

Edit: can't fix the url to make it clickable

Added it on the front page index here. SMF doesn't like the ! unless you put it inside the URL tags.  :-+

Odd.. found a file for a Wavepro/wavemaster bezel some time ago but the page is gone. I still have the files if anyone wants them but I guess there's a reason why it was redrawn so I'd rather not upload the files here...

Those who ever serviced one of those know why you'd want a replacement bezel   :-DD I actually considered having one 3D printed and perhaps order a small batch injection molded if the file was OK. If there's ever enough interest for that I may still attempt it...

Interesting it still turns up on the Yeggi search and you can view the page via a google archive but the file has been stripped for 'reasons' so it must have only been recently removed :-//
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Offline bson

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #62 on: March 15, 2019, 01:59:07 am »
Did you look at the Gcode on your slicer before printing? Switching off the 'detect thin wall' sorted mine out a lot on the flutes and they came out much cleaner.

Printed the other way up with no supports the alignment slots work fine due to the curved tops and the just the top of the main chamber finishes up a little fury until it bridges properly. This could be fixed by adding a 450 chamfer to the roof but it will likely require a shorter shaft or stick out further from it.

For a more generic knob cutting back the flutes to 12-15 would sort a lot of issues but then it wouldn't be a HP clone.

Interesting to see other printers results  :-+
By G-code, do you mean the actual .gcode or the layer breakdown?

I'm in the middle of switching from Cura to Simplify3D, and am experimenting with thin wall settings to see what I can come up with.  The HP knob is a pretty good, practical test case!
 

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #63 on: March 15, 2019, 02:13:16 am »
The issue you're seeing may be printer settings.  If it's doing the perimeter of the knob on each layer with a continuous outer path, then it could be excessive acceleration/jerk settings or maybe turn up the extrusion multiplier.  If the perimeter is printed inside and then the ridges are added in separate little segments, it's probably an extruder (likely retraction) issue.  I suspect the latter, but if your extruder is having to pick up and put down filament in each ridge, sometimes the amount it retracts and replaces is not consistent all the time, so you're getting these artifacts.  If that's the case, try slowing retraction speeds or looking around other forums for retraction tuning tips.
 

Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #64 on: March 15, 2019, 02:15:09 am »
In Sli3er for example after you slice the print you can look at a 3D preview of the print. I use this in most cases before starting longer prints. Go back to the last page and you will see the spaghetti version when reviewed with 'detect thin walls' on. https://www.eevblog.com/forum/testgear/replacement-knobs-feet-and-fittings-for-test-equipment/msg2257833/#msg2257833

Just for fun here is a 6 layer 40% infill in PLA of the 35mm Foot printed on the Ender Pro. My CR-10 with the glass Bed is where I will print the PETG ones for @Tautech is partially stripped down while I put it into an enclosure.

Sheared as expected at the screw head but even in PLA took a fairly severe whack to get that to happen, I would hope most of us don't treat our gear like that  ;) . PETG will give it more layer strength and a little more flex which will help it soak up some more punishment. The oposite end of the hammer is actually a PETG insert I made over a month ago and is holding up well unlike the PLA sample one which failed quickly.

https://youtu.be/H0vTK5Li-NQ
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #65 on: March 15, 2019, 02:56:01 am »
Holy hell Bean, that took a whack before it broke.  :o
Should be more than strong enough IMHO.  :-+
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #66 on: March 15, 2019, 03:13:30 am »
I did some similar strength tests on LeCroy scope feet I was printing, and tested a couple materials as well as a few different layer alignments (printed the model on its side, for example).  I was primarily looking at PLA and ABS, but PETG can be sort of inferred from it.

The PLA parts were harder, slightly heavier, and more resistant to small impacts (I tried both sides of the hammer), but when they failed they were likely to shatter if not chip in a large way.  The ABS parts showed visible damage with lighter swings, but held together much better with big damage - never entirely shattering a part.  PETG is a bit closer to ABS in consistency, but is somewhat between the two, and it's supposed to be pretty chemical resistant, so it would be a good choice for a lot of the external plastics on an instrument.  The advantage ABS has is that it's a bit easier to work (paint, glue, etc), and that it's cheaper, often close to half the price of PETG.

In any case, though, if you're at or above 25% infill and the model is made well, odds are good you're going to have a durable part in almost every plastic.  It's not until you need really high impact resistance or supporting a lot of weight that high infill percentages or specialized materials are really necessary.  Rather than strength, I think the primary issue with PLA is just that it will deform when near heat, so it's probably not a good choice for internal components in areas that get warm.
 

Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #67 on: March 15, 2019, 03:36:37 am »
I have got to like PETG and given the downsides of Printing ABS I am not that likely to adopt it in my on hand materials.

Some interesting work by Stefan @ CNCKitchen on Annealing PLA and much more controlled strength tests of various materials here for those who haven't seen them https://www.youtube.com/channel/UCiczXOhGpvoQGhOL16EZiTg It still doesn't fix the moisture issue in wet applications compared to ABS or PETG but interesting work.

Horizontal feet would cause a different set of problems with easier shearing of the fins and splitting lengthwise at the screw head with a blow like I gave my vertical one. Pros and cons of both. My preference would still be to go the long bolt vertical option to aid the layer adhesion but it seems to be up to the task unless you are a Rough as Guts NZ Sheep Farmer  >:D
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #68 on: March 15, 2019, 04:38:38 am »
I have got to like PETG and given the downsides of Printing ABS I am not that likely to adopt it in my on hand materials.

Some interesting work by Stefan @ CNCKitchen on Annealing PLA and much more controlled strength tests of various materials here for those who haven't seen them https://www.youtube.com/channel/UCiczXOhGpvoQGhOL16EZiTg It still doesn't fix the moisture issue in wet applications compared to ABS or PETG but interesting work.

Horizontal feet would cause a different set of problems with easier shearing of the fins and splitting lengthwise at the screw head with a blow like I gave my vertical one. Pros and cons of both. My preference would still be to go the long bolt vertical option to aid the layer adhesion but it seems to be up to the task unless you are a Rough as Guts NZ Sheep Farmer  >:D
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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #69 on: March 15, 2019, 06:15:53 am »
ABS is tougher to print, basically requires an enclosure to get good layer adhesion, especially on large parts.  And yeah, layers stacked up so that the bolt head presses on a complete layer does seem the strongest for that sort of mounting.  The trouble with annealing for this sort of thing is the non-uniform shrinkage.  If you can fully characterize your individual filament, it may be usable by printing effectively size-warped parts, but since the X/Y shrinkage is a different ratio than the Z shrinkage and certain printed structures (internal included) shrink differently, it could be really difficult to get proper sizing for parts that connect to something on more than one side.
 

Offline bson

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #70 on: March 16, 2019, 12:08:15 am »
I've been cranking out supports like these in various heights to use as equipment spacers.  I can stand on them!  Strong AF.  Just plain PLA, 2mm walls and not much infill (20% I think I used) - the strength is in the walls anyway.  50x50x25 (X Y Z).  I have some non-slip thin adhesive rubber that comes in sheets that I cut to shape and stick on them.  I have some serious boat anchors stacked using these...

I figured if I at 165 lbs can stand on one, then four of these can hold up anything I care to pile up.



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« Last Edit: March 16, 2019, 12:15:13 am by bson »
 

Offline Kean

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #71 on: March 16, 2019, 04:29:58 pm »
I figured if I at 165 lbs can stand on one, then four of these can hold up anything I care to pile up.

There is quite a big difference bewteen compression strength and shear strength (which is what beanflying was testing in his video).
FDM prints are generally pretty good for compression strength, but so-so for shear strength, and awful for tensile strength.
 

Offline beanflying

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #72 on: March 17, 2019, 02:05:55 am »
Great in compression strength. I have one of my large commercial Espresso machines (110kg) sitting on 4 PETG 40mm diameter feet and held onto the machine with a single M10 bolt straight into the Plastic.

Layer orientation or even splitting parts for strength is sometimes a necessary evil and certainly a consideration with FDM. Even minimising supports or better yet removing the need for them.

This Creality control box design below of mine prints without supports in spite of the level of detail because of the angle of the case split and then tweaking the internal structures to make them self support (under 450 or extend PCB mount rails to the floor). With a simple vertical split the support requirements would have been horrid.
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Offline bson

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #73 on: March 17, 2019, 04:31:47 am »
There is quite a big difference bewteen compression strength and shear strength (which is what beanflying was testing in his video).
FDM prints are generally pretty good for compression strength, but so-so for shear strength, and awful for tensile strength.
Ah.  I wasn't referring to the video... haven't watched it.
 

Offline GregDunn

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Re: Replacement Knobs, Feet and Fittings for Test Equipment
« Reply #74 on: March 18, 2019, 06:55:53 pm »
Bean, I had a friend print out the HP 3470-series rear foot and Defpom's 3-point snap-in feet (for my 3478A).  They all fit perfectly and with a little pad of adhesive foam on each one, even keep the gear from sliding around. Life is good!
 
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