Mechanics Tutorial

8/10/2019 Mechanics Tutorial

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TUTORIAL

Drawing a little mechanicalpart using LibreCAD

Tutorial by Claudio Guarnieri

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $ o% $&



Introduction

'ello e(eryone) This tutorial is a tutorial %or beginners and is made mainly %or peoplethat are not into LibreCAD* with the aim to help them to %amiliari+e with it and to ha(ethe opportunity to create immediately something reasonably ,producti(e-. LibreCADhas not yet a real completed manual* this tas/ has ta/en in charge by a group o% bra(emen* but you can %ind some piece o% ad(ice into the %orum0 moreo(er* e(en LibreCAD hasbeen totally rebuilt* an idea o% its use can be %ound on 1cad manual. 'ere I2m using the(ersion 3 o% LibreCAD.This tutorial is also %or people that simply need a 4uic/ re(iew about the program2scommands. In this little tutorial then* we are going to draw a little part in order to getpeople more into LibreCAD. I suggest to people that ha(e no idea about this programwor/s* to spend a little time playing with this nice program* I mean* the menus* the lists5bloc/ list and library browser6* the command line* the sub7menus* and so on. #eopleused to other cads will %ind easier to understand the icons2 logic.8inally I would li/e to than/ 9r. Ralla+ o% the de(elopers team* that ga(e me the drawingwe are going to replicate* in %act e(en i% I can use this LibreCAD I2m not in mechanics* so Ineeded something understandable realistic to draw... Than/s Ralla+ then)Now we can start our little :ourney in this drawing.'a(e %un)

Claudio

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age 3 o% $&



Getting started

;ell* we ha(e our program run and we are about to start.8irst* be%ore set the drawing* the layers and so on* this picture down here represents thedrawing that we are about to create* the %inal result!

8irst go to dit <Current Drawing #re%erences* then set the ,paper- section to A=landscape* then on ,grid- section select ,Orthogonal Grid-. ;e are not using ,splines-but about ,units- and ,dimensions- loo/ the picture below!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age > o% $&



;ell* now we can %inally set the layers. In order to set layers you need to ha(e the layerlist window acti(e* i% you do not see it :ust clic/ the right mouse button a %ree space onthe top bar and clic/ with the le%t mouse button near ,layer list- and... Ta daa))) ;e ha(ea layer list) 8ine* when you ha(e the list the highlited layer is the one you are wor/ing in*and i% you loo/ down here you can see the relati(e menu* and precisely

Remember* the %irst thing to do* especially in big drawings* is setting the layers* it sa(estime and sometimes /eeps the wor/ readable and understandable.#ersonally I le%t to layer ? its de%ault settings and I ga(e to the layers the %ollowingsettings as resumed down here!

Layer name Color Thickness Line type

@ections lue ?*B Continuous

Dimensions 9agenta ?*$ Continuous

'atches Grey ?*$> Continuousorders Green ?*$ Continuous

A es Red ?*3B Dash dot 5small6

Down here the inter%ace menu to set the layers* naturally each description is to set therelati(e parameter!

And %inally we ha(e set the layers))) Up to now it has not been too di%%icult* am I rightE

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age = o% $&

'ide all layers

Add a layer

Remo(e a layer

Layer proprieties

@how all layers

@howFhide relati(e layer5in this case layer ?6

Loc/Funloc/ thenear layer

#rint or do not printthe layer ob:ects



Snaps

I /now I /now* you want draw* but this is really important))) Let me spend some words)@naps are particular points that you can use as start points to create an ob:ect* asre%erence %or dimensioning and so on* they are important because without them wewould entirely type coordinates and coordinates and coordinates and coordinates andcoordinates and coordinates* well you /now... In this nice bar we ha(e also hori+ontal and(ertical constraints and the +ero positions. Now ta/e a loo/ down here* we ha(e!

Loo/ down here to ha(e an idea about how much important snaps are* the same try withthe snap grid turned on at the le%t and turned o%% at the right)

Ta/e %amiliarity with this bar* it will sa(e much time and will sa(e your er... nec/ many

times)

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age B o% $&

8ree

@nap on grid

@nap on endpoints*notice that this little

contour means thatthis snap is selected

@nap on entity

@nap center

@nap middle* this snapcan assign more than amiddle point to a line @nap distance

@napintersection

'ori+ontalconstraint

erticalconstraint

@et relati(e+ero position

Loc/ relati(e+ero position



First lines

8irst something about coordinates!Orthogonal coordinates: they are coordinates that are identi%ied through an abscissaand an ordinate.Polar coordinates: they are identi%ied through a distance and an angle.Now* no matter i% you use orthogonal or polar coordinates* i% you simply insertcoordinates * they will be re%erred to the absolute +ero 5the red cross into thewor/space6* i% you type the H simbol be%ore the coordinates you will insert thecoordinates relati(ely to the red cursor 5the little cirlcle with a cross inside it6.

O/ %riends* now it2s time to draw. ach drawing can ha(e a border or can ha(e it not.;e are going to put it0 the paper is an A= and we wants B units o% border* then ourborder will be 3 & 3?? units.As you can see LibreCAD has a menu on the le%t* this will be our closest %riend when weare using this program.Now* be sure to operate in layer ?* then clic/ 5le%t mouse button6 on the icon ,lines- andon the sub7menu ,rectangles-. On the command line we will read ,@peci%y %irst rectanglecorner- and we2ll type 0,0 . Then to gi(e the second corner we ha(e to insert !", 00 andour border will be set 5Remember an A= is 3 & 3$? millimeters6)Now we are going to draw the (ery part o% this tutorial* as you can see it is a crosssection drawing* the section is cutting in two hal(es this part.The order will be!

$. The orthogonal (iew03. The isometric (iew.

#art$!

;e are going to draw %irst the sectioned part 5the part %illed with obli4ue lines6. Nowbe sure to operate on the layer @ CTION@* and we can start. Loo/ at the picture! as youcan see there is a cylindrical hole ha(ing 3Bunits as diameter and &*B height. The s4uaredpart side is =B units* then the di%%erence on that area will be $?. The picture down heregi(es the dimensions o% the sectioned part i% you /eep reasoning in this way!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age J o% $&





...9odi%y<9irror))) @o* the description o% this second way is longer then the descriptiono% the %irst one* but once you2(e learned it2s really %ast. @o* switch to ORD R@ layer andselect lines CD* D and 8. @elect 9odi%y<9irror and gi(e con%irm* when LibreCAD as/sthe two points clic/ on the top and the bottom points o% the red a es* remember to /eepthe original* and les :eu son %aits) Now we are at this point* loo/ down

Now* select the new lines %rom point $ to point =* clic/ on 9odi%y< dit ntity Attributeand gi(e con%irm0 corresponding to the writing ,layer- select ORD R@

And %inally loo/ here! we ha(e the borders)

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age o% $&

$

3 >

=



;ell* now it remains to :oin the lines* so use 9odi%y< tend by amount* or... ;ell* this isthe (ery method I always use to :oin lines* loo/ down %riends

'ere I selected the segment $73 5image at page 6. I% you loo/ closely at the endpointsthere are two blue dots* they are important because i% I clic/ one o% the two endpointsand I /eep the le%t mouse button clic/ed* the line becomes elastic and I can drag itwhere(er I want* e(en to an endpoint snap) @o that2s the tric/) Notice that i% I selectmore than entity at once I2ll mo(e one point* but two entities will be modi%ied. Loo/down here

Anyway once you2ll ha(e learned well* you2ll %ind this %eature really help%ul as I did)Now the ne t step is create a hatch on the cut area* so we need to switch to 'ATC' @layer* then we ha(e to select all the blue polygon o% ,section- layer* now clic/ on Create'atch* gi(e con%irm and select on the dialog bo the hatch ,ansi>$- scale $ and angle ?.Down here I modi%ied the pre(iew in order to a(oid doubts* those lines are the hatch)

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age o% $&



The %inal step is gi(e dimensions to our wor/. @o :ust be sure to operate on DI9 N@ION@layer* then clic/ on Dimensions< hori+ontal dimensions Dimensions< (ertical dimensionsso using the snap bar to set the place to put them. Remember to add the diametersymbol o% the 3B and $J units diameters into the %ollowing Tool Option bar

As you may ha(e noticed* those two diameters are not yet li/e they appear in thedrawing at the beginning... ;ell* it2s time to another little tric/! %irst we are going toselect those two dimensions* then we ha(e to clic/ the icon 9odi%y< plode and gi(econ%irm. Now there are separates entities and we can delete the ones that we don2tneed) @imple isn2t itE And the orthogonal art is done))))

#art3! This part can seem more comple * but is simpler than it seems! in isometric drawingsthere are angles that ne(er change0 I mean that we subdi(ide the space in angles o% $3? .

Loo/ the arrow in the picture* it indicates how the rotation wor/s. I% you still do notunderstand I2ll try to answer to your 4uestions with the %ollowing image!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $? o% $&



Now I am 4uite sure that you ha(e understood the meaning o% that /ind o% cloc/ and I amalso sure that you understood that we are going to use polar coordinates.I intentionally a(oided to s/ip tal/ing about a es K* M and so %ar* because LibreCAD is a3D cad* then it would be %orcing it to ma/e its own something that does not belong to it*%or this reason I did not go %ar %rom the angles considerations.Anyway to suppose a hypothetical > a es system we would %ind someting as %ollowing

@o using polar coordinates means that K lines will ha(e angles o% >? or 3$? * M lines willha(e angles o% $B? or >>? * and lines will ha(e angles o% ? or 3&? .;ell* let2s go on then)))

eeping as re%erence the drawing on page >* there we ha(e all the dimensions we needto proceed* we :ust ha(e to /eep in mind that strange cloc/ at page $?.Down here I put the lines2 dimensions to gi(e %or the isometric part!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $$ o% $&

? or 3&?

K>? or 3$?

M$B? or >>?



Remember the input way! clic/ Lines< line with gi(en angle* then insert in Tool Optionsthe numbers) 'ere in the picture there is an angle o% $B? degrees* a length o% $? unitsand the snap point selected is start* this means that in this case you will enter the line%rom the start* but you can also choose to enter it %rom the end or %rom the middle.

The method is simple* remember that!$. a es has always the number and ? as angle03. K a es has the number and >? or 3$? *

depending on the snap insertion that youchoose* start or end0

>. M a es has the number and $B? or >>? *depending on the snap insertion that youchoose0

=. The command 9IRROR* in this case is e ploitableat $??P* once you ha(e done le%t or right theother side will already be done* :ust si clic/s)

Remember also to be sure o% being in the proper layer* i% you were not* is not necessaryto redraw e(erything* simply select the entities that need to change layer and go to9odi%y< dit ntity Attributes* then select the correct layer) O/* i% I am not mista/ingyou should be in a similar situation* depending i% you ha(e done the hatch* i% not* do it!

This is pretty unrealistic* isn2t itE In %act we are going immediately to add the roundborders)As e(eryone can assume* e(en i% in the reality round parts are circles* we are ob(iously

going to draw ellipses. I ha(e a particular method to draw them and remember that issimpler than it seems)

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $3 o% $&



Our little pro:ect has a =B units sided s4uare at the top* so %irst o% all* switch to a randomlayer that is not ORD R@* because what we are about to draw will be deleted once wewill ha(e created our ellipses. I am operating on layer ? anyway.Now* we ha(e to consider that a circle is always inscribed in a s4uare* and its diameter isthe hal% part o% the s4uare side* i% I ha(e not been clear enough :ust loo/ down here

Our drawing has B circles that creates cylinders o% the piece. Loo/ing at the orthogonalpart 5#art$6 and starting %rom the top their diameters are!

• 3B units0• 3B units 5e ternal circle60• $J units 5internal circle60• $J units 5internal circle60• =? units 5e ternal circle6.

@o we are going to draw %i(e s4uares in the isometric (iew.The %irst s4uare is 3Bunits sided* so let2s create its a es on the isometric piece0 thosea es will be use%ul %or the other ellipses too) Anyway loo/ here!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $> o% $&

M a esK a es

I :ust turned o%%'ATC' @ layer

I :ust turned o%%'ATC' @ layer



8ine* now go in a %ree area* and create a 3Bunits sided s4uare in isometric (iew* :ust usethe polar coordinates and K7M angles* then create a hori+ontal line %rom le%t to right(erte . 'ere the result 5naturally I ha(e :ust put dimensions to show6!

Ne t* using the command 9odi%y<9o(eFCopy mo(e this %igure using as %irst point thehori+ontal line middle point and as %inal point the intersection o% the two a es that weha(e drawn int the pre(ious page. ;e can delete the hori+ontal line. The result is li/e thepicture below* e cept %or the hori+ontal line that I le%t %or a better understanding!

Now we ha(e to create the %oci) To do that we need to :oin the high (erte o% the s4uareto the middle point o% the opposite sides and :oin the low (erte o% the s4uare to themiddle point o% the opposite sides* and here we are!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $= o% $&

8

D

A

C

' G



8inally we can switch to layer ORD R@* and it2s time to create our ellipse through thecommand... Arcs) Mep* you ha(e read well) @o clic/ on Arcs< Arc with Center #ointsAngles. Then select A as center* then select segment AC as radius* %inally* D as start pointand C as %inal point and... (oilQ)))Using the same w ay center in D* radius is D * the startpoint is and %inal point is 8) ure/a))) ;e ha(e create an ellipse) Loo/ down here!

The ne t thing to do is delete the s4uare and that we don2t need anymore* delete also,a- and ,b- lines. Ne t create a &*B units (ertical line %rom point 1 towards the bottom*&*B units because this is the measure in the drawing* loo/ the dimensions at page three)This is the segment 1 . Creating the second ellipse is really easy* :ust use the command9odi%y<9o(eFCopy and gi(e 1 as %irst point and as %inal point. Ta daaa)))

Then* 5I switched bac/ to layer ?6 create another s4uare $J units sided in a %ree space*create a es and ellipse construction lines* then mo(e it %rom its geometrical center to .'ere the result!

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $B o% $&

1

1

a b

I turned o%% AK @layer to ma/e morereadable this image



Now you should /now what to do* switch to layer ORD R@ and create the ellipse withthe appropriate centers and radiuses. Ne t create a (ertical line o% =B units %rom pointtowards the bottom 5dimension ta/en %rom drawing on page >6.8inally select this last ellipse and using the command 9odi%y<9o(eFCopy* copy it using as %irst point and L as endpoint.

8inally create a =? sideds4uare* a es* diagonals and so on* mo(e this %igure %rom its center to L point and createthe last ellipse. Then delete 1 and L segments. The %inal picture will be this one.

Remaining in ORD R@ layer* create (ertical lines %rom points U and T towards thes4uare borders to complete the picture. Now you can delete the s4uare)

And yo will ha(e :ust to delete the ellipses parts that are e ceeding. To to this go to9odi%y<Di(ide and choose %irst the entities to be cut* then where to cut 5use snaps)6

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $J o% $&

1

L

U T



And you will ha(e drawn the entire part* orthogonal (iew and isometric (iew))) That2s all)

Conclusions

;ell* I hope that you %ound this tutorial interesting* I am pretty sure that you may ha(e

%ound too long some parts and too short some others* I hope anyway that you ha(eta/en more %amiliarity with this use%ul program. There are a lot o% %eatures that hereha(e not been e(en considered* but :ust be curious* that2s the secret) I would li/e tothan/ carbonardo and LordO% i/es o% the %orum about the Lengthen command* that wasnot e plained properly in the pre(ious (ersion o% this #D8. I than/ you too %or readingand...

@ee ya)Claudio

CLAUDIO GUARNI RI! Drawing a little mechanical part using LibreCAD " #age $& o% $&

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