Ricci's Skram Subwoofer & Files

[klipsch]

9 hours ago, Ricci said:

Looks great. Yes I would use some lining in the vented section of the cab. Do not use any in the front section. Just make sure to clear the vents well.

Happy holidays.

Thank you on all accounts! Same to you! 

[peniku8]

Is that your CNC router @klipsch? What settings did you use for the holding tabs? Looks like you were using a 6mm (or quarter inch) bit, how long did it take cutting the wood for a single (or a pair) of Skrams?

[klipsch]

1 hour ago, peniku8 said:

Is that your CNC router @klipsch? What settings did you use for the holding tabs? Looks like you were using a 6mm (or quarter inch) bit, how long did it take cutting the wood for a single (or a pair) of Skrams?

Hey peniku.  Yes, that is my cnc.  I added, what may be, extra detail which made this a longer reply.  Hopefully adding some detail helps to better answer your questions.

For each of the sheets, no holding tabs were used.  Instead, about 5 hg of vacuum hold down was used.  For a few of the pieces requiring 2 sided work, the vacuum hold down was bumped up to 10 hg.  Onion skinning can work better for rigidity and finish in my experience vs tabs when working with quality plywood sheets.  What are your experiences?

Your eyes are good.  A 1/4 inch 2 flute compression bit was used throughout at about 250 ipm and ~12k rpm.  Single climbing passes were used for all pocket/groove/slot/recess cuts.  Two passes were used for the inside and outside profile cuts:  one climbing pass at about 98% depth and 1 conventional pass at 100% depth.  Those settings worked well throughout and I do not plan to change them for the 2nd skram.  I thought about using a 3/8 inch bit for most of the cutting to be able to run > 450 ipm, but that used a little bit more material and would need a slightly different layout. Since I'm not mass producing these for profit, I stuck with the cheaper 1/4 inch bit.

Looking back at my rough notes and machine logs, the following should be approximate cutting times for 1 skram:

• 12 mm baltic birch sheet:
  • ~18 minutes
• 18 mm baltic birch sheet1 with the left and right side...:
  • ~40 minutes
• 18 mm baltic birch sheet2 with hatch, bottom, top..:
  • ~20 minutes
• 18 mm baltic birch sheet3 with single driver cutout:
  • ~2 minutes

Each second side cutting for the parts that have handle recesses took less than 5 minutes total for set up and cutting for each.  There are 4 parts with 6 handle recesses, so I think a conservative estimate of 20 minutes total is accurate-ish (5 minutes x 4 parts).

The second side cutting for the back part which fits the hatch part took less than 10 minutes for set up and cutting.

Total time with setting up the sheets, parts, tooling, machine, and cutting for one skram is probably around 2 hours and 10 minutes with the 1/4 inch bit.

How long did it take you to cut one?

[peniku8]

2 hours ago, klipsch said:

Hey peniku.  Yes, that is my cnc.  I added, what may be, extra detail which made this a longer reply.  Hopefully adding some detail helps to better answer your questions.

For each of the sheets, no holding tabs were used.  Instead, about 5 hg of vacuum hold down was used.  For a few of the pieces requiring 2 sided work, the vacuum hold down was bumped up to 10 hg.  Onion skinning can work better for rigidity and finish in my experience vs tabs when working with quality plywood sheets.  What are your experiences?

Your eyes are good.  A 1/4 inch 2 flute compression bit was used throughout at about 250 ipm and ~12k rpm.  Single climbing passes were used for all pocket/groove/slot/recess cuts.  Two passes were used for the inside and outside profile cuts:  one climbing pass at about 98% depth and 1 conventional pass at 100% depth.  Those settings worked well throughout and I do not plan to change them for the 2nd skram.  I thought about using a 3/8 inch bit for most of the cutting to be able to run > 450 ipm, but that used a little bit more material and would need a slightly different layout. Since I'm not mass producing these for profit, I stuck with the cheaper 1/4 inch bit.

Looking back at my rough notes and machine logs, the following should be approximate cutting times for 1 skram:

• 12 mm baltic birch sheet:
  • ~18 minutes
• 18 mm baltic birch sheet1 with the left and right side...:
  • ~40 minutes
• 18 mm baltic birch sheet2 with hatch, bottom, top..:
  • ~20 minutes
• 18 mm baltic birch sheet3 with single driver cutout:
  • ~2 minutes

Each second side cutting for the parts that have handle recesses took less than 5 minutes total for set up and cutting for each.  There are 4 parts with 6 handle recesses, so I think a conservative estimate of 20 minutes total is accurate-ish (5 minutes x 4 parts).

The second side cutting for the back part which fits the hatch part took less than 10 minutes for set up and cutting.

Total time with setting up the sheets, parts, tooling, machine, and cutting for one skram is probably around 2 hours and 10 minutes with the 1/4 inch bit.

How long did it take you to cut one?

Thanks for your very detailed response! My CNC is quite a bit smaller and I have to cut a sheet of plywood (2.5m x 1.25m) into three pieces to fit them on the table, but the total machining time for a pair of my subs (a little smaller than the Skrams but also with dados and multiple handles etc) would be ~4 hours. I'm using an 8mm bit for all operations at 150ipm and 20k rpm because I don't want to change tools (I have a tool length sensor but no automatic tool changer). Maximum cut depth was half the total depth (2x9.5mm).

Here is a pic for one of the 9 sheets. Machining time for this one is 34 minutes.

 

Onion skinning on a vacuum table sounds like a great solution. I have a T-Nut table thou... I have tried onion skinning with the frame screwed to the waste board with little success. Aluminum does that, but not wood.

It looks like my holding tabs were too small because some parts are not perfect. Edges are not always 100% straight and some measurements are a little off (but max 2/100th of an inch). I used conventional passes throughout because those gave me a better surface finish. I used a simple straight bit; cuts against the grain do require some sanding, but nothing critical. Removing tabs from all the parts took me maybe 2 hours at most, but I prefer having the parts ready to be glued together straight out of the CNC.

I am thinking of selling those cabs (not the ones I made, just generally producing subs for customers), which overall process-optimization would make a lot of sense for of course.

My tabs were 3mm thick, 8mm long and were placed every 120mm. For the next project I'll try thicker tabs every 90mm and will also use a thicker waste board.

You can see the un-sanded surface in this photo.

[klipsch]

6 hours ago, peniku8 said:

Thanks for your very detailed response! My CNC is quite a bit smaller and I have to cut a sheet of plywood (2.5m x 1.25m) into three pieces to fit them on the table, but the total machining time for a pair of my subs (a little smaller than the Skrams but also with dados and multiple handles etc) would be ~4 hours. I'm using an 8mm bit for all operations at 150ipm and 20k rpm because I don't want to change tools (I have a tool length sensor but no automatic tool changer). Maximum cut depth was half the total depth (2x9.5mm).

Here is a pic for one of the 9 sheets. Machining time for this one is 34 minutes.
 

 

Onion skinning on a vacuum table sounds like a great solution. I have a T-Nut table thou... I have tried onion skinning with the frame screwed to the waste board with little success. Aluminum does that, but not wood.

It looks like my holding tabs were too small because some parts are not perfect. Edges are not always 100% straight and some measurements are a little off (but max 2/100th of an inch). I used conventional passes throughout because those gave me a better surface finish. I used a simple straight bit; cuts against the grain do require some sanding, but nothing critical. Removing tabs from all the parts took me maybe 2 hours at most, but I prefer having the parts ready to be glued together straight out of the CNC.

I am thinking of selling those cabs (not the ones I made, just generally producing subs for customers), which overall process-optimization would make a lot of sense for of course.

My tabs were 3mm thick, 8mm long and were placed every 120mm. For the next project I'll try thicker tabs every 90mm and will also use a thicker waste board.

You can see the un-sanded surface in this photo.

 

I ran a while without a vacuum hold down.  There are motors here in the US for about $160 that last about 1200 to 1500 hours. 2 or 3 of them with 2 sheets of melamine for a housing will get you over 5 hg if that is something you choose to pursue.  Not sure what you have available in your part of the world. 

Prior to the vacuum hold down, I would make tabs of .25" wide and .0625" thick.  They worked well, but took work when finishing like you've mentioned.  I then went to onion skinning from tabs and had much better results.  Using a down cut bit helped keep the material on the table without a vacuum, but meant any plunge cuts were not too clean (more of a burn than a cut).  To work around the plunge cut issues, ramps were used where they could be.  A compression bit gave me the ability to do plunge cuts cleanly and still have decent down pushing pressure on the material without a vacuum and using tabs.  Is the straight bit causing some "chatter"?

20,000 RPM at 150ipm for a single flute bit should produce a chipload around .008.  Is that about what you are making?  I only ask as when I was first starting out, I was running too high of RPM which made more heat and dulled my bits (was also using cheap bits).  When that happened, the onion skinning and tabs both suffered as the wood was being pushed more than cut.

[SME]

I had the problem of spinning the bit too fast with *hand-held* routing in my speaker builds.  I broke a couple 6 mm bits that way before I learned about RPMs and feed rates from the CNC forums.  So I dropped my speed setting to "2" out of "6" (about 10k RPM I think) and sped up my manual feed rate.  That helped a lot, but I still needed to make very shallow passes (like 3 mm or less) to avoid problems.  That's what I did with my subs.  Unfortunately the compression bit I used caused nasty tear-out because the tip of the bit is designed to be on the *other side* of the work-piece where it pushes chips up and towards the piece instead of away from it.

So I think for my next project I will use a down-cut bit with very shallow passes and hopefully be able to keep it sharp long enough to use on more than one project.  BB plywood just seems to be the worst enemy of cutters.  Maybe the material I'm getting is just particularly nasty?  It builds some damn good speakers and subs though.

 

[klipsch]

5 hours ago, SME said:

So I think for my next project I will use a down-cut bit with very shallow passes and hopefully be able to keep it sharp long enough to use on more than one project.  BB plywood just seems to be the worst enemy of cutters.  Maybe the material I'm getting is just particularly nasty?  It builds some damn good speakers and subs though.

 

I really like BB too. The Janka score can be around 1200 and I think as low as 1000. I think that's a decent range to account for when cutting. Over the years, there is a sound I've learned from others and my own work which helps figure out if the cutting rpm and feedrate are not good. Anything high pitch like a screech is typically not good. Visually speaking, if there is dust and not chips, then that is also usually bad (even for mdf). 

[Ricci]

Excellent posts about general CNC use and settings guys!

[peniku8]

On 12/27/2019 at 2:21 AM, klipsch said:

I ran a while without a vacuum hold down.  There are motors here in the US for about $160 that last about 1200 to 1500 hours. 2 or 3 of them with 2 sheets of melamine for a housing will get you over 5 hg if that is something you choose to pursue.  Not sure what you have available in your part of the world. 

Prior to the vacuum hold down, I would make tabs of .25" wide and .0625" thick.  They worked well, but took work when finishing like you've mentioned.  I then went to onion skinning from tabs and had much better results.  Using a down cut bit helped keep the material on the table without a vacuum, but meant any plunge cuts were not too clean (more of a burn than a cut).  To work around the plunge cut issues, ramps were used where they could be.  A compression bit gave me the ability to do plunge cuts cleanly and still have decent down pushing pressure on the material without a vacuum and using tabs.  Is the straight bit causing some "chatter"?

20,000 RPM at 150ipm for a single flute bit should produce a chipload around .008.  Is that about what you are making?  I only ask as when I was first starting out, I was running too high of RPM which made more heat and dulled my bits (was also using cheap bits).  When that happened, the onion skinning and tabs both suffered as the wood was being pushed more than cut.

Sounds like you made the table yourself? Guess you had fun drilling hundreds of holes! There is a vacuum bed for my CNC but it's 2.5 grand...

The straight bit I have was 20$ and it did all parts nicely; it's a double flute bit. There are some high performance bits for 30$ to 40$ which I might consider in the future. I just recently spent 400$ on bits, so I'm good for now. I got the CNC just a few months ago. I never CNC'd wood before, but I've got some experience in milling various metals. CNC'ing aluminum essentially uses very similar feed rates and speeds (if the machine is sturdy enough). There was an audible high pitched screetching while doing the cuts; I'll try lower RPM next time! Nothing burned and the chips produced were small, but definitely not dust.

This picture shows a part straight from the machine. All cuts parallel to the grain are pristine and those against the grain have some slight edge shatter, but nothing grave.

[klipsch]

20 hours ago, peniku8 said:

Sounds like you made the table yourself? Guess you had fun drilling hundreds of holes! There is a vacuum bed for my CNC but it's 2.5 grand...

The straight bit I have was 20$ and it did all parts nicely; it's a double flute bit. There are some high performance bits for 30$ to 40$ which I might consider in the future. I just recently spent 400$ on bits, so I'm good for now. I got the CNC just a few months ago. I never CNC'd wood before, but I've got some experience in milling various metals. CNC'ing aluminum essentially uses very similar feed rates and speeds (if the machine is sturdy enough). There was an audible high pitched screetching while doing the cuts; I'll try lower RPM next time! Nothing burned and the chips produced were small, but definitely not dust.

This picture shows a part straight from the machine. All cuts parallel to the grain are pristine and those against the grain have some slight edge shatter, but nothing grave.

Making a vacuum table is not too difficult. It may not be something you would want to do, but underneath an mdf or ultra light mdf spoilboard is a vacuum board with a pattern cut by the cnc that looks similar to the below. The vacuums connect from underneath to the hole cutouts in the vaccum board via pvc pipe. Different zones can be made on the vacuum board and then can control the vacuum to the zones with blast gates in-line with the pvc. The vacuums lower the barometric pressure beneath the surface of the spoilboard which creates push down force on the material resting on top of the spoilboard.  It has worked very well for many (me included). 

 

 

Without knowing the torque vector of your spindle or router, rigidity of your machine, etc., what works best for you and your machine is all that matters and chipload calculations and calculators can be a nuisance.  If it will help and you want, I attached a decent chipload calculator that could be used as a reference point. With my main 4.2 hp spindle and machine, I would start with a new material around the chipload recommended in "aggressive". With a router (not a spindle) around 3 hp for Baltic birch plywood, I would have started around a 0.004 - 0.006 chipload.  chipload calc.xls

This may not be your goal, but in order to extend my bit life, I like to be able to touch the bit after a job and it feel cool to the touch.  The speeds I want to cut at and the material finishes have worked well with that cool touch bit as well. Ran another skram sheet last night for the second skram. Here are some chips from the hatch (2 flute 1/4 inch compression bit, ~12,000 rpm @ 240 ipm climb leaving .04" material - nearly full depth profile cut - bit cool) : 

 

Added a quick 1st coat of wet stain on skram number 1 last night too:

[peniku8]

@klipsch I'll seriously consider a vacuum bed when I'm done with the next project and am still having problems with accuracy even with more tabs and a thicker waste board (thicker than 8mm of MDF to screw into). Of course I would also need some free time to take care of all that...

How does your table handle warped sheets?

I have yet to find the limits of my machine. The 2.5HP spindle should be able to handle it just fine, but my machine is outfitted with stepper motors. And instead of upgrading those to servos I'd rather buy a bigger machine. I'd love to have a water cooled spindle. This one is pretty noisy.

When working with metal, it is generally advised to use climb cutting only when you're removing less than half the bit's diameter. I found climb cutting to yield a slightly worse surface finish compared to conventional cutting. Do you see much of a difference?

Did you stain the cab to use less Duratex or will you leave it as is?

I assembled both my cabinets over the past few days and already have many changes I'll make in the CAD model for aid the assembly. Namely: more joints.

Do you glue and clamp? I used Kreg screws for this project for the first time and while I like the system itself, I hate the head. The bit is not grippy at all. Plus those push the boards outwards, which I had to find a workaround for (pic below).

 

I currently don't have any pics of an assembled cab, so here is the dry assembly:

Can't wait to get those finished and do some measurements!

[jay michael]

Looking good you guys! Jealous of your cnc machines

 

[klipsch]

2 hours ago, peniku8 said:

@klipsch I'll seriously consider a vacuum bed when I'm done with the next project and am still having problems with accuracy even with more tabs and a thicker waste board (thicker than 8mm of MDF to screw into). Of course I would also need some free time to take care of all that...

How does your table handle warped sheets?

I have yet to find the limits of my machine. The 2.5HP spindle should be able to handle it just fine, but my machine is outfitted with stepper motors. And instead of upgrading those to servos I'd rather buy a bigger machine. I'd love to have a water cooled spindle. This one is pretty noisy.

When working with metal, it is generally advised to use climb cutting only when you're removing less than half the bit's diameter. I found climb cutting to yield a slightly worse surface finish compared to conventional cutting. Do you see much of a difference?

Did you stain the cab to use less Duratex or will you leave it as is?

I assembled both my cabinets over the past few days and already have many changes I'll make in the CAD model for aid the assembly. Namely: more joints.

Do you glue and clamp? I used Kreg screws for this project for the first time and while I like the system itself, I hate the head. The bit is not grippy at all. Plus those push the boards outwards, which I had to find a workaround for (pic below).

 

 

I currently don't have any pics of an assembled cab, so here is the dry assembly:

 

Can't wait to get those finished and do some measurements!

Vacuum hold down will change everything :).  These cheap vac motors will take 1/2" warped sheets down flat. 3/4" warp sheets will go flat as well, but only if the warp is slight. If these cheap vac motors were replaced with a much more expensive regen vac motor, then there isn't much that wouldn't be flattened. Servos are very nice. Steppers work just fine too.

This HSD air cooled spindle is not loud at all. I can hold normal conversations with just the spindle on. The cutting of the material is far louder than the spindle motor and the vacuum motors. However, all of that is no where near as loud as the dust collection system. Water cooled spindles are quiet, but do have more things to do for maintenance and operation. 

In my experience, for wood, typically I'll use climbing for first pass and conventional for final pass. For dados/grooves/joints, I'll do full axial path in climb and leave a bit on radial. Then do full axial and radial conventional path to remove the remaining radial stock material. For profiles, I'll do climb and leave 0.04" axial and typically 0.02" radial. Then do the final pass with conventional for remaining. This usually yields good results regardless of grain direction. Climb can be less forgiving against the grain. Higher RPM can combat that, but then an increase in IPM is usually needed, etc. 

The wife wanted me to stain these like the other sub cabinets we have.  Current plan is to sand lightly and poly them. No duratex on these two. 

I really like your joints. They look nice for fit and great for final assembly. Long ago I used to glue and use brad nails, but have just been "gluing" with Pl premium 3x and clamping for years now.  With CNC cutting (assuming joints or similar like yours), screwing and nailing has not been needed for me or others. Heck, I've seen people use Pl premium and painters tape instead of clamps with joints like yours. The tape was enough to hold everything in place while the adhesive expands and cures. I've had 4 DO 18" sealed subs running for 6+ years with no issues with the Pl premium and clamp method.

I do use kregg's pocket jig and screws for things cut on a table or miter saw, even with that square headed bit

Some clamping action:

 

Have any pictures or models of the inside of that cab? 

[peniku8]

5 hours ago, klipsch said:

Vacuum hold down will change everything :).  These cheap vac motors will take 1/2" warped sheets down flat. 3/4" warp sheets will go flat as well, but only if the warp is slight. If these cheap vac motors were replaced with a much more expensive regen vac motor, then there isn't much that wouldn't be flattened. Servos are very nice. Steppers work just fine too.

This HSD air cooled spindle is not loud at all. I can hold normal conversations with just the spindle on. The cutting of the material is far louder than the spindle motor and the vacuum motors. However, all of that is no where near as loud as the dust collection system. Water cooled spindles are quiet, but do have more things to do for maintenance and operation. 

In my experience, for wood, typically I'll use climbing for first pass and conventional for final pass. For dados/grooves/joints, I'll do full axial path in climb and leave a bit on radial. Then do full axial and radial conventional path to remove the remaining radial stock material. For profiles, I'll do climb and leave 0.04" axial and typically 0.02" radial. Then do the final pass with conventional for remaining. This usually yields good results regardless of grain direction. Climb can be less forgiving against the grain. Higher RPM can combat that, but then an increase in IPM is usually needed, etc. 

The wife wanted me to stain these like the other sub cabinets we have.  Current plan is to sand lightly and poly them. No duratex on these two. 

I really like your joints. They look nice for fit and great for final assembly. Long ago I used to glue and use brad nails, but have just been "gluing" with Pl premium 3x and clamping for years now.  With CNC cutting (assuming joints or similar like yours), screwing and nailing has not been needed for me or others. Heck, I've seen people use Pl premium and painters tape instead of clamps with joints like yours. The tape was enough to hold everything in place while the adhesive expands and cures. I've had 4 DO 18" sealed subs running for 6+ years with no issues with the Pl premium and clamp method.

I do use kregg's pocket jig and screws for things cut on a table or miter saw, even with that square headed bit

Some clamping action:

 

Have any pictures or models of the inside of that cab? 

 

How much would a DIY vaccum table cost all in all? As far as I've read, it's basically just like 3 layers of MDF, of which the top layer is low density MDF to allow more air to flow through. Seems pretty simple with like 4 sections for a table. Add some PVC tubing and a motor or maybe several?

My dust collection system is pretty quiet, but I'll be getting a new one soon. Need better air flow also for the table saw.

 

So your wife wanted them to be stained huh.. that almost sounds like these will be an addition to your living room system?!

You got quite a lot of clamps there.. I guess I need to get some of those quick lock clamps as well. Mine are super heavy and the old school threaded system is a nuisance to work with.

Here are two pics of the inside of my cab. The second cab is mirrored. I will make a thread about those on AVS soon, if you want more info I'm happy to answer any questions via PM as I don't wanna discuss that in the thread dedicated to a different cabinet

The essence of the cab was getting flat response down to 30Hz in the smallest package possible while avoiding a direct radiator design. They'll be around 120lbs with the driver, which was the goal (easily movable with two people, possible to flip them onto the wheels alone).

 

[klipsch]

 

44 minutes ago, peniku8 said:

How much would a DIY vaccum table cost all in all? As far as I've read, it's basically just like 3 layers of MDF, of which the top layer is low density MDF to allow more air to flow through. Seems pretty simple with like 4 sections for a table. Add some PVC tubing and a motor or maybe several?

My dust collection system is pretty quiet, but I'll be getting a new one soon. Need better air flow also for the table saw.

So your wife wanted them to be stained huh.. that almost sounds like these will be an addition to your living room system?!

You got quite a lot of clamps there.. I guess I need to get some of those quick lock clamps as well. Mine are super heavy and the old school threaded system is a nuisance to work with.

Here are two pics of the inside of my cab. The second cab is mirrored. I will make a thread about those on AVS soon, if you want more info I'm happy to answer any questions via PM as I don't wanna discuss that in the thread dedicated to a different cabinet

The essence of the cab was getting flat response down to 30Hz in the smallest package possible while avoiding a direct radiator design. They'll be around 120lbs with the driver, which was the goal (easily movable with two people, possible to flip them onto the wheels alone).

A diy vac with 3 lighthouse motors will run around 700 bucks for melamine box (melamine makes sealing easy), pvc, mdf, pvc glue, circuit breaker, etc. I have two layers of mdf (one is the spoilboard). I made something similar to the below. It is based off of a Gary Campbell design: 

http://www.talkshopbot.com/forum/showthread.php?19556-Vac-box-setup-Complete

The two skrams will be going behind a screen in our basement. Probably only to be heard and never to be seen again. 

There is no such thing as too many clamps

Your cabs look great. Really nice job with the design and cnc work. Very clean. Looks like you and Kregg have been really busy too! I hope your design gets you that flat 30hz you're looking for in a transportable form. I'll find your avsforum post when you get to it. I am hoping to have these cabs done and running in the next 3 weeks. Doing some traveling... 

[peniku8]

20 hours ago, klipsch said:

 

A diy vac with 3 lighthouse motors will run around 700 bucks for melamine box (melamine makes sealing easy), pvc, mdf, pvc glue, circuit breaker, etc. I have two layers of mdf (one is the spoilboard). I made something similar to the below. It is based off of a Gary Campbell design: 

http://www.talkshopbot.com/forum/showthread.php?19556-Vac-box-setup-Complete

The two skrams will be going behind a screen in our basement. Probably only to be heard and never to be seen again. 

There is no such thing as too many clamps

Your cabs look great. Really nice job with the design and cnc work. Very clean. Looks like you and Kregg have been really busy too! I hope your design gets you that flat 30hz you're looking for in a transportable form. I'll find your avsforum post when you get to it. I am hoping to have these cabs done and running in the next 3 weeks. Doing some traveling... 

It's always the same. I spend 2 weeks on AVS and am convinced that I need at least two 21's on a clone amp (that's what I have now with the SKHorn in my living room).
I talked to my dad today (who will retire in a few months and is very interested in this whole CNC thing, especially since the machine sits in his basement 😅) and it took me about half an hour to convince him that we need a vacuum table. We agreed to split the cost 50:50, so the budget for the 4.5' by 3' table is about 1 grand now. It's decided. Gotta finish the two 21" cabs and also two 12" cabs for live gigs first, but after that I'll allocate some free time for this project. Doing the final assembly of the second cab today showed me that those parts seemed to have moved even more on the table, which made me want to get the vacuum table asap.

Anyways, I'll probably pester you with some questions about your build soon. I've looked into making the air grid from aluminum but that's darn expensive.

The reason why you're using 3 vacs is for the big surface area I guess? To my understanding, the increased air throughput also increases the vacuum strength.

2 Skrams in the basement sounds like a fun party room/home theater/both.

My next step is to coat the cabs in Duratex (called Warnex here in Europe). I'm planning to spray it for the most part, to achieve the pro look. Have never worked with this paint before, so I'd be glad if anybody has some tips for me. The Warnex PDF made me a little more confident already and I'll try on a scrap piece first.

[klipsch]

2 hours ago, peniku8 said:

It's always the same. I spend 2 weeks on AVS and am convinced that I need at least two 21's on a clone amp (that's what I have now with the SKHorn in my living room).
I talked to my dad today (who will retire in a few months and is very interested in this whole CNC thing, especially since the machine sits in his basement 😅) and it took me about half an hour to convince him that we need a vacuum table. We agreed to split the cost 50:50, so the budget for the 4.5' by 3' table is about 1 grand now. It's decided. Gotta finish the two 21" cabs and also two 12" cabs for live gigs first, but after that I'll allocate some free time for this project. Doing the final assembly of the second cab today showed me that those parts seemed to have moved even more on the table, which made me want to get the vacuum table asap.

Anyways, I'll probably pester you with some questions about your build soon. I've looked into making the air grid from aluminum but that's darn expensive.

The reason why you're using 3 vacs is for the big surface area I guess? To my understanding, the increased air throughput also increases the vacuum strength.

2 Skrams in the basement sounds like a fun party room/home theater/both.

My next step is to coat the cabs in Duratex (called Warnex here in Europe). I'm planning to spray it for the most part, to achieve the pro look. Have never worked with this paint before, so I'd be glad if anybody has some tips for me. The Warnex PDF made me a little more confident already and I'll try on a scrap piece first.

Haha about avsforum. I can relate - there may be 8 18" drivers in the room where the 2 skrams are going... 😯

I also have an extra b&c 8ohm 152 that needs a home. Build another skram? Buy another 152 and try a skhorn? 1st world problems... 

What type of clone Amp did you go with? I'm thinking of trying one for the 2 skrams. 

Maybe I should not have, but I suggested 3 vac motors as that is what I think I should have done. That is awesome that you and your Dad are working together. Congrats on his upcoming retirement. Right now, I have 4 vac motors. Can run either 2 at once or 4 at once. 2 is what I run 90% fof the time. 2 works for full 4x8 sheets. I've run 4 on large warped boards, but that was for material I ran for a few customers. Also run 4 for carving and cutting smaller pieces.  For your smaller work area, 2 would probably be great, but for when you upgrade or cut smaller pieces, 3 would probably be a good option. 

I've never sprayed Warnex, but I've sprayed duratex before. It was not the spray version of the duratex. I watered it down a bit and it sprayed well with a cheap Warner sprayer (maybe it was 5 to 1 mixture). However, I ran a thick nap roller on the sprayed surface after the spray to get the texture look. 

[peniku8]

9 hours ago, klipsch said:

Haha about avsforum. I can relate - there may be 8 18" drivers in the room where the 2 skrams are going... 😯

I also have an extra b&c 8ohm 152 that needs a home. Build another skram? Buy another 152 and try a skhorn? 1st world problems... 

What type of clone Amp did you go with? I'm thinking of trying one for the 2 skrams. 

Maybe I should not have, but I suggested 3 vac motors as that is what I think I should have done. That is awesome that you and your Dad are working together. Congrats on his upcoming retirement. Right now, I have 4 vac motors. Can run either 2 at once or 4 at once. 2 is what I run 90% fof the time. 2 works for full 4x8 sheets. I've run 4 on large warped boards, but that was for material I ran for a few customers. Also run 4 for carving and cutting smaller pieces.  For your smaller work area, 2 would probably be great, but for when you upgrade or cut smaller pieces, 3 would probably be a good option. 

I've never sprayed Warnex, but I've sprayed duratex before. It was not the spray version of the duratex. I watered it down a bit and it sprayed well with a cheap Warner sprayer (maybe it was 5 to 1 mixture). However, I ran a thick nap roller on the sprayed surface after the spray to get the texture look. 

I simmed the 152 in my cab and it somehow starts rolling off almost 5Hz earlier. While it has the same headroom than the DS, EQ'ing up the roll-off would probably introduce too much ringing for my taste. EQ'ing down that 70Hz spike which the DS produces is much more convenient. I don't even know the the SW starts rolling off sooner.

I got a Sanway FP13000 maybe 6-7 years ago. The old version that is. The newer ones are more stable into low impedance loads and can output more sustained power. Mine outputs enough power to dim the lights on a 230V circuit... Bad installation in this house here in France. I also have their 10k dsp amp with touch screen which I'd never buy again. The dsp clips long before you can reach maximum output power and is so unflexible that you can't find a workaround (there is no input gain, and the output gain can only be negative). Many on AVS seem to be happy with the Sinbosen 20k 4 channel amp. It outputs 8KW sustained total to 4 channels iirc. Nowadays I'd rather spend about twice the money and get a used name brand amp. For HT use these amps are phenomenal thou.

I'm planning to make a table with 2 vacuum sections. A smaller one about 1.5' x 2' and an L-shaped section around it to expand to the whole table.
I'll have a look at shipping costs of the Lighthouse motors, as I can't seem to find anything similar here. If I save alot buying multiples I'll go for 3 motors right away (using three in a 3 phase configuration would be pretty cool).
Are you masking the table when doing smaller parts?

I wasn't aware that there was a 'spray' version of Duratex, but as for Warnex it's all the same. And it actually seems that you only get proper texture when spraying.

[klipsch]

2 hours ago, peniku8 said:

I simmed the 152 in my cab and it somehow starts rolling off almost 5Hz earlier. While it has the same headroom than the DS, EQ'ing up the roll-off would probably introduce too much ringing for my taste. EQ'ing down that 70Hz spike which the DS produces is much more convenient. I don't even know the the SW starts rolling off sooner.

I got a Sanway FP13000 maybe 6-7 years ago. The old version that is. The newer ones are more stable into low impedance loads and can output more sustained power. Mine outputs enough power to dim the lights on a 230V circuit... Bad installation in this house here in France. I also have their 10k dsp amp with touch screen which I'd never buy again. The dsp clips long before you can reach maximum output power and is so unflexible that you can't find a workaround (there is no input gain, and the output gain can only be negative). Many on AVS seem to be happy with the Sinbosen 20k 4 channel amp. It outputs 8KW sustained total to 4 channels iirc. Nowadays I'd rather spend about twice the money and get a used name brand amp. For HT use these amps are phenomenal thou.

I'm planning to make a table with 2 vacuum sections. A smaller one about 1.5' x 2' and an L-shaped section around it to expand to the whole table.
I'll have a look at shipping costs of the Lighthouse motors, as I can't seem to find anything similar here. If I save alot buying multiples I'll go for 3 motors right away (using three in a 3 phase configuration would be pretty cool).
Are you masking the table when doing smaller parts?

I wasn't aware that there was a 'spray' version of Duratex, but as for Warnex it's all the same. And it actually seems that you only get proper texture when spraying.

Thanks for the detailed info about the Amps. I only have a dedicated 20amp 240v for the clone, so hopefully that would be enough for a 20k.  The xbs folks sent me a picture of a 20 Amp 240v plug they'd use (save me some work of rewiring). 

4 sided shapes may work better for vacuum VS an L or other shape with more than 4 sides. I think I remember reading about that somewhere. I do mask the table when the smallest vacuum zone I have is too large for the work material. I have a few small pieces around 6"x20" to put around the work piece to cover the vac zone area.  If the work pieces are really small, less than about 6"x6", I need to lower the IPM due to the smaller surface area.  I have this image printed from a long while back near the cnc. I think it is accurate based on sea level atmosphere to approximately determine the hold down force. 

 

Years ago when I sprayed the duratex, I don't think there was a spray version. I've seen that there are spray and roller grades now (think on parts express). I did not research to see if those grades are marketing or if it maybe is more economical to buy roller grade and thin it to make "spray" grade or any other details. 

[Ricci]

I've always used the roller grade Duratex. People used to suggest thinning it out for spraying but I believe that was before they released their own spray version. If the cabs are going to see real "road" use I'd do at least 3 coats with a sprayer. If rolling it the amount of texture in the finish will vary depending on the roller used. A heavier texture with thicker application might be preferred for toughness. YMMV. 

Either way the stuff is easy to use and clean up isn't too bad. The odor isn't too bad either. Make sure it's at least 55deg or higher when you apply it. It doesn't like cold weather. 

[peniku8]

@Ricci These cabs will be used for live gigs and rentals, so a durable coating is preferred. I rounded over all edges which come into contact with the environment with a quarter inch roundover bit, to prevent the coating from breaking too easily there. The 8lbs of Warnex I have should be more than enough for one cab at least. I will spray the cabs inside, with the windows open for some fresh air to breathe (although I think the low viscosity of the paint prevents it from evaporating to some extend). Gonna get some plastic wrap to cover the surroundings. I wanna keep the room as white as it is. I don't remember reading anything about diluting Warnex.

@klipsch I might be able to do 3 rectangular regions, depending on how flexible I am with mounting the T-Nut bed beneath.
I'm unsure what you mean by Melamine table. If I search that term online, I only find veneered MDF or plywood sheets. Making everything from MDF seems like a more simple solution to me. I can seal the bottom layer and use the same sheet of MDF for the top layer. Which thickness would you recommend?

[Tahoejmfc]

Hi Everyone, I have been following Data-Bass and the other forums for many years while building an art car. This year was its first year to the Playa after 4 years of work, a divorce, a child being born, etc etc. I teach illustrator, CNC Plasma, CNC Router, Laser and NFPA 160 Flame effects at a local makers space here in Truckee CA. I own a Boss Laser HP3655 Stainless Steel cutting 150Watt CO2 laser that I am using to make the art car with and helping other artists with their projects as well.

This project is a labor of love and not for profit.

  http://www.instagram.com/jackalotus  https://www.instagram.com/p/B2qSE1zhUI5/  https://www.instagram.com/p/B2ISZPCBKgp/

I currently have in mind building my own cabinets using two 21SW152's I currently own. I have been working on ported box designs for quite some time, but keep drooling over Ricci's awesome work on various forums going back to I think 2010. I plan on building tops with help from a Electrical engineer friend who works at Meyers Sound.

I have a stack of Baltic Birch sitting here in my garage waiting for the right design to build around my 21SW152's and I think I have decided to throw my ported designs in the waste basket and go with the SKRAM design of Ricci's that everyone here is building.

I plan on placing 2 of these boxes under the head of the PlayaPachederm.

My Question is... Is anyone willing to share/sell an Autodesk file or VCARVE file?

Also wondering how i can donate to all the hard work Ricci put in for us? Need anything laser cut out of stainless let me know

[klipsch]

1 hour ago, peniku8 said:

@Ricci These cabs will be used for live gigs and rentals, so a durable coating is preferred. I rounded over all edges which come into contact with the environment with a quarter inch roundover bit, to prevent the coating from breaking too easily there. The 8lbs of Warnex I have should be more than enough for one cab at least. I will spray the cabs inside, with the windows open for some fresh air to breathe (although I think the low viscosity of the paint prevents it from evaporating to some extend). Gonna get some plastic wrap to cover the surroundings. I wanna keep the room as white as it is. I don't remember reading anything about diluting Warnex.

@klipsch I might be able to do 3 rectangular regions, depending on how flexible I am with mounting the T-Nut bed beneath.
I'm unsure what you mean by Melamine table. If I search that term online, I only find veneered MDF or plywood sheets. Making everything from MDF seems like a more simple solution to me. I can seal the bottom layer and use the same sheet of MDF for the top layer. Which thickness would you recommend?

Sorry for the confusion. I was suggesting the use of melamine sheets to use for the vacuum housing box.  Phenolic lined sheets can be used too if they're cheaper in France.  Both are usually particleboard middles with lining of both materials on the outside (veneered like you mentioned). The melamine surface is well sealed to keep the multi-vacuum vac box chamber air tight.  However, making a box is not necessary. Some just hook 1 vac per zone.  The cost of mdf VS melamine in my area is the same. Making a vac box out of melamine saves time and money to seal the vac box if it is made of a porous material like mdf  or wood. Metal would work just as well (maybe better) if you have access to fabricate that cheaper. 

I used 3/4 mdf for the vacuum board and have used regular mdf and umdf for spoilboards. The ultralight mdf may have been slightly better for these motors. I just had a free mdf sheet on hand once I went through the last spoilboard. Each spoilboard has always started out as 3/4".

PS There are full phenolic sheets (no particleboard, but full phenolic throughout). Those sheets are several hundred each here in the States. High-end cnc machines use those as the vacboards. They just carve the pattern and need zero sealing due to the phenolic properties. MDF will expand and change with temperature and humidity, but phenolic supposedly does not. 

[peniku8]

5 hours ago, klipsch said:

Sorry for the confusion. I was suggesting the use of melamine sheets to use for the vacuum housing box.  Phenolic lined sheets can be used too if they're cheaper in France.  Both are usually particleboard middles with lining of both materials on the outside (veneered like you mentioned). The melamine surface is well sealed to keep the multi-vacuum vac box chamber air tight.  However, making a box is not necessary. Some just hook 1 vac per zone.  The cost of mdf VS melamine in my area is the same. Making a vac box out of melamine saves time and money to seal the vac box if it is made of a porous material like mdf  or wood. Metal would work just as well (maybe better) if you have access to fabricate that cheaper. 

I used 3/4 mdf for the vacuum board and have used regular mdf and umdf for spoilboards. The ultralight mdf may have been slightly better for these motors. I just had a free mdf sheet on hand once I went through the last spoilboard. Each spoilboard has always started out as 3/4".

PS There are full phenolic sheets (no particleboard, but full phenolic throughout). Those sheets are several hundred each here in the States. High-end cnc machines use those as the vacboards. They just carve the pattern and need zero sealing due to the phenolic properties. MDF will expand and change with temperature and humidity, but phenolic supposedly does not. 

I'd rather weld a steel box with a bunch of connections for PVC tubing to take care of the airflow and house all that inside an MDF box to keep the noise inside. This airtight case doesn't seem like a reliable idea to me.

Do you think bolting down the spoilboard with 4 screws at the corners would be sufficient? If I seal the sides, the vac should suck the spoilboard to the vac board so I would be able to prepare the spoilboard.

I found this material called Iberpan 400, which is ultra light MDF with a density of 400kg/m³. That's a little less than 2/3 of the usual MDF density. I just don't know a price since it seems that it's only available for commercial customers, plus the wood supplier where my company is registered doesn't seem to have it.

I thought about making the entire vac bed from aluminum, but the cost would be outrageous.

btw, @Ricci, I'm sorry for now completely derailing your Skram thread! Maybe we should start a dedicated CNC thread somewhere?

And btw, Happy New Year, y'all!

[klipsch]

Happy New Year!