old discussion: making drumpads

[nym]

hey folks, first post. i was introduced to this place by modnar from the mpc forums, and from a very brief search i realized almost immediately that this forum is RIGHT up my alley.

here's my story - i'm rebuilding the mpc1000 pads, notoriously bad and famously flawed. i'll tell the full story in another post and link you to it here.

but this is my question. i've found a material that allows for variable resistivity (velostat, son) but now i'm looking for something more simple -- sheet rubber w/ a shore hardness of about 50, give or take 10 to 15 on the durometer scale. i've done some initial googlin' and found a lot of custom order people, but i'm just lookign for some feedback from you guys as to stores you've worked with, etc. we're just talking about a solid sheet of rubber/whatever of about 1/8th inch thickness. any lenth/width is fine but of course i'd prefer not to buy in huge bulk til i know it works well.

thanks! can't wait to hear your thoughts.

nym

[Jidis]

Nym,

Check these guys-  http://www.mcmaster.com/

Thank RTurner for that one. ;)

George

PS- One of the few good DIY things I've found in this town is a sheet rubber supplier called Sutton Clark (http://www.suttonclark.com). I've bought sheets for drum pads before, but for full-size pads (not finger buttons).

[nym]

thanks! i will be checking these out immediately.

[nym]

JEEZ man mcmaster is amazingly specific, this is amazing...

[Mr modnaR]

hey nym, glad you finally joined the party!

a shore a hardness of 50 is pretty damn hard. is this for the pads? cos you could design your own mold using frontpanel express, and pour in silicone. that way you can change hardness as well. might be an idea for your kits you'll be doing?? one pad sheet instead of 16 individual bits.

[nym]

i ordered a sheet of stuff at 45A one time and it was incredibly flimsy...very easily stressed and didn't spring back to its original shape.

i may have to adapt my order though if you think 50 is too hard, because i ordered something at a little less than 1/16th thick at 60 A.

this i had planned to put underneath the metal frame of the mpc and call it a day. no raised pad surface at all. this would be cost effective, but i don't know how peopel would react to not having "THOSE PADS" even if the end result is the same

however, i really should bite the bullet and look into the whole molding/silicon process. how much more expensive would it be? i'd really have to hike up the price this way.

then again i could offer either or. i'd probably prefer the latter though just because i'm more used to it.

how much is self-curable silicon?

as for what you said before - the idea of 1 pad sheet instead of 16 individual bits. this is a must - or at least 4 equal sized squares/strips. having individual pads is one of the worst ideas i have ever heard of.

here's the other question - the thinnest part of the silicon (the "Sheet" part, the part that connects the pads to each other and fits under the frame grid) is gonna have to be about 1/16th of an inch thick. that's pretty small. does that run a risk of tearing? granted, once it's in there there's not gonna be much that really could tear it save some lunatic giving it a grapple with his teeth, but you see my concern.

time to look into frontpanel xpress.

[Mr modnaR]

well, i used some 12a in a button mold and although they were a little too rubbery they have cured further, and are about the hardness of a pencil eraser now. 1/16th thick is fairly thin, and may deteriorate if that's all you have. my advice: make a mold, and cast proper pads with air gaps and domed shapes beneath them in a large 4x4 sheet, and sell them at $30-50. it would be simpler to do solid pads, but at the thickness of the originals, you may find some feeling is lost. if you run into trouble with the mold design, don't hesitate to pm.

prices range from £25-£40 here for a 1kg tin plus catalyst. i'd estimate you could make 2-4 pad sheets with pads, or maybe 20-30 just plain sheets.

[nym]

"domed surface"

i have figured out that it's not area of contact that registers a harder hit. the domed surface's purpose is because of this:the active area is about the size of your thumbnail, a little smaller. the dome is there so that when you hit the corner of the mpc pad, the dome moves down and hits the contact area.

this presents a problem because i don't want to have an air gap in between the pad rubber and the sensor. this implies a moving part, and is not ideal for this given sensor setup. it works for interlink style FSRs but NOT for this unlaminated sensor technique. however, w/out a domed surface, a corner hit of the mpc pad won't make a trigger - you have to make a hit solidly in the middle of the goddamn pad. it works well, but it creates a smaller target area. people may not like this, but i don't think i'm willing as of now to make a domed underside because it's an inappropriate design...

UNLESS the active area of the sensor is expanded...which opens my next question. i want to continue this spiral so that there's more of an active area - with a carbon laden ink. i've been reading about this stuff - you paint it on w/ a little brush and then when it cures you scrape off the thin insulative surface overtop of it to bare the conductive. this would provide a low-conductive expansion so that even a corner hit would make some contact. it's either this or build my own new copper coil thing, but that might be a little much, i'm just looking to get back to 150% working condition.

this may be more for my own personal design, not for people who want a prefabbed technique. i don't expect this to be something that people will do on their own. i'm having a feeling i'm gonna have to start a little forat style thing where people send me their samplers and i do it all myself...might just be easier/safer for them...but who knows.

[nym]

at this point i'm afraid the topic has changed from "parts" to "design" and i'm afraid it may be in the wrong subforum, apologies to the mods

[Mr modnaR]

it'd be easier to make your own new pcb incorporating all the pads on one sheet than using this carbon heavy ink you talk of.  that might wear off. www.nymat.com ???  ;D

[nym]

appropriately named for me  :o

[nym]

yo back again, modnar. this Front Panel thing is ReaLLY cool, i like the little program, it's awesome for custom stuff. this is a brilliant find.

my question is this - since i'm figuring out this pgm, i want to at least design a domed underside pad sheet, ala the original design, rather than expand the existing sensors. this program makes it easier than i had thought, probably easier than the conductive ink idea.

SO

you're able to make "cavities," indented shapes. this is how i'm making the pad (1 rectangular cavity that's a quarter inch deep) and then additional cavities overtop the first - ie, the dome, roughly 1/32 deep. pardon my use of this idiotic measuring system, i regret that i only have a so called "standard" measuring tape at my immediate disposal.

NOW my question is this - are these depths cumulative?

i'll explain further in case i'm not being clear.

my steps:

1 - make rectangle cavity

2 - set itsdepth at 1/4 deep.

3 - make oval cavity IN rectangle cavity for dome.

4 - QUESTION: set depth of dome to 1/32 deep, OR 1/32 + 1/4 deep? is it already taking the preexisting cavity into consideration?

if you don't know this, it looks like they have a number i could easily call.

thanks man, this is going really well...

nym

[nym]

and let me say - you've been a major help all along, since day 1 on this whole thing.

modifying your gear is exciting as hell, man, i can't BELIEVE i'm the only person i know of doing this to their 1k.

[Mr modnaR]

re: fpe, i think all cavities are referenced from the zero plane unless you tell them otherwise (which you can do in the 'Remarks for Production' box when you send the order - reach this window by double clicking on an unused area of the panel or going File|Panel Properties). the only problem being that the 1mm cutter they use is only 4mm long, so it'll come up with an error if you go over that. if you use another size perhaps it's longer, you'd have to ask. i use FrontPanelDesigner, which is the German company, and i'm assuming the program is the same, so forgive me if what i said makes no sense!

re: mold, remember the bottoms of rectangular cavities used for the pads will become the tops of the pads when cast in silicone, so if you then cut further into the panel, you will end up with domes sticking out on the top of the pads. you probably want to use the cavity within cavity option which will cut away inside the outer boundary, and not cut away outside the inner boundary.

another little tip: because you are asking for quite a deep panel, can i suggest doing it in layers? make several panels with indexing holes around the edges, that way the panel will work out cheaper, as you can work is so that the rectangular shapes for the pads are holes rather than cavites, which works out cheaper. also, if you're clever, you can use an anodised panel to be the part of the mold for the top surface, this will give you a nice, finely textured surface on the pads, as opposed to the slight machining marks left over from cavity cutting.

hope this helps.

edit: just looked at the FPE website, and the use the same program, so all of what i said above should be applicable.

oh:

and let me say - you've been a major help all along, since day 1 on this whole thing.

no problem. i may actually return to the 1k if this comes off ok. the PCB need looking too, though i'd need a 1k infront of me to measure, and to design the board. i may yet try and pick a busted one up off ebay if anyone is selling one.

[DrBunsen]

you might also like to check out emachineshop.com

[Mr modnaR]

that's an excellent link, thank you.

[nym]

the PCB need looking too, though i'd need a 1k infront of me to measure, and to design the board

you mean the sensor board? what do you think you'd consider changing if you could? broader copper coils as i was blabbing on about?

you might also like to check out emachineshop.com

yeah man thanks, this looks great too.

[Mr modnaR]

you mean the sensor board? what do you think you'd consider changing if you could? broader copper coils as i was blabbing on about?

yeah i meant making one board for all 16 pads, which would be a better system in my view.

[nym]

oh absolutely. i've done that by just securing down the existing 16 boards to a central sheet. they ain't going anywhere, but i'd love to someday actually have my solid pcb in there, it'd be very cool, esp if i got some clear silicon to be the pads...haha but i'm getting ahead of myself again.

[Mr modnaR]

clear silicone, so you could see the velostat? greeaaat.... ;D you'd need clear velostat too, so you could see the copper.

[nym]

and clear copper, so you could see the -- nah, i've taken this too far.

[Mr modnaR]

| <-Line                                                                                                      You-> :D

[nym]

yo so here i am now. this is a trial run of using 2 faceplates like you said. imagine them on top of one another.

one goes over 2, 2 provides the dome.

they're the same size of course, just different zoomed screenshots

[Mr modnaR]

think you may have a problem with the mold there nym. as it is, they'll just be like flattened mushrooms.

you need to think of the space inside as the object. unless, of course, this is just the preliminary design for the pad, and you have yet to extend the mold to the rest of the pad sheet, in which case i apologise.  ;D

another thing worth mentioning is measurement. i assume that the mpc1000 was designed in Japan, and as such would have been designed using metric measurements. i'd really advise against using imperial measurements unless you have a set of dial calipers, as discrepancies of 1/64, although small, when multiplied out 4 times in each direction could mean the pad sheet being a disaster. just a thought. personally i'd get dial calipers anyway, just to make sure the measurements are as accurate as possible, this being a custom project, these pads could be made to fit more neatly than the originals by far, creating a pro finish.  8) post up some measurments, and i'll see what i can come up with in FPD.

[Mr modnaR]

here's my concept of what the mold should look like. NB: i know no measurments, and haven't included any means to pour silicone into the mold, so plese forgive the slapdashedness of my effort! also: the circles in the mold for the interior of the pads are just cylinders, so they'd need filling with something to make them like a dish, eg resin, before the silicone was poured in. the plate on the right would be anodised to give the tops of the pads a nice textured finish.

hope this helps.