With 18 teams there are 153 possible pairings, so with only 7 matches per round of play you need to play 21 rounds of 7 matches and 1 round of 6 matches. In other words there will be one round where 6 teams sit out. Below I have arranged this so the 6 match round comes first.
F1 F2 F3 F4 F5 F6 F7 Byes
Rnd
1 (A Q) (G O) (C N) (L M) (K P) (B J) (- -) (DEFHIR)
2 (I K) (E M) (A G) (N O) (F Q) (H R) (D P) (BCJL)
3 (C H) (J Q) (G P) (F M) (A D) (K L) (B E) (INOR)
4 (D L) (J M) (O R) (K Q) (G N) (C F) (H I) (ABEP)
5 (G K) (B R) (E F) (A H) (I L) (N P) (D M) (CJOQ)
6 (A O) (E G) (K M) (C I) (P Q) (L R) (J N) (BDFH)
7 (M O) (D H) (F I) (C P) (L N) (B G) (A K) (EJQR)
8 (E J) (K R) (H P) (B Q) (D O) (G M) (C L) (AFIN)
9 (C M) (H Q) (B L) (I N) (A J) (O P) (F R) (DEGK)
10 (H M) (D N) (F K) (A E) (C Q) (I P) (G J) (BLOR)
11 (J R) (F N) (B D) (G H) (E P) (L Q) (I O) (ACKM)
12 (E N) (C K) (I M) (D F) (H J) (A B) (G L) (OPQR)
13 (L P) (C J) (E H) (F O) (B M) (D I) (Q R) (AGKN)
14 (G R) (I Q) (D J) (B P) (E O) (K N) (A C) (FHLM)
15 (B H) (A F) (E L) (G Q) (I R) (J O) (M N) (CDKP)
16 (B I) (M P) (O Q) (A R) (F H) (C D) (E K) (GJLN)
17 (N Q) (H L) (J P) (E R) (C G) (A M) (B O) (DFIK)
18 (F L) (G I) (B C) (J K) (D R) (A N) (H O) (EMPQ)
19 (B F) (A P) (N R) (I J) (K O) (D E) (M Q) (CGHL)
20 (F P) (B N) (C R) (D G) (E I) (H K) (A L) (JMOQ)
21 (D K) (C O) (A I) (J L) (M R) (E Q) (F G) (BHNP)
22 (C E) (L O) (D Q) (H N) (B K) (F J) (P R) (AGIM)
If you have 7 different fields or venues available in each round then the schedule has best possible field balance with either 2 or 3 matches per team in each of the 7 columns. Finally note that no team has two or more consecutive byes.
Hope that helps.
Ian.
PS I have moved your request to this area as it is not possible to reply to messages in the comments area.
