Thanks Red,
Your comment is very instructive.
For Electronics, I feel confident. At last that reminds me University. :D
Even if I would, I'm affraid to be forced to advance step by step.
For three reasons :

1. First, I'll start when all will be checked, the whole plans learned and building lists verified.
2. Second, money because MM is not our family priority, just mine...
3. Third, I don't have a workshop ready for metal work, so I must invest on the necessary tools (at last a bench mounted drill, correct angle grinder...)

I guess it will be exciting, from start to end. :)

Axel,
1. You must produce the list all by yourself, consider it an examination on how much is your understanding on the plan.
2. Who doesn't worry about MONEY, :mad:
3. You can build with minimal tools. I built mine with a circular abrasive disc chop saw, an angle grinder, a tiny 350W bench drill (which is the cheapest bench drill which I can find for around 40euro) & a borrowed stick welding machine (I've bought a 120euro Chinese 140Amp welding machine since than), a power hand drill & a sledge hammer.

Axel,
Since you are a acoustic engineer, can you suggest a solution to the vacuum pump noise?

Thank you for your advices Ken.

There's solutions for the vacuum pump noise, of course. I thought about it.
The most simple may be to put an Electrical Relay on the spindle circuit :
the spindle is turning, the vacuum starts.
The cutting spindle should makes more noise than the vacuum.
If it's a workshop vacuuming station, you may isolate the wacuum in a box,
with specifications to avoid warming and aspiration noise.
Is there a dedicated topic where I could post roughs and schemes ?

I awnsered here : Quieting a vacuum system ;)

You were asking about using aluminium instead of steel to reduce mass, but see what this guy says about mass and vibrations:

:)

Absolutely true... :o

Salut Axel beau texte sur l'acoustic ,mais ce qui m'impressionne le plus c'est ton traducteur . C'est tu une personne en chair et en os ou un logiciel? Tout est tellement parfait .il n'y a pas d'erreur de syntaxe .J'ai jamais vu rien te tel,rendu la pas besoin d'apprendre d'autre langues . C'est quoi le nom du logiciel de traduction que tu utilise?

aussi j'oubliais connais tu ce site de cnc . Beaucoup d'info dans la langue de Molière

http://www.usinages.com/

Merci Normand, oui je connais le site. J'y suis également inscrit. Très bonne adresse pour l'usinage en général avec une petite section CNC. Ils parlent plus de l'usinage de précision, mais il y a beaucoup d'informations.

Je n'utilise aucun logiciel de traduction, je fais ça avec ma petite cervelle.
Ceci dit, tu es sans doute très indulgent, il doit y avoir largement à redire... :o

Hi all,
I move forward in the understanding of the steel construction of the MM.
I wonder if the flattening of tube tube ends (see #13 or #17 below) is structural (to give more strenght to the tubes)
or is it to make the welding more simple ?
How to flatten tube ends easily (without heavy equipment) ? With a vice ?
Another question : my supplyer have various tube diameters starting from 12 to 80mm tubes,
but only 2mm thick, is this ok for the table structure and to be flattened ?
http://i234.photobucket.com/albums/e...92/jason-1.jpg

I used hydraulic jack to flatten my pipes. Vice can be use if the pipe wall thickness in less than 2mm.
Sledge hammer can do the job too. Honest.

Flattening was only to make welding more simple. 2mm will be okay - you could flatten that with a vice.

Many thanks :)
I'll submit soon my table dimensions to the comunity wisdom. :o

Hi all,

Well, I bought a welding box, grinder and most of the metal work tools today. Budget 313€.
I'm affraid I started up without any idea of the final budget... :o

I spent all my freetime this week thinking about the main table and wakling around the house with a meter in hand.
I know the initial design is simple and perfect.
Unfortunately, I don't own a 60m² workshop, only a blind room in the cellar of my rented home.
First, that means the MM may be dismantled to move move with me someday.
Second, the wide side must be the Y axis otherwise I won't be able to feed the MM without diging some place into walls.
Third, because of this small room, I'll have to store new wood boards under the MM.

The max working board must be 1220x2440mm.
I dunno if this would be done someday, but I'ts wise to plan a 4th axis improvement to lathe r250mm stuff.

You know all about the specifications... :o

I tryed to adapt less as possible the initial design.
Bad news, mine is of course more complex and will cost a bit more (assumed).
But as far I'm not a mech engineer, I'm might be wrong on many subjects.

Please be indulgent. Here's the rough :
http://giemastruc.free.fr/Forums/MM_01_Perspective.jpg
Front view :
http://giemastruc.free.fr/Forums/MM_01_Front.jpg
Right view :
http://giemastruc.free.fr/Forums/MM_01_Right.jpg
Top view :
http://giemastruc.free.fr/Forums/MM_01_Top.jpg
Possible 4th axis :
http://giemastruc.free.fr/Forums/MM_01_4Axis.jpg
Elements view :
http://giemastruc.free.fr/Forums/MM_01_Eclaté.jpg

Let's explain a bit.
So the MM will be close to a wall corner in the rear Y axis and right X axis. A door opens near the left X axis. I only have two meters open space in front of the Y axis.
The control box and computer will be racked under the left X axis.
I thought the less bad idea was to weld each X axis parts together.
The two "ladders" on Y sides will be bolted on X axis, and several beams (to be bolted) will make the working table and the storage table.
The front Y "ladder" is wide open to help on load/unload.
I did not put the reinforcement tubes on X left, I may adapt triangulations to the control box dimensions "on the fly".

I tryed to be as optimized as possible on materials.
I live in the countryside, and not all the steep profiles are avalaible.
I manage to find UPN instead of C profiles.
The X beams are made of UPN 200x75mm.
The legs and work table are made of UPN 70x40mm.
The storage area are made of Square 40x40x2mm tube.
Reinforcements are made of Round 40x40x2mm tube.
Fixation deck are cuted into a flat 40x5mm steel bar.
As UPN don't have parallel profile, it's impossible to use sandwich bolts.
I thought about tapping the holes, they are at last 8,5mm thick.
I thought about using Allen M12 (X legs) and Allen M10 for beams.

What do you think ?
Before going forward I would like to check all this with the community.
Feel free to reveal my mistakes, I'm bashing proof ! :D

Don't know about that 250mm round stock, will it rack the table, maybe move legs a bit further upfront?
Also, gantry that wide has not been used until, mine is for 2050mm board and I think that's max. Maybe some more additional braces where the X motors are?
My gantry tubes (100x50) are 2550mm 3mm thick and I can sag them by pushing down with hand. They might vibrate at your length.
This really pushes the design to the limit

Is it mandatory for you to cut 1220x2440 board?
I concern more about safe working space...

Thanks Danilo,
You're right, my gantry tubes (2940mm - to be confirmed) should be at last 5 mm thick for this lenght to avoid low frequencies vibrations.
A topic is talking about huge Y dimensions : http://www.mechmate.com/forums/showthread.php?t=2083

I forget to say I need (reasonable) precision, rather than speed.

For the additional braces I don't know. The 10.20.451-452 are 5mm thick and could be increased to 6 or 8mm but I don't know the max cut possible with laser cutter.
The experts will say.

Increasing tube height is a more efficient solution, using a 50mmx150mmx3mm or 30 x 200mm if you are brave enough) square hollow section as gantry beams, it improve the deflection factor batter & its lighter too in comparison to 5mm thin 50x100 square hollow section...
What precision are you expecting? 0.0001mm? 0.1? or 0.3mm

@ Ken
Well 1220x2440 is the standard board size, available anywhere in France.
It seems to me logical to use this format, especialy I build a MM to work about furniture.
Entertainment units, beddings and cabinets calls large boards.
I wish using those boards would be possible.

@ Ken
Thanks for this precisions. Sorry, you post faster than I can reply :)

The larger gantry beams may induce a modification of the 10.20.451-452 parts, right ?
Those are lasercut parts, a very sensible subject in the MM building through.

When I talk about precision, I don't know exactly.
0,1mm will be pretty enough.
The most important is to get an accurate cut, especialy on curves.
The edges must be without defauts.
If the MM shape is good, I guess, it might be a question of motor reduction, rigidity and vibrations...

For example, I would avoid this :
http://www.mechmate.com/forums/attac...1&d=1282474513

In my humble opinion, 0.5mm is already "too accurate". In some occasions when I made an mistake or error in dimensions, even 3mm error is not visible.

with a taller gantry beam, youneed to modify 10.20.451~2 and also 10.20.456

The common solution to the chatters at curve are solved in 2 way,
1) Belt-reduction
2) Sand paper :D

Yep, sanding means also errors, especialy on curves, but it's unavoidable, anyway.
I guess I must also be very acurate on the build to minimize cuting defaults.
I'm realy affraid about any modification of the laser parts. :(
Any error conducts to problems and/or leads to new expensive laser parts.
As you said, I'm not brave enough ! :D

In this post : What is the max Gantry width allowable ?
Gerald says that he don't see big problems about 96" (3m) Y gantry.
Mine should be less than 3 meters (2940, to be confirmed by official plans, plans I must buy next month...).
For a 3,5m gantry, he says the static flex of a 4mm thick 3.5m tube is less than the static flex of a 2mm thick 2m tube, but he was thinking about low frequencies vibrations.

According my MM must have a belt reduction (to be calculated later), what about filling the Y beams to reduce vibrations ?
Does it have been tested yet ?
Polyurethane foam may limit the resonance but won't add significant weight.
Filling beams with concrete will, and reduce considerabily vibrations,
through, even with light weight concrete (styrofoam and nylon fiber charged) the weight can be too much important for motors and other parts.
The gantry manipulation will need at last 4 people ! :D

Well I don't know if it's a real good idea.
I would rather using the right shape with the right thickness...

Well... you can always build one & experiment with the filling. No one know to what degree vibration will start to affect your cut results... so it is really a shot in the dark.

remember to factor in the weight of the filling. never know if it will increase static deflection.

My philosophy... If you are not brave enough to modify the laser files, you should not waste time in customising your own & stick to the "standard" design, or build a smaller machine. or get a bigger work shop to house your machine.

I respect your philosophy, Ken.
I would love to have a huge workshop, it's still a goal...
Maybe in the future if the MM project is successfull and brings money back.

Modifying the laser parts path is not impossible. Technicaly, it's even easy.
But any change at this point might induce stunt changes.
I'll do it as a last resort.

I would like to make this project possible with the specifications I have to deal with.
I've read a lot the MM forum. My MM won't be se single that can be dismountable.
I've read also that large Y beams are possible.

I worked a lot on the table at this point.
I have by my side a cutting list optimised for 6000mm steel bars.
Except for the Y beam vibration factor which must be still discussed,
it seems to me as strong as possible compared to the standard design.
Profiles matches at last standard specifications and this is triangulation on each sides.
I wish I did not make too much mistakes on it...
I do not have the approval of the MM community yet.

For the gantry, let's follow Gerald advice and plan on 100x50x4mm beams.
If this profile's ok, I can test the filling method for the community, if it's not stupid.
What is the max weight the motors/rail/rollers can stand ?

uh... Anyone ? :o

http://content.yudu.com/Library/A1sc...log-Rev.-05-11

BWC #3 Vee wheels are rated each at:
382 # Axial
1326# Radial
for loading

The bigger issue is Torque with relation to drawbar required to accelerate, maintain and decelerate with respect to the mass.

I know from experience, that a 77" long gantry from 4 x 2 x 1/4" Steel Mechanical Tube is just fine with 7.2 OM motors. Average top speed of 325ipm, nominal 180-225ipm for most work. This is with a 40# extended Z-slide in place and spindle. SO, my machine "load package" in the y-car is about 60# heavier than all the rest.

Does this help?

Sean

Axel

Would you be able to load material over the rails, with your gantry parked at the end of your x? That way you would have a significantly less massive gantry?:rolleyes:
Just a thought...

Hi all, thanks a lot for your help.

Don, I thought about that, this could solve a lot of problems,
but the overall access to clamp parts and boards would be quickly unbearable...

Sean, thanks for the link and data. It seems the rollers can stand much more than they do usualy. But not the stepper motors.
you must have a very heavy gantry. I guess the cut is nice with this weight.
With 1/4" thick, your two 77" beams have a total weight of 106 pounds (1/4" = 6mm).
My Y beams must be a bit less than 116" long.
To stay in a close weight than yours, I should go to a 5/32" (4mm) thick tube.
It's the specifications Gerald gave in the topic about long gantrys.
So filling the tubes with concrete, is a bad idea because the motors will not stand that extra weight.
Even 5 or 6mm (16/64" or 1/4") thick tubes must be too heavy.
62kg (135 pounds) for the 5mm and 72kg (160 pounds) for the 6mm. Hum.
I wanted to order those. Hopefully, you warned me before.

Do you have a belt reduction Sean ?
Do you think a belt reduction can compensate an extra gantry weight ?

A new question for all, did you bought hot or cold rolled steel for your MM parts ?
I quess the best is hot-rolled steel but is the difference important for the MM ?

As I mentioned before, I am using the 7.2:1 Gearbox motors from Oriental Motors with 20T pinions. The highest reduction possible for the best resolution possible with most considered.

I am not a speed demon, but the machine performed well with this mass. I never pushed the machine beyond 350 on quick moves because of the added mass.

Thanks Sean, I did not get 7.2 was for the reduction, not for amperage.
Sorry, newbie inside.

Some people says "long" motors have more torque, is it right ?
At this point, I don't understand a lot about the steppers, are your "short" OM PK296A2A among the most powefull nema34 ?
Could other steppers be even better for heavy gantries ?
Otherhand, Gerald said that too big motors are not adapted to the MM...

Othewise, I searched on the forum and did not found if steel must be hot rolled or not...
I'll take Hot rolled steel anyway, it's more expensive but I guess it's better.

Hi all,
I've modified the table base according to comments above.
Can you tell me what's wrong or if it looks ok for your wise eyes ?
Thanks. ;)


Here's the rough :
http://giemastruc.free.fr/Forums/MM_02_Perspective.jpg
Front view :
http://giemastruc.free.fr/Forums/MM_02_Front.jpg
Right view :
http://giemastruc.free.fr/Forums/MM_02_Right.jpg

You solved nothing about racking when using indexer with that cross bearer. it should go straight to the ground to stabilize it.

Thank you for your message Danilo,
I get what you mean.

While 4th axis is not implemented, the Gantry will not have to go so far.
I'll fix the proximity sensors and the stopper near 1220mm for now.
I thought those cross bearers beeing here temporary.
And I had 1300mm left on my ⌀40 6m tube.
They might be of no use for now and for later... :o Hum, I'm sorry about that...
Maybe a plan will explain better than a simple view :
http://giemastruc.free.fr/Forums/MM_02_Top.jpg

I don't think using C-channel for the cross beam which support the cross-bearer is a good idea. I will strongly recommend 200x50x3mm RHS for the job.
Also, it will be better if you place the cross bearer on top of this 200x50x3mm RHS, it will be structurally more efficient & a lot easier to fabricate.
I sense that you want are building your machine for mainly storage cabinet because you removed all the critical supporting trusses from the table... You gotta make up you mind whether you want your table structure to be a storage cabinet or to support your MM mechanism. My philosophy says a multiple purpose equipment will never perform a single task perfectly because of all the compromises you design into it. Like all thing in life, you can't have it all...

Well your comment is full of sense ! Thank you.

I thougth storage in the table will add mass which may stabilise the basis.
But if there's some structural problems, I should reconsider.
To strenght the long table beam, I thought about a cable straightener (like in architecture), but I left it because it's not cheap and complicated to build.
The stock may be simply under the table, on a simple frame.

Aren't the 70x40mm UPN chanels in Gerald's original maps ? (I did not bought them yet, next month, I promiss :o)
Well with 8mm thick, UPN seems to me easy to tap and bolt.
Maybe It's possible to bolt the 200x50x3mm RHS, passing through them with long bolts.
I'll try to find if I can find some, and ask about their price.

Thank you for your help.

Axel, I am not going to spend time analysing your design in detail, but I can "feel" that it is quite weak. I estimate that if I sit on the front edge of your design, it will go down at least 2mm, maybe 5mm.

You can use your design, but you will have to reduce the cutting speeds to stop the system from vibrating/resonating and giving you a poor cut quality.

Axel, 3m is a long span any sort of structure beam...RHS will be lighter & more rigid. With this sort of extended span, I usually reduce the beam weight as far as I could to reduce sagging due to its own weight. You can add weight else where if you wish.
Cable suspension won't really help here as you load will be moving along the beam & the cable suspension will deform the beam differently when the car moves.
IF you wish to enjoy the easy work on UPN & have plenty of weight; Brude force method is use the same UPN which you use for your rail support to support your cross bearer. I can be very sure that will work.

I understand Gerald.
Thank you for your regard, the time spent, and your advice,
I must reconsider anyway. The table storage is a real bad idea.
And last, it's more expensive. Let's do simple and efficient.